THIN FILM PROCESSES

bull

~ 1LfL~ ~ LJ~ J w~

V-1

Chemical Etching

WERNER KERN AND CHERYL A DECKERT

RCA Laboratories Princeton New Jersey

L Introduction 401 [I Principles and Techniques of Etching 403

IV Tables of Echanh and Etching Coniltinns 413 A Guide to the 1I se of Tanle 4B R Insulators and Diclcctrics 4 ~

A Chemistry of Etching 40J B Factors AfTecting Etching Reactns 404 C Etching Techniques and Procc 405 i) Pattern Delineation Etching for Th Films 407 E SUlfate Contamination and Cleaninpound I cchniqucs 411

11 L Chemical Etching of Specific Materials 413 A Insulators and Dielectrics 41l B Semiconductof 424 C Conductors 4n D Miscellaneous Matcriah 432

C Elemental Semiconductors 4JR 0 Compound Semiconductors 451 E Conductors 463 F Miscellaneous Material 479

V Summary and Coneusions 481 Acknowledgments 481 References 4RI

I INTRODUCTION

Chemical etching in thin-film technology plays a prominent role in both the preparation and the utilization of thin films Regardless of the method of film deposition or formation the substrate must first be suitmiddot

401

) Im h~ Audtmic Prel~ I nl II ntthll fttlfuducIUlfl In any form Te(t~td

()tP2~1ltG

~

I

1 )

40~ WERNER KERN AND lE-RYl A DECKERT

uhly prepured either by removal of work damaged surface layers or by creating a relief structure of specific geometry In the first case chemical polish etching is usually the method of choice in the second case strucshytural etching is required Once a thin film has been deposited chemical etching is often used again this lime to create patterns in the approprishyately masked films

The aim of this review i~ to provide a broad outline of the subject of chemical etching and to present tables with references of etchants and etching conditions for inorganic materials

Numerous excellent books treatises and reviews are availuble on theoretical and practical aspects of chemical etching covering the chemshyistry [1-28] and electrochemistry [29-42] of etching processes A few partial bibliogmphies have been published on some aspects of etching [43 43a] However most information on specific etch ants for different mashyterials with the possible exception of semiconductors is widely scattered throughout the scientific literature and is often difficult to retrieve because etching is most frequently a means to an end and is usually not the prishymary subject matter of an investigation An attempt has been made to bring together essential information that should prove useful to the scienshytist or engineer who must select an etching process for a specific material It is obviously impossible to list all etchants for all materials Instead a selection has been attempted which is based in the authors opinion on the practical usefulness of an etchant and a solid material in thin-film techshynology The most recent and advanced information is generally given preference Special emphasis is placed on materials and processes used in semiconductor microelectronics because a substantial part of thin-film technology is applied in this area with which we are particularly familiar from pmctical experience

One important application of chemical etching is in the structural charshyacterization of materials especially the detection of lattice defects in semiconductors the study of distribution of localized impurities the deshylineation of layer structures and p-n junctions and the determination of composition This specialized field of analytical etching is outside the scope of the present review Physical-chemical dry etching processes such as sputter etching plasma etching and ion milling are covered in Chapter V-2 What will be covered is chemical and electrolytic etching of insulators semiconductors and conductors in solution and in the gas phase

Chemical formulas noted for reagents refer to the chemicals in the usual concentrated form as defined in Section IV A parts are by volume The crystallographic notifications used are those quoted by the author(s) of the reference cited

middotlil v-I (HIMICAt~~rUllNG II PRINCIPLES AND TECHNIQUES OF ETCHING

A Chemistry of Etching

Chemical etching may occur hy any of everal llitlrl1l1 pnHel [ I 2 81 The simplest mode of etching involves disolutwn of the maknI in a liquid solvent without uny change in the chemicltd natllllt 01 thl dis solved spedes Relatively few imlwtrially important Illatlrial ale etdHd in this munner Although this is the only clching PlllC fur which the word dissolution is properly used the krrn h Lome Into Cll[l11l1UIl USl for describing uny etching procedure carned Hit ill hljlllli media

Most etching processes involve nne 01 more chelllle reactiulls III

order to be truly an etching reuctinn the PIllCt fllllwd 1111t he uluhk in the etchunt medium or must at leat he carned awa~ 110m the UIfllC by the medium Various types of reuctiulh Whll mltlY he 111 dv1 all l idation-reduuion of which e1etrochellmal etching I a pecial case Lomplexation and gas phase etching

An lxidation-reduction or redllx ddling proCl IIlv)lve comci sion of the Illateriul hring rlched to it ~()Iuhlc hightl Iddtloll Iall

M -+ M ll~

Redox etching may occur either in a completely dlellllld itefll h~ Ill use of certain chemicull)xidizing agent stich Cr (II ill an dClilt rhemicul relllI)J by making the material to he lIdld the lIwdl lIld h applying a suitable eXlernal electromotive forre A tYPIC pllll I (UII(1l1

density versus tell v)ltage is given in Fig I thr vanous lag I lll ure noted Ektlrochelllical effects cun lead tIl cerLlIll 11 hit-ill III etc

Cormsion 124 ~i 4~1 is a special case (If iCltdlll1l1ld ctLlllIlg which occurs whrn surfan~ variations produce Illl1 alllldn 1Ilt (llhde When films of two dlssimilur mrtals arc in conlact thc reult1I1l gd lIlk uctton can cause undrrculling at the interfan during Ltdllllg 1441

Ui z w D oFig I Curren uenily yencru ~dl vullshy

age Region A -8 el~hing B -( Ihle z w

plateau with polihlng C -[) low ga I 0 ~tion with pilling D-E polhing lin IPIU U

ga evolution ~ o z

A Cell V()llAGt

c

t

1 404 WERNER KERN AND CHERYL A DECKERT

Complex formation is frequently involved in etching processes often in conjunction with a redox reaction The ligand groups surround and bond chemically to the etched species forming a complex ion or molecule that is readily soluble in the etchant medium

Gas phase etching may involve vaporization of the material being etched in a vacuum or inert atmosphere or may involve reaction of gasshyeous etchants with the surlace to produce volatile products Elevated temperatures are usually required

B Factors Affecting Etching Reactions

Etching reactions typically occur by a process involving several seshyquential steps [3 81 The observed dissolution kinetics depend upon the nature of the rate-limiting step of the process If the rate of this step is determined by the chemical reactivity of the species involved the process is said to be activation limited On the other hand if the rate is determined by the speed at which fresh reactant can be supplied to the surface the process is said to be dIffusion limited

If a series of materials are all etched in the same solution by a diffushysion-controlled prmess then the same etch rate is observed fur all Some etching processes are diffusion limited at low cuncentrations but are activation limited at higher concentrations [31 An increase in etching temperature may cause a change in the etching kinetics 145 J The presence of catalytic species in the etchant can also affect the etch rates markecly Agitation of the solution may increase etch rate if the reaction is diffusion limited it may decnase etch rate if for example lucalized solution heatshying occurs or it may have no effect if activation control is involved In pattern etching the slope of the pattern edges depends on the type of kishynetics involved 1461

Adsorption and desorption processes can affect the etching kinet1c~ profoundly Adsorption of reactant from the etchant solution onto the substrate may produce surface complexes which will facilitate the etching process however in many cases adsorption of nonreactive species or forshymation of passivating surface films can slow down or SlOp further etching [3] Oxide films on metals are a good example of this phenomenon Cershytain types of impurities in the etchant solution even though present at low concentrations may be adsorbed onto the substrate and hinder etching [8) Desorption of gaseous reaction products sometimes limits the rates of etching processes [31

The kinematic aspecb of etching [8 47 J should also be mentioned briefly This refers mainly to the tendency of various crystallographic

v-I (HIMICL titHING

-JI

planes to ehh at different rates Various llrientatilh oj Slllgle cl y(tI lIh

strates may thus etch very differently in a given cldlHnl alHI sllhlrdln ill varying roughness may also exhibit large differellc III clLli faIL

Several additional specific factors affecting etdllllg ieacliolh III 111 OtiS types of materials will be n()ll~d in the discUlllih of Hlsldahll til semiconductors (Sections IIIA and IIIB respectively)

C Etching Techniques and Processes

Thl choill of the etching tedwillle to be lIsed fOI it givclI tlilallull depends upon the material to be etched the reluirClllcllh of 101111111 gC1I eration the nClessary etlhing rcagellh the cllhing pnHecS 111 Ivn and other faltllrs slIlh as eCOnOllllC IOllslderatiolls

I illl III IJsioll

The simplc~t technilue is lilllid dlelllical immerSion 0 dip ell

where the masked or unmasked objllt i ~lIbmerged III IIll dlh 1111111 Mechallical agitation is usually desirable as it illlplOvn Ihe lilli 11111 oIlid

control of the ething proess by enhandng the Cdlallgc ltllld 11111111 (II ~pent etching ~lllulJon at the solid sllrlme with licsil ililI

OIl I h h

av()id~ local overheating in the case of exutlilllIlIc ICcllOlh (Ilcleb) maintaining a uniform and controllahle ctdllllg IaIL Huhhle I g

lu~ually H) that nwy form as a reaLlion prodULlelllcllllg I() IhL h iii face and inhibit uniform ehing The addition of llacc Icll v c dgnll I the etch solution can prevent bubhle aClulllUlalloll Unkllllll) LIliC

ratiu of ekhant tll material being dLhed should hc llliploycd III 1111 111111 IIc

reaClant depletion and to maintain the realliull tlllpC(illlrc oIlld Ihe lollof Illtack

Spray cthll1g IS lIeflll for gcnerating pal tern III IdlIIVd) (lil ~ lIilll or substrates especially if steep pallern wal Ill dLIILd 1IlcL Ihe pinging eth~oluti()n imparts a variable degrcl nl dll CCIIOIllill) III llil

process The ething rate is inreased llvcr thaI uf inllllLhlon Ltdllllg dllll an be regulated by the amount uf preslIre applild alld thl lc 111 thc droplets Good proes control Ilnd 1Illifonnily Cdll hl dlLIIIlld IgtcI1 fresh etchan is rilpidly and CUlhtantly uppliLd tu 111l 11acIillll Sill

the nactioll producl arc continuuusly rmOVL lkhlllg 1IIhself to automation

madllll C c dlldgtl 11many spelilic

r ~ 1~

f 406 WERNER KERN AND CHERYL A DECKERT

~ J Electrolytic Etching

Electrically conductive or semiconductive materials are frequently etched by application of external emf potentials Electropolishing of metals and semiconductors is a good example of this technique The rate and selectivity of etching can be controlled by the potential andor the

~ ~ current density applied Electrolytic etching is considerably more complishy

cated than other techniques but can yield results not otherwise attainshyable Specific conditions will be described for various materials in the text and in the etching tables

4 Gas-Phase Etching

High-temperature etching in the gas or vapor phase is generally used for chemically inert materiab that cannot be etched readily in liquid reshyagents A different application is for in situ etching of semiconductor subshystrates immediately prior to epitaxial film growth in the same reactor to avoid surface contamination that would result by other techniques

t ~ 5 Mechanical-Chemical Polishing

1 This technique is used in semiconductor wafer preparation when a relshyatively defect-free surfa(e is required The combination of slow liquid

~ ~ chemical surface etching with gentle mechanical abrasion to continuously

remove products from the etching reaction can result in a high-quality surshyface polish if carefully optimized conditions are observed as will be deshy j scribed in Section IllBp

$ i 6 Isotropic versus Anisotropic Procesusbull

Isotropic or nonpreferential etching proceeds at an equal rate in all dishyf rections Amorphous materials of uniform composition etch isotropicallyshyJ whereas many crystalline materials etch both isotropically and anisotropishycally Anisotropic or preferential etching depends on the crystallographici

1 orientation of the material and on the etching reagent used If polishing t action is desired isotropic etching conditions must be selected to achieve

a structureless surface If structural shaping is the objective as in the forshymation of deep depressions having side walls of a specific taper angle anishysotropic conditions are required Both liquid and gas-phase etching can be used for these two types of etching processes

7 Selective Etching PwcesJes

Selectivity refer~ to the differences in etch rate between different mashyteriah or between compositional or structural variations of the same ma-

T ) --shy

v-I UIEMI(AI lelnUNG ((

terial It is one of the most Important faclor III pplicd ell hili) gt1(

technological etching processes must he controllahly eeui lt 1gt1llI

the material to be etched is usually part of a trllctlile Ihal cnll ul on eral material components Seleclivily III etdlillg is Ihined h) 11 (Ipc I choie of etching techni411e and lt1(h1I1I LuJllj1IilJolI Wllhill tlil straints of the syskms

Various degrees of etching selecllvit ai dlII1hk Inl panlII1 pUI

poses For example pattern ellhillt (If SiN or 11)1111110 III 1 III() an eth-resistant deposikd SI() 111m III II IllaJ ilillstldl j

high degree of dching selectlvil) Oil Ihc olhel IiUld lnllll(llkd PIIIIJ etching seletivity of dielectric byel cOlllpoill 1 IIllIlllIlI III LIf1 cthing where a desired edge COlliolil clIlhl lILIIIId (Ill Ihl 11 01 el11 rate differemes of the componelll 1Yel In Ill d IILI Lklllllg til ehLtri taptrLolltrol layer i (lIIllL nvu Ihe Ikdll 10 he hkd

[461 Numerous uther important ltlpplicaliolh 01 lkcllVc lt1c1l11V l been descrihed [26 27 415 49 I

~ FIIlioll (11pound1 Other -IIC(I(I

(lrtam highly etlh-nsistant mllcria Ill h dbed h 11dllll1I1 with moltell salh (uften Lau~tics n hUla)) 11 11Igh IIIIIIC lt111 examples will be noted in Sections I V B and I V I)

Surface oxidltlon hy thermal or lIhldli tledllllnl (I1ed hI 1111 iGd strippillg of thc nxide films formed can aho he laquoIhlkl 111 cl llillg

proLI~S Howl~er only the econd tep the clillllg llhe laquoSide-- oil I dislIssid here (Section IILr)

D Pattern Delineation Etching for Thin Films

In rnany instan(cs elching pnlCisses arc used I) JIdIlC cllI1 111 terns in thin film~ Sdected portions of the Ijlm II 111Jcd by 111111lt1 thin film coating material which is undlcded by Ihe 111111 (0 hl 1Id Il patterning Etching is then canied (lut so as to re11lm lttilth 1JIIIIIIIdllll in the unprotected regions The proteClivc Loatillg lilill Ihl1 IIsllgtlI stripped leaving the desired pallen in Ihe lIndc) IIll thlll fillll

Pattern etching is obviuLJsly a Illllch 11111 dllllples PI)ll 11111 I pic overall sUIiaLc etching III additloll to lIeding Ih ctliHlI hII)l

masking material is of prime importance good aLlhnlolloIlitlS COlill) 1ltgt

the substrate Cllltlling integrity aJe4LJate reulutillll lIld I LlSldIlC hI 111 ethant arc the main Lonsiderations Lase in pattelllllll thc Inasl- L01I1I~ is important othClgtIltbe thi plOcedure beCOlllLS til IllIlIg PWlC 11middot11 requiring yet ullother mask

I

1 )

40~ WERNER KERN AND lE-RYl A DECKERT

uhly prepured either by removal of work damaged surface layers or by creating a relief structure of specific geometry In the first case chemical polish etching is usually the method of choice in the second case strucshytural etching is required Once a thin film has been deposited chemical etching is often used again this lime to create patterns in the approprishyately masked films

The aim of this review i~ to provide a broad outline of the subject of chemical etching and to present tables with references of etchants and etching conditions for inorganic materials

Numerous excellent books treatises and reviews are availuble on theoretical and practical aspects of chemical etching covering the chemshyistry [1-28] and electrochemistry [29-42] of etching processes A few partial bibliogmphies have been published on some aspects of etching [43 43a] However most information on specific etch ants for different mashyterials with the possible exception of semiconductors is widely scattered throughout the scientific literature and is often difficult to retrieve because etching is most frequently a means to an end and is usually not the prishymary subject matter of an investigation An attempt has been made to bring together essential information that should prove useful to the scienshytist or engineer who must select an etching process for a specific material It is obviously impossible to list all etchants for all materials Instead a selection has been attempted which is based in the authors opinion on the practical usefulness of an etchant and a solid material in thin-film techshynology The most recent and advanced information is generally given preference Special emphasis is placed on materials and processes used in semiconductor microelectronics because a substantial part of thin-film technology is applied in this area with which we are particularly familiar from pmctical experience

One important application of chemical etching is in the structural charshyacterization of materials especially the detection of lattice defects in semiconductors the study of distribution of localized impurities the deshylineation of layer structures and p-n junctions and the determination of composition This specialized field of analytical etching is outside the scope of the present review Physical-chemical dry etching processes such as sputter etching plasma etching and ion milling are covered in Chapter V-2 What will be covered is chemical and electrolytic etching of insulators semiconductors and conductors in solution and in the gas phase

Chemical formulas noted for reagents refer to the chemicals in the usual concentrated form as defined in Section IV A parts are by volume The crystallographic notifications used are those quoted by the author(s) of the reference cited

middotlil v-I (HIMICAt~~rUllNG II PRINCIPLES AND TECHNIQUES OF ETCHING

A Chemistry of Etching

Chemical etching may occur hy any of everal llitlrl1l1 pnHel [ I 2 81 The simplest mode of etching involves disolutwn of the maknI in a liquid solvent without uny change in the chemicltd natllllt 01 thl dis solved spedes Relatively few imlwtrially important Illatlrial ale etdHd in this munner Although this is the only clching PlllC fur which the word dissolution is properly used the krrn h Lome Into Cll[l11l1UIl USl for describing uny etching procedure carned Hit ill hljlllli media

Most etching processes involve nne 01 more chelllle reactiulls III

order to be truly an etching reuctinn the PIllCt fllllwd 1111t he uluhk in the etchunt medium or must at leat he carned awa~ 110m the UIfllC by the medium Various types of reuctiulh Whll mltlY he 111 dv1 all l idation-reduuion of which e1etrochellmal etching I a pecial case Lomplexation and gas phase etching

An lxidation-reduction or redllx ddling proCl IIlv)lve comci sion of the Illateriul hring rlched to it ~()Iuhlc hightl Iddtloll Iall

M -+ M ll~

Redox etching may occur either in a completely dlellllld itefll h~ Ill use of certain chemicull)xidizing agent stich Cr (II ill an dClilt rhemicul relllI)J by making the material to he lIdld the lIwdl lIld h applying a suitable eXlernal electromotive forre A tYPIC pllll I (UII(1l1

density versus tell v)ltage is given in Fig I thr vanous lag I lll ure noted Ektlrochelllical effects cun lead tIl cerLlIll 11 hit-ill III etc

Cormsion 124 ~i 4~1 is a special case (If iCltdlll1l1ld ctLlllIlg which occurs whrn surfan~ variations produce Illl1 alllldn 1Ilt (llhde When films of two dlssimilur mrtals arc in conlact thc reult1I1l gd lIlk uctton can cause undrrculling at the interfan during Ltdllllg 1441

Ui z w D oFig I Curren uenily yencru ~dl vullshy

age Region A -8 el~hing B -( Ihle z w

plateau with polihlng C -[) low ga I 0 ~tion with pilling D-E polhing lin IPIU U

ga evolution ~ o z

A Cell V()llAGt

c

t

1 404 WERNER KERN AND CHERYL A DECKERT

Complex formation is frequently involved in etching processes often in conjunction with a redox reaction The ligand groups surround and bond chemically to the etched species forming a complex ion or molecule that is readily soluble in the etchant medium

Gas phase etching may involve vaporization of the material being etched in a vacuum or inert atmosphere or may involve reaction of gasshyeous etchants with the surlace to produce volatile products Elevated temperatures are usually required

B Factors Affecting Etching Reactions

Etching reactions typically occur by a process involving several seshyquential steps [3 81 The observed dissolution kinetics depend upon the nature of the rate-limiting step of the process If the rate of this step is determined by the chemical reactivity of the species involved the process is said to be activation limited On the other hand if the rate is determined by the speed at which fresh reactant can be supplied to the surface the process is said to be dIffusion limited

If a series of materials are all etched in the same solution by a diffushysion-controlled prmess then the same etch rate is observed fur all Some etching processes are diffusion limited at low cuncentrations but are activation limited at higher concentrations [31 An increase in etching temperature may cause a change in the etching kinetics 145 J The presence of catalytic species in the etchant can also affect the etch rates markecly Agitation of the solution may increase etch rate if the reaction is diffusion limited it may decnase etch rate if for example lucalized solution heatshying occurs or it may have no effect if activation control is involved In pattern etching the slope of the pattern edges depends on the type of kishynetics involved 1461

Adsorption and desorption processes can affect the etching kinet1c~ profoundly Adsorption of reactant from the etchant solution onto the substrate may produce surface complexes which will facilitate the etching process however in many cases adsorption of nonreactive species or forshymation of passivating surface films can slow down or SlOp further etching [3] Oxide films on metals are a good example of this phenomenon Cershytain types of impurities in the etchant solution even though present at low concentrations may be adsorbed onto the substrate and hinder etching [8) Desorption of gaseous reaction products sometimes limits the rates of etching processes [31

The kinematic aspecb of etching [8 47 J should also be mentioned briefly This refers mainly to the tendency of various crystallographic

v-I (HIMICL titHING

-JI

planes to ehh at different rates Various llrientatilh oj Slllgle cl y(tI lIh

strates may thus etch very differently in a given cldlHnl alHI sllhlrdln ill varying roughness may also exhibit large differellc III clLli faIL

Several additional specific factors affecting etdllllg ieacliolh III 111 OtiS types of materials will be n()ll~d in the discUlllih of Hlsldahll til semiconductors (Sections IIIA and IIIB respectively)

C Etching Techniques and Processes

Thl choill of the etching tedwillle to be lIsed fOI it givclI tlilallull depends upon the material to be etched the reluirClllcllh of 101111111 gC1I eration the nClessary etlhing rcagellh the cllhing pnHecS 111 Ivn and other faltllrs slIlh as eCOnOllllC IOllslderatiolls

I illl III IJsioll

The simplc~t technilue is lilllid dlelllical immerSion 0 dip ell

where the masked or unmasked objllt i ~lIbmerged III IIll dlh 1111111 Mechallical agitation is usually desirable as it illlplOvn Ihe lilli 11111 oIlid

control of the ething proess by enhandng the Cdlallgc ltllld 11111111 (II ~pent etching ~lllulJon at the solid sllrlme with licsil ililI

OIl I h h

av()id~ local overheating in the case of exutlilllIlIc ICcllOlh (Ilcleb) maintaining a uniform and controllahle ctdllllg IaIL Huhhle I g

lu~ually H) that nwy form as a reaLlion prodULlelllcllllg I() IhL h iii face and inhibit uniform ehing The addition of llacc Icll v c dgnll I the etch solution can prevent bubhle aClulllUlalloll Unkllllll) LIliC

ratiu of ekhant tll material being dLhed should hc llliploycd III 1111 111111 IIc

reaClant depletion and to maintain the realliull tlllpC(illlrc oIlld Ihe lollof Illtack

Spray cthll1g IS lIeflll for gcnerating pal tern III IdlIIVd) (lil ~ lIilll or substrates especially if steep pallern wal Ill dLIILd 1IlcL Ihe pinging eth~oluti()n imparts a variable degrcl nl dll CCIIOIllill) III llil

process The ething rate is inreased llvcr thaI uf inllllLhlon Ltdllllg dllll an be regulated by the amount uf preslIre applild alld thl lc 111 thc droplets Good proes control Ilnd 1Illifonnily Cdll hl dlLIIIlld IgtcI1 fresh etchan is rilpidly and CUlhtantly uppliLd tu 111l 11acIillll Sill

the nactioll producl arc continuuusly rmOVL lkhlllg 1IIhself to automation

madllll C c dlldgtl 11many spelilic

r ~ 1~

f 406 WERNER KERN AND CHERYL A DECKERT

~ J Electrolytic Etching

Electrically conductive or semiconductive materials are frequently etched by application of external emf potentials Electropolishing of metals and semiconductors is a good example of this technique The rate and selectivity of etching can be controlled by the potential andor the

~ ~ current density applied Electrolytic etching is considerably more complishy

cated than other techniques but can yield results not otherwise attainshyable Specific conditions will be described for various materials in the text and in the etching tables

4 Gas-Phase Etching

High-temperature etching in the gas or vapor phase is generally used for chemically inert materiab that cannot be etched readily in liquid reshyagents A different application is for in situ etching of semiconductor subshystrates immediately prior to epitaxial film growth in the same reactor to avoid surface contamination that would result by other techniques

t ~ 5 Mechanical-Chemical Polishing

1 This technique is used in semiconductor wafer preparation when a relshyatively defect-free surfa(e is required The combination of slow liquid

~ ~ chemical surface etching with gentle mechanical abrasion to continuously

remove products from the etching reaction can result in a high-quality surshyface polish if carefully optimized conditions are observed as will be deshy j scribed in Section IllBp

$ i 6 Isotropic versus Anisotropic Procesusbull

Isotropic or nonpreferential etching proceeds at an equal rate in all dishyf rections Amorphous materials of uniform composition etch isotropicallyshyJ whereas many crystalline materials etch both isotropically and anisotropishycally Anisotropic or preferential etching depends on the crystallographici

1 orientation of the material and on the etching reagent used If polishing t action is desired isotropic etching conditions must be selected to achieve

a structureless surface If structural shaping is the objective as in the forshymation of deep depressions having side walls of a specific taper angle anishysotropic conditions are required Both liquid and gas-phase etching can be used for these two types of etching processes

7 Selective Etching PwcesJes

Selectivity refer~ to the differences in etch rate between different mashyteriah or between compositional or structural variations of the same ma-

T ) --shy

v-I UIEMI(AI lelnUNG ((

terial It is one of the most Important faclor III pplicd ell hili) gt1(

technological etching processes must he controllahly eeui lt 1gt1llI

the material to be etched is usually part of a trllctlile Ihal cnll ul on eral material components Seleclivily III etdlillg is Ihined h) 11 (Ipc I choie of etching techni411e and lt1(h1I1I LuJllj1IilJolI Wllhill tlil straints of the syskms

Various degrees of etching selecllvit ai dlII1hk Inl panlII1 pUI

poses For example pattern ellhillt (If SiN or 11)1111110 III 1 III() an eth-resistant deposikd SI() 111m III II IllaJ ilillstldl j

high degree of dching selectlvil) Oil Ihc olhel IiUld lnllll(llkd PIIIIJ etching seletivity of dielectric byel cOlllpoill 1 IIllIlllIlI III LIf1 cthing where a desired edge COlliolil clIlhl lILIIIId (Ill Ihl 11 01 el11 rate differemes of the componelll 1Yel In Ill d IILI Lklllllg til ehLtri taptrLolltrol layer i (lIIllL nvu Ihe Ikdll 10 he hkd

[461 Numerous uther important ltlpplicaliolh 01 lkcllVc lt1c1l11V l been descrihed [26 27 415 49 I

~ FIIlioll (11pound1 Other -IIC(I(I

(lrtam highly etlh-nsistant mllcria Ill h dbed h 11dllll1I1 with moltell salh (uften Lau~tics n hUla)) 11 11Igh IIIIIIC lt111 examples will be noted in Sections I V B and I V I)

Surface oxidltlon hy thermal or lIhldli tledllllnl (I1ed hI 1111 iGd strippillg of thc nxide films formed can aho he laquoIhlkl 111 cl llillg

proLI~S Howl~er only the econd tep the clillllg llhe laquoSide-- oil I dislIssid here (Section IILr)

D Pattern Delineation Etching for Thin Films

In rnany instan(cs elching pnlCisses arc used I) JIdIlC cllI1 111 terns in thin film~ Sdected portions of the Ijlm II 111Jcd by 111111lt1 thin film coating material which is undlcded by Ihe 111111 (0 hl 1Id Il patterning Etching is then canied (lut so as to re11lm lttilth 1JIIIIIIIdllll in the unprotected regions The proteClivc Loatillg lilill Ihl1 IIsllgtlI stripped leaving the desired pallen in Ihe lIndc) IIll thlll fillll

Pattern etching is obviuLJsly a Illllch 11111 dllllples PI)ll 11111 I pic overall sUIiaLc etching III additloll to lIeding Ih ctliHlI hII)l

masking material is of prime importance good aLlhnlolloIlitlS COlill) 1ltgt

the substrate Cllltlling integrity aJe4LJate reulutillll lIld I LlSldIlC hI 111 ethant arc the main Lonsiderations Lase in pattelllllll thc Inasl- L01I1I~ is important othClgtIltbe thi plOcedure beCOlllLS til IllIlIg PWlC 11middot11 requiring yet ullother mask

t

1 404 WERNER KERN AND CHERYL A DECKERT

Complex formation is frequently involved in etching processes often in conjunction with a redox reaction The ligand groups surround and bond chemically to the etched species forming a complex ion or molecule that is readily soluble in the etchant medium

Gas phase etching may involve vaporization of the material being etched in a vacuum or inert atmosphere or may involve reaction of gasshyeous etchants with the surlace to produce volatile products Elevated temperatures are usually required

B Factors Affecting Etching Reactions

Etching reactions typically occur by a process involving several seshyquential steps [3 81 The observed dissolution kinetics depend upon the nature of the rate-limiting step of the process If the rate of this step is determined by the chemical reactivity of the species involved the process is said to be activation limited On the other hand if the rate is determined by the speed at which fresh reactant can be supplied to the surface the process is said to be dIffusion limited

If a series of materials are all etched in the same solution by a diffushysion-controlled prmess then the same etch rate is observed fur all Some etching processes are diffusion limited at low cuncentrations but are activation limited at higher concentrations [31 An increase in etching temperature may cause a change in the etching kinetics 145 J The presence of catalytic species in the etchant can also affect the etch rates markecly Agitation of the solution may increase etch rate if the reaction is diffusion limited it may decnase etch rate if for example lucalized solution heatshying occurs or it may have no effect if activation control is involved In pattern etching the slope of the pattern edges depends on the type of kishynetics involved 1461

Adsorption and desorption processes can affect the etching kinet1c~ profoundly Adsorption of reactant from the etchant solution onto the substrate may produce surface complexes which will facilitate the etching process however in many cases adsorption of nonreactive species or forshymation of passivating surface films can slow down or SlOp further etching [3] Oxide films on metals are a good example of this phenomenon Cershytain types of impurities in the etchant solution even though present at low concentrations may be adsorbed onto the substrate and hinder etching [8) Desorption of gaseous reaction products sometimes limits the rates of etching processes [31

The kinematic aspecb of etching [8 47 J should also be mentioned briefly This refers mainly to the tendency of various crystallographic

v-I (HIMICL titHING

-JI

planes to ehh at different rates Various llrientatilh oj Slllgle cl y(tI lIh

strates may thus etch very differently in a given cldlHnl alHI sllhlrdln ill varying roughness may also exhibit large differellc III clLli faIL

Several additional specific factors affecting etdllllg ieacliolh III 111 OtiS types of materials will be n()ll~d in the discUlllih of Hlsldahll til semiconductors (Sections IIIA and IIIB respectively)

C Etching Techniques and Processes

Thl choill of the etching tedwillle to be lIsed fOI it givclI tlilallull depends upon the material to be etched the reluirClllcllh of 101111111 gC1I eration the nClessary etlhing rcagellh the cllhing pnHecS 111 Ivn and other faltllrs slIlh as eCOnOllllC IOllslderatiolls

I illl III IJsioll

The simplc~t technilue is lilllid dlelllical immerSion 0 dip ell

where the masked or unmasked objllt i ~lIbmerged III IIll dlh 1111111 Mechallical agitation is usually desirable as it illlplOvn Ihe lilli 11111 oIlid

control of the ething proess by enhandng the Cdlallgc ltllld 11111111 (II ~pent etching ~lllulJon at the solid sllrlme with licsil ililI

OIl I h h

av()id~ local overheating in the case of exutlilllIlIc ICcllOlh (Ilcleb) maintaining a uniform and controllahle ctdllllg IaIL Huhhle I g

lu~ually H) that nwy form as a reaLlion prodULlelllcllllg I() IhL h iii face and inhibit uniform ehing The addition of llacc Icll v c dgnll I the etch solution can prevent bubhle aClulllUlalloll Unkllllll) LIliC

ratiu of ekhant tll material being dLhed should hc llliploycd III 1111 111111 IIc

reaClant depletion and to maintain the realliull tlllpC(illlrc oIlld Ihe lollof Illtack

Spray cthll1g IS lIeflll for gcnerating pal tern III IdlIIVd) (lil ~ lIilll or substrates especially if steep pallern wal Ill dLIILd 1IlcL Ihe pinging eth~oluti()n imparts a variable degrcl nl dll CCIIOIllill) III llil

process The ething rate is inreased llvcr thaI uf inllllLhlon Ltdllllg dllll an be regulated by the amount uf preslIre applild alld thl lc 111 thc droplets Good proes control Ilnd 1Illifonnily Cdll hl dlLIIIlld IgtcI1 fresh etchan is rilpidly and CUlhtantly uppliLd tu 111l 11acIillll Sill

the nactioll producl arc continuuusly rmOVL lkhlllg 1IIhself to automation

madllll C c dlldgtl 11many spelilic

r ~ 1~

f 406 WERNER KERN AND CHERYL A DECKERT

~ J Electrolytic Etching

Electrically conductive or semiconductive materials are frequently etched by application of external emf potentials Electropolishing of metals and semiconductors is a good example of this technique The rate and selectivity of etching can be controlled by the potential andor the

~ ~ current density applied Electrolytic etching is considerably more complishy

cated than other techniques but can yield results not otherwise attainshyable Specific conditions will be described for various materials in the text and in the etching tables

4 Gas-Phase Etching

High-temperature etching in the gas or vapor phase is generally used for chemically inert materiab that cannot be etched readily in liquid reshyagents A different application is for in situ etching of semiconductor subshystrates immediately prior to epitaxial film growth in the same reactor to avoid surface contamination that would result by other techniques

t ~ 5 Mechanical-Chemical Polishing

1 This technique is used in semiconductor wafer preparation when a relshyatively defect-free surfa(e is required The combination of slow liquid

~ ~ chemical surface etching with gentle mechanical abrasion to continuously

remove products from the etching reaction can result in a high-quality surshyface polish if carefully optimized conditions are observed as will be deshy j scribed in Section IllBp

$ i 6 Isotropic versus Anisotropic Procesusbull

Isotropic or nonpreferential etching proceeds at an equal rate in all dishyf rections Amorphous materials of uniform composition etch isotropicallyshyJ whereas many crystalline materials etch both isotropically and anisotropishycally Anisotropic or preferential etching depends on the crystallographici

1 orientation of the material and on the etching reagent used If polishing t action is desired isotropic etching conditions must be selected to achieve

a structureless surface If structural shaping is the objective as in the forshymation of deep depressions having side walls of a specific taper angle anishysotropic conditions are required Both liquid and gas-phase etching can be used for these two types of etching processes

7 Selective Etching PwcesJes

Selectivity refer~ to the differences in etch rate between different mashyteriah or between compositional or structural variations of the same ma-

T ) --shy

v-I UIEMI(AI lelnUNG ((

terial It is one of the most Important faclor III pplicd ell hili) gt1(

technological etching processes must he controllahly eeui lt 1gt1llI

the material to be etched is usually part of a trllctlile Ihal cnll ul on eral material components Seleclivily III etdlillg is Ihined h) 11 (Ipc I choie of etching techni411e and lt1(h1I1I LuJllj1IilJolI Wllhill tlil straints of the syskms

Various degrees of etching selecllvit ai dlII1hk Inl panlII1 pUI

poses For example pattern ellhillt (If SiN or 11)1111110 III 1 III() an eth-resistant deposikd SI() 111m III II IllaJ ilillstldl j

high degree of dching selectlvil) Oil Ihc olhel IiUld lnllll(llkd PIIIIJ etching seletivity of dielectric byel cOlllpoill 1 IIllIlllIlI III LIf1 cthing where a desired edge COlliolil clIlhl lILIIIId (Ill Ihl 11 01 el11 rate differemes of the componelll 1Yel In Ill d IILI Lklllllg til ehLtri taptrLolltrol layer i (lIIllL nvu Ihe Ikdll 10 he hkd

[461 Numerous uther important ltlpplicaliolh 01 lkcllVc lt1c1l11V l been descrihed [26 27 415 49 I

~ FIIlioll (11pound1 Other -IIC(I(I

(lrtam highly etlh-nsistant mllcria Ill h dbed h 11dllll1I1 with moltell salh (uften Lau~tics n hUla)) 11 11Igh IIIIIIC lt111 examples will be noted in Sections I V B and I V I)

Surface oxidltlon hy thermal or lIhldli tledllllnl (I1ed hI 1111 iGd strippillg of thc nxide films formed can aho he laquoIhlkl 111 cl llillg

proLI~S Howl~er only the econd tep the clillllg llhe laquoSide-- oil I dislIssid here (Section IILr)

D Pattern Delineation Etching for Thin Films

In rnany instan(cs elching pnlCisses arc used I) JIdIlC cllI1 111 terns in thin film~ Sdected portions of the Ijlm II 111Jcd by 111111lt1 thin film coating material which is undlcded by Ihe 111111 (0 hl 1Id Il patterning Etching is then canied (lut so as to re11lm lttilth 1JIIIIIIIdllll in the unprotected regions The proteClivc Loatillg lilill Ihl1 IIsllgtlI stripped leaving the desired pallen in Ihe lIndc) IIll thlll fillll

Pattern etching is obviuLJsly a Illllch 11111 dllllples PI)ll 11111 I pic overall sUIiaLc etching III additloll to lIeding Ih ctliHlI hII)l

masking material is of prime importance good aLlhnlolloIlitlS COlill) 1ltgt

the substrate Cllltlling integrity aJe4LJate reulutillll lIld I LlSldIlC hI 111 ethant arc the main Lonsiderations Lase in pattelllllll thc Inasl- L01I1I~ is important othClgtIltbe thi plOcedure beCOlllLS til IllIlIg PWlC 11middot11 requiring yet ullother mask

r ~ 1~

f 406 WERNER KERN AND CHERYL A DECKERT

~ J Electrolytic Etching

Electrically conductive or semiconductive materials are frequently etched by application of external emf potentials Electropolishing of metals and semiconductors is a good example of this technique The rate and selectivity of etching can be controlled by the potential andor the

~ ~ current density applied Electrolytic etching is considerably more complishy

cated than other techniques but can yield results not otherwise attainshyable Specific conditions will be described for various materials in the text and in the etching tables

4 Gas-Phase Etching

High-temperature etching in the gas or vapor phase is generally used for chemically inert materiab that cannot be etched readily in liquid reshyagents A different application is for in situ etching of semiconductor subshystrates immediately prior to epitaxial film growth in the same reactor to avoid surface contamination that would result by other techniques

t ~ 5 Mechanical-Chemical Polishing

1 This technique is used in semiconductor wafer preparation when a relshyatively defect-free surfa(e is required The combination of slow liquid

~ ~ chemical surface etching with gentle mechanical abrasion to continuously

remove products from the etching reaction can result in a high-quality surshyface polish if carefully optimized conditions are observed as will be deshy j scribed in Section IllBp

$ i 6 Isotropic versus Anisotropic Procesusbull

Isotropic or nonpreferential etching proceeds at an equal rate in all dishyf rections Amorphous materials of uniform composition etch isotropicallyshyJ whereas many crystalline materials etch both isotropically and anisotropishycally Anisotropic or preferential etching depends on the crystallographici

1 orientation of the material and on the etching reagent used If polishing t action is desired isotropic etching conditions must be selected to achieve

a structureless surface If structural shaping is the objective as in the forshymation of deep depressions having side walls of a specific taper angle anishysotropic conditions are required Both liquid and gas-phase etching can be used for these two types of etching processes

7 Selective Etching PwcesJes

Selectivity refer~ to the differences in etch rate between different mashyteriah or between compositional or structural variations of the same ma-

T ) --shy

v-I UIEMI(AI lelnUNG ((

terial It is one of the most Important faclor III pplicd ell hili) gt1(

technological etching processes must he controllahly eeui lt 1gt1llI

the material to be etched is usually part of a trllctlile Ihal cnll ul on eral material components Seleclivily III etdlillg is Ihined h) 11 (Ipc I choie of etching techni411e and lt1(h1I1I LuJllj1IilJolI Wllhill tlil straints of the syskms

Various degrees of etching selecllvit ai dlII1hk Inl panlII1 pUI

poses For example pattern ellhillt (If SiN or 11)1111110 III 1 III() an eth-resistant deposikd SI() 111m III II IllaJ ilillstldl j

high degree of dching selectlvil) Oil Ihc olhel IiUld lnllll(llkd PIIIIJ etching seletivity of dielectric byel cOlllpoill 1 IIllIlllIlI III LIf1 cthing where a desired edge COlliolil clIlhl lILIIIId (Ill Ihl 11 01 el11 rate differemes of the componelll 1Yel In Ill d IILI Lklllllg til ehLtri taptrLolltrol layer i (lIIllL nvu Ihe Ikdll 10 he hkd

[461 Numerous uther important ltlpplicaliolh 01 lkcllVc lt1c1l11V l been descrihed [26 27 415 49 I

~ FIIlioll (11pound1 Other -IIC(I(I

(lrtam highly etlh-nsistant mllcria Ill h dbed h 11dllll1I1 with moltell salh (uften Lau~tics n hUla)) 11 11Igh IIIIIIC lt111 examples will be noted in Sections I V B and I V I)

Surface oxidltlon hy thermal or lIhldli tledllllnl (I1ed hI 1111 iGd strippillg of thc nxide films formed can aho he laquoIhlkl 111 cl llillg

proLI~S Howl~er only the econd tep the clillllg llhe laquoSide-- oil I dislIssid here (Section IILr)

D Pattern Delineation Etching for Thin Films

In rnany instan(cs elching pnlCisses arc used I) JIdIlC cllI1 111 terns in thin film~ Sdected portions of the Ijlm II 111Jcd by 111111lt1 thin film coating material which is undlcded by Ihe 111111 (0 hl 1Id Il patterning Etching is then canied (lut so as to re11lm lttilth 1JIIIIIIIdllll in the unprotected regions The proteClivc Loatillg lilill Ihl1 IIsllgtlI stripped leaving the desired pallen in Ihe lIndc) IIll thlll fillll

Pattern etching is obviuLJsly a Illllch 11111 dllllples PI)ll 11111 I pic overall sUIiaLc etching III additloll to lIeding Ih ctliHlI hII)l

masking material is of prime importance good aLlhnlolloIlitlS COlill) 1ltgt

the substrate Cllltlling integrity aJe4LJate reulutillll lIld I LlSldIlC hI 111 ethant arc the main Lonsiderations Lase in pattelllllll thc Inasl- L01I1I~ is important othClgtIltbe thi plOcedure beCOlllLS til IllIlIg PWlC 11middot11 requiring yet ullother mask

r1 T )1~ 1

OK WERNLR KERN AND CHERYL A DECKERT

I Mllsking Materials

The most often used masking materials for high resolution thin film patterning are photoresists (SOl organic polymers whose solubilitie~ in certain solvents change drastically as a result of exposure to uv radiation Usually exposure is carried out by placing a glass plate bearing the de~ sired pattern in an opaque material (such as photographic emulsion or chromium) over the photoresist-coated substrate and irradiating through the glass plate Negative photoresists become less soluble in the deshyveloping solution in areas that were irradiated thus producing a negative image of the pattern on the glass plate Positive photoresists become more soluble in exposed areas and thus produce a positive image of the origshyinal pattern Excellent photoresists are available commercially from a number of sources Negative photoresists are generally tougher than posishytive resists and can usually withstand more rigorous etching processes Positive resists are noted for their superior resolving power and pallerns as fine as I lim have been resolved using positive photoresist Electron beam and x-ray resists can produce very fine resolution but they have not yet come into widespread use because of high processing costs

When the etching process to be used in patterning the ~ubstrate inshyvolves extremes such as elevated temperatures or strong acids photore~ sist masks may not provide adequate protection In these cases metal or dielectric masks which can withstand the etching process more effecshytively are often used In such cases the mask is first patterned using a photoresist process For example chemically vapor-deposited (CYD) SiO~ is used as a masking material for CYD Si3N4 films which are typishycally etched at 180degC in HPO bull conditions which would quickly degrade photoresist films The Si01 itself is readily patterned usinl a room~temshyperature etching process with a photoresist mask

Sometimes a high temperature or extremely degrading chemical etchshying process can be replaced by an electrochemical procedure which uti~ Iizes a much milder solution thus allowing a photoresist mask to be em~ ployed [5

In cases where high resolution is not a requirement very simple maskshying procedures are possible Ordinary cellophane tape is used to mask against a variety of etchants Other masking films such as positive pho~ toresist or silver paste can be applied in the areas to be protected using an artists paint brush Certain waxes which melt at temperatures of 100shy250degC can be painted onto a hot substrate and will resist many etchants

2 Adhesion and Inlerace Problems

Good adhesion to the substrate film during etching is the prime reshytll1irfmfnl nflhe mn~k material Loss of adhesion usually occurs in one of

V~1 CHIMI(AL EIUIING -III j

two way~ 1521 (a) edge allaLk at the interfille by tlie tlchant (lIlltkn111 or (b) failure over a large area (lifting peeling CidlingJ

( fduC AIIUCh If mihk~to-lilm adhe~illn refl1aill~ ptrkLl thlullgl1I1 etching and if the etlhing process is isotropic a ddilllltllId Pdlllill Ilhe that in Fig 2a will re~ult If the cthant atlads Ih lulLlfde be(ll11 mask and suhslfatc film however the top edge of th pattelilld Ilhll oil

become ~Ioped quite gradually (iig 2h) This phcnol11elltHl is cidkd dercutting Ullderlutting is a common OlCLIlrelllC blealll 11I)sl masksubstrate film comhinaions involvc no chellliLal bonding Iel y lug solely on van dcr Waah fones for intcrfalial adhesion Thcc rorns al cmiddot

strong enough to good bond ~trength~ ullder oHlinay contiltgt1S ltie no ehhing) hut ~pelies in the ething ~oruti(ln~ 110 tlnd (raquo 11111 van dcr Waah honds to the mask and suhslrate film Slllrlt tlld III Iif in~tanes thescitlleraLlions can hI strongcr than the mkltllilsIlttll bond thus lalJsing adhesion failure at the edges of thc paltclnldllcItgt1I promoters such a~ hclmcthyldisihllalle which Icntin SiO llalS c

sentially nonpolar kad to bettcr etch reslstanltc Iql IIh plllOSIgt1 mub simply belallse thc polar ctchans arl less attladld I tlil Iillu face even though the alual van del Was forces hllHl1I till mudrlll SiO and the photlllcSlS1 may he smaller than Wililoll dlllSltl 11lt1111lt11(1

QUllC often it is (h~lrahk that a small amollnt or lllllllkd IlIhkl

SU~5TRATE

(a)

( bl

~ ~MASK=---FAST- ETCHINJCOATlN6 rlLM PATTERNED FILM

~ SUBSTRATE

(el

Fig 2 Diffcentnnl euge prlliiL- pnHJLJ~IJ from htllUU dlgrll1 (il lllldLjlUlllllg jiLt tllll

ma~k-to-film jujht~lon prlluulcI lht~ (Hk of tJgL tn) umlllllIlllllg 111gt IWIJ tI flIdf film lntcffill~ ie 11t~ of h gtLhn f1IT~~ L ~ II

T 410 wtRNER KERN AND CHERYL A DECKERT

ting take place since a sloped substrate edge is easier to coal uniformly than a sharp edge if additional layers are to be deposited subsequently In such cases a very thin layer of nraterial which dissolves in the etchant more rapidly than the substrate film may be deposited prior to masking in order to achieve controlled undercutting This is depkted in Fig 2c A recent example of this method is the beveling of permalloy films using a Ti overcoat [54]

h Large-Area Failure Sometimes masksubstrate film adhesion failshyure occurs over a large area of the interface This failure can show up in several ways A portion of mask coating may be lifted completely from the surface it may peel up either from the edges only or else craze and peel over the whole surface or it may blister or bubble across the surface These failures are usually due to differential stress buildup in the subshystrate film and mask layers Thermal or chemical treatments can cause the masking film to go into tensile stress relative to the substrate layers in which case peeling crazing or lifting can occur On the other hand if stresses in the mask become highly compressive compared with the thin filmsubstrate composite blisters and bubbles will appear in the mask layer These problems can be minimized by using a mask material either with a similar coefficient of thermal expansion to that of the substrate or witt sufficient elasticity to conform more easily to the substrate

3 Factors Affecting Image Resolution

The most obvious factor inHuencing image resolution is of course the resolving capability of the masking material As already mentioned negashytive photoresists have considerably poorer resolving power (- 3 I-Lm line widths or spacings) than positive resists (- I I-Lm) Metal and dielectric mask coatings are capable of generally finer resolution down to the order of the grain size Electron beam and x-ray resists cat also be imaged to very fine dimensions (-80 Aresolution has been reported

The thicknesses of both the masking material and substrate film limit their resolution capability when chemical developing and etching proceshydures are used Since isotropic chemical dissolution produces sloped edges a good rule of thumb is that the thickness of the layer to be patshyterned should be no more than one-third of the resolution to be achieved Dry etching processes such as plasma and sputter etching [56] can proshyduce very steep pattern edges and thus finer resolution can be attained with a given film thickness

Etching processes which involve gas evolution can lead to poor image resolution because of gas bubbles clinging to the substrate particularly along the edges This problem can usually be alleviated by the use of a

)v-I CHI MICA] 1IltllIl-i(i j I

suitable surfaclant in the etching ~ulutilln 1lI Ic~~ ~alfltt((llilly by hcat ing or good agitation throughout the clIhing pmcedun

In etching proces~e~ where the ~ubstralc IJlm becul11cs uxidilCd Ieg metals silicon) masks of a nobler met11 can lead tll acccicrated thus producing pronounced underciliting alld Ilh (II 1~ohHIOIl 1441 By the use of certain carefully cho~en chemical ctChII11~ thc can be markedly reduced [5758]

E Surface Contamination and Cleaning Techniques

The important subject or conlalllinllitlil and CklIillJ of surflIn hc fore and after etching is dosely aSSllllalcd Ilh praIi1 deh pruCIII) A detailed discussion of this separate topic is (1lIhllk Ihc opc I Ihi chapter howev~r some general guiuIine~ alld a hlld Illcr a[lIIe ~111 ce)

arc presented

Sudace contltlminltltion as rlated to elLhil1g call hc chldel cd 1111111

two aspetts (I) initially present contaminanb and thcIIIllhIV1 IHllil III

etching and (2) resiuual contaminanb ariSing frum lldllllg t rlmiddotIII11CII dlld

their removal as a postelch step if traces ur illlpuri[io e1I1I1lt11 hI lltlkl kd on the etched surface

Contamination on ~uliaces prior 10 etching Illay IlIllI1 til palllclIlale materials organic reidues or inorganic surface lililh dJferllll fOIll 111l

material to be etcheJ These impurities shuIIIJ he rClllucd Sille Ihq II interfere Wilh lhe etching by masking or unulsirablc 1lt11111 HI ilh I Iishyetchant Particulate removal tan be accomplished hy 1I1I11gt01l1C Ill11 ments in cleaning solutions use of compresslu gas jll IPphcdllon t IJ uid sprays or jetgt or simple mechamc1 mcan sudl as sUuhblllg III

Organic nsidues are removahle dllwn It) IllUllllaYI1 evcl h) dissolution in suitable organic solvenb or hy vapm IdhlXlllg in oigallic solvents or azeotropic ~olvent mixtures Cumpicle IClllod I gllIclltlll~ possible only by plasma ashing glow uicharge P Ill Illig I dltllllLl1 reaction leauing to dissolution Inorganic surface film 1ll1l~1 he aILdd by specific chemical reagents designeJ to pmullce sulllhlc nacllt)f prudlll~ that can be Hushed away

Whereas the treatments noteu ahllve lie geIKIdl ~inlpk 1I11l lively noncritical the effective nmovaillf rcsiduallrI clIlldlllllllllh I suiting from etching proce~~es b far nHlrc diflicult III acc Ulllphh SUI I contaminants are very critical in telhnoillgies sudl ulidldlL dn l processing where the nucleation growth dhesiIII tlllllllll and Iki fection of a depositeu hIm can be critically affcclLu h~ 111I1)[llill oil till substrate surface High-temperature pwcc_ing llIil dl~C Ieldlial ill

1 (

412 WERNER KERN AND CHERYL A DECKERT

face impurities to penetrate into the substrate and give rise to undesirable effects such as electrical instability of semiconductor devices

The deposition of impuritie~ especially heavy metals from liquid etchants onto semiconductor surfaces is well known since the early exshyperimental work by Holmes el ai 15591 and the reviews by Gatos and Lavine [8] and later by Faust 160] Kane and Larrabee [17] reviewed the literature up to 1969 on the deposition of chemical impurities from solushytion onto semiconductors More recently Kern reported results of comshyprehensive radioactive tracer adsorption studies of anionic and cationic etch components [61] and trace contaminants [62 63) on Si Ge GaAs and SiO~ surfaces [64] In addition a decontamination method based on sequential oxidative desorption and complexing with Ht 0 2 -NHOHshyH20 followed by H20cHCI-H20 was devised [64 65J Its remarkable efshyfectiveness was verified specifically [66-69al and indirectly (70-721 by several authors

Various additional aspects of cleaning Si surfaces have been reported [66 71-77] Surface contamination of GaAs has been reviewed by Stirshyland and Straughan 123) Meek PH] used Rutherford ion bachcatlering of high-energy ions as a sensitive surface analysis tool to determine the imshypurities left on clean Si surfaces from various etch components and orshyganic solvents Neutron activation analysis of Si slices that had been exshyposed to buffered HF etchant was employed to identify problematic trace contaminants in the NH4F component as As and Cu [79] purification of the etchant by treatment with Si chips (80) effectively removed the imshypurities

A series of 18 symposium papers on the preparation and characterizashytion of clean surfaces indudes theoretical and practical aspects related to surface contamination on a variety of materials [811 Ryan (I ai 1821 and De Forest [83] have described the preparation of clean surfaces prior to photoresist coating Holland [84] discussed cleaning treatments for glass surfaces Brown [85] and more recently Mattox (I (ii [86 H7] have reshyviewed those for thin film substrates of many types Short-wave uv radiashylion has been found effective for removing hydrocarbons from glass surshyfaces 187 88] and for removing photoresist residues tH9] Ozonization is an alternate method that offers several advantages [YO] Selection specifishycations and other aspects of surface preparation processes for numerous materials have been compiled by Snogren [911

Surface cleaning by glow discharge sputtering techniques can also be very effective [851 Most organic suMace contaminants are removable by chemical sputtering in 0 [92 -941 Sputter etching in Ar removes residual oxide layers on metals as noted in Chapter I Section Vc However uMace recontamination due to backscattering [95-97 J or ion migration

) v-I CflEMICAL IICHING middot11

can occur dunng rf sputtering treatillellh lllllc~~ processing condition~ arc employed [9111 Ultrahigh vacuum hltating ltlftn sputter deaning is effective for dlsorhing gasegt that Illay bltco[lll inlur porated into the substrate suMace during this operatlO[) IN -I 0 II

Finally glow discharge plasma cleaning should be Iloted I llill 01 Illl most effective methods for suMace decontamination Klfk I0211tvlw1 its application to semilollductor device processing alld Klllllilliak alld Mattox described reactive plasma cleaning of metab 11011 Many asplll associated with plasma reactions at solid surfale have hltell discused ~iI recent symposium 11041

Two additional very important aspech of urface treatment and storage of the cleaned material The final rilhillg ill Wi I cleaning and etching processes is usually done with water 111lt PUI ity I

the water i thenfore extremely critical Deionized and dilIllcd watll should be u~ed to void recontaminatIOn of tht ~urrace Highpurity lln

ic-grad isopropyl akohol i~ a good alttrnative find rillt al tlll wa~hing The removal of re~idual water or kohol i bet cfftLltd by gcn tic centrifugation rather than by baking Finally storage or LkalHd teriah ~hould bc minimized or preferably avoided altogether hy cilrry IlIg out the cleaning treatment immediately before the l1et pnLlslIlg Opctt tion If storage is necessary chemically cleaned clusld gLl COIllllI (such ltI Petri dishe) should be used and kept in a lOlltdllllllaliull lice dean-mom almosphne The frequently lI~ed plastIC CUlildlllll Ill IlIdd lluate for this purpose as they usually CdliSC reCl)(llIllllldtWIl I Lletll Sill faces due to the emissioll of organic vapor 17)1

III CHEMICAL ETCHING OF SPECIFIC MATERIALS

A Insulators and Dielectrics

I (jeleral COllsideril ioll

Important msulating and dielectric materials Il1clude glm~1I dlld dlpts ited vitreous and Lrystalline llxides chemically vapordcPlhllcli ICV I) I binary ilicates fused multicomponent silicate glasse (VI) 0 spullLT deposited nitrides and llxynitrides and several other Lllmpolllllh III film or bulk form The chemical dching properties III each f thll gnlufh of compounds will be discussed in this sectioll

In general insulating and dielectric material arc relatlvel) Iller( dlelll ically and hence require highly reactive media for etching Itchallh of technical importanc arc ammonium Iluoride-buflered hylirllllllllli dCld

T

414 WERNIR KERN AND CHERYL A DECKERT

t ~

tmiddot used for patterning by photolithographic techniques strong aqueous hyshy~ drofluoric acid at room temperature hot 85 phosphoric acid for pattern ~~ etching with oxide or metal masks and miscellaneous other etchants

usually strong mineral acids or bases Vapor or gas phase etching is used only in the preparation of insulator substrates

The majority of insulator and dielectric compounds being amorphous or extremely microcrystalline are classified as glasses Therefore etchshying in these cases proceeds isotropically and variations in the etch rate of a specific material in a given etchant are functions of chemkal composishytion film density residual stress defect density and microstructure The etch rate generally decreases as the density or crystallinity of a material increases

As in all etching processes selectivity is one of the most important etchant parameters in practical applications A survey of the uses of seshylective etching of dielectrics in semiconductor device processing and in analytical applications for compositional and structural characterization has been published recently 1271

A qualitative summary of etchants for important insulators and dielecshytrics is presented in Table II of Section IV A more concise compilation would be of questionable value because the etch rates depend very strongly on the exact conditions of film formation Furthermore materials consisting of more than one single component such as silicate glasses vary continuously in their etch ralC according to composition so that a graphical etch rate presentation is more instructive Emphasis in this secshytion is therefore placed on the discussion of general trends and a survey of specific results and references from the literature

1 Single Oxjde~

u SiO I Etchants for Si02 are based almost exclusively on aqueous flushyoride solutions usually HF with or without the addition of NH F The exact chemical mechanism of dissolution is quite complex it depends strongly on the ionic strength the solution pH and the etchant composishytion which determine the available quantities of solu tion species including Hfo2 HF F- H+ and various fluoride polymers Raman spectroscopy has indicated the presence of numerous reaction product species (such as hexafluorosilicate ions) in etch solution [281 Detailed studies of the reacshytion mechanism underlying etching of Si02 have been reported by several investigators [28 105-1111

Addition of NHF to HF to control the pH yield so-called buffered HF (BHF) it is imponant in pattern etching of Si02 films using photoreshysist masks ll4J where attack of the photoresist masking layer and the

v-I CHIMICAI ElUIlNG I I )

polymer dielectric inteliace must bL minimiled Ammolliul1l l1uuride illl

dition also prevents depletion of the Ilullnde ions thu lIlailllaining stahlL etching characteristics The actual rule of Nil F mali h one I 11

SiF(NH)2 precipitating or complexing agcllt mlher than Ihat (111111buffer 11061

Selcltivity in pattern etching of SiO laya HI AI devil llIett1Iitllllll can be improved over BHF by additIon of it dihydroxykllwIII12Iur 1 glycerollll3ltll the BHF to inhibit allalk of the llllal

Pattern etching of SiO tilms in vapnrs rurn aqlllolis III althulI-h used is an interesting alternative tn liquid ctehing iIl Ciln Yield

comparable results at rcasonabk rates 111011 It PHltI hy to l1Ilt1tiuli I tluosilicil alid which dissociates in the vlpor phase III Sil and III

As with insulator Iii illS in general the liquid eteh raiL dCPLlllb IIllt on etchant composition agitation and Itmpaature hilI ai Ull th It-n

porosity residual stress micmstrutlllc ddeLmiddott denlt y oad ltll and purity of SiO A subtantial IIlClcaL In Ihc ~tch Jilk )1

SiO hlms has been observed as I nuh uf dcleLl gLlIllation by cllLlJ1l1l beam irradiation [1151 Ar ion implantation 11161 alld IIlIl homhdrdlllelli [1171 Heat treatments of SiO lilms dcpllsikd OJ gl 0 II II j v ILIllPLI1 ture decrease the etch rate due to denilkalHlIl )f the 11111111 IIIX I~o the same holds for other dielectric lilm

Silicon dioxide films formed hy diffcrenl prOlSLS 11) wlJcly III Iltlll etch rate mainly because of dirferent in t)ILmiddothi()Jllll~middot IIlIClI IIIJLtlill

andor film density For exampk the etch rale of SI( I al OS ( in ILk (2 vol fiNO 707lt 3 vol HF 49 6() vul 1IOII12111(l1 tilLlmally )1(111

(lOO)degCl or densitied IihllS is 20 Asct for rf sputtered IllIns 01 I A l for organopyrolytil (undensified) hlms 6middot~() Ael 1111 lidlltlIl glill evaporated films 20-7ll Asec and for anodized lilms IX-22l1 Ael llX

Additional etlh rate values for variously prcpand Si( J lillll 111 III and in BHF etchants have been nponed for SiO gruv1I by thellll 01lt11

tlon[65105106 IOX1I01I1 122-1241dcpositedbypllttellngI12~ evaporation [16] halide reaction [1281 pyrolysi or vlr)middot oiLiall()11

of organics [16129-131] ()xidation of SiB at low (- SOOC 1119 12() 132-138] and high temperature [l39-142 anodizatiOll 116 101] I hy pill on reagent solutions [1441 and by plasma reaction 11015-10171 Norlllal ized etch rates for various types of Si02 lilms have hen pUhlhed 1I-l7a The effects of HF concentration and temperature [lOS 107-111 I-lX Iso and the effects of agitation 1109123 14XI on etching If SiOllilrn h been examined

In addition to HF-ontaining ethanh SiO i~ lrghlly ~lillblc II hili H)PO~ and hot au~til ~olutions For examph thelllwlly glllwn SI() I

etched bv SM KOH at 8ioC at 50 Amin 11511 and 011 NOH at J(lIlfll

T 410 wtRNER KERN AND CHERYL A DECKERT

ting take place since a sloped substrate edge is easier to coal uniformly than a sharp edge if additional layers are to be deposited subsequently In such cases a very thin layer of nraterial which dissolves in the etchant more rapidly than the substrate film may be deposited prior to masking in order to achieve controlled undercutting This is depkted in Fig 2c A recent example of this method is the beveling of permalloy films using a Ti overcoat [54]

h Large-Area Failure Sometimes masksubstrate film adhesion failshyure occurs over a large area of the interface This failure can show up in several ways A portion of mask coating may be lifted completely from the surface it may peel up either from the edges only or else craze and peel over the whole surface or it may blister or bubble across the surface These failures are usually due to differential stress buildup in the subshystrate film and mask layers Thermal or chemical treatments can cause the masking film to go into tensile stress relative to the substrate layers in which case peeling crazing or lifting can occur On the other hand if stresses in the mask become highly compressive compared with the thin filmsubstrate composite blisters and bubbles will appear in the mask layer These problems can be minimized by using a mask material either with a similar coefficient of thermal expansion to that of the substrate or witt sufficient elasticity to conform more easily to the substrate

3 Factors Affecting Image Resolution

The most obvious factor inHuencing image resolution is of course the resolving capability of the masking material As already mentioned negashytive photoresists have considerably poorer resolving power (- 3 I-Lm line widths or spacings) than positive resists (- I I-Lm) Metal and dielectric mask coatings are capable of generally finer resolution down to the order of the grain size Electron beam and x-ray resists cat also be imaged to very fine dimensions (-80 Aresolution has been reported

The thicknesses of both the masking material and substrate film limit their resolution capability when chemical developing and etching proceshydures are used Since isotropic chemical dissolution produces sloped edges a good rule of thumb is that the thickness of the layer to be patshyterned should be no more than one-third of the resolution to be achieved Dry etching processes such as plasma and sputter etching [56] can proshyduce very steep pattern edges and thus finer resolution can be attained with a given film thickness

Etching processes which involve gas evolution can lead to poor image resolution because of gas bubbles clinging to the substrate particularly along the edges This problem can usually be alleviated by the use of a

)v-I CHI MICA] 1IltllIl-i(i j I

suitable surfaclant in the etching ~ulutilln 1lI Ic~~ ~alfltt((llilly by hcat ing or good agitation throughout the clIhing pmcedun

In etching proces~e~ where the ~ubstralc IJlm becul11cs uxidilCd Ieg metals silicon) masks of a nobler met11 can lead tll acccicrated thus producing pronounced underciliting alld Ilh (II 1~ohHIOIl 1441 By the use of certain carefully cho~en chemical ctChII11~ thc can be markedly reduced [5758]

E Surface Contamination and Cleaning Techniques

The important subject or conlalllinllitlil and CklIillJ of surflIn hc fore and after etching is dosely aSSllllalcd Ilh praIi1 deh pruCIII) A detailed discussion of this separate topic is (1lIhllk Ihc opc I Ihi chapter howev~r some general guiuIine~ alld a hlld Illcr a[lIIe ~111 ce)

arc presented

Sudace contltlminltltion as rlated to elLhil1g call hc chldel cd 1111111

two aspetts (I) initially present contaminanb and thcIIIllhIV1 IHllil III

etching and (2) resiuual contaminanb ariSing frum lldllllg t rlmiddotIII11CII dlld

their removal as a postelch step if traces ur illlpuri[io e1I1I1lt11 hI lltlkl kd on the etched surface

Contamination on ~uliaces prior 10 etching Illay IlIllI1 til palllclIlale materials organic reidues or inorganic surface lililh dJferllll fOIll 111l

material to be etcheJ These impurities shuIIIJ he rClllucd Sille Ihq II interfere Wilh lhe etching by masking or unulsirablc 1lt11111 HI ilh I Iishyetchant Particulate removal tan be accomplished hy 1I1I11gt01l1C Ill11 ments in cleaning solutions use of compresslu gas jll IPphcdllon t IJ uid sprays or jetgt or simple mechamc1 mcan sudl as sUuhblllg III

Organic nsidues are removahle dllwn It) IllUllllaYI1 evcl h) dissolution in suitable organic solvenb or hy vapm IdhlXlllg in oigallic solvents or azeotropic ~olvent mixtures Cumpicle IClllod I gllIclltlll~ possible only by plasma ashing glow uicharge P Ill Illig I dltllllLl1 reaction leauing to dissolution Inorganic surface film 1ll1l~1 he aILdd by specific chemical reagents designeJ to pmullce sulllhlc nacllt)f prudlll~ that can be Hushed away

Whereas the treatments noteu ahllve lie geIKIdl ~inlpk 1I11l lively noncritical the effective nmovaillf rcsiduallrI clIlldlllllllllh I suiting from etching proce~~es b far nHlrc diflicult III acc Ulllphh SUI I contaminants are very critical in telhnoillgies sudl ulidldlL dn l processing where the nucleation growth dhesiIII tlllllllll and Iki fection of a depositeu hIm can be critically affcclLu h~ 111I1)[llill oil till substrate surface High-temperature pwcc_ing llIil dl~C Ieldlial ill

1 (

412 WERNER KERN AND CHERYL A DECKERT

face impurities to penetrate into the substrate and give rise to undesirable effects such as electrical instability of semiconductor devices

The deposition of impuritie~ especially heavy metals from liquid etchants onto semiconductor surfaces is well known since the early exshyperimental work by Holmes el ai 15591 and the reviews by Gatos and Lavine [8] and later by Faust 160] Kane and Larrabee [17] reviewed the literature up to 1969 on the deposition of chemical impurities from solushytion onto semiconductors More recently Kern reported results of comshyprehensive radioactive tracer adsorption studies of anionic and cationic etch components [61] and trace contaminants [62 63) on Si Ge GaAs and SiO~ surfaces [64] In addition a decontamination method based on sequential oxidative desorption and complexing with Ht 0 2 -NHOHshyH20 followed by H20cHCI-H20 was devised [64 65J Its remarkable efshyfectiveness was verified specifically [66-69al and indirectly (70-721 by several authors

Various additional aspects of cleaning Si surfaces have been reported [66 71-77] Surface contamination of GaAs has been reviewed by Stirshyland and Straughan 123) Meek PH] used Rutherford ion bachcatlering of high-energy ions as a sensitive surface analysis tool to determine the imshypurities left on clean Si surfaces from various etch components and orshyganic solvents Neutron activation analysis of Si slices that had been exshyposed to buffered HF etchant was employed to identify problematic trace contaminants in the NH4F component as As and Cu [79] purification of the etchant by treatment with Si chips (80) effectively removed the imshypurities

A series of 18 symposium papers on the preparation and characterizashytion of clean surfaces indudes theoretical and practical aspects related to surface contamination on a variety of materials [811 Ryan (I ai 1821 and De Forest [83] have described the preparation of clean surfaces prior to photoresist coating Holland [84] discussed cleaning treatments for glass surfaces Brown [85] and more recently Mattox (I (ii [86 H7] have reshyviewed those for thin film substrates of many types Short-wave uv radiashylion has been found effective for removing hydrocarbons from glass surshyfaces 187 88] and for removing photoresist residues tH9] Ozonization is an alternate method that offers several advantages [YO] Selection specifishycations and other aspects of surface preparation processes for numerous materials have been compiled by Snogren [911

Surface cleaning by glow discharge sputtering techniques can also be very effective [851 Most organic suMace contaminants are removable by chemical sputtering in 0 [92 -941 Sputter etching in Ar removes residual oxide layers on metals as noted in Chapter I Section Vc However uMace recontamination due to backscattering [95-97 J or ion migration

) v-I CflEMICAL IICHING middot11

can occur dunng rf sputtering treatillellh lllllc~~ processing condition~ arc employed [9111 Ultrahigh vacuum hltating ltlftn sputter deaning is effective for dlsorhing gasegt that Illay bltco[lll inlur porated into the substrate suMace during this operatlO[) IN -I 0 II

Finally glow discharge plasma cleaning should be Iloted I llill 01 Illl most effective methods for suMace decontamination Klfk I0211tvlw1 its application to semilollductor device processing alld Klllllilliak alld Mattox described reactive plasma cleaning of metab 11011 Many asplll associated with plasma reactions at solid surfale have hltell discused ~iI recent symposium 11041

Two additional very important aspech of urface treatment and storage of the cleaned material The final rilhillg ill Wi I cleaning and etching processes is usually done with water 111lt PUI ity I

the water i thenfore extremely critical Deionized and dilIllcd watll should be u~ed to void recontaminatIOn of tht ~urrace Highpurity lln

ic-grad isopropyl akohol i~ a good alttrnative find rillt al tlll wa~hing The removal of re~idual water or kohol i bet cfftLltd by gcn tic centrifugation rather than by baking Finally storage or LkalHd teriah ~hould bc minimized or preferably avoided altogether hy cilrry IlIg out the cleaning treatment immediately before the l1et pnLlslIlg Opctt tion If storage is necessary chemically cleaned clusld gLl COIllllI (such ltI Petri dishe) should be used and kept in a lOlltdllllllaliull lice dean-mom almosphne The frequently lI~ed plastIC CUlildlllll Ill IlIdd lluate for this purpose as they usually CdliSC reCl)(llIllllldtWIl I Lletll Sill faces due to the emissioll of organic vapor 17)1

III CHEMICAL ETCHING OF SPECIFIC MATERIALS

A Insulators and Dielectrics

I (jeleral COllsideril ioll

Important msulating and dielectric materials Il1clude glm~1I dlld dlpts ited vitreous and Lrystalline llxides chemically vapordcPlhllcli ICV I) I binary ilicates fused multicomponent silicate glasse (VI) 0 spullLT deposited nitrides and llxynitrides and several other Lllmpolllllh III film or bulk form The chemical dching properties III each f thll gnlufh of compounds will be discussed in this sectioll

In general insulating and dielectric material arc relatlvel) Iller( dlelll ically and hence require highly reactive media for etching Itchallh of technical importanc arc ammonium Iluoride-buflered hylirllllllllli dCld

T

414 WERNIR KERN AND CHERYL A DECKERT

t ~

tmiddot used for patterning by photolithographic techniques strong aqueous hyshy~ drofluoric acid at room temperature hot 85 phosphoric acid for pattern ~~ etching with oxide or metal masks and miscellaneous other etchants

usually strong mineral acids or bases Vapor or gas phase etching is used only in the preparation of insulator substrates

The majority of insulator and dielectric compounds being amorphous or extremely microcrystalline are classified as glasses Therefore etchshying in these cases proceeds isotropically and variations in the etch rate of a specific material in a given etchant are functions of chemkal composishytion film density residual stress defect density and microstructure The etch rate generally decreases as the density or crystallinity of a material increases

As in all etching processes selectivity is one of the most important etchant parameters in practical applications A survey of the uses of seshylective etching of dielectrics in semiconductor device processing and in analytical applications for compositional and structural characterization has been published recently 1271

A qualitative summary of etchants for important insulators and dielecshytrics is presented in Table II of Section IV A more concise compilation would be of questionable value because the etch rates depend very strongly on the exact conditions of film formation Furthermore materials consisting of more than one single component such as silicate glasses vary continuously in their etch ralC according to composition so that a graphical etch rate presentation is more instructive Emphasis in this secshytion is therefore placed on the discussion of general trends and a survey of specific results and references from the literature

1 Single Oxjde~

u SiO I Etchants for Si02 are based almost exclusively on aqueous flushyoride solutions usually HF with or without the addition of NH F The exact chemical mechanism of dissolution is quite complex it depends strongly on the ionic strength the solution pH and the etchant composishytion which determine the available quantities of solu tion species including Hfo2 HF F- H+ and various fluoride polymers Raman spectroscopy has indicated the presence of numerous reaction product species (such as hexafluorosilicate ions) in etch solution [281 Detailed studies of the reacshytion mechanism underlying etching of Si02 have been reported by several investigators [28 105-1111

Addition of NHF to HF to control the pH yield so-called buffered HF (BHF) it is imponant in pattern etching of Si02 films using photoreshysist masks ll4J where attack of the photoresist masking layer and the

v-I CHIMICAI ElUIlNG I I )

polymer dielectric inteliace must bL minimiled Ammolliul1l l1uuride illl

dition also prevents depletion of the Ilullnde ions thu lIlailllaining stahlL etching characteristics The actual rule of Nil F mali h one I 11

SiF(NH)2 precipitating or complexing agcllt mlher than Ihat (111111buffer 11061

Selcltivity in pattern etching of SiO laya HI AI devil llIett1Iitllllll can be improved over BHF by additIon of it dihydroxykllwIII12Iur 1 glycerollll3ltll the BHF to inhibit allalk of the llllal

Pattern etching of SiO tilms in vapnrs rurn aqlllolis III althulI-h used is an interesting alternative tn liquid ctehing iIl Ciln Yield

comparable results at rcasonabk rates 111011 It PHltI hy to l1Ilt1tiuli I tluosilicil alid which dissociates in the vlpor phase III Sil and III

As with insulator Iii illS in general the liquid eteh raiL dCPLlllb IIllt on etchant composition agitation and Itmpaature hilI ai Ull th It-n

porosity residual stress micmstrutlllc ddeLmiddott denlt y oad ltll and purity of SiO A subtantial IIlClcaL In Ihc ~tch Jilk )1

SiO hlms has been observed as I nuh uf dcleLl gLlIllation by cllLlJ1l1l beam irradiation [1151 Ar ion implantation 11161 alld IIlIl homhdrdlllelli [1171 Heat treatments of SiO lilms dcpllsikd OJ gl 0 II II j v ILIllPLI1 ture decrease the etch rate due to denilkalHlIl )f the 11111111 IIIX I~o the same holds for other dielectric lilm

Silicon dioxide films formed hy diffcrenl prOlSLS 11) wlJcly III Iltlll etch rate mainly because of dirferent in t)ILmiddothi()Jllll~middot IIlIClI IIIJLtlill

andor film density For exampk the etch rale of SI( I al OS ( in ILk (2 vol fiNO 707lt 3 vol HF 49 6() vul 1IOII12111(l1 tilLlmally )1(111

(lOO)degCl or densitied IihllS is 20 Asct for rf sputtered IllIns 01 I A l for organopyrolytil (undensified) hlms 6middot~() Ael 1111 lidlltlIl glill evaporated films 20-7ll Asec and for anodized lilms IX-22l1 Ael llX

Additional etlh rate values for variously prcpand Si( J lillll 111 III and in BHF etchants have been nponed for SiO gruv1I by thellll 01lt11

tlon[65105106 IOX1I01I1 122-1241dcpositedbypllttellngI12~ evaporation [16] halide reaction [1281 pyrolysi or vlr)middot oiLiall()11

of organics [16129-131] ()xidation of SiB at low (- SOOC 1119 12() 132-138] and high temperature [l39-142 anodizatiOll 116 101] I hy pill on reagent solutions [1441 and by plasma reaction 11015-10171 Norlllal ized etch rates for various types of Si02 lilms have hen pUhlhed 1I-l7a The effects of HF concentration and temperature [lOS 107-111 I-lX Iso and the effects of agitation 1109123 14XI on etching If SiOllilrn h been examined

In addition to HF-ontaining ethanh SiO i~ lrghlly ~lillblc II hili H)PO~ and hot au~til ~olutions For examph thelllwlly glllwn SI() I

etched bv SM KOH at 8ioC at 50 Amin 11511 and 011 NOH at J(lIlfll

1 (

412 WERNER KERN AND CHERYL A DECKERT

face impurities to penetrate into the substrate and give rise to undesirable effects such as electrical instability of semiconductor devices

The deposition of impuritie~ especially heavy metals from liquid etchants onto semiconductor surfaces is well known since the early exshyperimental work by Holmes el ai 15591 and the reviews by Gatos and Lavine [8] and later by Faust 160] Kane and Larrabee [17] reviewed the literature up to 1969 on the deposition of chemical impurities from solushytion onto semiconductors More recently Kern reported results of comshyprehensive radioactive tracer adsorption studies of anionic and cationic etch components [61] and trace contaminants [62 63) on Si Ge GaAs and SiO~ surfaces [64] In addition a decontamination method based on sequential oxidative desorption and complexing with Ht 0 2 -NHOHshyH20 followed by H20cHCI-H20 was devised [64 65J Its remarkable efshyfectiveness was verified specifically [66-69al and indirectly (70-721 by several authors

Various additional aspects of cleaning Si surfaces have been reported [66 71-77] Surface contamination of GaAs has been reviewed by Stirshyland and Straughan 123) Meek PH] used Rutherford ion bachcatlering of high-energy ions as a sensitive surface analysis tool to determine the imshypurities left on clean Si surfaces from various etch components and orshyganic solvents Neutron activation analysis of Si slices that had been exshyposed to buffered HF etchant was employed to identify problematic trace contaminants in the NH4F component as As and Cu [79] purification of the etchant by treatment with Si chips (80) effectively removed the imshypurities

A series of 18 symposium papers on the preparation and characterizashytion of clean surfaces indudes theoretical and practical aspects related to surface contamination on a variety of materials [811 Ryan (I ai 1821 and De Forest [83] have described the preparation of clean surfaces prior to photoresist coating Holland [84] discussed cleaning treatments for glass surfaces Brown [85] and more recently Mattox (I (ii [86 H7] have reshyviewed those for thin film substrates of many types Short-wave uv radiashylion has been found effective for removing hydrocarbons from glass surshyfaces 187 88] and for removing photoresist residues tH9] Ozonization is an alternate method that offers several advantages [YO] Selection specifishycations and other aspects of surface preparation processes for numerous materials have been compiled by Snogren [911

Surface cleaning by glow discharge sputtering techniques can also be very effective [851 Most organic suMace contaminants are removable by chemical sputtering in 0 [92 -941 Sputter etching in Ar removes residual oxide layers on metals as noted in Chapter I Section Vc However uMace recontamination due to backscattering [95-97 J or ion migration

) v-I CflEMICAL IICHING middot11

can occur dunng rf sputtering treatillellh lllllc~~ processing condition~ arc employed [9111 Ultrahigh vacuum hltating ltlftn sputter deaning is effective for dlsorhing gasegt that Illay bltco[lll inlur porated into the substrate suMace during this operatlO[) IN -I 0 II

Finally glow discharge plasma cleaning should be Iloted I llill 01 Illl most effective methods for suMace decontamination Klfk I0211tvlw1 its application to semilollductor device processing alld Klllllilliak alld Mattox described reactive plasma cleaning of metab 11011 Many asplll associated with plasma reactions at solid surfale have hltell discused ~iI recent symposium 11041

Two additional very important aspech of urface treatment and storage of the cleaned material The final rilhillg ill Wi I cleaning and etching processes is usually done with water 111lt PUI ity I

the water i thenfore extremely critical Deionized and dilIllcd watll should be u~ed to void recontaminatIOn of tht ~urrace Highpurity lln

ic-grad isopropyl akohol i~ a good alttrnative find rillt al tlll wa~hing The removal of re~idual water or kohol i bet cfftLltd by gcn tic centrifugation rather than by baking Finally storage or LkalHd teriah ~hould bc minimized or preferably avoided altogether hy cilrry IlIg out the cleaning treatment immediately before the l1et pnLlslIlg Opctt tion If storage is necessary chemically cleaned clusld gLl COIllllI (such ltI Petri dishe) should be used and kept in a lOlltdllllllaliull lice dean-mom almosphne The frequently lI~ed plastIC CUlildlllll Ill IlIdd lluate for this purpose as they usually CdliSC reCl)(llIllllldtWIl I Lletll Sill faces due to the emissioll of organic vapor 17)1

III CHEMICAL ETCHING OF SPECIFIC MATERIALS

A Insulators and Dielectrics

I (jeleral COllsideril ioll

Important msulating and dielectric materials Il1clude glm~1I dlld dlpts ited vitreous and Lrystalline llxides chemically vapordcPlhllcli ICV I) I binary ilicates fused multicomponent silicate glasse (VI) 0 spullLT deposited nitrides and llxynitrides and several other Lllmpolllllh III film or bulk form The chemical dching properties III each f thll gnlufh of compounds will be discussed in this sectioll

In general insulating and dielectric material arc relatlvel) Iller( dlelll ically and hence require highly reactive media for etching Itchallh of technical importanc arc ammonium Iluoride-buflered hylirllllllllli dCld

T

414 WERNIR KERN AND CHERYL A DECKERT

t ~

tmiddot used for patterning by photolithographic techniques strong aqueous hyshy~ drofluoric acid at room temperature hot 85 phosphoric acid for pattern ~~ etching with oxide or metal masks and miscellaneous other etchants

usually strong mineral acids or bases Vapor or gas phase etching is used only in the preparation of insulator substrates

The majority of insulator and dielectric compounds being amorphous or extremely microcrystalline are classified as glasses Therefore etchshying in these cases proceeds isotropically and variations in the etch rate of a specific material in a given etchant are functions of chemkal composishytion film density residual stress defect density and microstructure The etch rate generally decreases as the density or crystallinity of a material increases

As in all etching processes selectivity is one of the most important etchant parameters in practical applications A survey of the uses of seshylective etching of dielectrics in semiconductor device processing and in analytical applications for compositional and structural characterization has been published recently 1271

A qualitative summary of etchants for important insulators and dielecshytrics is presented in Table II of Section IV A more concise compilation would be of questionable value because the etch rates depend very strongly on the exact conditions of film formation Furthermore materials consisting of more than one single component such as silicate glasses vary continuously in their etch ralC according to composition so that a graphical etch rate presentation is more instructive Emphasis in this secshytion is therefore placed on the discussion of general trends and a survey of specific results and references from the literature

1 Single Oxjde~

u SiO I Etchants for Si02 are based almost exclusively on aqueous flushyoride solutions usually HF with or without the addition of NH F The exact chemical mechanism of dissolution is quite complex it depends strongly on the ionic strength the solution pH and the etchant composishytion which determine the available quantities of solu tion species including Hfo2 HF F- H+ and various fluoride polymers Raman spectroscopy has indicated the presence of numerous reaction product species (such as hexafluorosilicate ions) in etch solution [281 Detailed studies of the reacshytion mechanism underlying etching of Si02 have been reported by several investigators [28 105-1111

Addition of NHF to HF to control the pH yield so-called buffered HF (BHF) it is imponant in pattern etching of Si02 films using photoreshysist masks ll4J where attack of the photoresist masking layer and the

v-I CHIMICAI ElUIlNG I I )

polymer dielectric inteliace must bL minimiled Ammolliul1l l1uuride illl

dition also prevents depletion of the Ilullnde ions thu lIlailllaining stahlL etching characteristics The actual rule of Nil F mali h one I 11

SiF(NH)2 precipitating or complexing agcllt mlher than Ihat (111111buffer 11061

Selcltivity in pattern etching of SiO laya HI AI devil llIett1Iitllllll can be improved over BHF by additIon of it dihydroxykllwIII12Iur 1 glycerollll3ltll the BHF to inhibit allalk of the llllal

Pattern etching of SiO tilms in vapnrs rurn aqlllolis III althulI-h used is an interesting alternative tn liquid ctehing iIl Ciln Yield

comparable results at rcasonabk rates 111011 It PHltI hy to l1Ilt1tiuli I tluosilicil alid which dissociates in the vlpor phase III Sil and III

As with insulator Iii illS in general the liquid eteh raiL dCPLlllb IIllt on etchant composition agitation and Itmpaature hilI ai Ull th It-n

porosity residual stress micmstrutlllc ddeLmiddott denlt y oad ltll and purity of SiO A subtantial IIlClcaL In Ihc ~tch Jilk )1

SiO hlms has been observed as I nuh uf dcleLl gLlIllation by cllLlJ1l1l beam irradiation [1151 Ar ion implantation 11161 alld IIlIl homhdrdlllelli [1171 Heat treatments of SiO lilms dcpllsikd OJ gl 0 II II j v ILIllPLI1 ture decrease the etch rate due to denilkalHlIl )f the 11111111 IIIX I~o the same holds for other dielectric lilm

Silicon dioxide films formed hy diffcrenl prOlSLS 11) wlJcly III Iltlll etch rate mainly because of dirferent in t)ILmiddothi()Jllll~middot IIlIClI IIIJLtlill

andor film density For exampk the etch rale of SI( I al OS ( in ILk (2 vol fiNO 707lt 3 vol HF 49 6() vul 1IOII12111(l1 tilLlmally )1(111

(lOO)degCl or densitied IihllS is 20 Asct for rf sputtered IllIns 01 I A l for organopyrolytil (undensified) hlms 6middot~() Ael 1111 lidlltlIl glill evaporated films 20-7ll Asec and for anodized lilms IX-22l1 Ael llX

Additional etlh rate values for variously prcpand Si( J lillll 111 III and in BHF etchants have been nponed for SiO gruv1I by thellll 01lt11

tlon[65105106 IOX1I01I1 122-1241dcpositedbypllttellngI12~ evaporation [16] halide reaction [1281 pyrolysi or vlr)middot oiLiall()11

of organics [16129-131] ()xidation of SiB at low (- SOOC 1119 12() 132-138] and high temperature [l39-142 anodizatiOll 116 101] I hy pill on reagent solutions [1441 and by plasma reaction 11015-10171 Norlllal ized etch rates for various types of Si02 lilms have hen pUhlhed 1I-l7a The effects of HF concentration and temperature [lOS 107-111 I-lX Iso and the effects of agitation 1109123 14XI on etching If SiOllilrn h been examined

In addition to HF-ontaining ethanh SiO i~ lrghlly ~lillblc II hili H)PO~ and hot au~til ~olutions For examph thelllwlly glllwn SI() I

etched bv SM KOH at 8ioC at 50 Amin 11511 and 011 NOH at J(lIlfll

T

414 WERNIR KERN AND CHERYL A DECKERT

t ~

tmiddot used for patterning by photolithographic techniques strong aqueous hyshy~ drofluoric acid at room temperature hot 85 phosphoric acid for pattern ~~ etching with oxide or metal masks and miscellaneous other etchants

usually strong mineral acids or bases Vapor or gas phase etching is used only in the preparation of insulator substrates

The majority of insulator and dielectric compounds being amorphous or extremely microcrystalline are classified as glasses Therefore etchshying in these cases proceeds isotropically and variations in the etch rate of a specific material in a given etchant are functions of chemkal composishytion film density residual stress defect density and microstructure The etch rate generally decreases as the density or crystallinity of a material increases

As in all etching processes selectivity is one of the most important etchant parameters in practical applications A survey of the uses of seshylective etching of dielectrics in semiconductor device processing and in analytical applications for compositional and structural characterization has been published recently 1271

A qualitative summary of etchants for important insulators and dielecshytrics is presented in Table II of Section IV A more concise compilation would be of questionable value because the etch rates depend very strongly on the exact conditions of film formation Furthermore materials consisting of more than one single component such as silicate glasses vary continuously in their etch ralC according to composition so that a graphical etch rate presentation is more instructive Emphasis in this secshytion is therefore placed on the discussion of general trends and a survey of specific results and references from the literature

1 Single Oxjde~

u SiO I Etchants for Si02 are based almost exclusively on aqueous flushyoride solutions usually HF with or without the addition of NH F The exact chemical mechanism of dissolution is quite complex it depends strongly on the ionic strength the solution pH and the etchant composishytion which determine the available quantities of solu tion species including Hfo2 HF F- H+ and various fluoride polymers Raman spectroscopy has indicated the presence of numerous reaction product species (such as hexafluorosilicate ions) in etch solution [281 Detailed studies of the reacshytion mechanism underlying etching of Si02 have been reported by several investigators [28 105-1111

Addition of NHF to HF to control the pH yield so-called buffered HF (BHF) it is imponant in pattern etching of Si02 films using photoreshysist masks ll4J where attack of the photoresist masking layer and the

v-I CHIMICAI ElUIlNG I I )

polymer dielectric inteliace must bL minimiled Ammolliul1l l1uuride illl

dition also prevents depletion of the Ilullnde ions thu lIlailllaining stahlL etching characteristics The actual rule of Nil F mali h one I 11

SiF(NH)2 precipitating or complexing agcllt mlher than Ihat (111111buffer 11061

Selcltivity in pattern etching of SiO laya HI AI devil llIett1Iitllllll can be improved over BHF by additIon of it dihydroxykllwIII12Iur 1 glycerollll3ltll the BHF to inhibit allalk of the llllal

Pattern etching of SiO tilms in vapnrs rurn aqlllolis III althulI-h used is an interesting alternative tn liquid ctehing iIl Ciln Yield

comparable results at rcasonabk rates 111011 It PHltI hy to l1Ilt1tiuli I tluosilicil alid which dissociates in the vlpor phase III Sil and III

As with insulator Iii illS in general the liquid eteh raiL dCPLlllb IIllt on etchant composition agitation and Itmpaature hilI ai Ull th It-n

porosity residual stress micmstrutlllc ddeLmiddott denlt y oad ltll and purity of SiO A subtantial IIlClcaL In Ihc ~tch Jilk )1

SiO hlms has been observed as I nuh uf dcleLl gLlIllation by cllLlJ1l1l beam irradiation [1151 Ar ion implantation 11161 alld IIlIl homhdrdlllelli [1171 Heat treatments of SiO lilms dcpllsikd OJ gl 0 II II j v ILIllPLI1 ture decrease the etch rate due to denilkalHlIl )f the 11111111 IIIX I~o the same holds for other dielectric lilm

Silicon dioxide films formed hy diffcrenl prOlSLS 11) wlJcly III Iltlll etch rate mainly because of dirferent in t)ILmiddothi()Jllll~middot IIlIClI IIIJLtlill

andor film density For exampk the etch rale of SI( I al OS ( in ILk (2 vol fiNO 707lt 3 vol HF 49 6() vul 1IOII12111(l1 tilLlmally )1(111

(lOO)degCl or densitied IihllS is 20 Asct for rf sputtered IllIns 01 I A l for organopyrolytil (undensified) hlms 6middot~() Ael 1111 lidlltlIl glill evaporated films 20-7ll Asec and for anodized lilms IX-22l1 Ael llX

Additional etlh rate values for variously prcpand Si( J lillll 111 III and in BHF etchants have been nponed for SiO gruv1I by thellll 01lt11

tlon[65105106 IOX1I01I1 122-1241dcpositedbypllttellngI12~ evaporation [16] halide reaction [1281 pyrolysi or vlr)middot oiLiall()11

of organics [16129-131] ()xidation of SiB at low (- SOOC 1119 12() 132-138] and high temperature [l39-142 anodizatiOll 116 101] I hy pill on reagent solutions [1441 and by plasma reaction 11015-10171 Norlllal ized etch rates for various types of Si02 lilms have hen pUhlhed 1I-l7a The effects of HF concentration and temperature [lOS 107-111 I-lX Iso and the effects of agitation 1109123 14XI on etching If SiOllilrn h been examined

In addition to HF-ontaining ethanh SiO i~ lrghlly ~lillblc II hili H)PO~ and hot au~til ~olutions For examph thelllwlly glllwn SI() I

etched bv SM KOH at 8ioC at 50 Amin 11511 and 011 NOH at J(lIlfll

f

416 WERNER KERN AND CHERYL A DECKERT

temperature at 502 Amin [152J The etch rate in lO wt NaOH at 23degCf is 01 Amin at 55degC 5 Amin and at 9OdegC 500 Amin 1153] The etch rate of oxygen-deficient Si02 in HF solutions decreases and SiO requires the addition of HNOa to attain etchability Alternatively hot solutions of conshycentrated NfLF mixed with NHOH or alkali hydroxides can be used for etching SiO films [14]

b Ti02 Ta205 and Zr02 bull As a general rule dielectric films deposited at low temperature exhibit high etch rates (often due to their low density and amorphous structure) whereas films of the same compound that are anshynealed or deposited at high temperature exhibit consistently lower etch rates For example low-temperature (l50-3OOdegC) CVO Ti02 [154-156] is readily etchable in 05 HF or in warm 98 H2SObullbull whereas films anshynealed at IOOOdegC etch only slowly in 48 HF or in hot H2 S04 or H3 PO 154 154a 1551

Pyrolytic Taz0 5 films deposited at 500degC are soluble in dilute HF [157] Films of amorphous Ta~O~ (but not high-temperature crystalline Ta~O~ films 1158)) formed by anodization of deposited Ta films can be etched in HF-NHF solutions [159 160] Electron irradiation of Ta205 (and AlzOa) films decreases their etch rates [161] in contrast to SiOz films Tantalum penlOxide films can be patterned with 9 vol NaOH or KOH (30) plus I vol HD (3()) at 90degC using a Au mask the etch rate ranges from 1000 to 2000 Amin 1I62 1631

Monoclinic zr02 films prepared by CV 0 from ZrCl at 800-1000degC are slowly etchable only in hot H3 PD4 [164]

c AI20 a Films of AI2 prepared by CVO below 500degC [165-169]0 a grown by plasma oxidation [147 1701 formed anodically [161 171 172] or deposited at low temperature by evaporation [ 161 1731 obtained on Al by boiling in H 20 [174] or deposited by sputtering [175-1771 are etchable in HF BHF warm HaPO and etchants based on HaPObull Thermal densishyfication at 7oo-8oodegC tends to form crystalline modifications that exhibit much lower etch rates [165 168]

Aluminum oxide films deposited by the AICI3 hydrolysis process at 9OO-IOOOdegC are nearly unetchable even in concentrated HF solution and require boiling 85 HaPD [135 178-180) The etch rate in 85 HaP04 at 180degC is typically 100 Amin etch masks of CVO Si02 are useful for patshyterning these films [181]

Selective etching of anodic AI20 a on Al in multilevel integrated cirshycuits can be accomplished without attacking the AI by use of a solution containing HaPO and CrDa [182J

d Bulk Oxides Sapphire (a-AI20 J ) spinel (MgAI20~) and beryllia (BeD) ulled as substrates for heteroepitaxiaJ CVO of silicon layers are slowly

v-I CHEMICAL tmiddotT(tllNG

J17

etchable in )ollmg concentrated HPO-H2 SO mixtlln II~J IMI (ja~shyphase dchlng at high temperatures has abo been ugtld slIcclssfully for polishing sapphire [ISS) and spinel 1 1~61 OissollHion l)f surfacl irngul1 itles from crystalline AIO has been accomplished by trlalll]cnh IIIi molten V 0 above HOWe 11~7J mclls of KSO PhO PhF lttlld vn have been used for dissLllving sapphile 1I~~J lkO call be clLhcd III hOI (120() HCI

e OIlier oridls Films of Nb() ) 1~9J and CVIgt 1110 ) I~S IX)Jj IC

etehable in HF The etchability or (ieO depends Oil ils IT)stallllgldphlc moditkation as noted in Table I of Scction IV Stlal 01111 llxidcs I importance are classilied under Compound SlflllCllllllllclors and arc diS cussed in Section IIIB4

3 Einarv (llId tertiary Silicalpound GIIIII IItld Ordl1

a PIIOlphwiliclIlpoundS The inCLlrporation of I() III thL Si() lid Vgt 1I J

yields technically very importmt phosphosihmiddotat gtll (PS( i) Ihl tl Ii rate in bLlth HF and BHF increases wilh increaing p I shown in Fig 1 for a variety of tilm and etchant compositions Th Illw-lelllj1eratlll (V t) lilms were prepared by chemical vapor reactIon frulll Sill PH lIld () in N at 450deg( 1190-lnl Densitkation trlatmenh were dune in N d

1000( for 60 min as inditatcd [13~I The thelmallS(j layer Well taimd by remtmg vapors of PO(I II gt3lllr 10 II 9-l1 Will SiO al 1000 (

The graphs illustrate al a glance the prollllUIlCd 111 of COlllpusilllll1 and densily for a given phosphorus cllllcelltration lIld thl ntllIlLmiddot III Selectivity of a typical BHF compositIOn and VdflCly or IIl1hulttrcd III mixture Note that tht ekh rate of PSG ill Bill i Illlllh k allCCkd h

the film compositiolll137 1l)511han in the 1Il1hurfcred Illllurc Ilulll the logarithm of the cllh rate varies in all case linearly lIh Iht P eltHIC1I tration More complete graphs relating etch rate with Ijlm lomphllltill and CYO conditioos have been published clsewhen 117 1951

The eteh rates Llr PSG films deposited from Sill PH and () III 1 II

350degC and containing 0-9 mole Po exhibit a maximulll in i0 diluted buffer etch (48 HF40 NHF HO I 10 II hy Volume) llie increase in etch rate with increasing P CLHltent in the glass suggests lltal the SiOi component of the PSG is dissolved by the hufkred HI alld Ille 120 5 component principally by waleI 196

Additional etch rale studies have been nported IlII PSG Iilms Pleshypared by low-temperature (300-500degC) oxidation ofthc hydride 11361)7shy20 I] by high temperature (1000-1100() reaction of SIO wilh 10(1 oJ

P~05 [150 193 194 1972022031 and by pyrolyis I ligall)lIIettlli l (700-800degC) 1204J

~~~lt-~~~lt

() 41M WERNER KERN AND CHERYL A DECKERT

60001 ~ I r

4~OC

I HFZ HzOUC

10

I I

~THERMN HzO 2~ I HFI 2t 8 io4 6 12 14

GLASS COMPOSITION molt P2 0 5

Fig J Etch rates of phospho silicate glass films versus mol PO in the glass 450degC CVD films from SiH-PH-O-N IOOOdegC CVD film densified at IOOOdegC in N for I hr Thermal HFHO PHO SiO + POCIltOJ at IOOOdegC [193] Thermal P-etch SiO + PO(Nal at I02OC [1941 (from Kem [271 This figure was originally presemed at the 149th Sprinamp Mulinamp of The Electrochemical Society Inc in Washington DC)

b Borosilicates Binary borosilicate glasses (BSG) are important as dopshyant sources and in silicon passivation [77205] In early literature it was reported that the HF etch rate of CVD BSG typically deposited at 450degC from Sill B2~ and O2 in Nz increases strongly with increasing B conshytent whereas in BHF it decreases sharply with increasing B content to a minimum and then increases with further B increase [190199] These reshysults have since been confirmed [126 196 206-209] A series of graphs exemplifying the etching behavior of BSG films is shown in Fig 4 [1] Boron oxide at moderate concentrations in BSG existing as a borosilicate rather than as B20 3 appears to protect the SiOz from attack by buffered HF at high concentrations B20 3 bonding may be impaired and solubility in water becomes a more important factor resulting in an increased etch rate [196) Several other explanations have been proposed [28 199206 071

1000

x u

X y

450 I HFl2 XOL22

1 I

11 THERMAL ~ 2~

I -P-ETCH

------shyI I _ ~

-lt ER IlAL bull I J~-ETCH H

ZO24

1f

) v-I CHEMICAL lTCHINt

-J I

8001 r-----r T - - r

I 700 I

-I

1 z -I i

I

200 J I I

1 00 -i

I

1_L jdeg0 10 20 JO

IOLEI 80 IN GLASS

Fig 4 Etch rale al 26 IT uf heal[rea[ed horulicalc gl III III Bill 01 II

composi(ion~ veru~ mole percent H20 10 the glltlI ilthlllg 101111111111 LIt piLPdll~1 II)

adding di[IIlcd HO in [he proportion indicalcd [0 B H I ( I () vol N 111 ~IJ I 01 III ~~ Afler L~ lIln a[ 1000( III Ar ) IlXlX buffered HI () huflcled 111 bull 10 Idklcd

HF A 17lt buffered HF (frolll Tenney and Gheo 111 lellIll1ed h) lelllllIOIl 01 11

publiher The Eleclruchemlcdl Society Inc I

Etchant compo~ition~ for I3SG hav bn rpllrtcd lilal arc plIlll[1 larly selective with n~pect to the B tonlnIIIIX 1 IlI) ~()X ~I() 2111 these are useful III analytical and ProL~lng appllldIIUII IkniIl11 by thermal treatmenb lowers the etch ral of BS( III II eldldlll IIJI 19M 199212]

c Arsenosilicutes Chemically vapor-depo~lted arlIoillldll glc (AsSG) used as diffusion ~ources in ~iI[ton deVIl ldlllUlogy cln he pattern etched readily in BHF [200 213) Th ellil Id 1l1(VI) (

films densified at llOOQC in Ar increase logarithmilally ano IilllilOlllnllall) with increasing AS20 3 content from 0 to H mole I i )1 a h()wlI III Fig 5 with a nearly twofold increase III the etth rll mcr lhi UlIll1I tration range [196 214 J The incorporation of GeO~ in lhl fhS( I [[[l1111 e during CVD used to improve the ar~enit diffll~ion lillladelbllc en hances the etch rate of the film [215 J

d Auflillolilic(ltls Chemically vapor-depo~iteo ilLIIIlIlI)dlldll bl (AISG) films are abo u~ually ettmiddothable in H F and III B I F II h 7 I II) 2 I I

420

l WERNER KERN AND CHERYL A DECKERT

1500r----r----------y

1000 i

bull Ill

J l middot -~

deg0 __-L----L_ L_ _

I 2 bull

WOlt As 0 IN GLASS

Fig 5 Etch rates al 26 loe of heat-Ireated arsenosilicatc gla films in BHf versus mole percent AsQ in the glass Etching Mllutions were prepared as noted in Fig 4_ After 5 hr at Iloomiddote in Ar 010000 buffered Hf to 50 buffered HF bull 1000 huffered Hf bull 1 buffered HF (from Tenney and Ghezzo 111 reprinted by permiraquoion of the publisher The Electrochemical SocielY Inc)

217] The incorporation of AltOJ into the glass structure tends to decrease the P-etch rate of the AISG whereas the addition of PbO increases it in comparison with Si02 [16] High-temperature CVD films containing more than 5~ AI20 a are resistant to HF but are etchable in hot HaPO similar to AI2 0 a

e Other Silicates alld Oxides Additional binary and ternary silicate glass films synthesized by CVD bdow 500degC are all etchable in aqueous HF solutions and include zinc silicates zinc borosilicates aluminoshyborosilicates aluminophosphosilicates lead silicates and lead borosilishycates [190 191 199J Chemically vapor-deposited AltO containing sevshyeral percent TaJOs becomes amorphous and etchable with HF or BHF (218) Germanosilicates are etchable in BHF

Anodically grown native oxide films on GaAs are readily etched in dishylute HCI solutions Films heat treated at 600degC become unetchable in Hel HN03 bull NHOH or NaOH solutions but they can be etched in hot concentrated HaPO [2191 or concentrated HF

Plasma-grown oxide films on GaAs are practically insoluble in acids and alkalis except boiling HCI (50-80 Amin) [220) Plasma-grown oxides of complex composition on GaAsutiPo and GaP on the other hand arc easily soluble in acids amI alkalis 220J

- _------------shyf )

v-I CIH-MKAL ETUllNG -I bull I

4 Mliltic()llIpollt1I1 Silinlft Glac1

Lileralllre rdenntes on etching of llllllticompollltllt ililtltlt gldlt are very stant and are mostly conterned wllh hemical durahility and Ill wsion effects 1221 222J The essential component in all ~ihcate gla 1 11 ants is HF In general addition of 1320 3 bull ZnO and PhO to the SiO

t lIel

work imreases the etch rate whereas incorporatlllg AIO hd dereasing effect and leads to improved hcmical nhtallL of the glil [2221

Certain glass compositions reqllire thlt additIOn of eompicxlIlg aglIh

to minimize precipitation of insoluble metal iluoride nactants Ihat Ill and hinder smooth etching Agitation important III all lttching procltc_ may therefore prove particularly important in attainillg good lIllifolllll) Ultrasonic treatment during etthing can aho be useful Amiddotldmiddottabk 111

factants funuioning at low pH can be added to tilL ltIchanl tn ltIlhltlll wetting characteristics and in the ase ofpatkrn lttdllllg fUrlhltr impmllt pattern resolution Additlllll of HCI and HS04 to aqU Ulh 11 khanl Ltll convert insoluble fluorides into solllhk salts I~n 1

Some silicate glasses wilh very high Pb content ar lllllhk ill Illlt11o H NO 2241 A reagent containing ltltedwl and cthylellltlliailline t lliIlmiddot1 tic acid etches soda-Iimlt glass at a uniforlll rate of 10- 15 IlllLrfellll fringes per hour 122_~ I

Etch rates in P-et h of fused BSU and Pb-llSG lilllls have heell I ported [118 2261 Some lead borosilieate~ have et h ralc In I-ellt h lip (

SOU Ase as ompared to Corning 7740 Pyrex glao wilh II Awe alld thermal SiO with ~ Asc [2261 Etch ralc~ have alSll heelllltpllltcd III I II sputtered Corning code 172U AISG [2271 and (Jenelal lle lic (lSC 1 BS( i [22HI

Most siliatt glasses arc slowly ltLltaced by hot X~( ( po 1~1tmiddot_ for example cthes al a rate 01005 -Allli mill at I iW( I gt11 Pynx glil I~ also ethed slowly by hot 9H HSO --30~ 110 ( 1 II alld I hl Cllii

centrated solutions of NaOH or KOH 1791

Etch rates of several types of glasses in the forlll r pld ~ 11 nil

tained in our laboratory 1791 it summary of thl Icullgt pI ltltlltcd III

Table II (Section lVAI

5 Nitrides ami

Silicon nitride in thc form of thin lilms is uf grcal pla-llc1I IlllpUII~III in semicondUltor electronics because of lis ctlcctlVetleS ii ilil alali dil fusion barrier Chemially vapor-deposited SiN hlllh lIe deild al room temperature in concentrated IIF or Bill- III IU() at 140--00 ( in 49 H F -70 H NO (3 10) at 70C and in moltlt1l N a011 at 4)0 ( I 14

T

422 WERNER KERN AND CHERYL A DECKERT

230) The etch nile is strongly affected by the presence of any oxygen linkages in the films in HF and BHF it increases with increasing oxygen content while in H3PO~ it decreases

The dissolution process for CVD Si3N~ films in acidic fluoride media follows the same rate law as does thermal Si02 l23

R = A[HF] + B(HFil + C

whereR is in angstroms per minute and the concentrations are molar The rate constants for the dissolution processes are summarized in the accomshypanying tabulation

Film TempoC A B C

SiN 25 016 031 lt00001 60 19 37 - 002

Sio 25 250 966 014

60 104 486 102

Pattern etching of Si3N~ films is usually carried out by reflux boiling of 85 HaPO at 180degC with CVD SiOi as an etch mask The etch rate under these conditions is typically 100 Amin for CVD SiaN but only 0-25 Amin for the CVD Si02 etch mask and 3 Amin for any exposed singleshycrystal Si [232] It should be noted in this connection that boiling H3PO~ must be treated with special care because of its complex chemistry [232 233J Etch rate plots as a function of temperature and H3P04 concentrashytion are presented in Fig 61232]

Equal or similar etch rates for SiOi and Si3N~ are required in applicashytions where the etched composite structure must have patterned walls with uniform taper angle Hydrogen fluoride-water mixtures of optimal ratio at elevated temperature can etch composite layers of SiaN and Si02 at an equal rate lllO III J A 025 wt HF solution at 90DC etches thermally grown Si02 and typical CVD SiaN films at an equal rate of 70 Amin [234] A 020 wt HF solution at 90degC etches SiO at 45 Amin and SiaN at 60 Amin a near-unity etch rate ratio is generally preferable for film patshyterning of this type [234J Comparison of activation energies for Si3N4 and Si02 dissolution processes suggests [231] that achievement of equal etch rates is also facilitated by use of low pH etchants which maximize [HF] and minimize [HFi]

Films of silicon nitride deposited by plasma-enhanced CVD at low temperature [235] have very much higher etch rates than high-temperashyture CVD SiaN [137 146 147 236-240] These rates depend strongly upon the film composition which may be expressed as SirNwH [235] It has been suggested that these plasma silicon nitride films should be reshy

-l v-I CHEMICAL ITCHIN(

2

loor 8

6

41- 0 SN

0

E

10 SN AT CONST CONe Ofw

I- 8 94 HfgtO

6 x lt)

I-w 4

SO (660C S CI+ 0t + HI 2

__ I

26 f(K)llt 10

945 93 915 895 81 835 195 CONCETRATION (HPO)

Fig 6 Solid linc elch ralc of SIN SIO and Si III [diu hdlll) pilliI k h hi il

atmo~phcri pre-un a~ a fUIKIlOn ofhoiling lCmplratllfl and iIt ((lIhTOIIltWIl I) hld line etch raie l)f SI~N~ at a (on~tant comentratiun 1)1)4 )(t H~P()I I d jlllldlOIl tllllIIIPUl

lure only (from Van G~ldcr and liallr 1232) repnnled by permiI I Ill puhh I h

ElCLlroohemICal Sooely Inci

ganled as a polysilaLane with unique properlie~ iltlthel Ihdl1 1 val Ill I

silicon nitride 12401 Silion nitride film~ deposited by ~pllllering tehniqu hi) hill 11

quently lower eth rates than SiN I if they are kss d II e ~Ul1talll Ill gc

quantities of gases and luI nonslllihiolllltlli A very extensive review uf the IIkrature on di1ing dta or Si N j lIld

silicon oxynitrides was prepared by Mikk 12301 Mor leent resulh ul etching ~tudies have been reportd llll Si N I prepared hy ev J) 1110 I [ I 241-243] by sputtering tehniques [244 -2461 Ind 101 anodi UII1lt1I1

of SiN to SiO~ [247

~~~lt-~~~lt

() 41M WERNER KERN AND CHERYL A DECKERT

60001 ~ I r

4~OC

I HFZ HzOUC

10

I I

~THERMN HzO 2~ I HFI 2t 8 io4 6 12 14

GLASS COMPOSITION molt P2 0 5

Fig J Etch rates of phospho silicate glass films versus mol PO in the glass 450degC CVD films from SiH-PH-O-N IOOOdegC CVD film densified at IOOOdegC in N for I hr Thermal HFHO PHO SiO + POCIltOJ at IOOOdegC [193] Thermal P-etch SiO + PO(Nal at I02OC [1941 (from Kem [271 This figure was originally presemed at the 149th Sprinamp Mulinamp of The Electrochemical Society Inc in Washington DC)

b Borosilicates Binary borosilicate glasses (BSG) are important as dopshyant sources and in silicon passivation [77205] In early literature it was reported that the HF etch rate of CVD BSG typically deposited at 450degC from Sill B2~ and O2 in Nz increases strongly with increasing B conshytent whereas in BHF it decreases sharply with increasing B content to a minimum and then increases with further B increase [190199] These reshysults have since been confirmed [126 196 206-209] A series of graphs exemplifying the etching behavior of BSG films is shown in Fig 4 [1] Boron oxide at moderate concentrations in BSG existing as a borosilicate rather than as B20 3 appears to protect the SiOz from attack by buffered HF at high concentrations B20 3 bonding may be impaired and solubility in water becomes a more important factor resulting in an increased etch rate [196) Several other explanations have been proposed [28 199206 071

1000

x u

X y

450 I HFl2 XOL22

1 I

11 THERMAL ~ 2~

I -P-ETCH

------shyI I _ ~

-lt ER IlAL bull I J~-ETCH H

ZO24

1f

) v-I CHEMICAL lTCHINt

-J I

8001 r-----r T - - r

I 700 I

-I

1 z -I i

I

200 J I I

1 00 -i

I

1_L jdeg0 10 20 JO

IOLEI 80 IN GLASS

Fig 4 Etch rale al 26 IT uf heal[rea[ed horulicalc gl III III Bill 01 II

composi(ion~ veru~ mole percent H20 10 the glltlI ilthlllg 101111111111 LIt piLPdll~1 II)

adding di[IIlcd HO in [he proportion indicalcd [0 B H I ( I () vol N 111 ~IJ I 01 III ~~ Afler L~ lIln a[ 1000( III Ar ) IlXlX buffered HI () huflcled 111 bull 10 Idklcd

HF A 17lt buffered HF (frolll Tenney and Gheo 111 lellIll1ed h) lelllllIOIl 01 11

publiher The Eleclruchemlcdl Society Inc I

Etchant compo~ition~ for I3SG hav bn rpllrtcd lilal arc plIlll[1 larly selective with n~pect to the B tonlnIIIIX 1 IlI) ~()X ~I() 2111 these are useful III analytical and ProL~lng appllldIIUII IkniIl11 by thermal treatmenb lowers the etch ral of BS( III II eldldlll IIJI 19M 199212]

c Arsenosilicutes Chemically vapor-depo~lted arlIoillldll glc (AsSG) used as diffusion ~ources in ~iI[ton deVIl ldlllUlogy cln he pattern etched readily in BHF [200 213) Th ellil Id 1l1(VI) (

films densified at llOOQC in Ar increase logarithmilally ano IilllilOlllnllall) with increasing AS20 3 content from 0 to H mole I i )1 a h()wlI III Fig 5 with a nearly twofold increase III the etth rll mcr lhi UlIll1I tration range [196 214 J The incorporation of GeO~ in lhl fhS( I [[[l1111 e during CVD used to improve the ar~enit diffll~ion lillladelbllc en hances the etch rate of the film [215 J

d Auflillolilic(ltls Chemically vapor-depo~iteo ilLIIIlIlI)dlldll bl (AISG) films are abo u~ually ettmiddothable in H F and III B I F II h 7 I II) 2 I I

420

l WERNER KERN AND CHERYL A DECKERT

1500r----r----------y

1000 i

bull Ill

J l middot -~

deg0 __-L----L_ L_ _

I 2 bull

WOlt As 0 IN GLASS

Fig 5 Etch rates al 26 loe of heat-Ireated arsenosilicatc gla films in BHf versus mole percent AsQ in the glass Etching Mllutions were prepared as noted in Fig 4_ After 5 hr at Iloomiddote in Ar 010000 buffered Hf to 50 buffered HF bull 1000 huffered Hf bull 1 buffered HF (from Tenney and Ghezzo 111 reprinted by permiraquoion of the publisher The Electrochemical SocielY Inc)

217] The incorporation of AltOJ into the glass structure tends to decrease the P-etch rate of the AISG whereas the addition of PbO increases it in comparison with Si02 [16] High-temperature CVD films containing more than 5~ AI20 a are resistant to HF but are etchable in hot HaPO similar to AI2 0 a

e Other Silicates alld Oxides Additional binary and ternary silicate glass films synthesized by CVD bdow 500degC are all etchable in aqueous HF solutions and include zinc silicates zinc borosilicates aluminoshyborosilicates aluminophosphosilicates lead silicates and lead borosilishycates [190 191 199J Chemically vapor-deposited AltO containing sevshyeral percent TaJOs becomes amorphous and etchable with HF or BHF (218) Germanosilicates are etchable in BHF

Anodically grown native oxide films on GaAs are readily etched in dishylute HCI solutions Films heat treated at 600degC become unetchable in Hel HN03 bull NHOH or NaOH solutions but they can be etched in hot concentrated HaPO [2191 or concentrated HF

Plasma-grown oxide films on GaAs are practically insoluble in acids and alkalis except boiling HCI (50-80 Amin) [220) Plasma-grown oxides of complex composition on GaAsutiPo and GaP on the other hand arc easily soluble in acids amI alkalis 220J

- _------------shyf )

v-I CIH-MKAL ETUllNG -I bull I

4 Mliltic()llIpollt1I1 Silinlft Glac1

Lileralllre rdenntes on etching of llllllticompollltllt ililtltlt gldlt are very stant and are mostly conterned wllh hemical durahility and Ill wsion effects 1221 222J The essential component in all ~ihcate gla 1 11 ants is HF In general addition of 1320 3 bull ZnO and PhO to the SiO

t lIel

work imreases the etch rate whereas incorporatlllg AIO hd dereasing effect and leads to improved hcmical nhtallL of the glil [2221

Certain glass compositions reqllire thlt additIOn of eompicxlIlg aglIh

to minimize precipitation of insoluble metal iluoride nactants Ihat Ill and hinder smooth etching Agitation important III all lttching procltc_ may therefore prove particularly important in attainillg good lIllifolllll) Ultrasonic treatment during etthing can aho be useful Amiddotldmiddottabk 111

factants funuioning at low pH can be added to tilL ltIchanl tn ltIlhltlll wetting characteristics and in the ase ofpatkrn lttdllllg fUrlhltr impmllt pattern resolution Additlllll of HCI and HS04 to aqU Ulh 11 khanl Ltll convert insoluble fluorides into solllhk salts I~n 1

Some silicate glasses wilh very high Pb content ar lllllhk ill Illlt11o H NO 2241 A reagent containing ltltedwl and cthylellltlliailline t lliIlmiddot1 tic acid etches soda-Iimlt glass at a uniforlll rate of 10- 15 IlllLrfellll fringes per hour 122_~ I

Etch rates in P-et h of fused BSU and Pb-llSG lilllls have heell I ported [118 2261 Some lead borosilieate~ have et h ralc In I-ellt h lip (

SOU Ase as ompared to Corning 7740 Pyrex glao wilh II Awe alld thermal SiO with ~ Asc [2261 Etch ralc~ have alSll heelllltpllltcd III I II sputtered Corning code 172U AISG [2271 and (Jenelal lle lic (lSC 1 BS( i [22HI

Most siliatt glasses arc slowly ltLltaced by hot X~( ( po 1~1tmiddot_ for example cthes al a rate 01005 -Allli mill at I iW( I gt11 Pynx glil I~ also ethed slowly by hot 9H HSO --30~ 110 ( 1 II alld I hl Cllii

centrated solutions of NaOH or KOH 1791

Etch rates of several types of glasses in the forlll r pld ~ 11 nil

tained in our laboratory 1791 it summary of thl Icullgt pI ltltlltcd III

Table II (Section lVAI

5 Nitrides ami

Silicon nitride in thc form of thin lilms is uf grcal pla-llc1I IlllpUII~III in semicondUltor electronics because of lis ctlcctlVetleS ii ilil alali dil fusion barrier Chemially vapor-deposited SiN hlllh lIe deild al room temperature in concentrated IIF or Bill- III IU() at 140--00 ( in 49 H F -70 H NO (3 10) at 70C and in moltlt1l N a011 at 4)0 ( I 14

T

422 WERNER KERN AND CHERYL A DECKERT

230) The etch nile is strongly affected by the presence of any oxygen linkages in the films in HF and BHF it increases with increasing oxygen content while in H3PO~ it decreases

The dissolution process for CVD Si3N~ films in acidic fluoride media follows the same rate law as does thermal Si02 l23

R = A[HF] + B(HFil + C

whereR is in angstroms per minute and the concentrations are molar The rate constants for the dissolution processes are summarized in the accomshypanying tabulation

Film TempoC A B C

SiN 25 016 031 lt00001 60 19 37 - 002

Sio 25 250 966 014

60 104 486 102

Pattern etching of Si3N~ films is usually carried out by reflux boiling of 85 HaPO at 180degC with CVD SiOi as an etch mask The etch rate under these conditions is typically 100 Amin for CVD SiaN but only 0-25 Amin for the CVD Si02 etch mask and 3 Amin for any exposed singleshycrystal Si [232] It should be noted in this connection that boiling H3PO~ must be treated with special care because of its complex chemistry [232 233J Etch rate plots as a function of temperature and H3P04 concentrashytion are presented in Fig 61232]

Equal or similar etch rates for SiOi and Si3N~ are required in applicashytions where the etched composite structure must have patterned walls with uniform taper angle Hydrogen fluoride-water mixtures of optimal ratio at elevated temperature can etch composite layers of SiaN and Si02 at an equal rate lllO III J A 025 wt HF solution at 90DC etches thermally grown Si02 and typical CVD SiaN films at an equal rate of 70 Amin [234] A 020 wt HF solution at 90degC etches SiO at 45 Amin and SiaN at 60 Amin a near-unity etch rate ratio is generally preferable for film patshyterning of this type [234J Comparison of activation energies for Si3N4 and Si02 dissolution processes suggests [231] that achievement of equal etch rates is also facilitated by use of low pH etchants which maximize [HF] and minimize [HFi]

Films of silicon nitride deposited by plasma-enhanced CVD at low temperature [235] have very much higher etch rates than high-temperashyture CVD SiaN [137 146 147 236-240] These rates depend strongly upon the film composition which may be expressed as SirNwH [235] It has been suggested that these plasma silicon nitride films should be reshy

-l v-I CHEMICAL ITCHIN(

2

loor 8

6

41- 0 SN

0

E

10 SN AT CONST CONe Ofw

I- 8 94 HfgtO

6 x lt)

I-w 4

SO (660C S CI+ 0t + HI 2

__ I

26 f(K)llt 10

945 93 915 895 81 835 195 CONCETRATION (HPO)

Fig 6 Solid linc elch ralc of SIN SIO and Si III [diu hdlll) pilliI k h hi il

atmo~phcri pre-un a~ a fUIKIlOn ofhoiling lCmplratllfl and iIt ((lIhTOIIltWIl I) hld line etch raie l)f SI~N~ at a (on~tant comentratiun 1)1)4 )(t H~P()I I d jlllldlOIl tllllIIIPUl

lure only (from Van G~ldcr and liallr 1232) repnnled by permiI I Ill puhh I h

ElCLlroohemICal Sooely Inci

ganled as a polysilaLane with unique properlie~ iltlthel Ihdl1 1 val Ill I

silicon nitride 12401 Silion nitride film~ deposited by ~pllllering tehniqu hi) hill 11

quently lower eth rates than SiN I if they are kss d II e ~Ul1talll Ill gc

quantities of gases and luI nonslllihiolllltlli A very extensive review uf the IIkrature on di1ing dta or Si N j lIld

silicon oxynitrides was prepared by Mikk 12301 Mor leent resulh ul etching ~tudies have been reportd llll Si N I prepared hy ev J) 1110 I [ I 241-243] by sputtering tehniques [244 -2461 Ind 101 anodi UII1lt1I1

of SiN to SiO~ [247

420

l WERNER KERN AND CHERYL A DECKERT

1500r----r----------y

1000 i

bull Ill

J l middot -~

deg0 __-L----L_ L_ _

I 2 bull

WOlt As 0 IN GLASS

Fig 5 Etch rates al 26 loe of heat-Ireated arsenosilicatc gla films in BHf versus mole percent AsQ in the glass Etching Mllutions were prepared as noted in Fig 4_ After 5 hr at Iloomiddote in Ar 010000 buffered Hf to 50 buffered HF bull 1000 huffered Hf bull 1 buffered HF (from Tenney and Ghezzo 111 reprinted by permiraquoion of the publisher The Electrochemical SocielY Inc)

217] The incorporation of AltOJ into the glass structure tends to decrease the P-etch rate of the AISG whereas the addition of PbO increases it in comparison with Si02 [16] High-temperature CVD films containing more than 5~ AI20 a are resistant to HF but are etchable in hot HaPO similar to AI2 0 a

e Other Silicates alld Oxides Additional binary and ternary silicate glass films synthesized by CVD bdow 500degC are all etchable in aqueous HF solutions and include zinc silicates zinc borosilicates aluminoshyborosilicates aluminophosphosilicates lead silicates and lead borosilishycates [190 191 199J Chemically vapor-deposited AltO containing sevshyeral percent TaJOs becomes amorphous and etchable with HF or BHF (218) Germanosilicates are etchable in BHF

Anodically grown native oxide films on GaAs are readily etched in dishylute HCI solutions Films heat treated at 600degC become unetchable in Hel HN03 bull NHOH or NaOH solutions but they can be etched in hot concentrated HaPO [2191 or concentrated HF

Plasma-grown oxide films on GaAs are practically insoluble in acids and alkalis except boiling HCI (50-80 Amin) [220) Plasma-grown oxides of complex composition on GaAsutiPo and GaP on the other hand arc easily soluble in acids amI alkalis 220J

- _------------shyf )

v-I CIH-MKAL ETUllNG -I bull I

4 Mliltic()llIpollt1I1 Silinlft Glac1

Lileralllre rdenntes on etching of llllllticompollltllt ililtltlt gldlt are very stant and are mostly conterned wllh hemical durahility and Ill wsion effects 1221 222J The essential component in all ~ihcate gla 1 11 ants is HF In general addition of 1320 3 bull ZnO and PhO to the SiO

t lIel

work imreases the etch rate whereas incorporatlllg AIO hd dereasing effect and leads to improved hcmical nhtallL of the glil [2221

Certain glass compositions reqllire thlt additIOn of eompicxlIlg aglIh

to minimize precipitation of insoluble metal iluoride nactants Ihat Ill and hinder smooth etching Agitation important III all lttching procltc_ may therefore prove particularly important in attainillg good lIllifolllll) Ultrasonic treatment during etthing can aho be useful Amiddotldmiddottabk 111

factants funuioning at low pH can be added to tilL ltIchanl tn ltIlhltlll wetting characteristics and in the ase ofpatkrn lttdllllg fUrlhltr impmllt pattern resolution Additlllll of HCI and HS04 to aqU Ulh 11 khanl Ltll convert insoluble fluorides into solllhk salts I~n 1

Some silicate glasses wilh very high Pb content ar lllllhk ill Illlt11o H NO 2241 A reagent containing ltltedwl and cthylellltlliailline t lliIlmiddot1 tic acid etches soda-Iimlt glass at a uniforlll rate of 10- 15 IlllLrfellll fringes per hour 122_~ I

Etch rates in P-et h of fused BSU and Pb-llSG lilllls have heell I ported [118 2261 Some lead borosilieate~ have et h ralc In I-ellt h lip (

SOU Ase as ompared to Corning 7740 Pyrex glao wilh II Awe alld thermal SiO with ~ Asc [2261 Etch ralc~ have alSll heelllltpllltcd III I II sputtered Corning code 172U AISG [2271 and (Jenelal lle lic (lSC 1 BS( i [22HI

Most siliatt glasses arc slowly ltLltaced by hot X~( ( po 1~1tmiddot_ for example cthes al a rate 01005 -Allli mill at I iW( I gt11 Pynx glil I~ also ethed slowly by hot 9H HSO --30~ 110 ( 1 II alld I hl Cllii

centrated solutions of NaOH or KOH 1791

Etch rates of several types of glasses in the forlll r pld ~ 11 nil

tained in our laboratory 1791 it summary of thl Icullgt pI ltltlltcd III

Table II (Section lVAI

5 Nitrides ami

Silicon nitride in thc form of thin lilms is uf grcal pla-llc1I IlllpUII~III in semicondUltor electronics because of lis ctlcctlVetleS ii ilil alali dil fusion barrier Chemially vapor-deposited SiN hlllh lIe deild al room temperature in concentrated IIF or Bill- III IU() at 140--00 ( in 49 H F -70 H NO (3 10) at 70C and in moltlt1l N a011 at 4)0 ( I 14

T

422 WERNER KERN AND CHERYL A DECKERT

230) The etch nile is strongly affected by the presence of any oxygen linkages in the films in HF and BHF it increases with increasing oxygen content while in H3PO~ it decreases

The dissolution process for CVD Si3N~ films in acidic fluoride media follows the same rate law as does thermal Si02 l23

R = A[HF] + B(HFil + C

whereR is in angstroms per minute and the concentrations are molar The rate constants for the dissolution processes are summarized in the accomshypanying tabulation

Film TempoC A B C

SiN 25 016 031 lt00001 60 19 37 - 002

Sio 25 250 966 014

60 104 486 102

Pattern etching of Si3N~ films is usually carried out by reflux boiling of 85 HaPO at 180degC with CVD SiOi as an etch mask The etch rate under these conditions is typically 100 Amin for CVD SiaN but only 0-25 Amin for the CVD Si02 etch mask and 3 Amin for any exposed singleshycrystal Si [232] It should be noted in this connection that boiling H3PO~ must be treated with special care because of its complex chemistry [232 233J Etch rate plots as a function of temperature and H3P04 concentrashytion are presented in Fig 61232]

Equal or similar etch rates for SiOi and Si3N~ are required in applicashytions where the etched composite structure must have patterned walls with uniform taper angle Hydrogen fluoride-water mixtures of optimal ratio at elevated temperature can etch composite layers of SiaN and Si02 at an equal rate lllO III J A 025 wt HF solution at 90DC etches thermally grown Si02 and typical CVD SiaN films at an equal rate of 70 Amin [234] A 020 wt HF solution at 90degC etches SiO at 45 Amin and SiaN at 60 Amin a near-unity etch rate ratio is generally preferable for film patshyterning of this type [234J Comparison of activation energies for Si3N4 and Si02 dissolution processes suggests [231] that achievement of equal etch rates is also facilitated by use of low pH etchants which maximize [HF] and minimize [HFi]

Films of silicon nitride deposited by plasma-enhanced CVD at low temperature [235] have very much higher etch rates than high-temperashyture CVD SiaN [137 146 147 236-240] These rates depend strongly upon the film composition which may be expressed as SirNwH [235] It has been suggested that these plasma silicon nitride films should be reshy

-l v-I CHEMICAL ITCHIN(

2

loor 8

6

41- 0 SN

0

E

10 SN AT CONST CONe Ofw

I- 8 94 HfgtO

6 x lt)

I-w 4

SO (660C S CI+ 0t + HI 2

__ I

26 f(K)llt 10

945 93 915 895 81 835 195 CONCETRATION (HPO)

Fig 6 Solid linc elch ralc of SIN SIO and Si III [diu hdlll) pilliI k h hi il

atmo~phcri pre-un a~ a fUIKIlOn ofhoiling lCmplratllfl and iIt ((lIhTOIIltWIl I) hld line etch raie l)f SI~N~ at a (on~tant comentratiun 1)1)4 )(t H~P()I I d jlllldlOIl tllllIIIPUl

lure only (from Van G~ldcr and liallr 1232) repnnled by permiI I Ill puhh I h

ElCLlroohemICal Sooely Inci

ganled as a polysilaLane with unique properlie~ iltlthel Ihdl1 1 val Ill I

silicon nitride 12401 Silion nitride film~ deposited by ~pllllering tehniqu hi) hill 11

quently lower eth rates than SiN I if they are kss d II e ~Ul1talll Ill gc

quantities of gases and luI nonslllihiolllltlli A very extensive review uf the IIkrature on di1ing dta or Si N j lIld

silicon oxynitrides was prepared by Mikk 12301 Mor leent resulh ul etching ~tudies have been reportd llll Si N I prepared hy ev J) 1110 I [ I 241-243] by sputtering tehniques [244 -2461 Ind 101 anodi UII1lt1I1

of SiN to SiO~ [247

T

422 WERNER KERN AND CHERYL A DECKERT

230) The etch nile is strongly affected by the presence of any oxygen linkages in the films in HF and BHF it increases with increasing oxygen content while in H3PO~ it decreases

The dissolution process for CVD Si3N~ films in acidic fluoride media follows the same rate law as does thermal Si02 l23

R = A[HF] + B(HFil + C

whereR is in angstroms per minute and the concentrations are molar The rate constants for the dissolution processes are summarized in the accomshypanying tabulation

Film TempoC A B C

SiN 25 016 031 lt00001 60 19 37 - 002

Sio 25 250 966 014

60 104 486 102

Pattern etching of Si3N~ films is usually carried out by reflux boiling of 85 HaPO at 180degC with CVD SiOi as an etch mask The etch rate under these conditions is typically 100 Amin for CVD SiaN but only 0-25 Amin for the CVD Si02 etch mask and 3 Amin for any exposed singleshycrystal Si [232] It should be noted in this connection that boiling H3PO~ must be treated with special care because of its complex chemistry [232 233J Etch rate plots as a function of temperature and H3P04 concentrashytion are presented in Fig 61232]

Equal or similar etch rates for SiOi and Si3N~ are required in applicashytions where the etched composite structure must have patterned walls with uniform taper angle Hydrogen fluoride-water mixtures of optimal ratio at elevated temperature can etch composite layers of SiaN and Si02 at an equal rate lllO III J A 025 wt HF solution at 90DC etches thermally grown Si02 and typical CVD SiaN films at an equal rate of 70 Amin [234] A 020 wt HF solution at 90degC etches SiO at 45 Amin and SiaN at 60 Amin a near-unity etch rate ratio is generally preferable for film patshyterning of this type [234J Comparison of activation energies for Si3N4 and Si02 dissolution processes suggests [231] that achievement of equal etch rates is also facilitated by use of low pH etchants which maximize [HF] and minimize [HFi]

Films of silicon nitride deposited by plasma-enhanced CVD at low temperature [235] have very much higher etch rates than high-temperashyture CVD SiaN [137 146 147 236-240] These rates depend strongly upon the film composition which may be expressed as SirNwH [235] It has been suggested that these plasma silicon nitride films should be reshy

-l v-I CHEMICAL ITCHIN(

2

loor 8

6

41- 0 SN

0

E

10 SN AT CONST CONe Ofw

I- 8 94 HfgtO

6 x lt)

I-w 4

SO (660C S CI+ 0t + HI 2

__ I

26 f(K)llt 10

945 93 915 895 81 835 195 CONCETRATION (HPO)

Fig 6 Solid linc elch ralc of SIN SIO and Si III [diu hdlll) pilliI k h hi il

atmo~phcri pre-un a~ a fUIKIlOn ofhoiling lCmplratllfl and iIt ((lIhTOIIltWIl I) hld line etch raie l)f SI~N~ at a (on~tant comentratiun 1)1)4 )(t H~P()I I d jlllldlOIl tllllIIIPUl

lure only (from Van G~ldcr and liallr 1232) repnnled by permiI I Ill puhh I h

ElCLlroohemICal Sooely Inci

ganled as a polysilaLane with unique properlie~ iltlthel Ihdl1 1 val Ill I

silicon nitride 12401 Silion nitride film~ deposited by ~pllllering tehniqu hi) hill 11

quently lower eth rates than SiN I if they are kss d II e ~Ul1talll Ill gc

quantities of gases and luI nonslllihiolllltlli A very extensive review uf the IIkrature on di1ing dta or Si N j lIld

silicon oxynitrides was prepared by Mikk 12301 Mor leent resulh ul etching ~tudies have been reportd llll Si N I prepared hy ev J) 1110 I [ I 241-243] by sputtering tehniques [244 -2461 Ind 101 anodi UII1lt1I1

of SiN to SiO~ [247

shy ~~A W~RIoIR KERN AND CHERYL A DICKERT

Thl elch rall 01 gt11lun ltJA) 1IIlIhlI i1ml~ 01 lilt generi1ll1JnTIUI ~lJ ~ is strongly influenced by the depo~ition conditions and by film dengtity and stoichiometry 12301 Typical etth rates for CVD Si-NUO films (prepared from SiH bullbull NH 3 and NO) in 48 HF are 300-500 Amin as compand with 30000-50000 Amin for SiO~ and 130-150 Amin for SiN~ in tWc HJPO at l80aC the etch rates are 10-100 Amin (or SiNuO 8-10 Amin for SiOz and 60-100 Amin for SilN~ 1248) More recently some addl tional data have been published f249] including data for glow-disthargc deposited films 1147]

Other nitrides for which etching data are available include CVD amurshyphous G~N films that rapidly dissolve in concentrated HF HNO and hot HJPO [250 250al Aluminum nitride BN and GaN and have been included in Section IIIB4 on compound semiconductors

B Semiconductors

J Elemental Semiconductors

Silicon is by far the most important elemental semiconduttor betau~e of its widespread use in modern microelectronic and photovoltaic device~ Another elemental semiconductor germanium has beome of lesser immiddot portance Because of their similarities many of the etching processcs can be applied to both The discussion of Si and Ge etching shall be kept ier) brief because of space limitations A more detailed presentation has been published elsewhere [27a) Specific details on etchant tomposition ethmiddot ing conditions etch rates and applications are listed in thc tables of ampshytion IVC

Selenium is a group VI elcmental semiconductor for whith very lillie information on etching exists However all three forms of Sc are sulubk in HzSO bull In addition the amorphous modifications are soluble ahu In

CSt the monoclinic form in HN03 and the hexagonal crystal form In

CHCI3 bull

The discussion of elemental semiconductor etching that follows is tunmiddot cerned exc1usively with Si and Ge

a bmtropic Liquid Etching Isotropic chemical etching of semicondumiddot tors in liquid reagents is the most widely used etching proless for remu bull aJ of work-damaged surfaces for creating structures or planar surfaces In

single-crystal slices and for pallerning deposited semiconductor 1i10~ For Si etchants containing HF HNOa and H20 are most frequentl) used Ge etchants based on HF H20 Z and H20 are typical Extcnic gttudies have been reported on the mechanism ofSi etching in HF-HNO

) j ) v-I CHEMICAl [ICIllN(i

HF (49 ~)

50

40

30

H20 90 80 70 60 50 40 30 20 10 HN0 (bl ~l )

fig 7 Curvc of tonltwt fate of Ihangt of die loi(klll (I1ul Id 1IIIIliltlc gtwUlllllllltd

IU Si arcr ~urralC) d a funtion of ~thanl iolllpouillll III till Pi ffJ 70 Jflt

)Iem (from ScmiddothwurlJ und Ioholn [256) repnnkJ by perm I IIc puhlhcbull I Ill ~IcCIfl)herlll(al SlcI y Inc L

12521 in ternary mixtures of HF-HNO-HtO ami in HjUOIl

HF-HNO-CHaCOOH compositions 1253 -2561 In high III ddanh III HNOa (ofllcntration ddcrmincs the etth rate bCCltlll (lllbIIOn I III

rate-limiting step In high-HNOa compositiDn~ the etch 1lt11 alc a tUllc

lIuI1 of only the H F becallsl in this case dissolution is til (alllillli [(Ilg pi

ce~s 1253] In Figs 7 and i iSllctch rate contollr~ ol hUWIl lor III

HF ~9 7~Ql

b()

20 iO HNOil(J4bt)

fig 8 Curvelo of COn~lan rate of Ihunge of dH thilkIH~ ~md- PII HHUlil dHnhlllLd

10 SI wafer urfae) a a flndon of eldlanl ompoJiwno Ihc (0 III 9(1 IIN() gt lem the dYed of added talyl (NaNO) is ho n Ihe dheu IlIIe (110m Selman Hld

RobbinS 1256] reprinted hy permision of Ihe pubher The Ekelr(JclI Sclel)

426 WlRNlR KERN AND CHERYL A DECKlRI

t1f(4925)

O PEAKED CORNERS a EDGES

rnI SQUARE CORNERS IiiI a EDGES

rn ROUNDED CORNER a EDGES

t1 Z0

Fig 9 Resultant geometry of the etched Si die as a function of the etthant complthHlUO in the 48 HF-70 HNO system (from Schwartz and Robbins [256] reprinted by perm middot sion of the publisher The Electrochemical Sodety Inc)

HN03-H10 in normal and high concentration acids The resulting geommiddot etry effects on initially rectangular (I I I)-plane parallelepipeds (II-type 2n-cm dice) are indicated in Figs 9 and 10 for the same elcnants The acshy

tivation energies for both Si and Ge in HF-HNOa-CHaCOOH ehhant confirmed that the processes are diffusion controlled [257] Silicon is aho soluble to a very small extent in HF solutions and BHF [258-260J 110

Hf(59n1

o PEAKED EDGES a CORNERS

SQUARE EDGES aO CORNERS

mROUNDED EDGES a CORNERS

O CONIEX LENS SHAPED

H2 0

Fig 19 itesuJtant geometry of the etched Si die as a function of the etchant wmp I IR the 6OJI) HF-9O HNo system (from Schwanz and Robbins [2561 reprinted b) pelugt sion of the publisher The Electrochemical Society Incj

-v-I CHEfileAl EICHIN( 1

tropic liquid etching has been used for thinning tlf tie ami Si Ii~e 1261shy266] for prepassivation surface cleanup 12671 and fnr polihlflg 126X-2791

Germanium etchants based nn HNO-HF-IlO 01 HNO-lIF CH3COOH are difficult to control mainly hccaue III varlahk indll~lt(lll periods [280-2841 The HF-H~O~ -H) etch system alTolo mudl helllt1 control 280 2842851 Removal of thin layers Cie can h~ aC(llrnplished with 3 HO at pH 38[286] Additional iSHlropic ckhanb I X7 -2lt) I Ill( Gc have been included in Table IV of Section IV

b Allisotropic LicluiJ tchitlf In anislltmpi or orientaliolHJepcmkll1 etching the etch rate varies within the prin~ipal crYlallllglilphic lileltmiddot tions of the semiconductor single nyslal Orientation dlnh have been allributed III crystallographic pmpertie partiulady Ihi denSity of tilmiddot face free bonds the relative etch rate IIlcreaing wilh Ihe numher of avail able free bonds 18296-2981

Anisotropic liqlliu echants for Si arc 1I1Ially 11alill uiulillll led ltII

elevated temperature 121 124 29X-~ 121 The eenlial kdlilfe lor ilicun technology of all these solutions is their lip to 100 time IlIghltl el h ratt til the ( 100) uirection than in the ltII t) direction 1Jltn 10) I hll i)lIl1pk ill the case of the water-ethylenediamine-pynHatechol etchlIlt the illth rales of (100) (110) and (III) oriented Si are apprxlIllilILlj- ~O lli pmhr respectively J Ill Anisotropic etchinpound or (100) SI through pt1

temed SiO mask creates precise V grooves with Ih iug heing I II II planes at an angle of 54r rmlll the (IOU) lIrtace IllkrcllIid etcilllig allows fabrication of high-ucnsity monolithic imegrattd clrcUlh I~ 10 11

3141 Si-on-apphire integrateu ~ircuit I26X j051 altd )lllel SI dnicn that require structuring and patterning 1311 315 -3OI ilmlllloplC ek h in~ of Ge Im crystallographic studies has been reporled 13211

( Electrochemical (llld Selective Chellllcul Ercilillll Fkliillg ot ellllLllll ductms in liquid reagents by application o an extallal emf i 1Ied Illi preparing mirrorlike surfaces and creating very thin Ingk Ct yld tilin Fundamental theoretical and practical aspects of semlcondllctor ekcllll chemistry have been thoroughly treated in everal bo and reVllV ~ 130-3739-41]

Specific shapes can be imparted to Ge and Si ulltllllled localized electrochemical etching 1322-341 uf (J I allli Si has been achieved by several techniques 1325-32X I

Selective electrochemical etching of single-crystal Si ublIak hdVshy

ing suitable epitaxial structures has been empillyed fllr preparing very thin Si crystals [269329-336] P-type and heavily dllpeu Illypl SI call hi dissolved anodically in dilute (1-5 tv) HF al sufticiently In voltage hereas II-type Si does not dissolve Selective ele~tlll~hllllicallhiltnlllc I

f

~I

4~ WERNER KERN AND CHERYL A DECKERI

n -type Si substrates is also possible with alkali solutions in which Ihe etch rates are strongly dependent on the electrode potentials [303 337 338]

Anodic oxidation of Si in electrolyte solutions based on organic mela 339] followed by oxide dissolution has been described for sectioning 10

the determination of Si diffusion profiles 340J Objects in contact with the Si surface can either slow down or enhance the local etch rate considermiddot ably [34l Substrate and etching conditions in the anodic dissolution of Si in aqueous HF can lead to brown layers etch pits and porous channel) 1269322328329331-333337342-344] caused by preferential etching and partial dissolution at localized sites (251 331-333] Single-cry~ta1 films of porous Sit formed purposely from n- and p-type Si by anodic reacmiddot tion in concentrated HF 1329 344-346] are very similar or identical to these brown channeled layers

Selective etching to dissolve Si of different dopant types and regtigttiishyties can also be achieved by chemical technique without use of external electrodes [263268304347-3581 exemplified by Fig II and the data presented in Table VI of Section IV

d Gas- and Vapor-Phase Etching Gas- and vapor-phase etching ale widely used for polishing of Si substrate wafers in situ prior to epitaxld crystal growth The most successful reagent is sulfur hexafluoride Sf It produces a smooth mirrorlike surface when reacted in a dilution vith HI at 950degC [359) or (more usually) above I050degC according to the overall reaction [360]

4 Si () + 2 SF (gl -+ SiS- (gt or l) + 3 SiFt (8)middot

1 ~ I==PRfFfHpJ

l o Ogt~ l u w

I I

--r

1 )( 10 11 )( 10 8 )( 109 )( 1020

BORON CONCENTRATION

i II Selective etching of ilicon Si (100) etch rate per minute vergtu boron cuocn tralion Etchnl ~ystem i KOH-HO-igtopropyl alcohol at sire (from Kuhn anJ Itlllaquo (341) reprinted by permi~ion of the publisher The Electrochemical Society Inc)

j

v I CHEMICAl ETCHING middotL~J

Since the free energy of the reaction is 706ll1 10lt11111lt)1 at 140W( [361] the etching proceeds spontdneoll~ly and irrevcllhly pludulting volatile sulfides and fluorides of 5i as the readioll PWdlllth 13hOI The etch rate as a function of temperature for O I~( SF i tWWII in and as a function of SF partial pressure in Fig 11 11021 The of SF6 over other reagents lie in the nonltorroivellc 1l0lllOXlcity and low temperature needed in Jdditiun to the cxcellent plulanly attainahle which makes the process applicable for waleI thtnllillg

Other vapor etchants used fur polishing Si arc IICI I IlJ nO HBI [365[ HI [3713721 CI 2 [373] H2S [1741 HI-HI In l7hl and 110 [3773781

In general gas- and vapor-phase eteillng is not depelllkill 011 the lel tivity level or type of the Si Condition call be elected Jlt the tI(J -tl etching system that -result in anisotropic etching of vamgtI cl ~ st1I plalles al difTerent rates this has been exploitcd lechnolnglcally III eiclivl taxy 1367309370] as noted in Section IV Table VII

Similar to Si (IIIJ-Ge can be pulih etlthed With anh~dlHts IICI IIImiddot H H5-H 3t01 Superior results arc (lbtlinahle with II -II() vapul t

JOOC which produces clean structurces surfaces 11XOI

TCMPEIA i Ufll 121gt lIN

~

1l1tv

u ~ shy

gt- (ii 1 J

Fig 12 1 IJ

FIg 12 Vdpnf ph(1~t l~khlllg uf ~lli(lW SI ~kh Jth lj 11 UlhllII ht1IjtllWl Ill

~i pr~ul~ of 10 1 dun (fl ~)m Stlnofl tl al 11621 ICpl Inkd h) prllllgtjull 01 lilt pubhhLI rh( EkIl)chcmicJI SOClt y Inc

fig J3 Vapor phase ehhing DI dl(on Sf chh rak Vel Ill) SFji plillJtI pi t111 C d IUt)O (

trum Sun I ul 1621 rcplllTl~d b~ perm1 01 the puhlhhc I he licduclicllllc StJt1(ly Inc)

430 WERNER KERN AND CHERYL A DECKERl

e Chemical-Mechanical Polishing Polishing by combined chemical and mechanical processes is usually the last step in preparing flat and specshyular wafers in silicon device manufacture The generally preferred techshynique is the silica-sol (Syton [381]) method [382 383] The medium conshysists of a colloidal suspension of silica gel in aqueous NaOH solution of controlled pH and is dispensed on the polishing pad of a rotating poligthing machine Silicon removal proceeds by oxidation of the surface by water in the presence of the alkali ions and continuous dissolution of the surface oxide aided by the silica gel which serves as a mild abrasive [383-31561 The process can also be used for polishing Ge wafers but H20 2 mu~t be added to the dispersion to achieve a smooth surface finish [3153]

Another process for 5i employs an aqueous solution containing copper and fluoride ions [387 388] The Cu+ 2 ions are reduced by Si to metallic Cu and Si is oxidized to Si The Cu deposit on the wafer surface i~ reshymoved by a polishing cloth while the oxidized Si dissolves as fluosilicate

Mechanical polishing without use of abrasive particles can be commiddot bined with liquid chemical etching by moving the semiconductor wafer with uniform pressure on a polishing cloth soaked with the etchantliquid This technique has been used for Ge [389] and GaAs [390 391]

Several reviews are available on semiconductor slicing lapping an polishing and the damage introduced by these operations [5 352-3H5 387 392-394)

2 Compound Semiconductors

Several reviews are available on etching of compound semiconductor [257101319-23 43a) a very recent survey [27a] was prepared in conshyjunction with this chapter to complement the tables in Section lVD We shall therefore only outline this section and present the details later 10

Tables VlIl-XIII

a Group IV Compound Semiconductors The only group IV compoulki semiconductor of technical importance is silicon carbide (SiC) Etchanl consist of molten alkalis or borax [395-397 j Cla-Oa at 900degC and aJxle [396 398J and H2 above I 600degC (399J (Table VIII) Electrolytic etching III HF solution is specific for p-type SiC [397 400]

b Group III-V Compound Semiconductors The single most impor tant compound semiconductor is single-crystal gallium arsenide (GaA~1 Etching reactions of this as well as other compound semiconductor 4f(

complicated because of crystallographic surface orientation elTet ~ Chemical etching of GaAs (and other III-V and II - V I compound lgtCml conductors) proceeds by oxidation-reduction-complexing reaction~ aJl4I ogous in principle to the general mechanism for Si and Ge etching

)

vmiddotI ClllMICtI II CIlI N( HI

The mot commonly employed etchanh for (jaA an Ih (HUII -404] NaOH-HOt 1405 4061 HSO-HO-HO 1 4()6-40H I ltlnd

NUOH -HOt-HtO 1404 4091 High-viscosity ctlthanh lich a HCI-HNo are prderred for chemical polishing 14101 Jet etching amlol ~Iice rotation on a polishing pad have been used with several ethallh flI polishing and thinning 123 266 390 391 404 411 412

Orientation-dependent etching charaderisti of HHO - IHO IHSO were utilized for etching hanneb of VltI(iou geometric fur Gunneffect logic circuits 14131 and for superlatlice stllictUI es deposited by molecular beam epitaxy 14141 Gallium anenidc douhle heltrostfucshyture lasers have been fabricated using a SllHHJthly acting sekctive elcllant (onsisting of CHOH-HPO-HO 14151 Several addiliunal etehal1h have been used for crystallographiltally preferential ehhing 14tU 40K 4OJ 416-41-1 Older but useful chemical solution clehanh 140~ 419 4241 arc also listed in Section IV Table IX It should abo he noted that very thin ( 100 A) carbon films are imperviolls to C0l11111011 hilallts for 111 V ompounds and can therefore be usd as eXldlenl PltLtlltru ddillilllll1 masks 14251

Etching of GaAs can abo be accomplished by e lect 1111 IiI leLillllljllCS 10 alkali solutions [426-4301 in HCI-Htlt) 1411 J Ill in IINO I014121

Vapor-pha~e etching of GaAs substrates in preparatiull fur pltax y III duJes H-HO-N at IOOOdegC [4331 and anhydrou~ HCI inl II As alllbi ~nt above 1170deg( [4341 Since this laller process is rilildl) dqHndlIt upon the purity of the Hel elchant AsCIl which is availabk at VtIY

purity is an attractive alternate etchanl 1434a J Redox solutions of suitable composition and pH lan dth (laA~ ic

lively with respelt to Ga AI As or vice versa 122 43511 he same ht hvior is displayed by GaP-InGaP and GaP-GaAIAs hclnlStnttlIIrs Other redox systems etch selectively with re~pect to the dupal1l type III these materials Aquous redox solutions that are stabk in bllth alld alld alkaline solutions includ 12- KI K3Fe(CN )~- KJ(CN)6 alld CijH () CUOt (quinone-hydroquinone) Redox tchants thai al stable uilly III

the acid pH range are FeCI3-FClz and C(SO)2-Cc( NO) Gallium phosphide can be solulion etched in the redllX S slms Just

noted and in the etchants listed in Tabk X 120402436--4461 Sevelal electrochemical etchants have also been included 1266 432 441 447

+1111 Etching characteristics of other 111-V compound seflllcunJul)Js tUI

~hich data have been Dublishd are Jj sted ill Section I V Tahle X II 402 418423449-4651

bull Other Compound StlflinHlductorl Etching chara~middottelltil f(li II -V compound semiconductors [162466-47111 arc Iisled in lahk XII Iho

4Y2 WLIlt-IR KIR 1) (Hlllt I I)U IltUI

for selected other compound and alloy semiconductc 479-5011 are

summarized in Section IV Tahle XIII

C Conductors

Conducting materials may conveniently he divided into two cateshygories elemental metal and alloy~ Many general reference for metal etching arc availahle IlL 14 15242529384244 51 I

Electrochemical etching procedure have heen devi ed for virtually every condultor known 129 5OJI The material to he ctched i made the anode of an electrochemical cell the etch rate and gturfale Illli h are detershymined by the cell vollage current den ity and cathode material a well as by the etching medium amI other factors inv(llved in lhemical processes The method of potential can for etching metal 158 I involve determining the potenllal range Itil oxidation using electnlchemical methods and then ubstitliling a chemical reagent of iuitable oxidizing

for the applied voltage In the semiconductor device industry the metal most often involved

in pattern delineation processes i AI and acconJmgly many etchants for AI have been reported 114 46 57 58 i04 5051

An assortment of etchanh i lvailable for other important ciemented

metals eu and Ni 11415 i06-S091 Au and Ag 114 1558 i10-5121 Pd and Pt 114 507~n 5141 Rh 15141 Cr Mo and W 14 li 51 507 515-5211 Pb and Sn [15295131 Nb and Ta 114 9 16 53 522~231 Ti Zr and Hf114 15295075241 Mn 1469 5131 Co ~91 and Fe 129 4691

Details of etching proceduregt for these and otha elemental rnetals arc listed in Section IV Table X I V etlhant- for evcral i lpllltant alloy- apshypear in Table XV

D Miscellaneous Materials

Included in this category arc mal ~rial which may be etched in various thin film proce-ses bul vhich do not one of the categories already dicued insulator semiconductor or conmiddot ductor

The majority of entris in Setion I V Table XV I arc oxides of various metals Theory and procedures for oxide film disslliution have been reshyviewed 15251 Iron oxides [526-52H I are a particularly important example as are the garnet materials 529-53 II generally mixed llxidegt of rare-earth elements

A few nonmetallil element have been included in the miscellaneous

Y I - J l

materials categot a few other materials of known inter lllogttly silicide or carbiults the list

IV TABLES OF ETCHANTS AND ETCHING CONDITIONS

A Guide to the Use of Tables

In this Seltion w have compiled and referenced specific etchan and conditions used for numerous technically important thin lilm mashy

terials and substrate The cry tallographil orientatiun and the type and concentration or electrical resistivity of semiconductor materials have been defined where critical The average etch rate or recommended

of etching is also noted if the information wagt available TYPical are indicated in the lat column

The composition llf concentrated aqueous reaglnls noted in the tables arl civen in the aecomnanvinc tabulation

RC1gcnt WI Rlt~lnl iii

HC 37 fLO HI- 4~ (Hlhydrllinel M

HSO iii NfIOIl 2~ la NHI H O XI NOIl lt)7Imin HCIO 7() KOI X larrrtlx) HNO 70 Na Z0 2 bodium plroxiJl) Ii CIU()()H I~

Addititlnal definitions arc

EDTA stands for cthylencdiaminetetraaletic acid Aqua regia conish of 3 parts hy voillme of IICI piligt 1 part by volshyume of HNO BHF stands fur buffered HF prepared hy mixing NHF HO and HF at appropriate ratios ie 6 vol NH4F (40(i1 pili I vol HF The abhreviati(ln Be stands for Baumc dlignation (If olution dlnshytty Reagent ratios cited arc on a volume basis unless llthlrWlse recitied All etching temperatures retCr to degrees centigrade and arl room temperature unless otherwise noted The liquid diluent is deionized andor distilled HO unless otherwise indilated

Gaseous reagents are pure concentrated gases unless otherwise noted The abbreviation seE stands for saturated calomel electrode

10

f

~I

4~ WERNER KERN AND CHERYL A DECKERI

n -type Si substrates is also possible with alkali solutions in which Ihe etch rates are strongly dependent on the electrode potentials [303 337 338]

Anodic oxidation of Si in electrolyte solutions based on organic mela 339] followed by oxide dissolution has been described for sectioning 10

the determination of Si diffusion profiles 340J Objects in contact with the Si surface can either slow down or enhance the local etch rate considermiddot ably [34l Substrate and etching conditions in the anodic dissolution of Si in aqueous HF can lead to brown layers etch pits and porous channel) 1269322328329331-333337342-344] caused by preferential etching and partial dissolution at localized sites (251 331-333] Single-cry~ta1 films of porous Sit formed purposely from n- and p-type Si by anodic reacmiddot tion in concentrated HF 1329 344-346] are very similar or identical to these brown channeled layers

Selective etching to dissolve Si of different dopant types and regtigttiishyties can also be achieved by chemical technique without use of external electrodes [263268304347-3581 exemplified by Fig II and the data presented in Table VI of Section IV

d Gas- and Vapor-Phase Etching Gas- and vapor-phase etching ale widely used for polishing of Si substrate wafers in situ prior to epitaxld crystal growth The most successful reagent is sulfur hexafluoride Sf It produces a smooth mirrorlike surface when reacted in a dilution vith HI at 950degC [359) or (more usually) above I050degC according to the overall reaction [360]

4 Si () + 2 SF (gl -+ SiS- (gt or l) + 3 SiFt (8)middot

1 ~ I==PRfFfHpJ

l o Ogt~ l u w

I I

--r

1 )( 10 11 )( 10 8 )( 109 )( 1020

BORON CONCENTRATION

i II Selective etching of ilicon Si (100) etch rate per minute vergtu boron cuocn tralion Etchnl ~ystem i KOH-HO-igtopropyl alcohol at sire (from Kuhn anJ Itlllaquo (341) reprinted by permi~ion of the publisher The Electrochemical Society Inc)

j

v I CHEMICAl ETCHING middotL~J

Since the free energy of the reaction is 706ll1 10lt11111lt)1 at 140W( [361] the etching proceeds spontdneoll~ly and irrevcllhly pludulting volatile sulfides and fluorides of 5i as the readioll PWdlllth 13hOI The etch rate as a function of temperature for O I~( SF i tWWII in and as a function of SF partial pressure in Fig 11 11021 The of SF6 over other reagents lie in the nonltorroivellc 1l0lllOXlcity and low temperature needed in Jdditiun to the cxcellent plulanly attainahle which makes the process applicable for waleI thtnllillg

Other vapor etchants used fur polishing Si arc IICI I IlJ nO HBI [365[ HI [3713721 CI 2 [373] H2S [1741 HI-HI In l7hl and 110 [3773781

In general gas- and vapor-phase eteillng is not depelllkill 011 the lel tivity level or type of the Si Condition call be elected Jlt the tI(J -tl etching system that -result in anisotropic etching of vamgtI cl ~ st1I plalles al difTerent rates this has been exploitcd lechnolnglcally III eiclivl taxy 1367309370] as noted in Section IV Table VII

Similar to Si (IIIJ-Ge can be pulih etlthed With anh~dlHts IICI IIImiddot H H5-H 3t01 Superior results arc (lbtlinahle with II -II() vapul t

JOOC which produces clean structurces surfaces 11XOI

TCMPEIA i Ufll 121gt lIN

~

1l1tv

u ~ shy

gt- (ii 1 J

Fig 12 1 IJ

FIg 12 Vdpnf ph(1~t l~khlllg uf ~lli(lW SI ~kh Jth lj 11 UlhllII ht1IjtllWl Ill

~i pr~ul~ of 10 1 dun (fl ~)m Stlnofl tl al 11621 ICpl Inkd h) prllllgtjull 01 lilt pubhhLI rh( EkIl)chcmicJI SOClt y Inc

fig J3 Vapor phase ehhing DI dl(on Sf chh rak Vel Ill) SFji plillJtI pi t111 C d IUt)O (

trum Sun I ul 1621 rcplllTl~d b~ perm1 01 the puhlhhc I he licduclicllllc StJt1(ly Inc)

430 WERNER KERN AND CHERYL A DECKERl

e Chemical-Mechanical Polishing Polishing by combined chemical and mechanical processes is usually the last step in preparing flat and specshyular wafers in silicon device manufacture The generally preferred techshynique is the silica-sol (Syton [381]) method [382 383] The medium conshysists of a colloidal suspension of silica gel in aqueous NaOH solution of controlled pH and is dispensed on the polishing pad of a rotating poligthing machine Silicon removal proceeds by oxidation of the surface by water in the presence of the alkali ions and continuous dissolution of the surface oxide aided by the silica gel which serves as a mild abrasive [383-31561 The process can also be used for polishing Ge wafers but H20 2 mu~t be added to the dispersion to achieve a smooth surface finish [3153]

Another process for 5i employs an aqueous solution containing copper and fluoride ions [387 388] The Cu+ 2 ions are reduced by Si to metallic Cu and Si is oxidized to Si The Cu deposit on the wafer surface i~ reshymoved by a polishing cloth while the oxidized Si dissolves as fluosilicate

Mechanical polishing without use of abrasive particles can be commiddot bined with liquid chemical etching by moving the semiconductor wafer with uniform pressure on a polishing cloth soaked with the etchantliquid This technique has been used for Ge [389] and GaAs [390 391]

Several reviews are available on semiconductor slicing lapping an polishing and the damage introduced by these operations [5 352-3H5 387 392-394)

2 Compound Semiconductors

Several reviews are available on etching of compound semiconductor [257101319-23 43a) a very recent survey [27a] was prepared in conshyjunction with this chapter to complement the tables in Section lVD We shall therefore only outline this section and present the details later 10

Tables VlIl-XIII

a Group IV Compound Semiconductors The only group IV compoulki semiconductor of technical importance is silicon carbide (SiC) Etchanl consist of molten alkalis or borax [395-397 j Cla-Oa at 900degC and aJxle [396 398J and H2 above I 600degC (399J (Table VIII) Electrolytic etching III HF solution is specific for p-type SiC [397 400]

b Group III-V Compound Semiconductors The single most impor tant compound semiconductor is single-crystal gallium arsenide (GaA~1 Etching reactions of this as well as other compound semiconductor 4f(

complicated because of crystallographic surface orientation elTet ~ Chemical etching of GaAs (and other III-V and II - V I compound lgtCml conductors) proceeds by oxidation-reduction-complexing reaction~ aJl4I ogous in principle to the general mechanism for Si and Ge etching

)

vmiddotI ClllMICtI II CIlI N( HI

The mot commonly employed etchanh for (jaA an Ih (HUII -404] NaOH-HOt 1405 4061 HSO-HO-HO 1 4()6-40H I ltlnd

NUOH -HOt-HtO 1404 4091 High-viscosity ctlthanh lich a HCI-HNo are prderred for chemical polishing 14101 Jet etching amlol ~Iice rotation on a polishing pad have been used with several ethallh flI polishing and thinning 123 266 390 391 404 411 412

Orientation-dependent etching charaderisti of HHO - IHO IHSO were utilized for etching hanneb of VltI(iou geometric fur Gunneffect logic circuits 14131 and for superlatlice stllictUI es deposited by molecular beam epitaxy 14141 Gallium anenidc douhle heltrostfucshyture lasers have been fabricated using a SllHHJthly acting sekctive elcllant (onsisting of CHOH-HPO-HO 14151 Several addiliunal etehal1h have been used for crystallographiltally preferential ehhing 14tU 40K 4OJ 416-41-1 Older but useful chemical solution clehanh 140~ 419 4241 arc also listed in Section IV Table IX It should abo he noted that very thin ( 100 A) carbon films are imperviolls to C0l11111011 hilallts for 111 V ompounds and can therefore be usd as eXldlenl PltLtlltru ddillilllll1 masks 14251

Etching of GaAs can abo be accomplished by e lect 1111 IiI leLillllljllCS 10 alkali solutions [426-4301 in HCI-Htlt) 1411 J Ill in IINO I014121

Vapor-pha~e etching of GaAs substrates in preparatiull fur pltax y III duJes H-HO-N at IOOOdegC [4331 and anhydrou~ HCI inl II As alllbi ~nt above 1170deg( [4341 Since this laller process is rilildl) dqHndlIt upon the purity of the Hel elchant AsCIl which is availabk at VtIY

purity is an attractive alternate etchanl 1434a J Redox solutions of suitable composition and pH lan dth (laA~ ic

lively with respelt to Ga AI As or vice versa 122 43511 he same ht hvior is displayed by GaP-InGaP and GaP-GaAIAs hclnlStnttlIIrs Other redox systems etch selectively with re~pect to the dupal1l type III these materials Aquous redox solutions that are stabk in bllth alld alld alkaline solutions includ 12- KI K3Fe(CN )~- KJ(CN)6 alld CijH () CUOt (quinone-hydroquinone) Redox tchants thai al stable uilly III

the acid pH range are FeCI3-FClz and C(SO)2-Cc( NO) Gallium phosphide can be solulion etched in the redllX S slms Just

noted and in the etchants listed in Tabk X 120402436--4461 Sevelal electrochemical etchants have also been included 1266 432 441 447

+1111 Etching characteristics of other 111-V compound seflllcunJul)Js tUI

~hich data have been Dublishd are Jj sted ill Section I V Tahle X II 402 418423449-4651

bull Other Compound StlflinHlductorl Etching chara~middottelltil f(li II -V compound semiconductors [162466-47111 arc Iisled in lahk XII Iho

4Y2 WLIlt-IR KIR 1) (Hlllt I I)U IltUI

for selected other compound and alloy semiconductc 479-5011 are

summarized in Section IV Tahle XIII

C Conductors

Conducting materials may conveniently he divided into two cateshygories elemental metal and alloy~ Many general reference for metal etching arc availahle IlL 14 15242529384244 51 I

Electrochemical etching procedure have heen devi ed for virtually every condultor known 129 5OJI The material to he ctched i made the anode of an electrochemical cell the etch rate and gturfale Illli h are detershymined by the cell vollage current den ity and cathode material a well as by the etching medium amI other factors inv(llved in lhemical processes The method of potential can for etching metal 158 I involve determining the potenllal range Itil oxidation using electnlchemical methods and then ubstitliling a chemical reagent of iuitable oxidizing

for the applied voltage In the semiconductor device industry the metal most often involved

in pattern delineation processes i AI and acconJmgly many etchants for AI have been reported 114 46 57 58 i04 5051

An assortment of etchanh i lvailable for other important ciemented

metals eu and Ni 11415 i06-S091 Au and Ag 114 1558 i10-5121 Pd and Pt 114 507~n 5141 Rh 15141 Cr Mo and W 14 li 51 507 515-5211 Pb and Sn [15295131 Nb and Ta 114 9 16 53 522~231 Ti Zr and Hf114 15295075241 Mn 1469 5131 Co ~91 and Fe 129 4691

Details of etching proceduregt for these and otha elemental rnetals arc listed in Section IV Table X I V etlhant- for evcral i lpllltant alloy- apshypear in Table XV

D Miscellaneous Materials

Included in this category arc mal ~rial which may be etched in various thin film proce-ses bul vhich do not one of the categories already dicued insulator semiconductor or conmiddot ductor

The majority of entris in Setion I V Table XV I arc oxides of various metals Theory and procedures for oxide film disslliution have been reshyviewed 15251 Iron oxides [526-52H I are a particularly important example as are the garnet materials 529-53 II generally mixed llxidegt of rare-earth elements

A few nonmetallil element have been included in the miscellaneous

Y I - J l

materials categot a few other materials of known inter lllogttly silicide or carbiults the list

IV TABLES OF ETCHANTS AND ETCHING CONDITIONS

A Guide to the Use of Tables

In this Seltion w have compiled and referenced specific etchan and conditions used for numerous technically important thin lilm mashy

terials and substrate The cry tallographil orientatiun and the type and concentration or electrical resistivity of semiconductor materials have been defined where critical The average etch rate or recommended

of etching is also noted if the information wagt available TYPical are indicated in the lat column

The composition llf concentrated aqueous reaglnls noted in the tables arl civen in the aecomnanvinc tabulation

RC1gcnt WI Rlt~lnl iii

HC 37 fLO HI- 4~ (Hlhydrllinel M

HSO iii NfIOIl 2~ la NHI H O XI NOIl lt)7Imin HCIO 7() KOI X larrrtlx) HNO 70 Na Z0 2 bodium plroxiJl) Ii CIU()()H I~

Addititlnal definitions arc

EDTA stands for cthylencdiaminetetraaletic acid Aqua regia conish of 3 parts hy voillme of IICI piligt 1 part by volshyume of HNO BHF stands fur buffered HF prepared hy mixing NHF HO and HF at appropriate ratios ie 6 vol NH4F (40(i1 pili I vol HF The abhreviati(ln Be stands for Baumc dlignation (If olution dlnshytty Reagent ratios cited arc on a volume basis unless llthlrWlse recitied All etching temperatures retCr to degrees centigrade and arl room temperature unless otherwise noted The liquid diluent is deionized andor distilled HO unless otherwise indilated

Gaseous reagents are pure concentrated gases unless otherwise noted The abbreviation seE stands for saturated calomel electrode

10

430 WERNER KERN AND CHERYL A DECKERl

e Chemical-Mechanical Polishing Polishing by combined chemical and mechanical processes is usually the last step in preparing flat and specshyular wafers in silicon device manufacture The generally preferred techshynique is the silica-sol (Syton [381]) method [382 383] The medium conshysists of a colloidal suspension of silica gel in aqueous NaOH solution of controlled pH and is dispensed on the polishing pad of a rotating poligthing machine Silicon removal proceeds by oxidation of the surface by water in the presence of the alkali ions and continuous dissolution of the surface oxide aided by the silica gel which serves as a mild abrasive [383-31561 The process can also be used for polishing Ge wafers but H20 2 mu~t be added to the dispersion to achieve a smooth surface finish [3153]

Another process for 5i employs an aqueous solution containing copper and fluoride ions [387 388] The Cu+ 2 ions are reduced by Si to metallic Cu and Si is oxidized to Si The Cu deposit on the wafer surface i~ reshymoved by a polishing cloth while the oxidized Si dissolves as fluosilicate

Mechanical polishing without use of abrasive particles can be commiddot bined with liquid chemical etching by moving the semiconductor wafer with uniform pressure on a polishing cloth soaked with the etchantliquid This technique has been used for Ge [389] and GaAs [390 391]

Several reviews are available on semiconductor slicing lapping an polishing and the damage introduced by these operations [5 352-3H5 387 392-394)

2 Compound Semiconductors

Several reviews are available on etching of compound semiconductor [257101319-23 43a) a very recent survey [27a] was prepared in conshyjunction with this chapter to complement the tables in Section lVD We shall therefore only outline this section and present the details later 10

Tables VlIl-XIII

a Group IV Compound Semiconductors The only group IV compoulki semiconductor of technical importance is silicon carbide (SiC) Etchanl consist of molten alkalis or borax [395-397 j Cla-Oa at 900degC and aJxle [396 398J and H2 above I 600degC (399J (Table VIII) Electrolytic etching III HF solution is specific for p-type SiC [397 400]

b Group III-V Compound Semiconductors The single most impor tant compound semiconductor is single-crystal gallium arsenide (GaA~1 Etching reactions of this as well as other compound semiconductor 4f(

complicated because of crystallographic surface orientation elTet ~ Chemical etching of GaAs (and other III-V and II - V I compound lgtCml conductors) proceeds by oxidation-reduction-complexing reaction~ aJl4I ogous in principle to the general mechanism for Si and Ge etching

)

vmiddotI ClllMICtI II CIlI N( HI

The mot commonly employed etchanh for (jaA an Ih (HUII -404] NaOH-HOt 1405 4061 HSO-HO-HO 1 4()6-40H I ltlnd

NUOH -HOt-HtO 1404 4091 High-viscosity ctlthanh lich a HCI-HNo are prderred for chemical polishing 14101 Jet etching amlol ~Iice rotation on a polishing pad have been used with several ethallh flI polishing and thinning 123 266 390 391 404 411 412

Orientation-dependent etching charaderisti of HHO - IHO IHSO were utilized for etching hanneb of VltI(iou geometric fur Gunneffect logic circuits 14131 and for superlatlice stllictUI es deposited by molecular beam epitaxy 14141 Gallium anenidc douhle heltrostfucshyture lasers have been fabricated using a SllHHJthly acting sekctive elcllant (onsisting of CHOH-HPO-HO 14151 Several addiliunal etehal1h have been used for crystallographiltally preferential ehhing 14tU 40K 4OJ 416-41-1 Older but useful chemical solution clehanh 140~ 419 4241 arc also listed in Section IV Table IX It should abo he noted that very thin ( 100 A) carbon films are imperviolls to C0l11111011 hilallts for 111 V ompounds and can therefore be usd as eXldlenl PltLtlltru ddillilllll1 masks 14251

Etching of GaAs can abo be accomplished by e lect 1111 IiI leLillllljllCS 10 alkali solutions [426-4301 in HCI-Htlt) 1411 J Ill in IINO I014121

Vapor-pha~e etching of GaAs substrates in preparatiull fur pltax y III duJes H-HO-N at IOOOdegC [4331 and anhydrou~ HCI inl II As alllbi ~nt above 1170deg( [4341 Since this laller process is rilildl) dqHndlIt upon the purity of the Hel elchant AsCIl which is availabk at VtIY

purity is an attractive alternate etchanl 1434a J Redox solutions of suitable composition and pH lan dth (laA~ ic

lively with respelt to Ga AI As or vice versa 122 43511 he same ht hvior is displayed by GaP-InGaP and GaP-GaAIAs hclnlStnttlIIrs Other redox systems etch selectively with re~pect to the dupal1l type III these materials Aquous redox solutions that are stabk in bllth alld alld alkaline solutions includ 12- KI K3Fe(CN )~- KJ(CN)6 alld CijH () CUOt (quinone-hydroquinone) Redox tchants thai al stable uilly III

the acid pH range are FeCI3-FClz and C(SO)2-Cc( NO) Gallium phosphide can be solulion etched in the redllX S slms Just

noted and in the etchants listed in Tabk X 120402436--4461 Sevelal electrochemical etchants have also been included 1266 432 441 447

+1111 Etching characteristics of other 111-V compound seflllcunJul)Js tUI

~hich data have been Dublishd are Jj sted ill Section I V Tahle X II 402 418423449-4651

bull Other Compound StlflinHlductorl Etching chara~middottelltil f(li II -V compound semiconductors [162466-47111 arc Iisled in lahk XII Iho

4Y2 WLIlt-IR KIR 1) (Hlllt I I)U IltUI

for selected other compound and alloy semiconductc 479-5011 are

summarized in Section IV Tahle XIII

C Conductors

Conducting materials may conveniently he divided into two cateshygories elemental metal and alloy~ Many general reference for metal etching arc availahle IlL 14 15242529384244 51 I

Electrochemical etching procedure have heen devi ed for virtually every condultor known 129 5OJI The material to he ctched i made the anode of an electrochemical cell the etch rate and gturfale Illli h are detershymined by the cell vollage current den ity and cathode material a well as by the etching medium amI other factors inv(llved in lhemical processes The method of potential can for etching metal 158 I involve determining the potenllal range Itil oxidation using electnlchemical methods and then ubstitliling a chemical reagent of iuitable oxidizing

for the applied voltage In the semiconductor device industry the metal most often involved

in pattern delineation processes i AI and acconJmgly many etchants for AI have been reported 114 46 57 58 i04 5051

An assortment of etchanh i lvailable for other important ciemented

metals eu and Ni 11415 i06-S091 Au and Ag 114 1558 i10-5121 Pd and Pt 114 507~n 5141 Rh 15141 Cr Mo and W 14 li 51 507 515-5211 Pb and Sn [15295131 Nb and Ta 114 9 16 53 522~231 Ti Zr and Hf114 15295075241 Mn 1469 5131 Co ~91 and Fe 129 4691

Details of etching proceduregt for these and otha elemental rnetals arc listed in Section IV Table X I V etlhant- for evcral i lpllltant alloy- apshypear in Table XV

D Miscellaneous Materials

Included in this category arc mal ~rial which may be etched in various thin film proce-ses bul vhich do not one of the categories already dicued insulator semiconductor or conmiddot ductor

The majority of entris in Setion I V Table XV I arc oxides of various metals Theory and procedures for oxide film disslliution have been reshyviewed 15251 Iron oxides [526-52H I are a particularly important example as are the garnet materials 529-53 II generally mixed llxidegt of rare-earth elements

A few nonmetallil element have been included in the miscellaneous

Y I - J l

materials categot a few other materials of known inter lllogttly silicide or carbiults the list

IV TABLES OF ETCHANTS AND ETCHING CONDITIONS

A Guide to the Use of Tables

In this Seltion w have compiled and referenced specific etchan and conditions used for numerous technically important thin lilm mashy

terials and substrate The cry tallographil orientatiun and the type and concentration or electrical resistivity of semiconductor materials have been defined where critical The average etch rate or recommended

of etching is also noted if the information wagt available TYPical are indicated in the lat column

The composition llf concentrated aqueous reaglnls noted in the tables arl civen in the aecomnanvinc tabulation

RC1gcnt WI Rlt~lnl iii

HC 37 fLO HI- 4~ (Hlhydrllinel M

HSO iii NfIOIl 2~ la NHI H O XI NOIl lt)7Imin HCIO 7() KOI X larrrtlx) HNO 70 Na Z0 2 bodium plroxiJl) Ii CIU()()H I~

Addititlnal definitions arc

EDTA stands for cthylencdiaminetetraaletic acid Aqua regia conish of 3 parts hy voillme of IICI piligt 1 part by volshyume of HNO BHF stands fur buffered HF prepared hy mixing NHF HO and HF at appropriate ratios ie 6 vol NH4F (40(i1 pili I vol HF The abhreviati(ln Be stands for Baumc dlignation (If olution dlnshytty Reagent ratios cited arc on a volume basis unless llthlrWlse recitied All etching temperatures retCr to degrees centigrade and arl room temperature unless otherwise noted The liquid diluent is deionized andor distilled HO unless otherwise indilated

Gaseous reagents are pure concentrated gases unless otherwise noted The abbreviation seE stands for saturated calomel electrode

10

4Y2 WLIlt-IR KIR 1) (Hlllt I I)U IltUI

for selected other compound and alloy semiconductc 479-5011 are

summarized in Section IV Tahle XIII

C Conductors

Conducting materials may conveniently he divided into two cateshygories elemental metal and alloy~ Many general reference for metal etching arc availahle IlL 14 15242529384244 51 I

Electrochemical etching procedure have heen devi ed for virtually every condultor known 129 5OJI The material to he ctched i made the anode of an electrochemical cell the etch rate and gturfale Illli h are detershymined by the cell vollage current den ity and cathode material a well as by the etching medium amI other factors inv(llved in lhemical processes The method of potential can for etching metal 158 I involve determining the potenllal range Itil oxidation using electnlchemical methods and then ubstitliling a chemical reagent of iuitable oxidizing

for the applied voltage In the semiconductor device industry the metal most often involved

in pattern delineation processes i AI and acconJmgly many etchants for AI have been reported 114 46 57 58 i04 5051

An assortment of etchanh i lvailable for other important ciemented

metals eu and Ni 11415 i06-S091 Au and Ag 114 1558 i10-5121 Pd and Pt 114 507~n 5141 Rh 15141 Cr Mo and W 14 li 51 507 515-5211 Pb and Sn [15295131 Nb and Ta 114 9 16 53 522~231 Ti Zr and Hf114 15295075241 Mn 1469 5131 Co ~91 and Fe 129 4691

Details of etching proceduregt for these and otha elemental rnetals arc listed in Section IV Table X I V etlhant- for evcral i lpllltant alloy- apshypear in Table XV

D Miscellaneous Materials

Included in this category arc mal ~rial which may be etched in various thin film proce-ses bul vhich do not one of the categories already dicued insulator semiconductor or conmiddot ductor

The majority of entris in Setion I V Table XV I arc oxides of various metals Theory and procedures for oxide film disslliution have been reshyviewed 15251 Iron oxides [526-52H I are a particularly important example as are the garnet materials 529-53 II generally mixed llxidegt of rare-earth elements

A few nonmetallil element have been included in the miscellaneous

Y I - J l

materials categot a few other materials of known inter lllogttly silicide or carbiults the list

IV TABLES OF ETCHANTS AND ETCHING CONDITIONS

A Guide to the Use of Tables

In this Seltion w have compiled and referenced specific etchan and conditions used for numerous technically important thin lilm mashy

terials and substrate The cry tallographil orientatiun and the type and concentration or electrical resistivity of semiconductor materials have been defined where critical The average etch rate or recommended

of etching is also noted if the information wagt available TYPical are indicated in the lat column

The composition llf concentrated aqueous reaglnls noted in the tables arl civen in the aecomnanvinc tabulation

RC1gcnt WI Rlt~lnl iii

HC 37 fLO HI- 4~ (Hlhydrllinel M

HSO iii NfIOIl 2~ la NHI H O XI NOIl lt)7Imin HCIO 7() KOI X larrrtlx) HNO 70 Na Z0 2 bodium plroxiJl) Ii CIU()()H I~

Addititlnal definitions arc

EDTA stands for cthylencdiaminetetraaletic acid Aqua regia conish of 3 parts hy voillme of IICI piligt 1 part by volshyume of HNO BHF stands fur buffered HF prepared hy mixing NHF HO and HF at appropriate ratios ie 6 vol NH4F (40(i1 pili I vol HF The abhreviati(ln Be stands for Baumc dlignation (If olution dlnshytty Reagent ratios cited arc on a volume basis unless llthlrWlse recitied All etching temperatures retCr to degrees centigrade and arl room temperature unless otherwise noted The liquid diluent is deionized andor distilled HO unless otherwise indilated

Gaseous reagents are pure concentrated gases unless otherwise noted The abbreviation seE stands for saturated calomel electrode

10

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C Elemental Semiconductors Table III

Isotropic Uquid Etching Si

No Etchant Substrate etching conditions Application etch rate remarks Refs

2

3 oc

-4

-f)

7

r

~

t -~

9

10

II

1~

HF HNO HO or CHCOOH

HF HNO HO or CHCOOH

HF HNO

(al 98 HNO 2 HF (b) 98 HNCl 2 HF (c) 98 HNO 2 HF (d) 91 HNCl 9 HF Ie) 84 HNCl 16 HF (f) 75 HNCl 25 HF (g) 66 HNCl 34 HF

900 ml HNO 95 ml HF 5 ml CHCOOH 14 g NaClO

I~HN() ~HF 3CHCOOH

UU PI nnM

IUUN() V) tHt- Y

One of the followmg (a) 5HNO 3HF 3CH3 COOB (hl 17 ml ethylene diamine

8 ml HO J g pyrocatechol (Ref JIll

74SHNO (65) 10SHF (4oq) KBCOOH (96J1 7SHCIO poq)

One of the follOWing

ta) 9S ml HNO (6SJ) 5 ml BF (4WY) 10 g NaNO

1 l1o tin 100 HNO(6SJ)40HO

6HF 14oq)

~4 50 ml HF 50 ml CHCOOH

200 mg KMnO (freshl

la) BF (in 4HO I HF I() ml HO 2 ml HF 43 g

~aF

108 ml HF and 350 g NHF per 1000 ml

( I II Si nmiddottype 2 flmiddotcm 25) bath stir ring sample in agitated Teflon basket

(I Ill (l0raquo (110) Si n-type 3 fl-cm Pt beaker 0-5() Pt-mesh sample basket agitation

(II) Si n-type 005-8 fl-cm p-type 12shy78 fl-cm stirring and sample rotation 3()

orlmin 45 rlmin 88 rlmin 88 rmin 88 rmin 88 rlmin 88 rmin

SI wafers 05 litermin CO bubble stream in illumin Teflon apI floatshymounted

IImiddot and HYpe Si planetary jel polishing apll wuh ~clprocall nozzle al

910 qmiddotclCfUft em 1 aIr

bull ~IVithr ~2t~mtht bull lnCr mtn)

bubbk gtHeam n lium Tellon appl wafer rotale II r mlO onoff 2 1

(100) SI 0~5-mm thICk wafers For bulk Ihlnning followed by (hl For final thinning

S power device wafers (pnp) elch for I() gtec

n and p-Iype Si except high cone B doped poly Si epi Si ( 00) nand p doped bulk Si (100) low doped pol Si epi Si (1001 nand [ doped bulk S 1100) 10 doped

1111) (100) ell Si n[ 2 10 1R

(III) Si nlype 2 I-em ~5

Soogie-ery stal Si nmiddottpe 0~-06 ncm pmiddotlype 04 l-cm [Iype ISOem

Ternary diagrams of isoetch rale conshytours and resultant geometry versus composition of etchants allows selecshytion of optimal cond for any app (see Figs 7-10)

Graphs of reaction rales versus I IT for several compositions En ranging from 4 to 20 kcalmol

General etching no difference in etch rates for nmiddot p- n-p-type

025 ILmmin 060 ILmlmin rotation effects 092 ILm mm

50 ILmmin best control with JO Immin good results using

-20 ILmlmin lt65 HF etchants 50 ILmlmin

For large-area wafer thinning to lt25 Im 15 Immin uniform plusmn25 Im indeshypendent of orienl or resistivity blemish-free

For polishinjl and Ihinnina n- and p-type Si nonpreferential smooth surfllce to bull 2Om IhickM -O~ mt

I-or mIImiddotCJil iIwalCf Ihtnnlnw J m

111-1~ -LmlmlO unform 10 lt03 Im

For wafer thooning to 2 Im - 25 Immin to -5 Im thickness 08 jmimin to 2 I-m thickness

For prcpassvation surface etching )700 Alo sec 18 MIlem HO nnse

For pallem etching with SiO mask

I-mmin smooth pallern edges 4 I-mmln nonlinear pallern edges 4 I-mmlO nonlinear pattern edges OS jm min smooth pattern edges 0( jm mm nonlinear pattern edges OSI-m min nonlInear pattern edges

For ep S elchlng -0 2 I-mJmin

For surface etchoog OJ() A min O4~ A moo ()7( A mm

For cp S etchmg 041 0)8 Almin 04lt 0)8 Almin 021 ()) Amm

[256 253 254]

[255J

1252]

[264)

[2661

bull 4 12bl

[263]

1267J

[268]

(269J

1258J

r~591

I( onllni~( J J

-F~~--~gtlth~middotmiddot

Table III (Continued)

No Etchant Substrate etching condition ApphcatlOn etch rate remarb Refs

13 15HNO 5CHCOOH 2HF Si For general etching [270] (planar etch)

14 110 ml CHCOOH 100 ml Si For general etching [9J HNO 50 ml HF 3 g I (iodine etch)

15 30HNO 20HF INaHPO Si For general etching produces superior [271] (2) surface finish

16 30HNOJ 25CHJ COOH 20HF Si For polishing [271] I NaHPO (2)

17 9HNOJ IHF (white etch) Si 15 sec For polishing [272] c 18 14CHCOOH 10HF 5HNOJ Si 05-3 min For pohshing [273]

19 5HNO 3HF 3CHCOOH Si 2-3 min For slow polishing (sfi(htly preferential [274] for crystal defects)

20 5HNO 3HF 3CHJ COOH (III) (100) Si 2-3 min For fast polishing 25 Immin (chemishy [274] O06Br (CP-4) cal polish No4)

21 10 ml HO (33) 37 g NHF Si For polishing I Lm14 min [275]

22 1000 ml HO 100 g NHF 2 ml HO

Si For pattern etching low degree of undershycutting of photoresist mask because of

[276] r

nearly neutral pH

23 95HNOJ 5HF Si wafer attached to Teflon holder ro- For wafer thinning [277 278] tating

24 9HNOIHF Si Jet techmque For wafer thinmng microscopy [261]

2 MOB 14lt I add NMO(l (4if I SI oal Mf~r Icomen Hppro KO For thonnon~ hce for electron mIcromiddot [279[ unlll nt) U r Culu un S Of)

bullbull d 11 III 1m u bull 7 bull 4

Table IV

hotrop Liquid Etchin Ge r~

Nl __ Etchant Substrate etching conditions Application etch rate remarks Refs

50 wt oc HF 50 wt oc HO

175 ml HO 0-4OC 1 25 ml

02 M KHPO containing 12 ml HPO per liter

5HO IHO

4 4HO IHF IHO (No2 etch superool etch I

(100) (110) (III) Ge n-type 3 fl-cm preetched solution used within 05shy4 hr 250

agitated 11(0) (III)

(110)

(III) 11(0) (201) Ge n-type high resismiddot tivity magnetIc stirrer Etchanl commiddot position yields 27-30i HO of pH 38

(111) Ge 26

110011111) Ge 1-3 mon

For general etching and polishing orishyentation dependent triaxial composishytion ver~us etch rate given

112 Immin 211Lmmin 393 Immin

For controlled fractional-Im removal etch rate m~enitive to concentration and orientatIon a( pH 38 002 Lmmin senSItive to pH (min at pH 4)

For general etching

For general etching slo to attack polshyished surfaces rna develop etch figures

[285]

[286]

[287[

[287288 289J

(eonrinued)

Table TV (Colftilfud)

No Etehan Suhsrate etching condition Application etch rate remark Refs ~-~---------~

5 100 ml HO no vol 1 8 g NaOH

Ge 70 Freshly prepared After I hr

For controlled etching 5 ummin 125 Imlmin

[290]

6 5HNO 3HF 3CHCOOH with 01)6 Br (CP4)

(100) (Ill) Ge 15 min for general etchshying 22 min for polishing

For general etching and polishing slightly preferential for crystal defects

[288291 292J

J

7

8

5HNO 3HF 3CHCOOH (CP4A CP-6 CP-8)

II ml CHCOOH with 30 mg I dissolved 10 ml HNO 5 ml HF (iodine etch AI

Ge 2l-70 2-3 min

(100) till) Ge 4 min

For slow polishing much slower than CP4 at 23deg

For general etching and polishing better than CP4 for (100) Ge

1288293]

(294]

9 INaOCI (10) IOHO

9HFIHNO

(100) (Ill) Ge 4040 min or as required for thinning

Ge jet technique

For general etching and thmning

For small-area thinning for electron mishycroscopy

[295]

[261] 0~-

II NaOCI HO Ge warm float specimen For thinning slices for electron microsshyscopy

[279]

t1 liT fig bull - bull bull bullbullU8 I117~--Tblltr V

i m~otopic Liquid ElchinR Si

No Etchant

KOH solutio

tal

IIgt I

Ie)

KOH (4 V)

6KOH t4 VI I isopropanol

6KOH 16V) I isopropanol

-

50 ml HO 15 g KOH IS ml isopropanol

100KOH 12 MI 25 isopropanol

4

~

KOH solutlOns hydrazlOe ta) KOB 13-501) Ihl 60 hydrazine 40BO

Hydrazine-HO equimolar

Substrate etching conditions

(100) epi Si n-type 001-10 nmiddotcm 6f

P doped - 15 x 10lem Si B doped lt 5 x 10lem Si

(100) epi Si 1100 bulk Si poly Si

(1001 Si 44-4SC

~ f)-ohm p-type

(100) Si 70-90 510 maked 110 10 mm unmasked

SI bu Ik crystaL 12ltf 11001 S

Application etch rate remarks Refs

For pallerning epi Si on sapphire conshy (305) rsiderably lower etch rates wilh p-type

Si 60 Asec

27 Asec diffusion controlled for -4 V KOH

35 Asec activation controlled for

5v KOH

For patterning epi Si on sapphire or (268) spinel B dopinggt5 x 10em lowers etch rate 09lmimin 11 Imlmin 07lmmin

For preparing planar recessed SI strucshy [313] tures - 10 Aisec

Forte~ tunzlOg and V Irooving solar cells I3IIlJ for V-groove etching Ino texturizingl for diffuse-reflectivity textunzing

For structural etching in presence of AI 1296J SiO 200 Imhr 11111 minimum 0 III maximum etch rale

(Contlnufd j

-~---~~-lt--

~--~---~~- bull ~f-~middotmiddot-1-middot

Table V (Continued I

No

6

EIhanl

Hydrazine-HO

7

(a) 65 hydraztne 35H0 (bl 80 hydrazine 20H0

17 ml ethylene damine 8 ml HO 3 g pyrocatechol

8 Tetramethylammonium hydroxmiddot ide or trimethylmiddot2middothydroxymiddot ethyl ammonlUm hydroxide (05 WI 1

9 4 M NHF-I M Cu(NOl

10 100 g KOH m 100 ml HO

II 6LI t ff HO 234 1 h KOH 11 wI ( iwpngtpanol

SutgtSlrale etching condtlOn

(1001 SI 3-5 nmiddotcmc I()() reflux

nmiddotp-types 0001-100 11middotcm reSISL N bubbling reflux 110 + =I (100) (110) (Ill)

SIO

(100) (l11l Si 80-90 (100) n Iype (100) p Type (Ill) n type Thermal SiO CVD SiO

n-type S 10-100 Omiddotcm 22

(100) (110) (Ill)

(110) Si SiO masked boiling

(110l moat etching

(III) tlOO) Si bulk

( dd wllh J bull P St a IUO dod 11 J bull P Stgt

Applicallon etch rate remarh Ref

For shaping Si bulk and films higher etch rate inlt 100gt direction than along ltIIIgt

[310J

16 -Lmmin V middotgroove patterns 07 -Lmmin Hatmiddotbottom patterns

For shaping of Si films [311J

50-Lmhr 30-Lmhr

3-Lmhr -200 Ahr suitahle as etch mask

For alkali-free SI etching 3600 Amin 2300 Amin

163 Amin 3 Amin suitable as etch mask 7 Amin suitable as etch mask

[312]

For very high resolution pallerning anmiddot isotropic displacement etching 0185 -Lmmin 01l 7 -L mmin 0012-Lmmin

[298]

For vertical deep etching of moats (110) Si 50 jJm6 min

in 1301]

For structural etching independent of reslSuvity 097 Immin 004 mlmn lhul no rgtf 8 dltgtfCdi

[304J

- f_Jrln( hrmlt uJ und ldIITltl (h(mi all(hiffK 51

No

~ff HF

Etchant

~ 5lt( HF

5 wt ff HF

4 IHF IHSObull 5H0 freshl mixed

Substrale etching condlllOns

Epi Si bulk Sic PI eath 150 m iem ~6

n-epi Si gtO~ llmiddotcm on n- bulk S lt0015 nmiddotem

pepi Si gt05 f)-em on nmiddotepi on n bulk Si lt0015 ii-em

(1111 (1001 Si np type PI gauze cath PI wire to n S 10 V 18-5 em scp darkne No gt3 )( 10jcm (001 Omiddotcm) N 3 x 10 - 2 1016cm 1001shy

0 nmiddotcmi --2 x 1016em 3 1gt03 O-cml lV gt5 10icm (gt3 11-cml

( II L ( 100) Si n- middottype 75-175 ILm thick best Ptmiddotmesh eath ~ PI wres to n Si I em sep darkne controlled rate of Si immeron fill L 00012 Omiddotcm 115 mAem 43 V 1l111000lSlcm 80mAm-5c (lIl)OOJ3ncm 70mAcm58 (100100035 nmiddotcm 12 mAlem 5 V (10010011 flmiddotcm 135mAcm63V

p bulk Si nmiddotep SL Ii 2 x JO6cm- PI cath 0 V agitatIOn n darkne needed ROmAcm a1220(lmA -em at 6

Application results remarks

Selective substrates diolve leaVIng thin cpi S films 105-20 ftm thick 10 cm) n dsolves leaving n cpi

n- dIssolves anodically n cpi is etched off chemically leaving p epi

Preferential etching and thinmng

complete dissolution partial dissolution decreases with N

forming brown porous struclure no etching di~solution increae~ with A cone

Polishing and thlnmng of n Sic thinning of nn leaving n-epl laye

optimum conditions for elective smooth thinning Wllhout fOrmlO1 brown film

Preferenllal etchIng of p Si 1haul for matlon of bro n film or rough surface

Refs

[329J

shy

[269]

130]

1311)

13331

I( ~mIlnJttu I

r c ~c ~~~~~ -J -

0 00006 yen r c -j 5 -gt E sect ~ t ~ - i

-gt ~

E j -gti )

1 -gtI rshy-gt ~6 ~ ~ c ~Z r

N c c - -gt - E - c r

-gt if ) c

1 e u E -gt ~ c c -5 C c

r r

9 j Q ~ i c

Q c ) c ~ a ~ lI 56w pound ~ ~ ~ ) ll-I

2 c c i c ~ 2$ c lt c -gtVI 5 I r -gt ~

r J ~ -gt

g c

+ + 2shy ~

rshyE

~ ~ ~(gt

o Q ~j~ z shy C3c u Ishy 5

J lt u i u

8c uu J 3 ~gt ~ It ~ or 0 ~ ~ - N

r N r- r- ~ r- =gt r- r r- ltgt r- =gt shy) =gt i2 5 5

or

c S t v S ~ r-- J

r-

s~mS 1~q ~IIJ IP13 WnlPW IIU q~13 bull

loq ~lnleJdw~1 lUq~13 J

qllq IPJ q=gt13 p

ple~lpu SIMJqlo sSlun Pl0) )lnleJdw1 lIulqgt13 o Q

jd r r J

IJH jOH I I I (j

I r (j

8 j 8 j jiI J

ONH ) iI I j p

1 ~ p I

19 l (j I I

(jJDH ~ (j I

(j r 1 1

11) IJH 1 i I if

(II Iqell 1J j 1iI I

UJjIII ~lnleJdW)1 lIuIIPl3 IIU ~IIU q)13 bull

101 IIJ q13 bull qihq uA ~IIU ql] J

PlePUI dSIIJ)ql0 slun GA) poqlW UOillSod~~

J

J

I

I

)

)

I

P I

I

p

lnq 0001 Inq 0001lt

lnq 0001lt

O~~-OOv

()O9-00

ewsld O~Z

OOOI-OOL

OOOI-()()L

Jlpoue 009 ewspld 00poundgt

UOlsn) 0001 lt

leUOSIJI)1 leuollxH

Jlqwolj~

JIUIPOUOyt

sno4dlOwy

sno4dJowy

snoqdJowy

snoqdJowy

sn04dlOwy sno4dJowy

snoljdJowy

0)9

OqN

OJH

N~9

HNrIS cNIS

NOrIS

S)Plxo-sY9

llegt111lll

(lully 1~)()t 1 OSH OdH JH8 JH Uodwjj Jnl)OJIS l1u)IW jueqJ)) J)q10 HON ldUU Jl) UO IlI1YpoW

UOIlipUOJ pue I1J 4Jl) SIUBIPI3 tUlJllBW10l

(Pi1UOJ ) I alqll1

C Elemental Semiconductors Table III

Isotropic Uquid Etching Si

No Etchant Substrate etching conditions Application etch rate remarks Refs

2

3 oc

-4

-f)

7

r

~

t -~

9

10

II

1~

HF HNO HO or CHCOOH

HF HNO HO or CHCOOH

HF HNO

(al 98 HNO 2 HF (b) 98 HNCl 2 HF (c) 98 HNO 2 HF (d) 91 HNCl 9 HF Ie) 84 HNCl 16 HF (f) 75 HNCl 25 HF (g) 66 HNCl 34 HF

900 ml HNO 95 ml HF 5 ml CHCOOH 14 g NaClO

I~HN() ~HF 3CHCOOH

UU PI nnM

IUUN() V) tHt- Y

One of the followmg (a) 5HNO 3HF 3CH3 COOB (hl 17 ml ethylene diamine

8 ml HO J g pyrocatechol (Ref JIll

74SHNO (65) 10SHF (4oq) KBCOOH (96J1 7SHCIO poq)

One of the follOWing

ta) 9S ml HNO (6SJ) 5 ml BF (4WY) 10 g NaNO

1 l1o tin 100 HNO(6SJ)40HO

6HF 14oq)

~4 50 ml HF 50 ml CHCOOH

200 mg KMnO (freshl

la) BF (in 4HO I HF I() ml HO 2 ml HF 43 g

~aF

108 ml HF and 350 g NHF per 1000 ml

( I II Si nmiddottype 2 flmiddotcm 25) bath stir ring sample in agitated Teflon basket

(I Ill (l0raquo (110) Si n-type 3 fl-cm Pt beaker 0-5() Pt-mesh sample basket agitation

(II) Si n-type 005-8 fl-cm p-type 12shy78 fl-cm stirring and sample rotation 3()

orlmin 45 rlmin 88 rlmin 88 rmin 88 rmin 88 rlmin 88 rmin

SI wafers 05 litermin CO bubble stream in illumin Teflon apI floatshymounted

IImiddot and HYpe Si planetary jel polishing apll wuh ~clprocall nozzle al

910 qmiddotclCfUft em 1 aIr

bull ~IVithr ~2t~mtht bull lnCr mtn)

bubbk gtHeam n lium Tellon appl wafer rotale II r mlO onoff 2 1

(100) SI 0~5-mm thICk wafers For bulk Ihlnning followed by (hl For final thinning

S power device wafers (pnp) elch for I() gtec

n and p-Iype Si except high cone B doped poly Si epi Si ( 00) nand p doped bulk Si (100) low doped pol Si epi Si (1001 nand [ doped bulk S 1100) 10 doped

1111) (100) ell Si n[ 2 10 1R

(III) Si nlype 2 I-em ~5

Soogie-ery stal Si nmiddottpe 0~-06 ncm pmiddotlype 04 l-cm [Iype ISOem

Ternary diagrams of isoetch rale conshytours and resultant geometry versus composition of etchants allows selecshytion of optimal cond for any app (see Figs 7-10)

Graphs of reaction rales versus I IT for several compositions En ranging from 4 to 20 kcalmol

General etching no difference in etch rates for nmiddot p- n-p-type

025 ILmmin 060 ILmlmin rotation effects 092 ILm mm

50 ILmmin best control with JO Immin good results using

-20 ILmlmin lt65 HF etchants 50 ILmlmin

For large-area wafer thinning to lt25 Im 15 Immin uniform plusmn25 Im indeshypendent of orienl or resistivity blemish-free

For polishinjl and Ihinnina n- and p-type Si nonpreferential smooth surfllce to bull 2Om IhickM -O~ mt

I-or mIImiddotCJil iIwalCf Ihtnnlnw J m

111-1~ -LmlmlO unform 10 lt03 Im

For wafer thooning to 2 Im - 25 Immin to -5 Im thickness 08 jmimin to 2 I-m thickness

For prcpassvation surface etching )700 Alo sec 18 MIlem HO nnse

For pallem etching with SiO mask

I-mmin smooth pallern edges 4 I-mmln nonlinear pallern edges 4 I-mmlO nonlinear pattern edges OS jm min smooth pattern edges 0( jm mm nonlinear pattern edges OSI-m min nonlInear pattern edges

For ep S elchlng -0 2 I-mJmin

For surface etchoog OJ() A min O4~ A moo ()7( A mm

For cp S etchmg 041 0)8 Almin 04lt 0)8 Almin 021 ()) Amm

[256 253 254]

[255J

1252]

[264)

[2661

bull 4 12bl

[263]

1267J

[268]

(269J

1258J

r~591

I( onllni~( J J

-F~~--~gtlth~middotmiddot

Table III (Continued)

No Etchant Substrate etching condition ApphcatlOn etch rate remarb Refs

13 15HNO 5CHCOOH 2HF Si For general etching [270] (planar etch)

14 110 ml CHCOOH 100 ml Si For general etching [9J HNO 50 ml HF 3 g I (iodine etch)

15 30HNO 20HF INaHPO Si For general etching produces superior [271] (2) surface finish

16 30HNOJ 25CHJ COOH 20HF Si For polishing [271] I NaHPO (2)

17 9HNOJ IHF (white etch) Si 15 sec For polishing [272] c 18 14CHCOOH 10HF 5HNOJ Si 05-3 min For pohshing [273]

19 5HNO 3HF 3CHCOOH Si 2-3 min For slow polishing (sfi(htly preferential [274] for crystal defects)

20 5HNO 3HF 3CHJ COOH (III) (100) Si 2-3 min For fast polishing 25 Immin (chemishy [274] O06Br (CP-4) cal polish No4)

21 10 ml HO (33) 37 g NHF Si For polishing I Lm14 min [275]

22 1000 ml HO 100 g NHF 2 ml HO

Si For pattern etching low degree of undershycutting of photoresist mask because of

[276] r

nearly neutral pH

23 95HNOJ 5HF Si wafer attached to Teflon holder ro- For wafer thinning [277 278] tating

24 9HNOIHF Si Jet techmque For wafer thinmng microscopy [261]

2 MOB 14lt I add NMO(l (4if I SI oal Mf~r Icomen Hppro KO For thonnon~ hce for electron mIcromiddot [279[ unlll nt) U r Culu un S Of)

bullbull d 11 III 1m u bull 7 bull 4

Table IV

hotrop Liquid Etchin Ge r~

Nl __ Etchant Substrate etching conditions Application etch rate remarks Refs

50 wt oc HF 50 wt oc HO

175 ml HO 0-4OC 1 25 ml

02 M KHPO containing 12 ml HPO per liter

5HO IHO

4 4HO IHF IHO (No2 etch superool etch I

(100) (110) (III) Ge n-type 3 fl-cm preetched solution used within 05shy4 hr 250

agitated 11(0) (III)

(110)

(III) 11(0) (201) Ge n-type high resismiddot tivity magnetIc stirrer Etchanl commiddot position yields 27-30i HO of pH 38

(111) Ge 26

110011111) Ge 1-3 mon

For general etching and polishing orishyentation dependent triaxial composishytion ver~us etch rate given

112 Immin 211Lmmin 393 Immin

For controlled fractional-Im removal etch rate m~enitive to concentration and orientatIon a( pH 38 002 Lmmin senSItive to pH (min at pH 4)

For general etching

For general etching slo to attack polshyished surfaces rna develop etch figures

[285]

[286]

[287[

[287288 289J

(eonrinued)

Table TV (Colftilfud)

No Etehan Suhsrate etching condition Application etch rate remark Refs ~-~---------~

5 100 ml HO no vol 1 8 g NaOH

Ge 70 Freshly prepared After I hr

For controlled etching 5 ummin 125 Imlmin

[290]

6 5HNO 3HF 3CHCOOH with 01)6 Br (CP4)

(100) (Ill) Ge 15 min for general etchshying 22 min for polishing

For general etching and polishing slightly preferential for crystal defects

[288291 292J

J

7

8

5HNO 3HF 3CHCOOH (CP4A CP-6 CP-8)

II ml CHCOOH with 30 mg I dissolved 10 ml HNO 5 ml HF (iodine etch AI

Ge 2l-70 2-3 min

(100) till) Ge 4 min

For slow polishing much slower than CP4 at 23deg

For general etching and polishing better than CP4 for (100) Ge

1288293]

(294]

9 INaOCI (10) IOHO

9HFIHNO

(100) (Ill) Ge 4040 min or as required for thinning

Ge jet technique

For general etching and thmning

For small-area thinning for electron mishycroscopy

[295]

[261] 0~-

II NaOCI HO Ge warm float specimen For thinning slices for electron microsshyscopy

[279]

t1 liT fig bull - bull bull bullbullU8 I117~--Tblltr V

i m~otopic Liquid ElchinR Si

No Etchant

KOH solutio

tal

IIgt I

Ie)

KOH (4 V)

6KOH t4 VI I isopropanol

6KOH 16V) I isopropanol

-

50 ml HO 15 g KOH IS ml isopropanol

100KOH 12 MI 25 isopropanol

4

~

KOH solutlOns hydrazlOe ta) KOB 13-501) Ihl 60 hydrazine 40BO

Hydrazine-HO equimolar

Substrate etching conditions

(100) epi Si n-type 001-10 nmiddotcm 6f

P doped - 15 x 10lem Si B doped lt 5 x 10lem Si

(100) epi Si 1100 bulk Si poly Si

(1001 Si 44-4SC

~ f)-ohm p-type

(100) Si 70-90 510 maked 110 10 mm unmasked

SI bu Ik crystaL 12ltf 11001 S

Application etch rate remarks Refs

For pallerning epi Si on sapphire conshy (305) rsiderably lower etch rates wilh p-type

Si 60 Asec

27 Asec diffusion controlled for -4 V KOH

35 Asec activation controlled for

5v KOH

For patterning epi Si on sapphire or (268) spinel B dopinggt5 x 10em lowers etch rate 09lmimin 11 Imlmin 07lmmin

For preparing planar recessed SI strucshy [313] tures - 10 Aisec

Forte~ tunzlOg and V Irooving solar cells I3IIlJ for V-groove etching Ino texturizingl for diffuse-reflectivity textunzing

For structural etching in presence of AI 1296J SiO 200 Imhr 11111 minimum 0 III maximum etch rale

(Contlnufd j

-~---~~-lt--

~--~---~~- bull ~f-~middotmiddot-1-middot

Table V (Continued I

No

6

EIhanl

Hydrazine-HO

7

(a) 65 hydraztne 35H0 (bl 80 hydrazine 20H0

17 ml ethylene damine 8 ml HO 3 g pyrocatechol

8 Tetramethylammonium hydroxmiddot ide or trimethylmiddot2middothydroxymiddot ethyl ammonlUm hydroxide (05 WI 1

9 4 M NHF-I M Cu(NOl

10 100 g KOH m 100 ml HO

II 6LI t ff HO 234 1 h KOH 11 wI ( iwpngtpanol

SutgtSlrale etching condtlOn

(1001 SI 3-5 nmiddotcmc I()() reflux

nmiddotp-types 0001-100 11middotcm reSISL N bubbling reflux 110 + =I (100) (110) (Ill)

SIO

(100) (l11l Si 80-90 (100) n Iype (100) p Type (Ill) n type Thermal SiO CVD SiO

n-type S 10-100 Omiddotcm 22

(100) (110) (Ill)

(110) Si SiO masked boiling

(110l moat etching

(III) tlOO) Si bulk

( dd wllh J bull P St a IUO dod 11 J bull P Stgt

Applicallon etch rate remarh Ref

For shaping Si bulk and films higher etch rate inlt 100gt direction than along ltIIIgt

[310J

16 -Lmmin V middotgroove patterns 07 -Lmmin Hatmiddotbottom patterns

For shaping of Si films [311J

50-Lmhr 30-Lmhr

3-Lmhr -200 Ahr suitahle as etch mask

For alkali-free SI etching 3600 Amin 2300 Amin

163 Amin 3 Amin suitable as etch mask 7 Amin suitable as etch mask

[312]

For very high resolution pallerning anmiddot isotropic displacement etching 0185 -Lmmin 01l 7 -L mmin 0012-Lmmin

[298]

For vertical deep etching of moats (110) Si 50 jJm6 min

in 1301]

For structural etching independent of reslSuvity 097 Immin 004 mlmn lhul no rgtf 8 dltgtfCdi

[304J

- f_Jrln( hrmlt uJ und ldIITltl (h(mi all(hiffK 51

No

~ff HF

Etchant

~ 5lt( HF

5 wt ff HF

4 IHF IHSObull 5H0 freshl mixed

Substrale etching condlllOns

Epi Si bulk Sic PI eath 150 m iem ~6

n-epi Si gtO~ llmiddotcm on n- bulk S lt0015 nmiddotem

pepi Si gt05 f)-em on nmiddotepi on n bulk Si lt0015 ii-em

(1111 (1001 Si np type PI gauze cath PI wire to n S 10 V 18-5 em scp darkne No gt3 )( 10jcm (001 Omiddotcm) N 3 x 10 - 2 1016cm 1001shy

0 nmiddotcmi --2 x 1016em 3 1gt03 O-cml lV gt5 10icm (gt3 11-cml

( II L ( 100) Si n- middottype 75-175 ILm thick best Ptmiddotmesh eath ~ PI wres to n Si I em sep darkne controlled rate of Si immeron fill L 00012 Omiddotcm 115 mAem 43 V 1l111000lSlcm 80mAm-5c (lIl)OOJ3ncm 70mAcm58 (100100035 nmiddotcm 12 mAlem 5 V (10010011 flmiddotcm 135mAcm63V

p bulk Si nmiddotep SL Ii 2 x JO6cm- PI cath 0 V agitatIOn n darkne needed ROmAcm a1220(lmA -em at 6

Application results remarks

Selective substrates diolve leaVIng thin cpi S films 105-20 ftm thick 10 cm) n dsolves leaving n cpi

n- dIssolves anodically n cpi is etched off chemically leaving p epi

Preferential etching and thinmng

complete dissolution partial dissolution decreases with N

forming brown porous struclure no etching di~solution increae~ with A cone

Polishing and thlnmng of n Sic thinning of nn leaving n-epl laye

optimum conditions for elective smooth thinning Wllhout fOrmlO1 brown film

Preferenllal etchIng of p Si 1haul for matlon of bro n film or rough surface

Refs

[329J

shy

[269]

130]

1311)

13331

I( ~mIlnJttu I

C Elemental Semiconductors Table III

Isotropic Uquid Etching Si

No Etchant Substrate etching conditions Application etch rate remarks Refs

2

3 oc

-4

-f)

7

r

~

t -~

9

10

II

1~

HF HNO HO or CHCOOH

HF HNO HO or CHCOOH

HF HNO

(al 98 HNO 2 HF (b) 98 HNCl 2 HF (c) 98 HNO 2 HF (d) 91 HNCl 9 HF Ie) 84 HNCl 16 HF (f) 75 HNCl 25 HF (g) 66 HNCl 34 HF

900 ml HNO 95 ml HF 5 ml CHCOOH 14 g NaClO

I~HN() ~HF 3CHCOOH

UU PI nnM

IUUN() V) tHt- Y

One of the followmg (a) 5HNO 3HF 3CH3 COOB (hl 17 ml ethylene diamine

8 ml HO J g pyrocatechol (Ref JIll

74SHNO (65) 10SHF (4oq) KBCOOH (96J1 7SHCIO poq)

One of the follOWing

ta) 9S ml HNO (6SJ) 5 ml BF (4WY) 10 g NaNO

1 l1o tin 100 HNO(6SJ)40HO

6HF 14oq)

~4 50 ml HF 50 ml CHCOOH

200 mg KMnO (freshl

la) BF (in 4HO I HF I() ml HO 2 ml HF 43 g

~aF

108 ml HF and 350 g NHF per 1000 ml

( I II Si nmiddottype 2 flmiddotcm 25) bath stir ring sample in agitated Teflon basket

(I Ill (l0raquo (110) Si n-type 3 fl-cm Pt beaker 0-5() Pt-mesh sample basket agitation

(II) Si n-type 005-8 fl-cm p-type 12shy78 fl-cm stirring and sample rotation 3()

orlmin 45 rlmin 88 rlmin 88 rmin 88 rmin 88 rlmin 88 rmin

SI wafers 05 litermin CO bubble stream in illumin Teflon apI floatshymounted

IImiddot and HYpe Si planetary jel polishing apll wuh ~clprocall nozzle al

910 qmiddotclCfUft em 1 aIr

bull ~IVithr ~2t~mtht bull lnCr mtn)

bubbk gtHeam n lium Tellon appl wafer rotale II r mlO onoff 2 1

(100) SI 0~5-mm thICk wafers For bulk Ihlnning followed by (hl For final thinning

S power device wafers (pnp) elch for I() gtec

n and p-Iype Si except high cone B doped poly Si epi Si ( 00) nand p doped bulk Si (100) low doped pol Si epi Si (1001 nand [ doped bulk S 1100) 10 doped

1111) (100) ell Si n[ 2 10 1R

(III) Si nlype 2 I-em ~5

Soogie-ery stal Si nmiddottpe 0~-06 ncm pmiddotlype 04 l-cm [Iype ISOem

Ternary diagrams of isoetch rale conshytours and resultant geometry versus composition of etchants allows selecshytion of optimal cond for any app (see Figs 7-10)

Graphs of reaction rales versus I IT for several compositions En ranging from 4 to 20 kcalmol

General etching no difference in etch rates for nmiddot p- n-p-type

025 ILmmin 060 ILmlmin rotation effects 092 ILm mm

50 ILmmin best control with JO Immin good results using

-20 ILmlmin lt65 HF etchants 50 ILmlmin

For large-area wafer thinning to lt25 Im 15 Immin uniform plusmn25 Im indeshypendent of orienl or resistivity blemish-free

For polishinjl and Ihinnina n- and p-type Si nonpreferential smooth surfllce to bull 2Om IhickM -O~ mt

I-or mIImiddotCJil iIwalCf Ihtnnlnw J m

111-1~ -LmlmlO unform 10 lt03 Im

For wafer thooning to 2 Im - 25 Immin to -5 Im thickness 08 jmimin to 2 I-m thickness

For prcpassvation surface etching )700 Alo sec 18 MIlem HO nnse

For pallem etching with SiO mask

I-mmin smooth pallern edges 4 I-mmln nonlinear pallern edges 4 I-mmlO nonlinear pattern edges OS jm min smooth pattern edges 0( jm mm nonlinear pattern edges OSI-m min nonlInear pattern edges

For ep S elchlng -0 2 I-mJmin

For surface etchoog OJ() A min O4~ A moo ()7( A mm

For cp S etchmg 041 0)8 Almin 04lt 0)8 Almin 021 ()) Amm

[256 253 254]

[255J

1252]

[264)

[2661

bull 4 12bl

[263]

1267J

[268]

(269J

1258J

r~591

I( onllni~( J J

-F~~--~gtlth~middotmiddot

Table III (Continued)

No Etchant Substrate etching condition ApphcatlOn etch rate remarb Refs

13 15HNO 5CHCOOH 2HF Si For general etching [270] (planar etch)

14 110 ml CHCOOH 100 ml Si For general etching [9J HNO 50 ml HF 3 g I (iodine etch)

15 30HNO 20HF INaHPO Si For general etching produces superior [271] (2) surface finish

16 30HNOJ 25CHJ COOH 20HF Si For polishing [271] I NaHPO (2)

17 9HNOJ IHF (white etch) Si 15 sec For polishing [272] c 18 14CHCOOH 10HF 5HNOJ Si 05-3 min For pohshing [273]

19 5HNO 3HF 3CHCOOH Si 2-3 min For slow polishing (sfi(htly preferential [274] for crystal defects)

20 5HNO 3HF 3CHJ COOH (III) (100) Si 2-3 min For fast polishing 25 Immin (chemishy [274] O06Br (CP-4) cal polish No4)

21 10 ml HO (33) 37 g NHF Si For polishing I Lm14 min [275]

22 1000 ml HO 100 g NHF 2 ml HO

Si For pattern etching low degree of undershycutting of photoresist mask because of

[276] r

nearly neutral pH

23 95HNOJ 5HF Si wafer attached to Teflon holder ro- For wafer thinning [277 278] tating

24 9HNOIHF Si Jet techmque For wafer thinmng microscopy [261]

2 MOB 14lt I add NMO(l (4if I SI oal Mf~r Icomen Hppro KO For thonnon~ hce for electron mIcromiddot [279[ unlll nt) U r Culu un S Of)

bullbull d 11 III 1m u bull 7 bull 4

Table IV

hotrop Liquid Etchin Ge r~

Nl __ Etchant Substrate etching conditions Application etch rate remarks Refs

50 wt oc HF 50 wt oc HO

175 ml HO 0-4OC 1 25 ml

02 M KHPO containing 12 ml HPO per liter

5HO IHO

4 4HO IHF IHO (No2 etch superool etch I

(100) (110) (III) Ge n-type 3 fl-cm preetched solution used within 05shy4 hr 250

agitated 11(0) (III)

(110)

(III) 11(0) (201) Ge n-type high resismiddot tivity magnetIc stirrer Etchanl commiddot position yields 27-30i HO of pH 38

(111) Ge 26

110011111) Ge 1-3 mon

For general etching and polishing orishyentation dependent triaxial composishytion ver~us etch rate given

112 Immin 211Lmmin 393 Immin

For controlled fractional-Im removal etch rate m~enitive to concentration and orientatIon a( pH 38 002 Lmmin senSItive to pH (min at pH 4)

For general etching

For general etching slo to attack polshyished surfaces rna develop etch figures

[285]

[286]

[287[

[287288 289J

(eonrinued)

Table TV (Colftilfud)

No Etehan Suhsrate etching condition Application etch rate remark Refs ~-~---------~

5 100 ml HO no vol 1 8 g NaOH

Ge 70 Freshly prepared After I hr

For controlled etching 5 ummin 125 Imlmin

[290]

6 5HNO 3HF 3CHCOOH with 01)6 Br (CP4)

(100) (Ill) Ge 15 min for general etchshying 22 min for polishing

For general etching and polishing slightly preferential for crystal defects

[288291 292J

J

7

8

5HNO 3HF 3CHCOOH (CP4A CP-6 CP-8)

II ml CHCOOH with 30 mg I dissolved 10 ml HNO 5 ml HF (iodine etch AI

Ge 2l-70 2-3 min

(100) till) Ge 4 min

For slow polishing much slower than CP4 at 23deg

For general etching and polishing better than CP4 for (100) Ge

1288293]

(294]

9 INaOCI (10) IOHO

9HFIHNO

(100) (Ill) Ge 4040 min or as required for thinning

Ge jet technique

For general etching and thmning

For small-area thinning for electron mishycroscopy

[295]

[261] 0~-

II NaOCI HO Ge warm float specimen For thinning slices for electron microsshyscopy

[279]

t1 liT fig bull - bull bull bullbullU8 I117~--Tblltr V

i m~otopic Liquid ElchinR Si

No Etchant

KOH solutio

tal

IIgt I

Ie)

KOH (4 V)

6KOH t4 VI I isopropanol

6KOH 16V) I isopropanol

-

50 ml HO 15 g KOH IS ml isopropanol

100KOH 12 MI 25 isopropanol

4

~

KOH solutlOns hydrazlOe ta) KOB 13-501) Ihl 60 hydrazine 40BO

Hydrazine-HO equimolar

Substrate etching conditions

(100) epi Si n-type 001-10 nmiddotcm 6f

P doped - 15 x 10lem Si B doped lt 5 x 10lem Si

(100) epi Si 1100 bulk Si poly Si

(1001 Si 44-4SC

~ f)-ohm p-type

(100) Si 70-90 510 maked 110 10 mm unmasked

SI bu Ik crystaL 12ltf 11001 S

Application etch rate remarks Refs

For pallerning epi Si on sapphire conshy (305) rsiderably lower etch rates wilh p-type

Si 60 Asec

27 Asec diffusion controlled for -4 V KOH

35 Asec activation controlled for

5v KOH

For patterning epi Si on sapphire or (268) spinel B dopinggt5 x 10em lowers etch rate 09lmimin 11 Imlmin 07lmmin

For preparing planar recessed SI strucshy [313] tures - 10 Aisec

Forte~ tunzlOg and V Irooving solar cells I3IIlJ for V-groove etching Ino texturizingl for diffuse-reflectivity textunzing

For structural etching in presence of AI 1296J SiO 200 Imhr 11111 minimum 0 III maximum etch rale

(Contlnufd j

-~---~~-lt--

~--~---~~- bull ~f-~middotmiddot-1-middot

Table V (Continued I

No

6

EIhanl

Hydrazine-HO

7

(a) 65 hydraztne 35H0 (bl 80 hydrazine 20H0

17 ml ethylene damine 8 ml HO 3 g pyrocatechol

8 Tetramethylammonium hydroxmiddot ide or trimethylmiddot2middothydroxymiddot ethyl ammonlUm hydroxide (05 WI 1

9 4 M NHF-I M Cu(NOl

10 100 g KOH m 100 ml HO

II 6LI t ff HO 234 1 h KOH 11 wI ( iwpngtpanol

SutgtSlrale etching condtlOn

(1001 SI 3-5 nmiddotcmc I()() reflux

nmiddotp-types 0001-100 11middotcm reSISL N bubbling reflux 110 + =I (100) (110) (Ill)

SIO

(100) (l11l Si 80-90 (100) n Iype (100) p Type (Ill) n type Thermal SiO CVD SiO

n-type S 10-100 Omiddotcm 22

(100) (110) (Ill)

(110) Si SiO masked boiling

(110l moat etching

(III) tlOO) Si bulk

( dd wllh J bull P St a IUO dod 11 J bull P Stgt

Applicallon etch rate remarh Ref

For shaping Si bulk and films higher etch rate inlt 100gt direction than along ltIIIgt

[310J

16 -Lmmin V middotgroove patterns 07 -Lmmin Hatmiddotbottom patterns

For shaping of Si films [311J

50-Lmhr 30-Lmhr

3-Lmhr -200 Ahr suitahle as etch mask

For alkali-free SI etching 3600 Amin 2300 Amin

163 Amin 3 Amin suitable as etch mask 7 Amin suitable as etch mask

[312]

For very high resolution pallerning anmiddot isotropic displacement etching 0185 -Lmmin 01l 7 -L mmin 0012-Lmmin

[298]

For vertical deep etching of moats (110) Si 50 jJm6 min

in 1301]

For structural etching independent of reslSuvity 097 Immin 004 mlmn lhul no rgtf 8 dltgtfCdi

[304J

- f_Jrln( hrmlt uJ und ldIITltl (h(mi all(hiffK 51

No

~ff HF

Etchant

~ 5lt( HF

5 wt ff HF

4 IHF IHSObull 5H0 freshl mixed

Substrale etching condlllOns

Epi Si bulk Sic PI eath 150 m iem ~6

n-epi Si gtO~ llmiddotcm on n- bulk S lt0015 nmiddotem

pepi Si gt05 f)-em on nmiddotepi on n bulk Si lt0015 ii-em

(1111 (1001 Si np type PI gauze cath PI wire to n S 10 V 18-5 em scp darkne No gt3 )( 10jcm (001 Omiddotcm) N 3 x 10 - 2 1016cm 1001shy

0 nmiddotcmi --2 x 1016em 3 1gt03 O-cml lV gt5 10icm (gt3 11-cml

( II L ( 100) Si n- middottype 75-175 ILm thick best Ptmiddotmesh eath ~ PI wres to n Si I em sep darkne controlled rate of Si immeron fill L 00012 Omiddotcm 115 mAem 43 V 1l111000lSlcm 80mAm-5c (lIl)OOJ3ncm 70mAcm58 (100100035 nmiddotcm 12 mAlem 5 V (10010011 flmiddotcm 135mAcm63V

p bulk Si nmiddotep SL Ii 2 x JO6cm- PI cath 0 V agitatIOn n darkne needed ROmAcm a1220(lmA -em at 6

Application results remarks

Selective substrates diolve leaVIng thin cpi S films 105-20 ftm thick 10 cm) n dsolves leaving n cpi

n- dIssolves anodically n cpi is etched off chemically leaving p epi

Preferential etching and thinmng

complete dissolution partial dissolution decreases with N

forming brown porous struclure no etching di~solution increae~ with A cone

Polishing and thlnmng of n Sic thinning of nn leaving n-epl laye

optimum conditions for elective smooth thinning Wllhout fOrmlO1 brown film

Preferenllal etchIng of p Si 1haul for matlon of bro n film or rough surface

Refs

[329J

shy

[269]

130]

1311)

13331

I( ~mIlnJttu I

Table III (Continued)

No Etchant Substrate etching condition ApphcatlOn etch rate remarb Refs

13 15HNO 5CHCOOH 2HF Si For general etching [270] (planar etch)

14 110 ml CHCOOH 100 ml Si For general etching [9J HNO 50 ml HF 3 g I (iodine etch)

15 30HNO 20HF INaHPO Si For general etching produces superior [271] (2) surface finish

16 30HNOJ 25CHJ COOH 20HF Si For polishing [271] I NaHPO (2)

17 9HNOJ IHF (white etch) Si 15 sec For polishing [272] c 18 14CHCOOH 10HF 5HNOJ Si 05-3 min For pohshing [273]

19 5HNO 3HF 3CHCOOH Si 2-3 min For slow polishing (sfi(htly preferential [274] for crystal defects)

20 5HNO 3HF 3CHJ COOH (III) (100) Si 2-3 min For fast polishing 25 Immin (chemishy [274] O06Br (CP-4) cal polish No4)

21 10 ml HO (33) 37 g NHF Si For polishing I Lm14 min [275]

22 1000 ml HO 100 g NHF 2 ml HO

Si For pattern etching low degree of undershycutting of photoresist mask because of

[276] r

nearly neutral pH

23 95HNOJ 5HF Si wafer attached to Teflon holder ro- For wafer thinning [277 278] tating

24 9HNOIHF Si Jet techmque For wafer thinmng microscopy [261]

2 MOB 14lt I add NMO(l (4if I SI oal Mf~r Icomen Hppro KO For thonnon~ hce for electron mIcromiddot [279[ unlll nt) U r Culu un S Of)

bullbull d 11 III 1m u bull 7 bull 4

Table IV

hotrop Liquid Etchin Ge r~

Nl __ Etchant Substrate etching conditions Application etch rate remarks Refs

50 wt oc HF 50 wt oc HO

175 ml HO 0-4OC 1 25 ml

02 M KHPO containing 12 ml HPO per liter

5HO IHO

4 4HO IHF IHO (No2 etch superool etch I

(100) (110) (III) Ge n-type 3 fl-cm preetched solution used within 05shy4 hr 250

agitated 11(0) (III)

(110)

(III) 11(0) (201) Ge n-type high resismiddot tivity magnetIc stirrer Etchanl commiddot position yields 27-30i HO of pH 38

(111) Ge 26

110011111) Ge 1-3 mon

For general etching and polishing orishyentation dependent triaxial composishytion ver~us etch rate given

112 Immin 211Lmmin 393 Immin

For controlled fractional-Im removal etch rate m~enitive to concentration and orientatIon a( pH 38 002 Lmmin senSItive to pH (min at pH 4)

For general etching

For general etching slo to attack polshyished surfaces rna develop etch figures

[285]

[286]

[287[

[287288 289J

(eonrinued)

Table TV (Colftilfud)

No Etehan Suhsrate etching condition Application etch rate remark Refs ~-~---------~

5 100 ml HO no vol 1 8 g NaOH

Ge 70 Freshly prepared After I hr

For controlled etching 5 ummin 125 Imlmin

[290]

6 5HNO 3HF 3CHCOOH with 01)6 Br (CP4)

(100) (Ill) Ge 15 min for general etchshying 22 min for polishing

For general etching and polishing slightly preferential for crystal defects

[288291 292J

J

7

8

5HNO 3HF 3CHCOOH (CP4A CP-6 CP-8)

II ml CHCOOH with 30 mg I dissolved 10 ml HNO 5 ml HF (iodine etch AI

Ge 2l-70 2-3 min

(100) till) Ge 4 min

For slow polishing much slower than CP4 at 23deg

For general etching and polishing better than CP4 for (100) Ge

1288293]

(294]

9 INaOCI (10) IOHO

9HFIHNO

(100) (Ill) Ge 4040 min or as required for thinning

Ge jet technique

For general etching and thmning

For small-area thinning for electron mishycroscopy

[295]

[261] 0~-

II NaOCI HO Ge warm float specimen For thinning slices for electron microsshyscopy

[279]

t1 liT fig bull - bull bull bullbullU8 I117~--Tblltr V

i m~otopic Liquid ElchinR Si

No Etchant

KOH solutio

tal

IIgt I

Ie)

KOH (4 V)

6KOH t4 VI I isopropanol

6KOH 16V) I isopropanol

-

50 ml HO 15 g KOH IS ml isopropanol

100KOH 12 MI 25 isopropanol

4

~

KOH solutlOns hydrazlOe ta) KOB 13-501) Ihl 60 hydrazine 40BO

Hydrazine-HO equimolar

Substrate etching conditions

(100) epi Si n-type 001-10 nmiddotcm 6f

P doped - 15 x 10lem Si B doped lt 5 x 10lem Si

(100) epi Si 1100 bulk Si poly Si

(1001 Si 44-4SC

~ f)-ohm p-type

(100) Si 70-90 510 maked 110 10 mm unmasked

SI bu Ik crystaL 12ltf 11001 S

Application etch rate remarks Refs

For pallerning epi Si on sapphire conshy (305) rsiderably lower etch rates wilh p-type

Si 60 Asec

27 Asec diffusion controlled for -4 V KOH

35 Asec activation controlled for

5v KOH

For patterning epi Si on sapphire or (268) spinel B dopinggt5 x 10em lowers etch rate 09lmimin 11 Imlmin 07lmmin

For preparing planar recessed SI strucshy [313] tures - 10 Aisec

Forte~ tunzlOg and V Irooving solar cells I3IIlJ for V-groove etching Ino texturizingl for diffuse-reflectivity textunzing

For structural etching in presence of AI 1296J SiO 200 Imhr 11111 minimum 0 III maximum etch rale

(Contlnufd j

-~---~~-lt--

~--~---~~- bull ~f-~middotmiddot-1-middot

Table V (Continued I

No

6

EIhanl

Hydrazine-HO

7

(a) 65 hydraztne 35H0 (bl 80 hydrazine 20H0

17 ml ethylene damine 8 ml HO 3 g pyrocatechol

8 Tetramethylammonium hydroxmiddot ide or trimethylmiddot2middothydroxymiddot ethyl ammonlUm hydroxide (05 WI 1

9 4 M NHF-I M Cu(NOl

10 100 g KOH m 100 ml HO

II 6LI t ff HO 234 1 h KOH 11 wI ( iwpngtpanol

SutgtSlrale etching condtlOn

(1001 SI 3-5 nmiddotcmc I()() reflux

nmiddotp-types 0001-100 11middotcm reSISL N bubbling reflux 110 + =I (100) (110) (Ill)

SIO

(100) (l11l Si 80-90 (100) n Iype (100) p Type (Ill) n type Thermal SiO CVD SiO

n-type S 10-100 Omiddotcm 22

(100) (110) (Ill)

(110) Si SiO masked boiling

(110l moat etching

(III) tlOO) Si bulk

( dd wllh J bull P St a IUO dod 11 J bull P Stgt

Applicallon etch rate remarh Ref

For shaping Si bulk and films higher etch rate inlt 100gt direction than along ltIIIgt

[310J

16 -Lmmin V middotgroove patterns 07 -Lmmin Hatmiddotbottom patterns

For shaping of Si films [311J

50-Lmhr 30-Lmhr

3-Lmhr -200 Ahr suitahle as etch mask

For alkali-free SI etching 3600 Amin 2300 Amin

163 Amin 3 Amin suitable as etch mask 7 Amin suitable as etch mask

[312]

For very high resolution pallerning anmiddot isotropic displacement etching 0185 -Lmmin 01l 7 -L mmin 0012-Lmmin

[298]

For vertical deep etching of moats (110) Si 50 jJm6 min

in 1301]

For structural etching independent of reslSuvity 097 Immin 004 mlmn lhul no rgtf 8 dltgtfCdi

[304J

- f_Jrln( hrmlt uJ und ldIITltl (h(mi all(hiffK 51

No

~ff HF

Etchant

~ 5lt( HF

5 wt ff HF

4 IHF IHSObull 5H0 freshl mixed

Substrale etching condlllOns

Epi Si bulk Sic PI eath 150 m iem ~6

n-epi Si gtO~ llmiddotcm on n- bulk S lt0015 nmiddotem

pepi Si gt05 f)-em on nmiddotepi on n bulk Si lt0015 ii-em

(1111 (1001 Si np type PI gauze cath PI wire to n S 10 V 18-5 em scp darkne No gt3 )( 10jcm (001 Omiddotcm) N 3 x 10 - 2 1016cm 1001shy

0 nmiddotcmi --2 x 1016em 3 1gt03 O-cml lV gt5 10icm (gt3 11-cml

( II L ( 100) Si n- middottype 75-175 ILm thick best Ptmiddotmesh eath ~ PI wres to n Si I em sep darkne controlled rate of Si immeron fill L 00012 Omiddotcm 115 mAem 43 V 1l111000lSlcm 80mAm-5c (lIl)OOJ3ncm 70mAcm58 (100100035 nmiddotcm 12 mAlem 5 V (10010011 flmiddotcm 135mAcm63V

p bulk Si nmiddotep SL Ii 2 x JO6cm- PI cath 0 V agitatIOn n darkne needed ROmAcm a1220(lmA -em at 6

Application results remarks

Selective substrates diolve leaVIng thin cpi S films 105-20 ftm thick 10 cm) n dsolves leaving n cpi

n- dIssolves anodically n cpi is etched off chemically leaving p epi

Preferential etching and thinmng

complete dissolution partial dissolution decreases with N

forming brown porous struclure no etching di~solution increae~ with A cone

Polishing and thlnmng of n Sic thinning of nn leaving n-epl laye

optimum conditions for elective smooth thinning Wllhout fOrmlO1 brown film

Preferenllal etchIng of p Si 1haul for matlon of bro n film or rough surface

Refs

[329J

shy

[269]

130]

1311)

13331

I( ~mIlnJttu I

Table TV (Colftilfud)

No Etehan Suhsrate etching condition Application etch rate remark Refs ~-~---------~

5 100 ml HO no vol 1 8 g NaOH

Ge 70 Freshly prepared After I hr

For controlled etching 5 ummin 125 Imlmin

[290]

6 5HNO 3HF 3CHCOOH with 01)6 Br (CP4)

(100) (Ill) Ge 15 min for general etchshying 22 min for polishing

For general etching and polishing slightly preferential for crystal defects

[288291 292J

J

7

8

5HNO 3HF 3CHCOOH (CP4A CP-6 CP-8)

II ml CHCOOH with 30 mg I dissolved 10 ml HNO 5 ml HF (iodine etch AI

Ge 2l-70 2-3 min

(100) till) Ge 4 min

For slow polishing much slower than CP4 at 23deg

For general etching and polishing better than CP4 for (100) Ge

1288293]

(294]

9 INaOCI (10) IOHO

9HFIHNO

(100) (Ill) Ge 4040 min or as required for thinning

Ge jet technique

For general etching and thmning

For small-area thinning for electron mishycroscopy

[295]

[261] 0~-

II NaOCI HO Ge warm float specimen For thinning slices for electron microsshyscopy

[279]

t1 liT fig bull - bull bull bullbullU8 I117~--Tblltr V

i m~otopic Liquid ElchinR Si

No Etchant

KOH solutio

tal

IIgt I

Ie)

KOH (4 V)

6KOH t4 VI I isopropanol

6KOH 16V) I isopropanol

-

50 ml HO 15 g KOH IS ml isopropanol

100KOH 12 MI 25 isopropanol

4

~

KOH solutlOns hydrazlOe ta) KOB 13-501) Ihl 60 hydrazine 40BO

Hydrazine-HO equimolar

Substrate etching conditions

(100) epi Si n-type 001-10 nmiddotcm 6f

P doped - 15 x 10lem Si B doped lt 5 x 10lem Si

(100) epi Si 1100 bulk Si poly Si

(1001 Si 44-4SC

~ f)-ohm p-type

(100) Si 70-90 510 maked 110 10 mm unmasked

SI bu Ik crystaL 12ltf 11001 S

Application etch rate remarks Refs

For pallerning epi Si on sapphire conshy (305) rsiderably lower etch rates wilh p-type

Si 60 Asec

27 Asec diffusion controlled for -4 V KOH

35 Asec activation controlled for

5v KOH

For patterning epi Si on sapphire or (268) spinel B dopinggt5 x 10em lowers etch rate 09lmimin 11 Imlmin 07lmmin

For preparing planar recessed SI strucshy [313] tures - 10 Aisec

Forte~ tunzlOg and V Irooving solar cells I3IIlJ for V-groove etching Ino texturizingl for diffuse-reflectivity textunzing

For structural etching in presence of AI 1296J SiO 200 Imhr 11111 minimum 0 III maximum etch rale

(Contlnufd j

-~---~~-lt--

~--~---~~- bull ~f-~middotmiddot-1-middot

Table V (Continued I

No

6

EIhanl

Hydrazine-HO

7

(a) 65 hydraztne 35H0 (bl 80 hydrazine 20H0

17 ml ethylene damine 8 ml HO 3 g pyrocatechol

8 Tetramethylammonium hydroxmiddot ide or trimethylmiddot2middothydroxymiddot ethyl ammonlUm hydroxide (05 WI 1

9 4 M NHF-I M Cu(NOl

10 100 g KOH m 100 ml HO

II 6LI t ff HO 234 1 h KOH 11 wI ( iwpngtpanol

SutgtSlrale etching condtlOn

(1001 SI 3-5 nmiddotcmc I()() reflux

nmiddotp-types 0001-100 11middotcm reSISL N bubbling reflux 110 + =I (100) (110) (Ill)

SIO

(100) (l11l Si 80-90 (100) n Iype (100) p Type (Ill) n type Thermal SiO CVD SiO

n-type S 10-100 Omiddotcm 22

(100) (110) (Ill)

(110) Si SiO masked boiling

(110l moat etching

(III) tlOO) Si bulk

( dd wllh J bull P St a IUO dod 11 J bull P Stgt

Applicallon etch rate remarh Ref

For shaping Si bulk and films higher etch rate inlt 100gt direction than along ltIIIgt

[310J

16 -Lmmin V middotgroove patterns 07 -Lmmin Hatmiddotbottom patterns

For shaping of Si films [311J

50-Lmhr 30-Lmhr

3-Lmhr -200 Ahr suitahle as etch mask

For alkali-free SI etching 3600 Amin 2300 Amin

163 Amin 3 Amin suitable as etch mask 7 Amin suitable as etch mask

[312]

For very high resolution pallerning anmiddot isotropic displacement etching 0185 -Lmmin 01l 7 -L mmin 0012-Lmmin

[298]

For vertical deep etching of moats (110) Si 50 jJm6 min

in 1301]

For structural etching independent of reslSuvity 097 Immin 004 mlmn lhul no rgtf 8 dltgtfCdi

[304J

- f_Jrln( hrmlt uJ und ldIITltl (h(mi all(hiffK 51

No

~ff HF

Etchant

~ 5lt( HF

5 wt ff HF

4 IHF IHSObull 5H0 freshl mixed

Substrale etching condlllOns

Epi Si bulk Sic PI eath 150 m iem ~6

n-epi Si gtO~ llmiddotcm on n- bulk S lt0015 nmiddotem

pepi Si gt05 f)-em on nmiddotepi on n bulk Si lt0015 ii-em

(1111 (1001 Si np type PI gauze cath PI wire to n S 10 V 18-5 em scp darkne No gt3 )( 10jcm (001 Omiddotcm) N 3 x 10 - 2 1016cm 1001shy

0 nmiddotcmi --2 x 1016em 3 1gt03 O-cml lV gt5 10icm (gt3 11-cml

( II L ( 100) Si n- middottype 75-175 ILm thick best Ptmiddotmesh eath ~ PI wres to n Si I em sep darkne controlled rate of Si immeron fill L 00012 Omiddotcm 115 mAem 43 V 1l111000lSlcm 80mAm-5c (lIl)OOJ3ncm 70mAcm58 (100100035 nmiddotcm 12 mAlem 5 V (10010011 flmiddotcm 135mAcm63V

p bulk Si nmiddotep SL Ii 2 x JO6cm- PI cath 0 V agitatIOn n darkne needed ROmAcm a1220(lmA -em at 6

Application results remarks

Selective substrates diolve leaVIng thin cpi S films 105-20 ftm thick 10 cm) n dsolves leaving n cpi

n- dIssolves anodically n cpi is etched off chemically leaving p epi

Preferential etching and thinmng

complete dissolution partial dissolution decreases with N

forming brown porous struclure no etching di~solution increae~ with A cone

Polishing and thlnmng of n Sic thinning of nn leaving n-epl laye

optimum conditions for elective smooth thinning Wllhout fOrmlO1 brown film

Preferenllal etchIng of p Si 1haul for matlon of bro n film or rough surface

Refs

[329J

shy

[269]

130]

1311)

13331

I( ~mIlnJttu I

Table V (Continued I

No

6

EIhanl

Hydrazine-HO

7

(a) 65 hydraztne 35H0 (bl 80 hydrazine 20H0

17 ml ethylene damine 8 ml HO 3 g pyrocatechol

8 Tetramethylammonium hydroxmiddot ide or trimethylmiddot2middothydroxymiddot ethyl ammonlUm hydroxide (05 WI 1

9 4 M NHF-I M Cu(NOl

10 100 g KOH m 100 ml HO

II 6LI t ff HO 234 1 h KOH 11 wI ( iwpngtpanol

SutgtSlrale etching condtlOn

(1001 SI 3-5 nmiddotcmc I()() reflux

nmiddotp-types 0001-100 11middotcm reSISL N bubbling reflux 110 + =I (100) (110) (Ill)

SIO

(100) (l11l Si 80-90 (100) n Iype (100) p Type (Ill) n type Thermal SiO CVD SiO

n-type S 10-100 Omiddotcm 22

(100) (110) (Ill)

(110) Si SiO masked boiling

(110l moat etching

(III) tlOO) Si bulk

( dd wllh J bull P St a IUO dod 11 J bull P Stgt

Applicallon etch rate remarh Ref

For shaping Si bulk and films higher etch rate inlt 100gt direction than along ltIIIgt

[310J

16 -Lmmin V middotgroove patterns 07 -Lmmin Hatmiddotbottom patterns

For shaping of Si films [311J

50-Lmhr 30-Lmhr

3-Lmhr -200 Ahr suitahle as etch mask

For alkali-free SI etching 3600 Amin 2300 Amin

163 Amin 3 Amin suitable as etch mask 7 Amin suitable as etch mask

[312]

For very high resolution pallerning anmiddot isotropic displacement etching 0185 -Lmmin 01l 7 -L mmin 0012-Lmmin

[298]

For vertical deep etching of moats (110) Si 50 jJm6 min

in 1301]

For structural etching independent of reslSuvity 097 Immin 004 mlmn lhul no rgtf 8 dltgtfCdi

[304J

- f_Jrln( hrmlt uJ und ldIITltl (h(mi all(hiffK 51

No

~ff HF

Etchant

~ 5lt( HF

5 wt ff HF

4 IHF IHSObull 5H0 freshl mixed

Substrale etching condlllOns

Epi Si bulk Sic PI eath 150 m iem ~6

n-epi Si gtO~ llmiddotcm on n- bulk S lt0015 nmiddotem

pepi Si gt05 f)-em on nmiddotepi on n bulk Si lt0015 ii-em

(1111 (1001 Si np type PI gauze cath PI wire to n S 10 V 18-5 em scp darkne No gt3 )( 10jcm (001 Omiddotcm) N 3 x 10 - 2 1016cm 1001shy

0 nmiddotcmi --2 x 1016em 3 1gt03 O-cml lV gt5 10icm (gt3 11-cml

( II L ( 100) Si n- middottype 75-175 ILm thick best Ptmiddotmesh eath ~ PI wres to n Si I em sep darkne controlled rate of Si immeron fill L 00012 Omiddotcm 115 mAem 43 V 1l111000lSlcm 80mAm-5c (lIl)OOJ3ncm 70mAcm58 (100100035 nmiddotcm 12 mAlem 5 V (10010011 flmiddotcm 135mAcm63V

p bulk Si nmiddotep SL Ii 2 x JO6cm- PI cath 0 V agitatIOn n darkne needed ROmAcm a1220(lmA -em at 6

Application results remarks

Selective substrates diolve leaVIng thin cpi S films 105-20 ftm thick 10 cm) n dsolves leaving n cpi

n- dIssolves anodically n cpi is etched off chemically leaving p epi

Preferential etching and thinmng

complete dissolution partial dissolution decreases with N

forming brown porous struclure no etching di~solution increae~ with A cone

Polishing and thlnmng of n Sic thinning of nn leaving n-epl laye

optimum conditions for elective smooth thinning Wllhout fOrmlO1 brown film

Preferenllal etchIng of p Si 1haul for matlon of bro n film or rough surface

Refs

[329J

shy

[269]

130]

1311)

13331

I( ~mIlnJttu I

Table VI (Contillu~d)

No Etchant Substrate etching conditions Application results remarks Refs

5 5 wI HF (25 N

6 5HF

7 Ethylene glycol with 004 N KNO 25 HO 1-2 gliler AI(NOh middot9H0

~

8 633 wt HO 234 wt KOH 133 wi isopropanol

9 KOH (4 NI

(III) (100) Si Pt-mesh cath 2 em sep 20 N bubbling darkness n 0001-001 n-em 65-150 mAcml

35-6 V p 001-1 U-cm 120-160 mAeml 4 V

(111) (1l0J(100) Sin-N gt 2 x 101 em conditions as In Ref 269 -130 rnAem 10 V Nogt 2 x 10

eml

lt130mAem ltIOVN gt 2 x 10 em3

-130 rnAem 10 V ND 2 x 10 em

n- and p-type Si illumination 2-ll rnAem 90-280 V 15 -20 wafer holder back of high resist Si metalmiddot hzed

No sIOdegem and N A S 3 x 10cm

(100) Si B doped no electrodes 80 (100) doped with B 10-10em (100) doped with B 10cm (100) doped with B lOWem

(100) epi Si on sapphire 60 11 type 0001-10 middotcm p Iyplt OOI-IOU-cm

Polishing and thinning n p Si

optimum polish thinning

optimum polish thinning

Polishing n S

bright finish results

brown layer forms

brown pitted surface resuhs

Analytical sectioning Anodization folshylowed by oxide stripping n- bull p Si

anodization 22 Av (linear) ndep of dopant type and resistivity

For selective electrodeless etching 099-095 Lmmin 063Lmmin oLmmin

For etching epi Si on sapphire IO Alsec IO An

(328)

(331)

[340J

o 1304J

1305J

10 8CHCOOH 3HNO IHF Slnglemiddotcrystal S 11 and p type doped For Itctlve e1ectrodele etching of nmiddot 1351 3~~J with As P Sb or B no electrodes and pmiddottype Si for resistivities lt001 O-cm 07 -3 Lmmln for resistivities gt0068 l-cm no etching occurs (same for SIN) for SiO films 005Lm min

II 33CHCOOH 26HNO JaF Poly Si undoped B doped (9JIr) For poly-Si etching (353)undopcd -1500 Amln -- B doped lt001 ll-cm 1000 Amin

12 KOH oluliom (1001 SI bulk crystal For anotropic etching a a function of (349J nand p type dopant type R ~ surface roughness

etch deplh (() 50 g KOH ]00 ml HO 85 0

50 ml CHOH P- 0018 norm 5 x 10 Bcm IOb Lmminj

pO 35 H-cm -3 x 10 Bem 138Lmmin R 004 n - 001 n-cm 4 x 10 Sbcm ]38 Lmmm n- 95 H-cm 5 10 Pcm 138Lmmin

(hi 50 g IltOH 100 ml 2middotpropashy 80 noL 50 ml CHOH p 080 L mminl R

P n- n I as in (a I 017104 Lmmin I (e) 50 g KOH ]00 ml Butyl 92ltgt

cellosolve 50 ml CHOH 116Lmmin~l 153 11m mIn a~ In (01 R ~ 014

n J 13~ Lm min n 160 Lm min

(d I H ydrazine n 110 Lm mIn

p 130 Lm minP 07a In to 1n- R - IOOLm min n 123 urn mm

Table VII

Gas and Vapor Phase Etchin Si Ge

No Etchant Substrate etching conditions Application etch rate remarh Refs

SF-H (Q006()Q2 vol SF)

2 SF-H 00--10- atm SF)

3 SF-H or He (I(-Io- atm SF)

-- 4 HCI-H 1 I 3-6 vol Hell

HCI-H (35-S4 mole HCIl

(111) Sip type 0004 30 O-cm B doped polished and BHF etched 950-1100 75-20 liter min- H 950C 00110 SF 75 liter mm H II000C 0(21 SFbull 10 litermin H

(111) Si poli5hed IO~O-I 100 quam tube reactor - 100 litermin H (-25 emsee linear velocityl

1050C 2 x HI atm SF 1050C 1 x 10- atm SF

II II) Si p-type 50 O-cm 75 cm-diameshyter tube reactor 1060-1100 linear velocity 100 emsec H He

1060 2 x 10- aIm SF 1060 I x 10- atm SF

1III) Si lapped or polished 1180-1275c

quar1z tube reaclor 127Y 2 HCI 12753 HCI 1275 56c HCI

EPI Sin-Iype quar1l lUbe reactor 1100shy1350 1125-1350 )5 mole c HCI 117~-I3~middot ~ mule h HCI

11m I bull bull shy HCI-H i 15-5 mole Hell

HCI-H 1lt HCIl

~ Hel 115-20 mole )

9 HBr-H lt1-6 mole HBn

I() HI-HF-He-H W5-2R gt

HI atm HI 10- HF Ror He 21V HI

111115bull chemlCall) polhed tuhe reac lOr 6 litermin H 1300 emmm hnear velocIty) 1150middot 1300 1280 14 mole c HCI 128030 mole Hel 12110 lt() mole HCI

1100111101 till) S IISOmiddot12()(Y

(III) Si 1200 (110) Si 1200 (100) Si 1200

100) Si n-Iype epi reactor 1050-1250 1050 20 mole lti- HCI

II()() 20 mole HCI 120020 mole c HCI 1250 20 mole lt( HCl

(III) 5 chemIcal polished tuhe reacwr ( Iller mm H l~()(l em minI 1050shy1300 126(1 20 mole lt( HBr 1260 )0 mole HBr 116050 mole lt( HBr

(III J 11001 S polished nand p-Iype hIgh and 10 resist 10 hler mm t 50 em ~e L 90(1 qUor17 tuhe reactor

12 10 - aIm HI I II atm HI

For in situ polishing pnor to epitaxy [359] smooth reflecting at 950-11ooC rough al 900C 0235 Imi min 0755 Immin

For wafer thinmng and in situ polishing [360]

prior to epitaxy smooth etching at 2 1050 preferential -middot850C SiO masks severely undercut 02 JLffimin 09 Immin

For in situ polishing prior to epitaxy [362J smooth etching at 100000C preferenshytial 1050 SiO attackedgt 1060 (see Figs 12 13) 02I-mmin 10I-mmin o

For polishing with good control [363J

L5l-mmln 30 Immin gO I-mmin

For etchmg in conjunction with epi Si (3M] from SiC~ 1l-mmin 23 Immin

bull bta- bull - 1bull _I

For polishing independent of resistivity 13M) and dopant type

I0l-mmln 2 61 mm 481 mm

For onenlallOn-dependent etching in dshy [367] electric isolation 148 Immin 3() Immin 34 Immin

For anisotropic etching in epitaxy 1370] 20 I-mmin strongly anisotropic

(100) 20 Immin 2ll-mmin 25I-mmin weakly aniltolropic (100)

For polishing superior to HCI no 6 inmiddot 1365] dependent of resislivlly and dopanl Iype only IToderate temp dependence 10 Immin 18 Immin 40 Immin

For lo-temperature polishing n() dlfmiddot (375 376J ference helween nHypes It hIgh reSIstlVll 11111 11()(11 o 12 Im mm smlxHh 040 Im mm stepped atm HI

ICllnUtd I

II

Table VII (ConJinlltd) ------~--------------------------------------

No Etchant

CI-He (02 Cl)

12 HS-H HO-H HCI-H

J3 HCI-H (15 HCI)

14 HI-H

15 H-HO

Substrate etching conditions

(Ill) Si low resist p-type polished quartz tube reactor 1000-1100

1000 1040 1100

(1IBSi polished horiz reactor 100hter min H 1=25 cmsecl 2 1100-1200 1200 HS ~5 x 10-3 atm 1200 HO 13 x Itr aim 1200 HCI 10 x Itr atm

(III) Ge no Po pO_type precleaned quanz tube reactor 820 --830

I 14 litermin HCI-H I 10 sec 122 litermin HCI-H 110 sec

(211) Ge p-type 001 I-em preetched with NaOCI soln 36 mm id quartz tube reactor 911deg I 140 cmmin linear velocity 700 emmin linear velocity

(11)(110) (1001 Gen-andp-type premiddot etched with I etch 25 and 5S-em id quartz tube reactors 90026 Torr HO partial pressure 4 litermin H-HO 30 mlO

Application etch rate remarks Refs

For rapid polishing smooth finish beshytween 1000-1100 and 1 CI Prefshyerential lt 1000 073 jLmmin 087 jLmmin 10 jLmmin

For gtery rapid polishing Faster and smoother than HO or HCI 151 jLmmin 0071 jLmmin 0183 jLmmin

For polish etching (Ill) Ge etch rate indep of temp gt800 mirror bright optically flat surface (100) Ge dev square pits 5 Im1I0 see

J3 jLm 110 sec

For polish etching (211) Ge temperature most critical for smoothness

23 mg5 min for 139 em 39 mg5 min for 139 em

For polish etching clean structureless surfaces large exeess H (but not Ar) impedes etch rate superior to H-HS under similar conditions

[373]

(374J

[379J

[371]

o [380]

m tim$[ III III 1Wlr TI III 1ISf If 1lfl IU I J 1 11_ f- shyD Compound Semiconductors

Table VIII

Group IV Compound SemlconducfOrs SiC

No Etchan

KOH or NaOH

N a0

4

NaOmiddot2BOmiddotIOHO (borax)

H

26 O-ot( CI in Ar

Substrate etching cltmditions

SiC fu~ion at gt600 900 for 2 min

SiC fusion between 350 and 900

500 900

SC fusion at I 000 for 2 mtn

Sc hexagonal horiz quartz lUbe furmiddot nace gas-phase 25 litermin (85

emsec linear velOCIty) 1600 1650

1700 1750

l-SiC crystal 900

Solution-grown crytah EpI crystals undored

Applications etch rate remarks Refs ~-------

General etching [395]

General etching rapid etching at the higher temshy [395] perature 01 mgcmmiddotmin J mgcm2~min

General etchtng excess borax removed with [395J NaOH soln

Preparing smooth SiC crystal surfaces nonprefmiddot [399J erential etch

Face A 0) jLmmin Face B 02 tmlmin 15tm mln 08 jLmmin

tm mIn 08 jLmmin 4 jLmmln 2 Jimmin

Patem etching imiddotSiC similar to a-SiC (I I I Iface smooth but with etch pits (III i 3J face no pHS thermal oxide etch mask 03-05 jLmmin 002 tmmiddotmlO

Table IX

Graul ffl-V Compound Semiconductors GaA

Substrate etching condtions Application eteh rate remarks Refs No Etchant

-------~~----------------------~-

Fast etching - 3 Immin [406J4HSObull IHD IHO (100) GaAs 50

Slow etching 02 Immin [406J2 I~H (I M) tHO(076M) (100) GaAs 30

(100) () Ii )GaAs Cr doped rotating Jet polishing nonpreferential -8 Immin [266]28r 98CHOH

slices jet nozzle smooth flat

(100) (1)) Ii jj)GaAs rotating slices Planar polishing nonpreferential -18 Imhr [404]4 700HO INHOH (295)

on polishing pad

POOl l1l)A 111)8 GaAs freely rotatmiddot Planar polishing nonpreferential - 25 Im3 hr [39O412J ()5 OHO INaOC ing sUees on polishing pad 0

GaAs 60 polishing pad Planar polishing - I IJm5 min [412]SA 3HSO IHO (33) IHO

III GaAs 013 fl-cm n-type High polishing 037 mgCrtr-mlO [410J6 8 glycerol lHC IHNO

lOO) GaAs epi Structural etching SiD mask 8 Immin lateral [410J7 8HO IHSO 1 H20 dis depends on mask alignment

99 WI 7r CHOH I wt7r Br IOI IIIB 0001 l1I)A GaA Preferential structural etching etch rate I 110) (403J8 II I)B I 001 gt IIIIIA

11bull rn 9 973HO 20NHOH 7HO (111)8 (100) ( I J)A G

Selecllv rmoval through SiO mash flat pro [4091files reduced underculling

(111)8 020 IJmmin(100) O1 2 IJmmin(l1I)A 0037 IJmmin

10 10 citric acid (50 wt aq sol) IIIlIB (100) (J lilA GaAs Preferential etching through photoresist masks [418JIHO ftat ~oltomed holes no attack of resist Etch rates (11118 (100) (1l1lA

II 3CHOH IHPO IHO [IIOJIIOO) Ga [IIIJ GaAs Preferential structural etching - 2 Immin exshy (415) cept Gar Ill] reduced twofold

12 1-20Br 99-80CHOH GaA~ (for solution or pad etching) Polishing [402412J J3 3HNO 2HO 1HF GaAs Rapid polish etching [419J

J 14 2HCl 2HO IH~OJ (111)GaAslOmin~ General etching of (i j j) plane [420J 1~ ~~aOH 15) IHO GaA 5 min Fast etching 1O-15IJmmin 1421J 16 8-12Aamp~O 117r) 5HNO] (1111 (IIi) GaA EtChing both till) and (j j i ) planes [419JIHF

17 75HO 20HSO SHO GaAs Polish etching 1423J 18 40HCI 4HO IHO GaAs jet etching 20 Thinning specimen for electron microscopy 14221

(Continued

Tampble IX (Colltillll~d)

No Etchant Substrate etching conditions Application etch rate remarks Refs

19 25HCI0bull 75CHCOOH GaAs electrolytic gently flowing from Thinning specimens for electron microscopy [424J an orifice above sample at 42 V

20 10--40 KOH or NaOH GaAs p type and heavily doped n type Electropolishing to mirror-smooth surfaces [428J

electrolytic 1-5 Acm

21 10 KOH (100) (110) (III) GaAs n type electroshy Anodic dissolution [426J

lytic flowing 10 KOH

22 3 M NaOH (100) GaAs p type spray electrolytic Selective removal of p-type substrate leaving [429J

100 mAcm n-type epi GaAs or GaAsP ~ 23 0025M NaOH-OOOI M EDTA (100) (III) Ga (1111 As GaAs n type Electropolishing (430J

electrolytic illumination

24 HCI-HO GaAs n type electrolytic Controlled thinning [431]

25 001-1 N HNO (100) GaAs n type electrolytic 10-20 Controlled electroetching [432]

mAcm 2-3 V

26 H AsH HC) (900 3 2 (100) (III) GaAs Te Zn Si Cr doped Substrate polishing prior to epitaxy 7-11 (434]

cmmin) vapor phase 9000 Lmmin nonpreferential specular 0 27 IOOCHOHIBr GaAs General etching 8 Lmhr

28 5HSObull IH0 GaAs Polishing 25 Lmhr

29 70HO 20HO 10 fonnic acd GaAs Surface cleanup

30 95CHOH 58r (100) GaAs n-type CVD SiO as etch Preferential etching of (32) Ga plane (416) mak

If r I j t 11 ~_ p bull mbull [ bullbullbull1middot ~~ rlIIJIUII _

Tampble X

Group I- Compound Semiconductors GaP

No Etchant Substrate etching conditions Application etch rate remarks Refs - 1-20 Br 99-80 CHOH GaP (solution

niques) or Pelion cloth techshy Generll etching and polishing (402J

2

4

6

R

9

1 Br 997r- CHOH

2HCI IHNO IHO

2HCI 2H0 I HNO

2HCI 2HO I HNO

Aqua rega

2HCI 2HSObull 2HO IHNO

3HSObull IHO (33(-) IHO

CHOH sal with Br I HPObull freshly mIXed

GaP

III) GaP hot

P (J II) GaP

(III) (ijj) (100) GaP 601-2 min

(ijj) GaP

P III GaP 5 min cold then 50 or 10 sec etching on Pelion cloth

GaP 60 5 min

(II J) GaP chem-mech technrque wafer rotates face down

Polishing highest-quality surface -025 Lmmin

Polishing III surface

Polishing P III surface

Polishing

Groove and pattern etching SiO mask

Polishing P III surface Ga III face pitting etch rate depends on Te carrier conc

Surface etching for saw damage removal I Lm5 min etches p-type preferentially

Work damage remoal prior to no 10 elch

120)

1438)

(439]

[442]

1441]

1440J

[443444)

14364311

10

II

5HSObull IHO IHO

Etchant no 9

( III) GaP 80 mrn

( III ) GaP 50

SunSlrale preparation for ep growth after no 9

and before no II etch 06 Lm mm optimal

Substrate final etch for epi growth Immediatel

after no 10 etch 15 Lmmin optimal

1431)

1437)

-------shy --------shy(ConlinUld I

- -~-~~ ~--~-~- - shy

Table X (Continued

No Etcnant Substrate etcnlng conditions Application etch rate remarklt Rdbull

11 10 M KFe(CN)-O) M KOH (1001 () II) GaP and p-type 60_95 Polishing and mesa etching SiO or Ti mask [445] sllrring

POll) -type 95deg 260 mhr polished Ga(llll Hype SO I J5 mnr smooth textured

P(lOO) -type SO 210 mihr polished

13 Cl-HO sat soln (III) (1001 GaP p epi on n substrate PoliShing -05 mmin [446J

14 HPO (iii) (1111 (1001 GaP 150-200C Groove etching Au mask V grooves result 1442)

15 IHfIHO GaP p type on n substrate Preferential etching of p-type GaP on n type (443) r ~ 16 7NaOCI (525 wt ) IHCI GaP n type on p substrate electrolytic Preferential etching of n-type [443) middottype anode PI cathode

17 16H0 2NaOCI 2HCI III) GaP plii h by chemicaliet etching Polishing lIat smooth surfaces [2(6) Ga(lll) by jet electroetching

18 Cl CHOH (concentration not Ga( III) PI Ill) GaP electrolytic jet Localized Ihinning of specimens for transmission [447)

specified) electron microscopy

n --~3 N NaOH GaO II) P( ii j) GaP 20 electrolytic PI Anodic dissolution and selective etching [448J

cathode

20 01 N HNo (ill) GaP mAlem

Hype electrolytic 20 Anodic dissolution 1250 300 sec (432J

21 2HNOIHCI GaP 1-2 min Polishing of some orientations (437aJ

~ 0 (HOHat soln GaP immer~e sample while (I bubnle Ihroullh 1 onln 20 mtn

Poli_hlnj 40~J

171 lJ r tlrt r r 111[ II NI1I 1 I 11111 bullbullbull 11 IFF HI II 1 illMil 111 4-Table XI

Other Group IIl-V Compound Semiconducfon

~=-terial No Etchant Conditions Application etch rate remarks Rerf ---~

AIN IO laOH or hot HPO 30-80 (NaOH) General etching (449]

BN ~ HPO or HO 0laquo1 Hot General etching of pyrolytic films (450 450a]

BP 3 10 NaOH Electrolytic in dark 01-10 Aem Electrochem etching pmiddottype etches (451J gt IOOx faster than nmiddott ype

J AISb 4 lal IHF IHO IHO I min (a) followed by 2 sec (h) Etching (l ii) face (452J _4

(h) IHC IHNO

Gal 5O7r NaOH L9O General etching [453J 6 01 NaOH Electrolytic jet etching Selective etching of singlemiddotcrystal (454]

vapor-transpon grown films

7 Hf() HOI Etches but develops etch figures (455J

GaSp 8 99-800f CHOH 1-2or Br General polishml [402J 9 9HNOIHF 1-) min General pollhing 402J

10 2HNQ IHF ICHCOOH I) sec Pollshmg develops pits on (I J J I face (452J II IHF lHNn IHO Etching I j j j 1 face 1457] 12 10 citric aCid ()O wI 7r I 1HO pmiddottype 5) photoresist masks Pallern etching (100) face 10 Asec 418J

_--__w-_~ _~_ -~--~ltf

J

Table XI (Continued)

Matenal No Etchant CondItion Application etch rate remarks Reh ~---------- --~-----~-~--~

InAs 13 Etchant no 1 Polishing (II J) and ell il faces (460]

14 5HNo 3HF 3CHCC)()H 006 Br General etching (458J (CP4)

15 75HNO UHF 15CHCOOH 006 Br 55 Etching d i lJ face etch pits on ( II) face [458J

16 HCI 75 General etdng 5 mgcm min 1457 459J

17 04 M Fe -WHCI General etching (452] v 0lt 18 996 ml CHCOOH 04 g Br General polishing 1423J

InP 19 99CHOH IBror9OCHOH IOBr General polishing 40246IJ

20 IHCIIHNO Etching (100) face hillocks on (l j h face [46IJ

inSb 21 I CHOH (concentration not specified) General polishing (402J

22 Etchant no 17 General etching [452]

23 IHF IHNO 2-5 sec Polishing (ii i) and (110) faces no etchshy [423465] 0

ing on (III) or (100) faces ltj

24 5HF 5HNO 2HO 20 sec Etching (100) and (110) faces [8]

25 5HNO bull 3HF 3CHCOOH (CP-4AI 5-30 sec General polishing [463464]

26 IHO ICHCOOH 1 CP4 1 min Etching ( i I) (i Ii) faces etc 1463)

27 2HF IHNO ICHCOOH 5-30 sec Polishing etch pits on (III) face [452J

2X 4HO IHF IHO 5-10 sec Etching (i jj) face [457)

2V Etchanl no 12 311 pholnrt mllk Pallem etchinjl 11001 race 60 Aec 1418)

n II 11 1IUIiI1r Ir PI IF IflTlE 71 bullbull bull bull bull -t

Table XII

Group II-VI Compound Semiconductors

Material No Etchant Conditions Application etch rate remarks Refs

10 KOH General etching 1162468) 2 HCI 120 General etching (467] 3 HPO-HSO boiling General etching at low rate [467468]

CdO 4 Mineral acids or NH salts General etching [4691

CdS 5 100 ml HO 1 mI HSO 008 g CrO 80 10 min Etching of [IOTO) face [471) J Jgt -c

6 16 N HSO-05 M KCrO 955-10 min General etching and polishing etch pits on (jj j) face

[472J

7 300 ml precip sihca 90 ml HNO 10 g AICIlner HO

Chem-mech pOlishing Poromenc disk 240 rlmin 370 gcm

Pohshing (0001) face [475]

8 70HO 30HCI Rotating on Pelion cloth Polishing Cd S and prismatic faces [473J 9 1000 ml HO 137 g KCl 05 ml Hel pH 25 Politegt Pix pad 58 rlmin

025-)40 kgem Polishing Cd face [476J

10 1000 mI HO 131 g KCI 16 ml HC) pH 10 same as no 9 Folishing S face 1476]

CdSe II 30HNO 20HSO IOCHCOOH 40 S sec General etChing thick films forming (472) OIHCI are soluble in HSO

CdTe 12 3HF2HOIHO Polistung (J III and (iii) faces etch 14711 pitgt on (ill) face

(Continued I

---_-_~_~~~IC-Ymiddot

Table XII (Continued)

Malenai --lt--ltshy

Nolt Etchanl Condition Application etch rale remark Reflt

13 2HNO 2HC lHO Polishing [477]

14

15

20 ml HO 10 ml HNO

995 CHOH 05Br

4g KCrO

Slnp deposil 45 min

formed wth Cs

Polishong 10 mirrorlike surface

General etching

[477J

[478]

CdTe 1005)-HgTe (095)

16 6HNOIHCI Rinse in IHCI-ICHOH Polishing 1479]

~

HgSe 17 50HNO 20HSO (18 N) IOCHCOOH IHCI

4010-15 min Polishing 1472]

HgTe 18 6HNO IHC IHO 10-15 min Polishing [472]

ZnO 19 Mineral acids solns

or alkali or NHCI General etching [469

ZnS 20 Elchant nolt 6 95deg 10 min Polishing to high polish etch pits on ( Ill) face

1472J

21 Elchant no 15 Same as nolt 15 General etching etch pits on (Ill)

face (478)

ZnTe 22

23

4HF3HNO

Etchant no 15

Stnpfilm formed with HCI then HO

Same as no 15

General etching and polishing 14721

1478)

p F II I bullbullbull jill bull M U bull bull bull TbW lUll

Orhrr Sritutd Compound gtrmlnmduc(on

Malerial No Elchant Condition Application etch rale remarks Refs

AgSe 5HSO lHO 50 ~ min rinse in EDTA solution then Polishing of some orientations 1479J H 20

2 2KOH sat) 2 ethylene glycol 80 2 min following damage removal Polishing 14791 IHO with etchant no I

Aile ~ 3iHOH2HO Remove film by brushing under water Polishing of some onentaions 1479]

BiSe 4 IHO tHCI Damaged layer following much polshy Polishing and removal of workshy 1470J ishing damaged layers

2HNOIHCI May be diluted with H20 Cleaning and etching 1470 481]

BIltTe 6 Etchant io 5 Cleaning and etching [470 481J

Hg fCdI1e 7 80CHOH20Br Rinse with CHOH Removal of surface 1482483]

InO Sn doped

8

I

HSO

HCI

50-60 Cr film etch mask Pattern etching -05 Amhr

Pattern etching

1484]

14851 10 10 M oxalic acid aqlt soln 50 Shiple~ AZ1350 etch mask Pattern etchmg of annealed films 1486]

InO Sno 14 ltII

II 5~S HI Immerse sample vertically Shipley AZ- 1350H mask postbaked 90 min

Precision pattern etching 25 Asec [4871

I~O

12 2HCI IHO Zn pder Paint Zn powder-HO slurr) on submiddot Rapid etchm~ 150 Asec 1487J trate Immerse hOrlZ IOto HCI-HO 0 mask as 10 nt I(I

In-Je I 19CHCOOH acidlt 1 Br

sat with citric FInish b~ ftooding with CHCOOH sat with cllnc aCid

Polishing 1488]

Inle ISr alh~ shy

14 4 clfn aCld ~uln

~H~() IHF at vlth Bi Polhinf 1488

-~~~-~~-- -----~-~--~

(ConllnUfd i

_~_F-lt--~-_-~__~

4

Table XIII iCollrillutd)

Material 0 Etchant ConditIons Applications etch rate remarks Refs

PbS 15 30HCI 10HNO ICHCOOH 50 few min CHCOOH

then rinse with 10 Polishing [489]

16 HNO 70 Rapid etching [489]

PbSe 17 5KOH (45) 5 ethylene glycol IHO

Electrolytic add HO during etching to maintain rate remove stains with 5()f

CHCOOH

Thinning specimens for electron transmission microscopy

[490]

18 Etchant no 17 403 min Polihino [480]

PbTe 19

20

45 ml HO 35 ml glycerol 20 ml CHOH 20 g KOH

Etchant no 19

Electrolytic 4-6 V 02 Aem

Electrolytic 10 V rinse in CHOH

Thinning specimens for electron transmission microscopy

Polishing

[493]

1492) (494)

~gtb_rSnrSe 21 10 ethylene glycol 10KOH (sat aq soln at 25deg) I HO

Felt covered etch ant

wheel saturated with Polishing [495) [496]

Pb_SnTe 22 Etchant no 19 Electrolytic 10 V rinse in CHOH Polishing [492) [494)

23 95HBr 5Sr 1-2 min rinse many times with CHOH followed with slight etching with no 22

Polishing faster than etchant no 22 [494)

sr 24 3-IOHOIHCI Electrolytic 5-40 mAcm Pattern mask

precision etching SiO used 1600 Almin at 20

[498J

mAcm

25 HCI Zn powder Zn powder in photoresist in Ref 500 Paltern etching 497499

500)

SnO Sb doped

26 HC Zn powder Pattern etchinB 150IJ

E Conductors

Table XI

Elemental Metal

Etch rate or Etching conditions etch time Remarks Refs

Aluminum

4HPO 4CHCOOH lHNO IHO 350 Amm Polishing etch contact to noble metals is possible withshyout increases in etch rate and undercutting

[57504J

2 75 NaCO 35 g NaPO12HO 16 g KFe(CN) bull 05 liter HO

1300 Amin Polishing etch contact to noble metals is possible withshyout increase in etch rate and undercutting

[57]

16-J9HPObull IHNO 0-4HO 40 stirring 1500-2500 Amin Gas evolution OCcurs [14J

4

5

IHCIO ICHCO~O

74IHPO 185HO 73HNO 500

3 mimin

9000 Amin

(29]

[46505]

6

7

8

9

1 HC 4HO 8ltr

2Ok NaOH 60-90

FeCI 12-36degBlt

IOHCI IHSO 9HO 49 25-50 mmm

For fine hne etchmg photoresist masks can be used

Photoresist mask can be used

[507 532J

114507)

[15513J

[15]

10 01 M KB0051 M KOH06M KFe(CNt pH 13tgt

Immm No H j eJlved 158]

II 1 Electngt Glo 100 (Electro Glo Co ChIcago) ~HPO bull 79 7-10 006 Acm PI cathode

ElectrOChemical polish excellent polishing occurs (533J

12 Olher eIlaquoIr(Khemlal etche 291

~( dnlttrlUJ j

~~---~~-~ - --~----~- -----~

- - _H-~~~~~_W __

Table XIV (Continued)

Elch ralr or Etchl ng conditIons etch time Remark Refs

~----

Antimony

Aqua regIa or hot HSO 1469J

2 5ltlt AgNO [5341

3 I g FeCI 3 ml HC 12 ml HO 1534J --~--- ---- shy

Aroenic --------------- --------- --------~

HNO 1469J

Beryllium 5 g HSObull 75 g HPO(98) 7 g crO 13 ml HO 49- JLmmin Passive film formed removable by immersion for 15- [29468)

50 30 sec in 10 HSO

2 HCI 1535J

1 H2SO preset voltage 30 V 2240 Almin Electrochemical etch [468J

4 1 KOH preset voltage 50 V 260 Amin Electrochemical etch [468] f

bull ~middot-ther electrochemical etches 129 536J

Bismuth

Hot HSO 469J

2 5ltlt AgNO [534J

3 lt49 ml sal KI soln I ml HCI 5-7 V 20 Adm stainmiddot Penltxh of 30 sec Electrochemical etch allo brown film formed 10 dismiddot 129] Ic IlrC or cKrhon cathode Ive een elchml period

bull bull bull - - bull I 1 -4 CadmIum

3 fuming HNO (type not specified) IHO

7CHCOOH 3 fuming HNO (type not specified)

I g I 3 g Kl 10 ml HO

olectrochemical etches and polishes

Periods 00-10 sec

30 sec-) min

Etchmg periods stream of H20

are followed by rinsing in a rapid 129)

[291

15341

[29 537 538J

ChromIUm

t 2

3

4

5

6

8

9

1 vol t 1 g NaOH 2 ml HOi 3 vo(J g K[Fe(CN) 3 mlf50IOOOAmin H20J

I g CeISOh2(NH)SOmiddot2HO 5 ml HNO 25 ml 85 Almin HO 28

1645 CeISO)2(NH)SO~H() 43 m HClO HO to make I Iller 25-50

2FeCI47BeIHCI80

HCI

454 g AICImiddot6HO 135 I ZnCl 30 ml HPObull 40() ml HO

9 sat Ce(SO soln IHNO

Dilute HCI or HNO

gt1500 Aimin

800 Amm

IHCIObull 2OCHCOOH4~-~OI-20A dm slammiddot cJ(l~er

Ie steel cathode

Does not require depassivation for etching Cr masks and vacuum-deposited Cr in general photoresist mask can be used

Oxide coating etches at 200 Amin

Recommended for precision patterning ofCr masks on glass substrates

Good for plated Cr photoresist mask can be used

Must depassivate with Zn rod

Photoresist mas~ can be used

Electnxhemlral polh

[14 15507 510J

[519J

1520J

[IS507J

[14516)

(14)

[14517)

[15507513 S17)

[29]

(ConlinLlfd

-- - - --

2

Table XlV (tontid)

Etch rate or Etchmg conditIo etch time Remarkgt Refs

Cobalt

I HC IcHOH 8-9 V 250 AdTn stainless steel 05-15 min Electrochemical polish bluish-green anodic film is sol- [29J uble in HO gIve polished surface WIth slight grain cathode boundary delineatIon

ElectrochemIcal pohsh sohd black film forms which is (29]HPO (98) - 15 V 1-2 Adm Co cathode 5-10 min removed by WIping WIth cotton wool

1539 540JOther electrochemical etc he

Copper ~---~~~-----

0 FeCI 42Be 49 50 Immin Use more dilute solution for slower etching 114 15 50s 509J

2 20-30 HSObull 10-20 crO or KCrO 49 37 Immin (14 15509]

1 g (NH)SO 3 ml HO 32-49 25 Immin Addition of 5 ppm Hg as HgCI activates etehant at [15513 lower temperatures 541-543J

4 5HNO 5CHCOOH 2HSO dilute with HO as Etches Cu and Cumiddotbased alloys at same rate as Ni and (506J

- desired

g KI I g 14 ml H2 0 dip into etch rinse remove

N i-based alloys

Rapid etch but undercutting is limited by formation of [14J

residue with Neutra-clean (Shipley Co Newton an insoluble Cu compound at line edges

Mas)

6 4HNO IIHPO (98) 5CHCOOH 6O-7if 1-2 min Polishing etch (29J

7 2HPOt98I IHO 15-2 V 6-8 Adm Cu cathode 15-30 mm Electrochemical polish [429544 545

()tmiddot~t clflru-hcml1 chhf I~l

fa RIP bull WI1 bull Til bull bull ~-~--~-~-------~-------------~-----~~------------~------

Gallium

Mineral acids or alkali solutions Must be processed below meltmg point (469J

Gold -----~~~~~---~~--~~-~--------~--------------~~------~--------------

)- 4 g KL I g I 40 ml HO 05-1 Immin Better contr~1 of line edges than in more concentnlled [141551 solution solution is opaque so removal from solu tion to observe end point is required

2 3HCL IHNO 32-38 25-50 Immin (IS]

NaCN HO HO mixtures (unspecified composition) [14 15J

4 05 g 12 g NHL 10 ml HO 15 ml cHOH 2if 700 Amin Converts the surface of an underlying Ag layer to the [5101 +shy

iodide thus preventing undercutting -- 04 M KFe(CN) 02 M KCN 01 M KOH 600 Amin Fresh solution must be used no atack on Pd is obshy [58]

served

6 tOO ml HO 05-10 ml HCL 10-JO g NaCl 4-5 V Electrochemical elch which retains bright surface only 1547] 65-2 Adm Mo cathode 20-40 small amount Cl evolved

7 Other electrOChemical etches 129548]

Hafnium

I-cltf HF

lt-6HCIO IOOCHCOOH 18 V Slamle steel cathmiddot ode U several SUCCegtlH dIps with continued agitation

5-10 sec dips

Negative photoreSIst can be ued as mask

ElectrochemICal pohsh -)

[14549J

[29J

See Zircomum etch fltl [291

CConHnurd

--- ---~- --~ -~-------- ~---~ -

Table X (Corllid

Etching condition~

Etch rate or etch lime Remarh Refs

Indium

Mineral acid [469J

IHNO 3CHOH 40-50 V 30 Adm stainless steel cathode cool bath

1-2 min Electrochemical polish [291

Iron

3HNO 7HCI 30H0 6O-7r 2-3 min Dense brown viscous layer forms on surface layer is soluble in solution

[29J

j CgtshyOlt

2

3

4

-I()o( KAI(SOl 12HO

3 liter 1O7c HNO 03 mhr 0 injected 3r

1 HCIO 2OCHCOOH 45-60 V 40-80 Adm stainmiddot less steel cathode

30 mmin

15-30 sec

Slowly soluble

Etches iron plate smoothly 0 removes passive film

Electrochemical polish solid film sometimes forms on the surface during washing removable with dil HF

[469J

[550J

[29J

5 Other electrochemical polishes _

[29J

Lead -----shy----------------------------------------------------------

FeC~ 36-42Be 43-54 [IS 513J -~

9FeCI 42Be IHCI 2rBe 43-49

I HtObull 4CHCOOH Periods 00-10 sec Alternate with immersion in a soln of 10 g molybdic acid and 140 ml NHOH in 240 ml HO to which 60 ml HNO is finally added

[ 15]

(29J

4

5

6

IHNO19HO

35HCIO 63(CHCO)0 20H0 lt3r 50-70 V 9-12 5-10 min A Idm Ph or Cu cathode

()the- k-tdmJ Pbullbulltw

ltlhtum

-------------------

Electrochemical polish

(534J

[291

1191 bull CHOH 30 sec Surface achIeves high luster and is smooth [551]

Magnesium

240-400 g FeCI 330 ml Hel HO to make I liter [469]

1-3HNO 17-19HO [507513 534]

3 fuming HNO type not specifiedl IHO wash imme Periods of 3 sec Reaction rcac Imot explosive violence after -I [29J diately after removal from solution min if allowed to continue it ceases after several

minutes leaving a polished surface

4 7HPO(987cL I3CHOH 1-2V05Admstainle 025 mmin Electrochemical pohsh there is considerable initial [29)

steel or cathode gassing shake anode to remove adhering bubbles

5 5 Other electrochemical etches [29J ~

Manganese

2

IHel IHO

Other dilute mineral acids

1513)

14691

Mercury

Sloght_ diluted HNO

Molybdenum

1469J

5HPO 3HNO 2HO Polishing elch contact to noble metals possible withmiddot OUI mcrcase in etch ratc and undercutling

[57J

IHSO IHNO 1-5H0 ~5-4 J~ 11m imin I~lt I ~ ftm min (~4

Photoresist mask can be used al 25 115507 518

(( OnltnUtJ I

- -~~~ ~ -- --~~-~middotltli0kmiddotmiddot-

Elching condtlons

Tb xrv (Co(Hu~d)

Elch fale or etch tme

Molybdenum (Continuedl

-------shy ~-~---------

Remarh Reh

o

4

6

7

20011 K[Fe(CN))2011 NaOH 3-35 g sodium oxalate add HO 10 make I liter

38HPO 15HNO 3OCHCOOH 75HO

IHSO 7CHOH 80-120 Adm stainless steel cathmiddot ode no agilation

100 ml HPO 20 ml HSObull 40 ml HO 025 II MoO 7(18 V 06-09 Acm slainless sleel graphite or PI cathode stlmng

Other etches

-ltmmin

05t m mrn

I min

94tmmm

Neplunium

Also usable as electrochem etch usinll stainless cathode al 6 V pholoresisl masks applicable

Photoresist mask can be used

Electrochenca polish

Electrochemical pohsh supenor surface finish

steel [14 1551 5075521

1518]

29]

1553

[29 38 57 554-5561

HCI 1557

5HNO 5CHCOOH 2HSObull HO as desired

IHNO IHCI 3HO

FeCI 42-49B 43-54

4

Igt

3HNO IHSO I HPO 198) 5CHCOOH 85-95

IHNO IHO or 9HPO IHNO or 9OHPO 15HNO 4HCL IHO

IOHSo OHO HPO lt-1 NISO JO ~ltr

Nickel

12 -25 tm min

05-1 min

1-2mmln

Etches Ni and Nimiddotbased alloys at same rale as Cu and (506)

Cumiddotbased alloys

Spray elching recommended 1507] o

Photoresist mask may be used [15507513)

Gives very llood polish 1291

Polishing elchants for eleclrol N-P very undercutllng despile conlacl to noble melah

hllie 1571

For ecclrole N film nu undCrcuttmJL mll r fMlfhnn uc-ful (Of ~ittrnl(H Cu

com I ~S8j

bull ~ 8

~7HSObull 4)H 1 U 0 ~ ALm

Other electrochemical polishegt 2 min mm1n lJellrtKht 1~lil1 rulnh

15~ 5601

129J

NiobIum

2 Lacue acid IHSO bull IHF 15~20 V PI cathode sIllmiddot 5-10 mm nng EleClrochemical polish

129]

7HF 7HNO 26HO 49 12-20 V 20~34 Adrn PI cathode Electrochemical etch 14(9) _

9HSO IHF H-45 50 V 2 Adrn PI Or carbon 5-10 min

cathode Electrochem etch temp nses during use cool bath [29]

~--~-----~----~----~----Osmium

Aqua regia 1557)

Palladium

IHCI 10HNO IOCHCOOH 1000 Aim

Aqua rega 15611

1513) Platinum

SHO 7HCI I HNO 85 400-500 AImln 2 f562 563)Aqua regIa precede etchin by 30 sec ImmersIOn in HF

EtCh tIme mlled because photoreSIst mask demiddot 114 507i strayed

3 M HCI 03-+ 14 V versus SeE modIfied Inangumiddot -1000 Almln lar waveform -600 Hz magneuc slmng Electrochem elch good resolu[lOn either po or neg 15141

photoreslS[ usable

Plutonium

I HPOI981 1 diethlene glvcol 5 V ltAdm lainmiddot L 10 mm less steel carhode Electrochemical pohsh

1291

(Conllnttf d

~--~~- - ~ -_ --__~ ~- h __ ~_

Table XIV (Cotiu~d) ~~------- ~---~----~~-~-~-----

Etch rate or Etchmg conditIOns tch time Remarks Ref

Polonium

Dilute mineral acid [557J

Potassium

CHOH or iCH)CHOH 3 sec (ethanoB or 10 SeC (Ioproshypanol)

Brilliant smooth surface obtained [551]

Praesiodymium

Mineral acid -~-~--~-~----------~~------ -------shy

Rhenium

[557]

Dilute HNO [557]

Rhodium

3 M HC -03- + 14 V versus SCE modified triangumiddot ElectTOchem etch I Im line spacings ofRh films over [514]

lar waveform -600 Hz magnetic stirring 5000 ATi on 5i dearly resolved

Ruthenium --------------------~----------------

Fused alkalis [557]

Samarium

Minual acids (557J

Sdenium

HStl ~( IM tf U undtf CkmCnl1 womtunduton 11 bull ~---~--~~-----

Silver

11 g Fe(NO) 9 ml HO 44-49 20 IJmmm Photoresist mask can be used [14 15 507J

2 5-9HNO1-5HO39-49 12-251Jmmin 11415517J

3 35 g AgCN 37 g KCN 38 g KCO 100 ml HO 25- 10 min Electrochem etch best polishing in region of voltage (29) 30 V 1 Alent Ag cathode 10 stirring and currel1t instability

4 3HNO 19H0 2 V [ainle steel cathode ElectrOChemical etch [507)

5 Kl-I etches listed for Cu and Ag O3-llJmsec Immersion followed by HO rinse [14]

60 Asec Useful for pattern etching with photoresist mask rinse [512] quickly after etching

6 4(HOH INHOH IHO

Sodium-

CHtCH)CHOH (nonyl alcohol) 30 sec Brilliant smooth surface [551)

Stronlium

Liquid ammonia [557]

Tanlalum

2

9NaOH or KOH 00laquo) IHO heal alka to 9(t Ihen add HO

5HSObull 2HNO 2HF

1-2HNO IHF 1-2H0

100(l-~OO(l A min

5-20 sec

4 9HSObull IHf (-4 50 cathgtd

A urn 11 1 carb -1(1 rnln

Metal (eg Au) rna muq be used very httle undermiddot cutting etche TO and Ta- al same rale 3 Ta

116~ 16~J

POlishing elch [29 522 5~~

HO rna) be omllled ftgtr fasler elch espeCially if film coniaim oxygen and reslsh etching fasler etch reshyduce re t al1a(~

(14 5 HI

Eletruchernlal etch temp of solUlion ne dunng ue and 11 rna he nece ar~ tp cool hath

129

- -~-~-=-

-4

2

Tabl Xf (Colltlllud)

Etch ratr or Etching condtion rtch time Remarks Refs

Tellurium

2HND3HO [513]

240 g (NH~So bring to I liter with HO [513J

Terbium

M ine 1 acid~ [557]

Thallium

to

HND or HSO

Thonum

------------~----

[557]

14CHCOOH 4HCIO IHO -1060 Adrn stain- 7-12 sec Electrochemical polish [29] less steel cathode

Tin

FeCI 36-42B 32-54 ~------~-

[15 513)

2 IHNO49CHOH [534] (

j iCIO lt35 5O-W V 40 Adrn AI cathode hold piece vertically and rotate at 50-100 r Imin

420 fLmmin Electrochemical polish on large sunaces orange peel effect may occur

(29]

4 Other electrochemical polishes [29]

Titanium

9H0 IHF 3gt 12 fLmmin Photorist mllsk may be used 114 15 507]

2 7Hli 21iNII IH~ n IImmln PhOI maoa m~ be uWd 114155071

bull - bull bull bull

tllO mllHOH 2U ml middotbutyl hoI t2 II Alll ~ II I-JeC1fochcml41 fKlhh 14m) zne 30-50 V 12 Adm ~Utinle Ied cathode

4 3HCIO 5OCHCOOH 200 30 V 30-40 Adm Ti 2 min E)ectrochem etch anode to cathode distance about 129] cathode 3 cm

5 Other electrochemical etches [29 564 5651

6 See Zirconium etch no [29]

Tungsten ~--~~-----~ -------~-------~----~---~~-----------------~~----~~-~--~~~-~---~--~--~------

34 g KHPO 134 g KOH 33 g KFeICN) HO to 1600 Amin Photoresist mask may be used high resolution (1- (515] make I liter 2 Lml can be achieved

2 5 KOH 5 KFe(CN) 1 sunaclant -2302 --23Lmmin Electrochem etch photoresist mask can be used good [51J Acm PI cathode pauem resolution

5-10 NaOH 6 V 3-6 Adm stainless steel cathode Electrochem etch rotation of anode or agitation of [29 513 566deg) - electrolyte with N is necessary

4 Other etches [5158515 555 567]

Uranium

1-2HClO 2OCHCOOH 5O-W v 5 Adrn stainless 19 fLmmill Electrochemical polish (29) steel cathode

2 Other electrochemical pohshe [29]

VanadIum __----------------___---------__-_

1-2HClO 18-19CHCOOH lt35 50-60 V 16-24 1-2 min Electrocherrucal polish a second polishing ofabout the f29] Adm stainless steel cathode sarne duration ill a fresh soln sometimes necessary

---~-~-----~----~--

Ytlcrbium -----~---------------~-----

lhneraJ aCid 1557j

fCwwj

II

Table VII (ConJinlltd) ------~--------------------------------------

No Etchant

CI-He (02 Cl)

12 HS-H HO-H HCI-H

J3 HCI-H (15 HCI)

14 HI-H

15 H-HO

Substrate etching conditions

(Ill) Si low resist p-type polished quartz tube reactor 1000-1100

1000 1040 1100

(1IBSi polished horiz reactor 100hter min H 1=25 cmsecl 2 1100-1200 1200 HS ~5 x 10-3 atm 1200 HO 13 x Itr aim 1200 HCI 10 x Itr atm

(III) Ge no Po pO_type precleaned quanz tube reactor 820 --830

I 14 litermin HCI-H I 10 sec 122 litermin HCI-H 110 sec

(211) Ge p-type 001 I-em preetched with NaOCI soln 36 mm id quartz tube reactor 911deg I 140 cmmin linear velocity 700 emmin linear velocity

(11)(110) (1001 Gen-andp-type premiddot etched with I etch 25 and 5S-em id quartz tube reactors 90026 Torr HO partial pressure 4 litermin H-HO 30 mlO

Application etch rate remarks Refs

For rapid polishing smooth finish beshytween 1000-1100 and 1 CI Prefshyerential lt 1000 073 jLmmin 087 jLmmin 10 jLmmin

For gtery rapid polishing Faster and smoother than HO or HCI 151 jLmmin 0071 jLmmin 0183 jLmmin

For polish etching (Ill) Ge etch rate indep of temp gt800 mirror bright optically flat surface (100) Ge dev square pits 5 Im1I0 see

J3 jLm 110 sec

For polish etching (211) Ge temperature most critical for smoothness

23 mg5 min for 139 em 39 mg5 min for 139 em

For polish etching clean structureless surfaces large exeess H (but not Ar) impedes etch rate superior to H-HS under similar conditions

[373]

(374J

[379J

[371]

o [380]

m tim$[ III III 1Wlr TI III 1ISf If 1lfl IU I J 1 11_ f- shyD Compound Semiconductors

Table VIII

Group IV Compound SemlconducfOrs SiC

No Etchan

KOH or NaOH

N a0

4

NaOmiddot2BOmiddotIOHO (borax)

H

26 O-ot( CI in Ar

Substrate etching cltmditions

SiC fu~ion at gt600 900 for 2 min

SiC fusion between 350 and 900

500 900

SC fusion at I 000 for 2 mtn

Sc hexagonal horiz quartz lUbe furmiddot nace gas-phase 25 litermin (85

emsec linear velOCIty) 1600 1650

1700 1750

l-SiC crystal 900

Solution-grown crytah EpI crystals undored

Applications etch rate remarks Refs ~-------

General etching [395]

General etching rapid etching at the higher temshy [395] perature 01 mgcmmiddotmin J mgcm2~min

General etchtng excess borax removed with [395J NaOH soln

Preparing smooth SiC crystal surfaces nonprefmiddot [399J erential etch

Face A 0) jLmmin Face B 02 tmlmin 15tm mln 08 jLmmin

tm mIn 08 jLmmin 4 jLmmln 2 Jimmin

Patem etching imiddotSiC similar to a-SiC (I I I Iface smooth but with etch pits (III i 3J face no pHS thermal oxide etch mask 03-05 jLmmin 002 tmmiddotmlO

Table IX

Graul ffl-V Compound Semiconductors GaA

Substrate etching condtions Application eteh rate remarks Refs No Etchant

-------~~----------------------~-

Fast etching - 3 Immin [406J4HSObull IHD IHO (100) GaAs 50

Slow etching 02 Immin [406J2 I~H (I M) tHO(076M) (100) GaAs 30

(100) () Ii )GaAs Cr doped rotating Jet polishing nonpreferential -8 Immin [266]28r 98CHOH

slices jet nozzle smooth flat

(100) (1)) Ii jj)GaAs rotating slices Planar polishing nonpreferential -18 Imhr [404]4 700HO INHOH (295)

on polishing pad

POOl l1l)A 111)8 GaAs freely rotatmiddot Planar polishing nonpreferential - 25 Im3 hr [39O412J ()5 OHO INaOC ing sUees on polishing pad 0

GaAs 60 polishing pad Planar polishing - I IJm5 min [412]SA 3HSO IHO (33) IHO

III GaAs 013 fl-cm n-type High polishing 037 mgCrtr-mlO [410J6 8 glycerol lHC IHNO

lOO) GaAs epi Structural etching SiD mask 8 Immin lateral [410J7 8HO IHSO 1 H20 dis depends on mask alignment

99 WI 7r CHOH I wt7r Br IOI IIIB 0001 l1I)A GaA Preferential structural etching etch rate I 110) (403J8 II I)B I 001 gt IIIIIA

11bull rn 9 973HO 20NHOH 7HO (111)8 (100) ( I J)A G

Selecllv rmoval through SiO mash flat pro [4091files reduced underculling

(111)8 020 IJmmin(100) O1 2 IJmmin(l1I)A 0037 IJmmin

10 10 citric acid (50 wt aq sol) IIIlIB (100) (J lilA GaAs Preferential etching through photoresist masks [418JIHO ftat ~oltomed holes no attack of resist Etch rates (11118 (100) (1l1lA

II 3CHOH IHPO IHO [IIOJIIOO) Ga [IIIJ GaAs Preferential structural etching - 2 Immin exshy (415) cept Gar Ill] reduced twofold

12 1-20Br 99-80CHOH GaA~ (for solution or pad etching) Polishing [402412J J3 3HNO 2HO 1HF GaAs Rapid polish etching [419J

J 14 2HCl 2HO IH~OJ (111)GaAslOmin~ General etching of (i j j) plane [420J 1~ ~~aOH 15) IHO GaA 5 min Fast etching 1O-15IJmmin 1421J 16 8-12Aamp~O 117r) 5HNO] (1111 (IIi) GaA EtChing both till) and (j j i ) planes [419JIHF

17 75HO 20HSO SHO GaAs Polish etching 1423J 18 40HCI 4HO IHO GaAs jet etching 20 Thinning specimen for electron microscopy 14221

(Continued

Tampble IX (Colltillll~d)

No Etchant Substrate etching conditions Application etch rate remarks Refs

19 25HCI0bull 75CHCOOH GaAs electrolytic gently flowing from Thinning specimens for electron microscopy [424J an orifice above sample at 42 V

20 10--40 KOH or NaOH GaAs p type and heavily doped n type Electropolishing to mirror-smooth surfaces [428J

electrolytic 1-5 Acm

21 10 KOH (100) (110) (III) GaAs n type electroshy Anodic dissolution [426J

lytic flowing 10 KOH

22 3 M NaOH (100) GaAs p type spray electrolytic Selective removal of p-type substrate leaving [429J

100 mAcm n-type epi GaAs or GaAsP ~ 23 0025M NaOH-OOOI M EDTA (100) (III) Ga (1111 As GaAs n type Electropolishing (430J

electrolytic illumination

24 HCI-HO GaAs n type electrolytic Controlled thinning [431]

25 001-1 N HNO (100) GaAs n type electrolytic 10-20 Controlled electroetching [432]

mAcm 2-3 V

26 H AsH HC) (900 3 2 (100) (III) GaAs Te Zn Si Cr doped Substrate polishing prior to epitaxy 7-11 (434]

cmmin) vapor phase 9000 Lmmin nonpreferential specular 0 27 IOOCHOHIBr GaAs General etching 8 Lmhr

28 5HSObull IH0 GaAs Polishing 25 Lmhr

29 70HO 20HO 10 fonnic acd GaAs Surface cleanup

30 95CHOH 58r (100) GaAs n-type CVD SiO as etch Preferential etching of (32) Ga plane (416) mak

If r I j t 11 ~_ p bull mbull [ bullbullbull1middot ~~ rlIIJIUII _

Tampble X

Group I- Compound Semiconductors GaP

No Etchant Substrate etching conditions Application etch rate remarks Refs - 1-20 Br 99-80 CHOH GaP (solution

niques) or Pelion cloth techshy Generll etching and polishing (402J

2

4

6

R

9

1 Br 997r- CHOH

2HCI IHNO IHO

2HCI 2H0 I HNO

2HCI 2HO I HNO

Aqua rega

2HCI 2HSObull 2HO IHNO

3HSObull IHO (33(-) IHO

CHOH sal with Br I HPObull freshly mIXed

GaP

III) GaP hot

P (J II) GaP

(III) (ijj) (100) GaP 601-2 min

(ijj) GaP

P III GaP 5 min cold then 50 or 10 sec etching on Pelion cloth

GaP 60 5 min

(II J) GaP chem-mech technrque wafer rotates face down

Polishing highest-quality surface -025 Lmmin

Polishing III surface

Polishing P III surface

Polishing

Groove and pattern etching SiO mask

Polishing P III surface Ga III face pitting etch rate depends on Te carrier conc

Surface etching for saw damage removal I Lm5 min etches p-type preferentially

Work damage remoal prior to no 10 elch

120)

1438)

(439]

[442]

1441]

1440J

[443444)

14364311

10

II

5HSObull IHO IHO

Etchant no 9

( III) GaP 80 mrn

( III ) GaP 50

SunSlrale preparation for ep growth after no 9

and before no II etch 06 Lm mm optimal

Substrate final etch for epi growth Immediatel

after no 10 etch 15 Lmmin optimal

1431)

1437)

-------shy --------shy(ConlinUld I

- -~-~~ ~--~-~- - shy

Table X (Continued

No Etcnant Substrate etcnlng conditions Application etch rate remarklt Rdbull

11 10 M KFe(CN)-O) M KOH (1001 () II) GaP and p-type 60_95 Polishing and mesa etching SiO or Ti mask [445] sllrring

POll) -type 95deg 260 mhr polished Ga(llll Hype SO I J5 mnr smooth textured

P(lOO) -type SO 210 mihr polished

13 Cl-HO sat soln (III) (1001 GaP p epi on n substrate PoliShing -05 mmin [446J

14 HPO (iii) (1111 (1001 GaP 150-200C Groove etching Au mask V grooves result 1442)

15 IHfIHO GaP p type on n substrate Preferential etching of p-type GaP on n type (443) r ~ 16 7NaOCI (525 wt ) IHCI GaP n type on p substrate electrolytic Preferential etching of n-type [443) middottype anode PI cathode

17 16H0 2NaOCI 2HCI III) GaP plii h by chemicaliet etching Polishing lIat smooth surfaces [2(6) Ga(lll) by jet electroetching

18 Cl CHOH (concentration not Ga( III) PI Ill) GaP electrolytic jet Localized Ihinning of specimens for transmission [447)

specified) electron microscopy

n --~3 N NaOH GaO II) P( ii j) GaP 20 electrolytic PI Anodic dissolution and selective etching [448J

cathode

20 01 N HNo (ill) GaP mAlem

Hype electrolytic 20 Anodic dissolution 1250 300 sec (432J

21 2HNOIHCI GaP 1-2 min Polishing of some orientations (437aJ

~ 0 (HOHat soln GaP immer~e sample while (I bubnle Ihroullh 1 onln 20 mtn

Poli_hlnj 40~J

171 lJ r tlrt r r 111[ II NI1I 1 I 11111 bullbullbull 11 IFF HI II 1 illMil 111 4-Table XI

Other Group IIl-V Compound Semiconducfon

~=-terial No Etchant Conditions Application etch rate remarks Rerf ---~

AIN IO laOH or hot HPO 30-80 (NaOH) General etching (449]

BN ~ HPO or HO 0laquo1 Hot General etching of pyrolytic films (450 450a]

BP 3 10 NaOH Electrolytic in dark 01-10 Aem Electrochem etching pmiddottype etches (451J gt IOOx faster than nmiddott ype

J AISb 4 lal IHF IHO IHO I min (a) followed by 2 sec (h) Etching (l ii) face (452J _4

(h) IHC IHNO

Gal 5O7r NaOH L9O General etching [453J 6 01 NaOH Electrolytic jet etching Selective etching of singlemiddotcrystal (454]

vapor-transpon grown films

7 Hf() HOI Etches but develops etch figures (455J

GaSp 8 99-800f CHOH 1-2or Br General polishml [402J 9 9HNOIHF 1-) min General pollhing 402J

10 2HNQ IHF ICHCOOH I) sec Pollshmg develops pits on (I J J I face (452J II IHF lHNn IHO Etching I j j j 1 face 1457] 12 10 citric aCid ()O wI 7r I 1HO pmiddottype 5) photoresist masks Pallern etching (100) face 10 Asec 418J

_--__w-_~ _~_ -~--~ltf

J

Table XI (Continued)

Matenal No Etchant CondItion Application etch rate remarks Reh ~---------- --~-----~-~--~

InAs 13 Etchant no 1 Polishing (II J) and ell il faces (460]

14 5HNo 3HF 3CHCC)()H 006 Br General etching (458J (CP4)

15 75HNO UHF 15CHCOOH 006 Br 55 Etching d i lJ face etch pits on ( II) face [458J

16 HCI 75 General etdng 5 mgcm min 1457 459J

17 04 M Fe -WHCI General etching (452] v 0lt 18 996 ml CHCOOH 04 g Br General polishing 1423J

InP 19 99CHOH IBror9OCHOH IOBr General polishing 40246IJ

20 IHCIIHNO Etching (100) face hillocks on (l j h face [46IJ

inSb 21 I CHOH (concentration not specified) General polishing (402J

22 Etchant no 17 General etching [452]

23 IHF IHNO 2-5 sec Polishing (ii i) and (110) faces no etchshy [423465] 0

ing on (III) or (100) faces ltj

24 5HF 5HNO 2HO 20 sec Etching (100) and (110) faces [8]

25 5HNO bull 3HF 3CHCOOH (CP-4AI 5-30 sec General polishing [463464]

26 IHO ICHCOOH 1 CP4 1 min Etching ( i I) (i Ii) faces etc 1463)

27 2HF IHNO ICHCOOH 5-30 sec Polishing etch pits on (III) face [452J

2X 4HO IHF IHO 5-10 sec Etching (i jj) face [457)

2V Etchanl no 12 311 pholnrt mllk Pallem etchinjl 11001 race 60 Aec 1418)

n II 11 1IUIiI1r Ir PI IF IflTlE 71 bullbull bull bull bull -t

Table XII

Group II-VI Compound Semiconductors

Material No Etchant Conditions Application etch rate remarks Refs

10 KOH General etching 1162468) 2 HCI 120 General etching (467] 3 HPO-HSO boiling General etching at low rate [467468]

CdO 4 Mineral acids or NH salts General etching [4691

CdS 5 100 ml HO 1 mI HSO 008 g CrO 80 10 min Etching of [IOTO) face [471) J Jgt -c

6 16 N HSO-05 M KCrO 955-10 min General etching and polishing etch pits on (jj j) face

[472J

7 300 ml precip sihca 90 ml HNO 10 g AICIlner HO

Chem-mech pOlishing Poromenc disk 240 rlmin 370 gcm

Pohshing (0001) face [475]

8 70HO 30HCI Rotating on Pelion cloth Polishing Cd S and prismatic faces [473J 9 1000 ml HO 137 g KCl 05 ml Hel pH 25 Politegt Pix pad 58 rlmin

025-)40 kgem Polishing Cd face [476J

10 1000 mI HO 131 g KCI 16 ml HC) pH 10 same as no 9 Folishing S face 1476]

CdSe II 30HNO 20HSO IOCHCOOH 40 S sec General etChing thick films forming (472) OIHCI are soluble in HSO

CdTe 12 3HF2HOIHO Polistung (J III and (iii) faces etch 14711 pitgt on (ill) face

(Continued I

---_-_~_~~~IC-Ymiddot

Table XII (Continued)

Malenai --lt--ltshy

Nolt Etchanl Condition Application etch rale remark Reflt

13 2HNO 2HC lHO Polishing [477]

14

15

20 ml HO 10 ml HNO

995 CHOH 05Br

4g KCrO

Slnp deposil 45 min

formed wth Cs

Polishong 10 mirrorlike surface

General etching

[477J

[478]

CdTe 1005)-HgTe (095)

16 6HNOIHCI Rinse in IHCI-ICHOH Polishing 1479]

~

HgSe 17 50HNO 20HSO (18 N) IOCHCOOH IHCI

4010-15 min Polishing 1472]

HgTe 18 6HNO IHC IHO 10-15 min Polishing [472]

ZnO 19 Mineral acids solns

or alkali or NHCI General etching [469

ZnS 20 Elchant nolt 6 95deg 10 min Polishing to high polish etch pits on ( Ill) face

1472J

21 Elchant no 15 Same as nolt 15 General etching etch pits on (Ill)

face (478)

ZnTe 22

23

4HF3HNO

Etchant no 15

Stnpfilm formed with HCI then HO

Same as no 15

General etching and polishing 14721

1478)

p F II I bullbullbull jill bull M U bull bull bull TbW lUll

Orhrr Sritutd Compound gtrmlnmduc(on

Malerial No Elchant Condition Application etch rale remarks Refs

AgSe 5HSO lHO 50 ~ min rinse in EDTA solution then Polishing of some orientations 1479J H 20

2 2KOH sat) 2 ethylene glycol 80 2 min following damage removal Polishing 14791 IHO with etchant no I

Aile ~ 3iHOH2HO Remove film by brushing under water Polishing of some onentaions 1479]

BiSe 4 IHO tHCI Damaged layer following much polshy Polishing and removal of workshy 1470J ishing damaged layers

2HNOIHCI May be diluted with H20 Cleaning and etching 1470 481]

BIltTe 6 Etchant io 5 Cleaning and etching [470 481J

Hg fCdI1e 7 80CHOH20Br Rinse with CHOH Removal of surface 1482483]

InO Sn doped

8

I

HSO

HCI

50-60 Cr film etch mask Pattern etching -05 Amhr

Pattern etching

1484]

14851 10 10 M oxalic acid aqlt soln 50 Shiple~ AZ1350 etch mask Pattern etchmg of annealed films 1486]

InO Sno 14 ltII

II 5~S HI Immerse sample vertically Shipley AZ- 1350H mask postbaked 90 min

Precision pattern etching 25 Asec [4871

I~O

12 2HCI IHO Zn pder Paint Zn powder-HO slurr) on submiddot Rapid etchm~ 150 Asec 1487J trate Immerse hOrlZ IOto HCI-HO 0 mask as 10 nt I(I

In-Je I 19CHCOOH acidlt 1 Br

sat with citric FInish b~ ftooding with CHCOOH sat with cllnc aCid

Polishing 1488]

Inle ISr alh~ shy

14 4 clfn aCld ~uln

~H~() IHF at vlth Bi Polhinf 1488

-~~~-~~-- -----~-~--~

(ConllnUfd i

_~_F-lt--~-_-~__~

4

Table XIII iCollrillutd)

Material 0 Etchant ConditIons Applications etch rate remarks Refs

PbS 15 30HCI 10HNO ICHCOOH 50 few min CHCOOH

then rinse with 10 Polishing [489]

16 HNO 70 Rapid etching [489]

PbSe 17 5KOH (45) 5 ethylene glycol IHO

Electrolytic add HO during etching to maintain rate remove stains with 5()f

CHCOOH

Thinning specimens for electron transmission microscopy

[490]

18 Etchant no 17 403 min Polihino [480]

PbTe 19

20

45 ml HO 35 ml glycerol 20 ml CHOH 20 g KOH

Etchant no 19

Electrolytic 4-6 V 02 Aem

Electrolytic 10 V rinse in CHOH

Thinning specimens for electron transmission microscopy

Polishing

[493]

1492) (494)

~gtb_rSnrSe 21 10 ethylene glycol 10KOH (sat aq soln at 25deg) I HO

Felt covered etch ant

wheel saturated with Polishing [495) [496]

Pb_SnTe 22 Etchant no 19 Electrolytic 10 V rinse in CHOH Polishing [492) [494)

23 95HBr 5Sr 1-2 min rinse many times with CHOH followed with slight etching with no 22

Polishing faster than etchant no 22 [494)

sr 24 3-IOHOIHCI Electrolytic 5-40 mAcm Pattern mask

precision etching SiO used 1600 Almin at 20

[498J

mAcm

25 HCI Zn powder Zn powder in photoresist in Ref 500 Paltern etching 497499

500)

SnO Sb doped

26 HC Zn powder Pattern etchinB 150IJ

E Conductors

Table XI

Elemental Metal

Etch rate or Etching conditions etch time Remarks Refs

Aluminum

4HPO 4CHCOOH lHNO IHO 350 Amm Polishing etch contact to noble metals is possible withshyout increases in etch rate and undercutting

[57504J

2 75 NaCO 35 g NaPO12HO 16 g KFe(CN) bull 05 liter HO

1300 Amin Polishing etch contact to noble metals is possible withshyout increase in etch rate and undercutting

[57]

16-J9HPObull IHNO 0-4HO 40 stirring 1500-2500 Amin Gas evolution OCcurs [14J

4

5

IHCIO ICHCO~O

74IHPO 185HO 73HNO 500

3 mimin

9000 Amin

(29]

[46505]

6

7

8

9

1 HC 4HO 8ltr

2Ok NaOH 60-90

FeCI 12-36degBlt

IOHCI IHSO 9HO 49 25-50 mmm

For fine hne etchmg photoresist masks can be used

Photoresist mask can be used

[507 532J

114507)

[15513J

[15]

10 01 M KB0051 M KOH06M KFe(CNt pH 13tgt

Immm No H j eJlved 158]

II 1 Electngt Glo 100 (Electro Glo Co ChIcago) ~HPO bull 79 7-10 006 Acm PI cathode

ElectrOChemical polish excellent polishing occurs (533J

12 Olher eIlaquoIr(Khemlal etche 291

~( dnlttrlUJ j

~~---~~-~ - --~----~- -----~

- - _H-~~~~~_W __

Table XIV (Continued)

Elch ralr or Etchl ng conditIons etch time Remark Refs

~----

Antimony

Aqua regIa or hot HSO 1469J

2 5ltlt AgNO [5341

3 I g FeCI 3 ml HC 12 ml HO 1534J --~--- ---- shy

Aroenic --------------- --------- --------~

HNO 1469J

Beryllium 5 g HSObull 75 g HPO(98) 7 g crO 13 ml HO 49- JLmmin Passive film formed removable by immersion for 15- [29468)

50 30 sec in 10 HSO

2 HCI 1535J

1 H2SO preset voltage 30 V 2240 Almin Electrochemical etch [468J

4 1 KOH preset voltage 50 V 260 Amin Electrochemical etch [468] f

bull ~middot-ther electrochemical etches 129 536J

Bismuth

Hot HSO 469J

2 5ltlt AgNO [534J

3 lt49 ml sal KI soln I ml HCI 5-7 V 20 Adm stainmiddot Penltxh of 30 sec Electrochemical etch allo brown film formed 10 dismiddot 129] Ic IlrC or cKrhon cathode Ive een elchml period

bull bull bull - - bull I 1 -4 CadmIum

3 fuming HNO (type not specified) IHO

7CHCOOH 3 fuming HNO (type not specified)

I g I 3 g Kl 10 ml HO

olectrochemical etches and polishes

Periods 00-10 sec

30 sec-) min

Etchmg periods stream of H20

are followed by rinsing in a rapid 129)

[291

15341

[29 537 538J

ChromIUm

t 2

3

4

5

6

8

9

1 vol t 1 g NaOH 2 ml HOi 3 vo(J g K[Fe(CN) 3 mlf50IOOOAmin H20J

I g CeISOh2(NH)SOmiddot2HO 5 ml HNO 25 ml 85 Almin HO 28

1645 CeISO)2(NH)SO~H() 43 m HClO HO to make I Iller 25-50

2FeCI47BeIHCI80

HCI

454 g AICImiddot6HO 135 I ZnCl 30 ml HPObull 40() ml HO

9 sat Ce(SO soln IHNO

Dilute HCI or HNO

gt1500 Aimin

800 Amm

IHCIObull 2OCHCOOH4~-~OI-20A dm slammiddot cJ(l~er

Ie steel cathode

Does not require depassivation for etching Cr masks and vacuum-deposited Cr in general photoresist mask can be used

Oxide coating etches at 200 Amin

Recommended for precision patterning ofCr masks on glass substrates

Good for plated Cr photoresist mask can be used

Must depassivate with Zn rod

Photoresist mas~ can be used

Electnxhemlral polh

[14 15507 510J

[519J

1520J

[IS507J

[14516)

(14)

[14517)

[15507513 S17)

[29]

(ConlinLlfd

-- - - --

2

Table XlV (tontid)

Etch rate or Etchmg conditIo etch time Remarkgt Refs

Cobalt

I HC IcHOH 8-9 V 250 AdTn stainless steel 05-15 min Electrochemical polish bluish-green anodic film is sol- [29J uble in HO gIve polished surface WIth slight grain cathode boundary delineatIon

ElectrochemIcal pohsh sohd black film forms which is (29]HPO (98) - 15 V 1-2 Adm Co cathode 5-10 min removed by WIping WIth cotton wool

1539 540JOther electrochemical etc he

Copper ~---~~~-----

0 FeCI 42Be 49 50 Immin Use more dilute solution for slower etching 114 15 50s 509J

2 20-30 HSObull 10-20 crO or KCrO 49 37 Immin (14 15509]

1 g (NH)SO 3 ml HO 32-49 25 Immin Addition of 5 ppm Hg as HgCI activates etehant at [15513 lower temperatures 541-543J

4 5HNO 5CHCOOH 2HSO dilute with HO as Etches Cu and Cumiddotbased alloys at same rate as Ni and (506J

- desired

g KI I g 14 ml H2 0 dip into etch rinse remove

N i-based alloys

Rapid etch but undercutting is limited by formation of [14J

residue with Neutra-clean (Shipley Co Newton an insoluble Cu compound at line edges

Mas)

6 4HNO IIHPO (98) 5CHCOOH 6O-7if 1-2 min Polishing etch (29J

7 2HPOt98I IHO 15-2 V 6-8 Adm Cu cathode 15-30 mm Electrochemical polish [429544 545

()tmiddot~t clflru-hcml1 chhf I~l

fa RIP bull WI1 bull Til bull bull ~-~--~-~-------~-------------~-----~~------------~------

Gallium

Mineral acids or alkali solutions Must be processed below meltmg point (469J

Gold -----~~~~~---~~--~~-~--------~--------------~~------~--------------

)- 4 g KL I g I 40 ml HO 05-1 Immin Better contr~1 of line edges than in more concentnlled [141551 solution solution is opaque so removal from solu tion to observe end point is required

2 3HCL IHNO 32-38 25-50 Immin (IS]

NaCN HO HO mixtures (unspecified composition) [14 15J

4 05 g 12 g NHL 10 ml HO 15 ml cHOH 2if 700 Amin Converts the surface of an underlying Ag layer to the [5101 +shy

iodide thus preventing undercutting -- 04 M KFe(CN) 02 M KCN 01 M KOH 600 Amin Fresh solution must be used no atack on Pd is obshy [58]

served

6 tOO ml HO 05-10 ml HCL 10-JO g NaCl 4-5 V Electrochemical elch which retains bright surface only 1547] 65-2 Adm Mo cathode 20-40 small amount Cl evolved

7 Other electrOChemical etches 129548]

Hafnium

I-cltf HF

lt-6HCIO IOOCHCOOH 18 V Slamle steel cathmiddot ode U several SUCCegtlH dIps with continued agitation

5-10 sec dips

Negative photoreSIst can be ued as mask

ElectrochemICal pohsh -)

[14549J

[29J

See Zircomum etch fltl [291

CConHnurd

--- ---~- --~ -~-------- ~---~ -

Table X (Corllid

Etching condition~

Etch rate or etch lime Remarh Refs

Indium

Mineral acid [469J

IHNO 3CHOH 40-50 V 30 Adm stainless steel cathode cool bath

1-2 min Electrochemical polish [291

Iron

3HNO 7HCI 30H0 6O-7r 2-3 min Dense brown viscous layer forms on surface layer is soluble in solution

[29J

j CgtshyOlt

2

3

4

-I()o( KAI(SOl 12HO

3 liter 1O7c HNO 03 mhr 0 injected 3r

1 HCIO 2OCHCOOH 45-60 V 40-80 Adm stainmiddot less steel cathode

30 mmin

15-30 sec

Slowly soluble

Etches iron plate smoothly 0 removes passive film

Electrochemical polish solid film sometimes forms on the surface during washing removable with dil HF

[469J

[550J

[29J

5 Other electrochemical polishes _

[29J

Lead -----shy----------------------------------------------------------

FeC~ 36-42Be 43-54 [IS 513J -~

9FeCI 42Be IHCI 2rBe 43-49

I HtObull 4CHCOOH Periods 00-10 sec Alternate with immersion in a soln of 10 g molybdic acid and 140 ml NHOH in 240 ml HO to which 60 ml HNO is finally added

[ 15]

(29J

4

5

6

IHNO19HO

35HCIO 63(CHCO)0 20H0 lt3r 50-70 V 9-12 5-10 min A Idm Ph or Cu cathode

()the- k-tdmJ Pbullbulltw

ltlhtum

-------------------

Electrochemical polish

(534J

[291

1191 bull CHOH 30 sec Surface achIeves high luster and is smooth [551]

Magnesium

240-400 g FeCI 330 ml Hel HO to make I liter [469]

1-3HNO 17-19HO [507513 534]

3 fuming HNO type not specifiedl IHO wash imme Periods of 3 sec Reaction rcac Imot explosive violence after -I [29J diately after removal from solution min if allowed to continue it ceases after several

minutes leaving a polished surface

4 7HPO(987cL I3CHOH 1-2V05Admstainle 025 mmin Electrochemical pohsh there is considerable initial [29)

steel or cathode gassing shake anode to remove adhering bubbles

5 5 Other electrochemical etches [29J ~

Manganese

2

IHel IHO

Other dilute mineral acids

1513)

14691

Mercury

Sloght_ diluted HNO

Molybdenum

1469J

5HPO 3HNO 2HO Polishing elch contact to noble metals possible withmiddot OUI mcrcase in etch ratc and undercutling

[57J

IHSO IHNO 1-5H0 ~5-4 J~ 11m imin I~lt I ~ ftm min (~4

Photoresist mask can be used al 25 115507 518

(( OnltnUtJ I

- -~~~ ~ -- --~~-~middotltli0kmiddotmiddot-

Elching condtlons

Tb xrv (Co(Hu~d)

Elch fale or etch tme

Molybdenum (Continuedl

-------shy ~-~---------

Remarh Reh

o

4

6

7

20011 K[Fe(CN))2011 NaOH 3-35 g sodium oxalate add HO 10 make I liter

38HPO 15HNO 3OCHCOOH 75HO

IHSO 7CHOH 80-120 Adm stainless steel cathmiddot ode no agilation

100 ml HPO 20 ml HSObull 40 ml HO 025 II MoO 7(18 V 06-09 Acm slainless sleel graphite or PI cathode stlmng

Other etches

-ltmmin

05t m mrn

I min

94tmmm

Neplunium

Also usable as electrochem etch usinll stainless cathode al 6 V pholoresisl masks applicable

Photoresist mask can be used

Electrochenca polish

Electrochemical pohsh supenor surface finish

steel [14 1551 5075521

1518]

29]

1553

[29 38 57 554-5561

HCI 1557

5HNO 5CHCOOH 2HSObull HO as desired

IHNO IHCI 3HO

FeCI 42-49B 43-54

4

Igt

3HNO IHSO I HPO 198) 5CHCOOH 85-95

IHNO IHO or 9HPO IHNO or 9OHPO 15HNO 4HCL IHO

IOHSo OHO HPO lt-1 NISO JO ~ltr

Nickel

12 -25 tm min

05-1 min

1-2mmln

Etches Ni and Nimiddotbased alloys at same rale as Cu and (506)

Cumiddotbased alloys

Spray elching recommended 1507] o

Photoresist mask may be used [15507513)

Gives very llood polish 1291

Polishing elchants for eleclrol N-P very undercutllng despile conlacl to noble melah

hllie 1571

For ecclrole N film nu undCrcuttmJL mll r fMlfhnn uc-ful (Of ~ittrnl(H Cu

com I ~S8j

bull ~ 8

~7HSObull 4)H 1 U 0 ~ ALm

Other electrochemical polishegt 2 min mm1n lJellrtKht 1~lil1 rulnh

15~ 5601

129J

NiobIum

2 Lacue acid IHSO bull IHF 15~20 V PI cathode sIllmiddot 5-10 mm nng EleClrochemical polish

129]

7HF 7HNO 26HO 49 12-20 V 20~34 Adrn PI cathode Electrochemical etch 14(9) _

9HSO IHF H-45 50 V 2 Adrn PI Or carbon 5-10 min

cathode Electrochem etch temp nses during use cool bath [29]

~--~-----~----~----~----Osmium

Aqua regia 1557)

Palladium

IHCI 10HNO IOCHCOOH 1000 Aim

Aqua rega 15611

1513) Platinum

SHO 7HCI I HNO 85 400-500 AImln 2 f562 563)Aqua regIa precede etchin by 30 sec ImmersIOn in HF

EtCh tIme mlled because photoreSIst mask demiddot 114 507i strayed

3 M HCI 03-+ 14 V versus SeE modIfied Inangumiddot -1000 Almln lar waveform -600 Hz magneuc slmng Electrochem elch good resolu[lOn either po or neg 15141

photoreslS[ usable

Plutonium

I HPOI981 1 diethlene glvcol 5 V ltAdm lainmiddot L 10 mm less steel carhode Electrochemical pohsh

1291

(Conllnttf d

~--~~- - ~ -_ --__~ ~- h __ ~_

Table XIV (Cotiu~d) ~~------- ~---~----~~-~-~-----

Etch rate or Etchmg conditIOns tch time Remarks Ref

Polonium

Dilute mineral acid [557J

Potassium

CHOH or iCH)CHOH 3 sec (ethanoB or 10 SeC (Ioproshypanol)

Brilliant smooth surface obtained [551]

Praesiodymium

Mineral acid -~-~--~-~----------~~------ -------shy

Rhenium

[557]

Dilute HNO [557]

Rhodium

3 M HC -03- + 14 V versus SCE modified triangumiddot ElectTOchem etch I Im line spacings ofRh films over [514]

lar waveform -600 Hz magnetic stirring 5000 ATi on 5i dearly resolved

Ruthenium --------------------~----------------

Fused alkalis [557]

Samarium

Minual acids (557J

Sdenium

HStl ~( IM tf U undtf CkmCnl1 womtunduton 11 bull ~---~--~~-----

Silver

11 g Fe(NO) 9 ml HO 44-49 20 IJmmm Photoresist mask can be used [14 15 507J

2 5-9HNO1-5HO39-49 12-251Jmmin 11415517J

3 35 g AgCN 37 g KCN 38 g KCO 100 ml HO 25- 10 min Electrochem etch best polishing in region of voltage (29) 30 V 1 Alent Ag cathode 10 stirring and currel1t instability

4 3HNO 19H0 2 V [ainle steel cathode ElectrOChemical etch [507)

5 Kl-I etches listed for Cu and Ag O3-llJmsec Immersion followed by HO rinse [14]

60 Asec Useful for pattern etching with photoresist mask rinse [512] quickly after etching

6 4(HOH INHOH IHO

Sodium-

CHtCH)CHOH (nonyl alcohol) 30 sec Brilliant smooth surface [551)

Stronlium

Liquid ammonia [557]

Tanlalum

2

9NaOH or KOH 00laquo) IHO heal alka to 9(t Ihen add HO

5HSObull 2HNO 2HF

1-2HNO IHF 1-2H0

100(l-~OO(l A min

5-20 sec

4 9HSObull IHf (-4 50 cathgtd

A urn 11 1 carb -1(1 rnln

Metal (eg Au) rna muq be used very httle undermiddot cutting etche TO and Ta- al same rale 3 Ta

116~ 16~J

POlishing elch [29 522 5~~

HO rna) be omllled ftgtr fasler elch espeCially if film coniaim oxygen and reslsh etching fasler etch reshyduce re t al1a(~

(14 5 HI

Eletruchernlal etch temp of solUlion ne dunng ue and 11 rna he nece ar~ tp cool hath

129

- -~-~-=-

-4

2

Tabl Xf (Colltlllud)

Etch ratr or Etching condtion rtch time Remarks Refs

Tellurium

2HND3HO [513]

240 g (NH~So bring to I liter with HO [513J

Terbium

M ine 1 acid~ [557]

Thallium

to

HND or HSO

Thonum

------------~----

[557]

14CHCOOH 4HCIO IHO -1060 Adrn stain- 7-12 sec Electrochemical polish [29] less steel cathode

Tin

FeCI 36-42B 32-54 ~------~-

[15 513)

2 IHNO49CHOH [534] (

j iCIO lt35 5O-W V 40 Adrn AI cathode hold piece vertically and rotate at 50-100 r Imin

420 fLmmin Electrochemical polish on large sunaces orange peel effect may occur

(29]

4 Other electrochemical polishes [29]

Titanium

9H0 IHF 3gt 12 fLmmin Photorist mllsk may be used 114 15 507]

2 7Hli 21iNII IH~ n IImmln PhOI maoa m~ be uWd 114155071

bull - bull bull bull

tllO mllHOH 2U ml middotbutyl hoI t2 II Alll ~ II I-JeC1fochcml41 fKlhh 14m) zne 30-50 V 12 Adm ~Utinle Ied cathode

4 3HCIO 5OCHCOOH 200 30 V 30-40 Adm Ti 2 min E)ectrochem etch anode to cathode distance about 129] cathode 3 cm

5 Other electrochemical etches [29 564 5651

6 See Zirconium etch no [29]

Tungsten ~--~~-----~ -------~-------~----~---~~-----------------~~----~~-~--~~~-~---~--~--~------

34 g KHPO 134 g KOH 33 g KFeICN) HO to 1600 Amin Photoresist mask may be used high resolution (1- (515] make I liter 2 Lml can be achieved

2 5 KOH 5 KFe(CN) 1 sunaclant -2302 --23Lmmin Electrochem etch photoresist mask can be used good [51J Acm PI cathode pauem resolution

5-10 NaOH 6 V 3-6 Adm stainless steel cathode Electrochem etch rotation of anode or agitation of [29 513 566deg) - electrolyte with N is necessary

4 Other etches [5158515 555 567]

Uranium

1-2HClO 2OCHCOOH 5O-W v 5 Adrn stainless 19 fLmmill Electrochemical polish (29) steel cathode

2 Other electrochemical pohshe [29]

VanadIum __----------------___---------__-_

1-2HClO 18-19CHCOOH lt35 50-60 V 16-24 1-2 min Electrocherrucal polish a second polishing ofabout the f29] Adm stainless steel cathode sarne duration ill a fresh soln sometimes necessary

---~-~-----~----~--

Ytlcrbium -----~---------------~-----

lhneraJ aCid 1557j

fCwwj

Table IX

Graul ffl-V Compound Semiconductors GaA

Substrate etching condtions Application eteh rate remarks Refs No Etchant

-------~~----------------------~-

Fast etching - 3 Immin [406J4HSObull IHD IHO (100) GaAs 50

Slow etching 02 Immin [406J2 I~H (I M) tHO(076M) (100) GaAs 30

(100) () Ii )GaAs Cr doped rotating Jet polishing nonpreferential -8 Immin [266]28r 98CHOH

slices jet nozzle smooth flat

(100) (1)) Ii jj)GaAs rotating slices Planar polishing nonpreferential -18 Imhr [404]4 700HO INHOH (295)

on polishing pad

POOl l1l)A 111)8 GaAs freely rotatmiddot Planar polishing nonpreferential - 25 Im3 hr [39O412J ()5 OHO INaOC ing sUees on polishing pad 0

GaAs 60 polishing pad Planar polishing - I IJm5 min [412]SA 3HSO IHO (33) IHO

III GaAs 013 fl-cm n-type High polishing 037 mgCrtr-mlO [410J6 8 glycerol lHC IHNO

lOO) GaAs epi Structural etching SiD mask 8 Immin lateral [410J7 8HO IHSO 1 H20 dis depends on mask alignment

99 WI 7r CHOH I wt7r Br IOI IIIB 0001 l1I)A GaA Preferential structural etching etch rate I 110) (403J8 II I)B I 001 gt IIIIIA

11bull rn 9 973HO 20NHOH 7HO (111)8 (100) ( I J)A G

Selecllv rmoval through SiO mash flat pro [4091files reduced underculling

(111)8 020 IJmmin(100) O1 2 IJmmin(l1I)A 0037 IJmmin

10 10 citric acid (50 wt aq sol) IIIlIB (100) (J lilA GaAs Preferential etching through photoresist masks [418JIHO ftat ~oltomed holes no attack of resist Etch rates (11118 (100) (1l1lA

II 3CHOH IHPO IHO [IIOJIIOO) Ga [IIIJ GaAs Preferential structural etching - 2 Immin exshy (415) cept Gar Ill] reduced twofold

12 1-20Br 99-80CHOH GaA~ (for solution or pad etching) Polishing [402412J J3 3HNO 2HO 1HF GaAs Rapid polish etching [419J

J 14 2HCl 2HO IH~OJ (111)GaAslOmin~ General etching of (i j j) plane [420J 1~ ~~aOH 15) IHO GaA 5 min Fast etching 1O-15IJmmin 1421J 16 8-12Aamp~O 117r) 5HNO] (1111 (IIi) GaA EtChing both till) and (j j i ) planes [419JIHF

17 75HO 20HSO SHO GaAs Polish etching 1423J 18 40HCI 4HO IHO GaAs jet etching 20 Thinning specimen for electron microscopy 14221

(Continued

Tampble IX (Colltillll~d)

No Etchant Substrate etching conditions Application etch rate remarks Refs

19 25HCI0bull 75CHCOOH GaAs electrolytic gently flowing from Thinning specimens for electron microscopy [424J an orifice above sample at 42 V

20 10--40 KOH or NaOH GaAs p type and heavily doped n type Electropolishing to mirror-smooth surfaces [428J

electrolytic 1-5 Acm

21 10 KOH (100) (110) (III) GaAs n type electroshy Anodic dissolution [426J

lytic flowing 10 KOH

22 3 M NaOH (100) GaAs p type spray electrolytic Selective removal of p-type substrate leaving [429J

100 mAcm n-type epi GaAs or GaAsP ~ 23 0025M NaOH-OOOI M EDTA (100) (III) Ga (1111 As GaAs n type Electropolishing (430J

electrolytic illumination

24 HCI-HO GaAs n type electrolytic Controlled thinning [431]

25 001-1 N HNO (100) GaAs n type electrolytic 10-20 Controlled electroetching [432]

mAcm 2-3 V

26 H AsH HC) (900 3 2 (100) (III) GaAs Te Zn Si Cr doped Substrate polishing prior to epitaxy 7-11 (434]

cmmin) vapor phase 9000 Lmmin nonpreferential specular 0 27 IOOCHOHIBr GaAs General etching 8 Lmhr

28 5HSObull IH0 GaAs Polishing 25 Lmhr

29 70HO 20HO 10 fonnic acd GaAs Surface cleanup

30 95CHOH 58r (100) GaAs n-type CVD SiO as etch Preferential etching of (32) Ga plane (416) mak

If r I j t 11 ~_ p bull mbull [ bullbullbull1middot ~~ rlIIJIUII _

Tampble X

Group I- Compound Semiconductors GaP

No Etchant Substrate etching conditions Application etch rate remarks Refs - 1-20 Br 99-80 CHOH GaP (solution

niques) or Pelion cloth techshy Generll etching and polishing (402J

2

4

6

R

9

1 Br 997r- CHOH

2HCI IHNO IHO

2HCI 2H0 I HNO

2HCI 2HO I HNO

Aqua rega

2HCI 2HSObull 2HO IHNO

3HSObull IHO (33(-) IHO

CHOH sal with Br I HPObull freshly mIXed

GaP

III) GaP hot

P (J II) GaP

(III) (ijj) (100) GaP 601-2 min

(ijj) GaP

P III GaP 5 min cold then 50 or 10 sec etching on Pelion cloth

GaP 60 5 min

(II J) GaP chem-mech technrque wafer rotates face down

Polishing highest-quality surface -025 Lmmin

Polishing III surface

Polishing P III surface

Polishing

Groove and pattern etching SiO mask

Polishing P III surface Ga III face pitting etch rate depends on Te carrier conc

Surface etching for saw damage removal I Lm5 min etches p-type preferentially

Work damage remoal prior to no 10 elch

120)

1438)

(439]

[442]

1441]

1440J

[443444)

14364311

10

II

5HSObull IHO IHO

Etchant no 9

( III) GaP 80 mrn

( III ) GaP 50

SunSlrale preparation for ep growth after no 9

and before no II etch 06 Lm mm optimal

Substrate final etch for epi growth Immediatel

after no 10 etch 15 Lmmin optimal

1431)

1437)

-------shy --------shy(ConlinUld I

- -~-~~ ~--~-~- - shy

Table X (Continued

No Etcnant Substrate etcnlng conditions Application etch rate remarklt Rdbull

11 10 M KFe(CN)-O) M KOH (1001 () II) GaP and p-type 60_95 Polishing and mesa etching SiO or Ti mask [445] sllrring

POll) -type 95deg 260 mhr polished Ga(llll Hype SO I J5 mnr smooth textured

P(lOO) -type SO 210 mihr polished

13 Cl-HO sat soln (III) (1001 GaP p epi on n substrate PoliShing -05 mmin [446J

14 HPO (iii) (1111 (1001 GaP 150-200C Groove etching Au mask V grooves result 1442)

15 IHfIHO GaP p type on n substrate Preferential etching of p-type GaP on n type (443) r ~ 16 7NaOCI (525 wt ) IHCI GaP n type on p substrate electrolytic Preferential etching of n-type [443) middottype anode PI cathode

17 16H0 2NaOCI 2HCI III) GaP plii h by chemicaliet etching Polishing lIat smooth surfaces [2(6) Ga(lll) by jet electroetching

18 Cl CHOH (concentration not Ga( III) PI Ill) GaP electrolytic jet Localized Ihinning of specimens for transmission [447)

specified) electron microscopy

n --~3 N NaOH GaO II) P( ii j) GaP 20 electrolytic PI Anodic dissolution and selective etching [448J

cathode

20 01 N HNo (ill) GaP mAlem

Hype electrolytic 20 Anodic dissolution 1250 300 sec (432J

21 2HNOIHCI GaP 1-2 min Polishing of some orientations (437aJ

~ 0 (HOHat soln GaP immer~e sample while (I bubnle Ihroullh 1 onln 20 mtn

Poli_hlnj 40~J

171 lJ r tlrt r r 111[ II NI1I 1 I 11111 bullbullbull 11 IFF HI II 1 illMil 111 4-Table XI

Other Group IIl-V Compound Semiconducfon

~=-terial No Etchant Conditions Application etch rate remarks Rerf ---~

AIN IO laOH or hot HPO 30-80 (NaOH) General etching (449]

BN ~ HPO or HO 0laquo1 Hot General etching of pyrolytic films (450 450a]

BP 3 10 NaOH Electrolytic in dark 01-10 Aem Electrochem etching pmiddottype etches (451J gt IOOx faster than nmiddott ype

J AISb 4 lal IHF IHO IHO I min (a) followed by 2 sec (h) Etching (l ii) face (452J _4

(h) IHC IHNO

Gal 5O7r NaOH L9O General etching [453J 6 01 NaOH Electrolytic jet etching Selective etching of singlemiddotcrystal (454]

vapor-transpon grown films

7 Hf() HOI Etches but develops etch figures (455J

GaSp 8 99-800f CHOH 1-2or Br General polishml [402J 9 9HNOIHF 1-) min General pollhing 402J

10 2HNQ IHF ICHCOOH I) sec Pollshmg develops pits on (I J J I face (452J II IHF lHNn IHO Etching I j j j 1 face 1457] 12 10 citric aCid ()O wI 7r I 1HO pmiddottype 5) photoresist masks Pallern etching (100) face 10 Asec 418J

_--__w-_~ _~_ -~--~ltf

J

Table XI (Continued)

Matenal No Etchant CondItion Application etch rate remarks Reh ~---------- --~-----~-~--~

InAs 13 Etchant no 1 Polishing (II J) and ell il faces (460]

14 5HNo 3HF 3CHCC)()H 006 Br General etching (458J (CP4)

15 75HNO UHF 15CHCOOH 006 Br 55 Etching d i lJ face etch pits on ( II) face [458J

16 HCI 75 General etdng 5 mgcm min 1457 459J

17 04 M Fe -WHCI General etching (452] v 0lt 18 996 ml CHCOOH 04 g Br General polishing 1423J

InP 19 99CHOH IBror9OCHOH IOBr General polishing 40246IJ

20 IHCIIHNO Etching (100) face hillocks on (l j h face [46IJ

inSb 21 I CHOH (concentration not specified) General polishing (402J

22 Etchant no 17 General etching [452]

23 IHF IHNO 2-5 sec Polishing (ii i) and (110) faces no etchshy [423465] 0

ing on (III) or (100) faces ltj

24 5HF 5HNO 2HO 20 sec Etching (100) and (110) faces [8]

25 5HNO bull 3HF 3CHCOOH (CP-4AI 5-30 sec General polishing [463464]

26 IHO ICHCOOH 1 CP4 1 min Etching ( i I) (i Ii) faces etc 1463)

27 2HF IHNO ICHCOOH 5-30 sec Polishing etch pits on (III) face [452J

2X 4HO IHF IHO 5-10 sec Etching (i jj) face [457)

2V Etchanl no 12 311 pholnrt mllk Pallem etchinjl 11001 race 60 Aec 1418)

n II 11 1IUIiI1r Ir PI IF IflTlE 71 bullbull bull bull bull -t

Table XII

Group II-VI Compound Semiconductors

Material No Etchant Conditions Application etch rate remarks Refs

10 KOH General etching 1162468) 2 HCI 120 General etching (467] 3 HPO-HSO boiling General etching at low rate [467468]

CdO 4 Mineral acids or NH salts General etching [4691

CdS 5 100 ml HO 1 mI HSO 008 g CrO 80 10 min Etching of [IOTO) face [471) J Jgt -c

6 16 N HSO-05 M KCrO 955-10 min General etching and polishing etch pits on (jj j) face

[472J

7 300 ml precip sihca 90 ml HNO 10 g AICIlner HO

Chem-mech pOlishing Poromenc disk 240 rlmin 370 gcm

Pohshing (0001) face [475]

8 70HO 30HCI Rotating on Pelion cloth Polishing Cd S and prismatic faces [473J 9 1000 ml HO 137 g KCl 05 ml Hel pH 25 Politegt Pix pad 58 rlmin

025-)40 kgem Polishing Cd face [476J

10 1000 mI HO 131 g KCI 16 ml HC) pH 10 same as no 9 Folishing S face 1476]

CdSe II 30HNO 20HSO IOCHCOOH 40 S sec General etChing thick films forming (472) OIHCI are soluble in HSO

CdTe 12 3HF2HOIHO Polistung (J III and (iii) faces etch 14711 pitgt on (ill) face

(Continued I

---_-_~_~~~IC-Ymiddot

Table XII (Continued)

Malenai --lt--ltshy

Nolt Etchanl Condition Application etch rale remark Reflt

13 2HNO 2HC lHO Polishing [477]

14

15

20 ml HO 10 ml HNO

995 CHOH 05Br

4g KCrO

Slnp deposil 45 min

formed wth Cs

Polishong 10 mirrorlike surface

General etching

[477J

[478]

CdTe 1005)-HgTe (095)

16 6HNOIHCI Rinse in IHCI-ICHOH Polishing 1479]

~

HgSe 17 50HNO 20HSO (18 N) IOCHCOOH IHCI

4010-15 min Polishing 1472]

HgTe 18 6HNO IHC IHO 10-15 min Polishing [472]

ZnO 19 Mineral acids solns

or alkali or NHCI General etching [469

ZnS 20 Elchant nolt 6 95deg 10 min Polishing to high polish etch pits on ( Ill) face

1472J

21 Elchant no 15 Same as nolt 15 General etching etch pits on (Ill)

face (478)

ZnTe 22

23

4HF3HNO

Etchant no 15

Stnpfilm formed with HCI then HO

Same as no 15

General etching and polishing 14721

1478)

p F II I bullbullbull jill bull M U bull bull bull TbW lUll

Orhrr Sritutd Compound gtrmlnmduc(on

Malerial No Elchant Condition Application etch rale remarks Refs

AgSe 5HSO lHO 50 ~ min rinse in EDTA solution then Polishing of some orientations 1479J H 20

2 2KOH sat) 2 ethylene glycol 80 2 min following damage removal Polishing 14791 IHO with etchant no I

Aile ~ 3iHOH2HO Remove film by brushing under water Polishing of some onentaions 1479]

BiSe 4 IHO tHCI Damaged layer following much polshy Polishing and removal of workshy 1470J ishing damaged layers

2HNOIHCI May be diluted with H20 Cleaning and etching 1470 481]

BIltTe 6 Etchant io 5 Cleaning and etching [470 481J

Hg fCdI1e 7 80CHOH20Br Rinse with CHOH Removal of surface 1482483]

InO Sn doped

8

I

HSO

HCI

50-60 Cr film etch mask Pattern etching -05 Amhr

Pattern etching

1484]

14851 10 10 M oxalic acid aqlt soln 50 Shiple~ AZ1350 etch mask Pattern etchmg of annealed films 1486]

InO Sno 14 ltII

II 5~S HI Immerse sample vertically Shipley AZ- 1350H mask postbaked 90 min

Precision pattern etching 25 Asec [4871

I~O

12 2HCI IHO Zn pder Paint Zn powder-HO slurr) on submiddot Rapid etchm~ 150 Asec 1487J trate Immerse hOrlZ IOto HCI-HO 0 mask as 10 nt I(I

In-Je I 19CHCOOH acidlt 1 Br

sat with citric FInish b~ ftooding with CHCOOH sat with cllnc aCid

Polishing 1488]

Inle ISr alh~ shy

14 4 clfn aCld ~uln

~H~() IHF at vlth Bi Polhinf 1488

-~~~-~~-- -----~-~--~

(ConllnUfd i

_~_F-lt--~-_-~__~

4

Table XIII iCollrillutd)

Material 0 Etchant ConditIons Applications etch rate remarks Refs

PbS 15 30HCI 10HNO ICHCOOH 50 few min CHCOOH

then rinse with 10 Polishing [489]

16 HNO 70 Rapid etching [489]

PbSe 17 5KOH (45) 5 ethylene glycol IHO

Electrolytic add HO during etching to maintain rate remove stains with 5()f

CHCOOH

Thinning specimens for electron transmission microscopy

[490]

18 Etchant no 17 403 min Polihino [480]

PbTe 19

20

45 ml HO 35 ml glycerol 20 ml CHOH 20 g KOH

Etchant no 19

Electrolytic 4-6 V 02 Aem

Electrolytic 10 V rinse in CHOH

Thinning specimens for electron transmission microscopy

Polishing

[493]

1492) (494)

~gtb_rSnrSe 21 10 ethylene glycol 10KOH (sat aq soln at 25deg) I HO

Felt covered etch ant

wheel saturated with Polishing [495) [496]

Pb_SnTe 22 Etchant no 19 Electrolytic 10 V rinse in CHOH Polishing [492) [494)

23 95HBr 5Sr 1-2 min rinse many times with CHOH followed with slight etching with no 22

Polishing faster than etchant no 22 [494)

sr 24 3-IOHOIHCI Electrolytic 5-40 mAcm Pattern mask

precision etching SiO used 1600 Almin at 20

[498J

mAcm

25 HCI Zn powder Zn powder in photoresist in Ref 500 Paltern etching 497499

500)

SnO Sb doped

26 HC Zn powder Pattern etchinB 150IJ

E Conductors

Table XI

Elemental Metal

Etch rate or Etching conditions etch time Remarks Refs

Aluminum

4HPO 4CHCOOH lHNO IHO 350 Amm Polishing etch contact to noble metals is possible withshyout increases in etch rate and undercutting

[57504J

2 75 NaCO 35 g NaPO12HO 16 g KFe(CN) bull 05 liter HO

1300 Amin Polishing etch contact to noble metals is possible withshyout increase in etch rate and undercutting

[57]

16-J9HPObull IHNO 0-4HO 40 stirring 1500-2500 Amin Gas evolution OCcurs [14J

4

5

IHCIO ICHCO~O

74IHPO 185HO 73HNO 500

3 mimin

9000 Amin

(29]

[46505]

6

7

8

9

1 HC 4HO 8ltr

2Ok NaOH 60-90

FeCI 12-36degBlt

IOHCI IHSO 9HO 49 25-50 mmm

For fine hne etchmg photoresist masks can be used

Photoresist mask can be used

[507 532J

114507)

[15513J

[15]

10 01 M KB0051 M KOH06M KFe(CNt pH 13tgt

Immm No H j eJlved 158]

II 1 Electngt Glo 100 (Electro Glo Co ChIcago) ~HPO bull 79 7-10 006 Acm PI cathode

ElectrOChemical polish excellent polishing occurs (533J

12 Olher eIlaquoIr(Khemlal etche 291

~( dnlttrlUJ j

~~---~~-~ - --~----~- -----~

- - _H-~~~~~_W __

Table XIV (Continued)

Elch ralr or Etchl ng conditIons etch time Remark Refs

~----

Antimony

Aqua regIa or hot HSO 1469J

2 5ltlt AgNO [5341

3 I g FeCI 3 ml HC 12 ml HO 1534J --~--- ---- shy

Aroenic --------------- --------- --------~

HNO 1469J

Beryllium 5 g HSObull 75 g HPO(98) 7 g crO 13 ml HO 49- JLmmin Passive film formed removable by immersion for 15- [29468)

50 30 sec in 10 HSO

2 HCI 1535J

1 H2SO preset voltage 30 V 2240 Almin Electrochemical etch [468J

4 1 KOH preset voltage 50 V 260 Amin Electrochemical etch [468] f

bull ~middot-ther electrochemical etches 129 536J

Bismuth

Hot HSO 469J

2 5ltlt AgNO [534J

3 lt49 ml sal KI soln I ml HCI 5-7 V 20 Adm stainmiddot Penltxh of 30 sec Electrochemical etch allo brown film formed 10 dismiddot 129] Ic IlrC or cKrhon cathode Ive een elchml period

bull bull bull - - bull I 1 -4 CadmIum

3 fuming HNO (type not specified) IHO

7CHCOOH 3 fuming HNO (type not specified)

I g I 3 g Kl 10 ml HO

olectrochemical etches and polishes

Periods 00-10 sec

30 sec-) min

Etchmg periods stream of H20

are followed by rinsing in a rapid 129)

[291

15341

[29 537 538J

ChromIUm

t 2

3

4

5

6

8

9

1 vol t 1 g NaOH 2 ml HOi 3 vo(J g K[Fe(CN) 3 mlf50IOOOAmin H20J

I g CeISOh2(NH)SOmiddot2HO 5 ml HNO 25 ml 85 Almin HO 28

1645 CeISO)2(NH)SO~H() 43 m HClO HO to make I Iller 25-50

2FeCI47BeIHCI80

HCI

454 g AICImiddot6HO 135 I ZnCl 30 ml HPObull 40() ml HO

9 sat Ce(SO soln IHNO

Dilute HCI or HNO

gt1500 Aimin

800 Amm

IHCIObull 2OCHCOOH4~-~OI-20A dm slammiddot cJ(l~er

Ie steel cathode

Does not require depassivation for etching Cr masks and vacuum-deposited Cr in general photoresist mask can be used

Oxide coating etches at 200 Amin

Recommended for precision patterning ofCr masks on glass substrates

Good for plated Cr photoresist mask can be used

Must depassivate with Zn rod

Photoresist mas~ can be used

Electnxhemlral polh

[14 15507 510J

[519J

1520J

[IS507J

[14516)

(14)

[14517)

[15507513 S17)

[29]

(ConlinLlfd

-- - - --

2

Table XlV (tontid)

Etch rate or Etchmg conditIo etch time Remarkgt Refs

Cobalt

I HC IcHOH 8-9 V 250 AdTn stainless steel 05-15 min Electrochemical polish bluish-green anodic film is sol- [29J uble in HO gIve polished surface WIth slight grain cathode boundary delineatIon

ElectrochemIcal pohsh sohd black film forms which is (29]HPO (98) - 15 V 1-2 Adm Co cathode 5-10 min removed by WIping WIth cotton wool

1539 540JOther electrochemical etc he

Copper ~---~~~-----

0 FeCI 42Be 49 50 Immin Use more dilute solution for slower etching 114 15 50s 509J

2 20-30 HSObull 10-20 crO or KCrO 49 37 Immin (14 15509]

1 g (NH)SO 3 ml HO 32-49 25 Immin Addition of 5 ppm Hg as HgCI activates etehant at [15513 lower temperatures 541-543J

4 5HNO 5CHCOOH 2HSO dilute with HO as Etches Cu and Cumiddotbased alloys at same rate as Ni and (506J

- desired

g KI I g 14 ml H2 0 dip into etch rinse remove

N i-based alloys

Rapid etch but undercutting is limited by formation of [14J

residue with Neutra-clean (Shipley Co Newton an insoluble Cu compound at line edges

Mas)

6 4HNO IIHPO (98) 5CHCOOH 6O-7if 1-2 min Polishing etch (29J

7 2HPOt98I IHO 15-2 V 6-8 Adm Cu cathode 15-30 mm Electrochemical polish [429544 545

()tmiddot~t clflru-hcml1 chhf I~l

fa RIP bull WI1 bull Til bull bull ~-~--~-~-------~-------------~-----~~------------~------

Gallium

Mineral acids or alkali solutions Must be processed below meltmg point (469J

Gold -----~~~~~---~~--~~-~--------~--------------~~------~--------------

)- 4 g KL I g I 40 ml HO 05-1 Immin Better contr~1 of line edges than in more concentnlled [141551 solution solution is opaque so removal from solu tion to observe end point is required

2 3HCL IHNO 32-38 25-50 Immin (IS]

NaCN HO HO mixtures (unspecified composition) [14 15J

4 05 g 12 g NHL 10 ml HO 15 ml cHOH 2if 700 Amin Converts the surface of an underlying Ag layer to the [5101 +shy

iodide thus preventing undercutting -- 04 M KFe(CN) 02 M KCN 01 M KOH 600 Amin Fresh solution must be used no atack on Pd is obshy [58]

served

6 tOO ml HO 05-10 ml HCL 10-JO g NaCl 4-5 V Electrochemical elch which retains bright surface only 1547] 65-2 Adm Mo cathode 20-40 small amount Cl evolved

7 Other electrOChemical etches 129548]

Hafnium

I-cltf HF

lt-6HCIO IOOCHCOOH 18 V Slamle steel cathmiddot ode U several SUCCegtlH dIps with continued agitation

5-10 sec dips

Negative photoreSIst can be ued as mask

ElectrochemICal pohsh -)

[14549J

[29J

See Zircomum etch fltl [291

CConHnurd

--- ---~- --~ -~-------- ~---~ -

Table X (Corllid

Etching condition~

Etch rate or etch lime Remarh Refs

Indium

Mineral acid [469J

IHNO 3CHOH 40-50 V 30 Adm stainless steel cathode cool bath

1-2 min Electrochemical polish [291

Iron

3HNO 7HCI 30H0 6O-7r 2-3 min Dense brown viscous layer forms on surface layer is soluble in solution

[29J

j CgtshyOlt

2

3

4

-I()o( KAI(SOl 12HO

3 liter 1O7c HNO 03 mhr 0 injected 3r

1 HCIO 2OCHCOOH 45-60 V 40-80 Adm stainmiddot less steel cathode

30 mmin

15-30 sec

Slowly soluble

Etches iron plate smoothly 0 removes passive film

Electrochemical polish solid film sometimes forms on the surface during washing removable with dil HF

[469J

[550J

[29J

5 Other electrochemical polishes _

[29J

Lead -----shy----------------------------------------------------------

FeC~ 36-42Be 43-54 [IS 513J -~

9FeCI 42Be IHCI 2rBe 43-49

I HtObull 4CHCOOH Periods 00-10 sec Alternate with immersion in a soln of 10 g molybdic acid and 140 ml NHOH in 240 ml HO to which 60 ml HNO is finally added

[ 15]

(29J

4

5

6

IHNO19HO

35HCIO 63(CHCO)0 20H0 lt3r 50-70 V 9-12 5-10 min A Idm Ph or Cu cathode

()the- k-tdmJ Pbullbulltw

ltlhtum

-------------------

Electrochemical polish

(534J

[291

1191 bull CHOH 30 sec Surface achIeves high luster and is smooth [551]

Magnesium

240-400 g FeCI 330 ml Hel HO to make I liter [469]

1-3HNO 17-19HO [507513 534]

3 fuming HNO type not specifiedl IHO wash imme Periods of 3 sec Reaction rcac Imot explosive violence after -I [29J diately after removal from solution min if allowed to continue it ceases after several

minutes leaving a polished surface

4 7HPO(987cL I3CHOH 1-2V05Admstainle 025 mmin Electrochemical pohsh there is considerable initial [29)

steel or cathode gassing shake anode to remove adhering bubbles

5 5 Other electrochemical etches [29J ~

Manganese

2

IHel IHO

Other dilute mineral acids

1513)

14691

Mercury

Sloght_ diluted HNO

Molybdenum

1469J

5HPO 3HNO 2HO Polishing elch contact to noble metals possible withmiddot OUI mcrcase in etch ratc and undercutling

[57J

IHSO IHNO 1-5H0 ~5-4 J~ 11m imin I~lt I ~ ftm min (~4

Photoresist mask can be used al 25 115507 518

(( OnltnUtJ I

- -~~~ ~ -- --~~-~middotltli0kmiddotmiddot-

Elching condtlons

Tb xrv (Co(Hu~d)

Elch fale or etch tme

Molybdenum (Continuedl

-------shy ~-~---------

Remarh Reh

o

4

6

7

20011 K[Fe(CN))2011 NaOH 3-35 g sodium oxalate add HO 10 make I liter

38HPO 15HNO 3OCHCOOH 75HO

IHSO 7CHOH 80-120 Adm stainless steel cathmiddot ode no agilation

100 ml HPO 20 ml HSObull 40 ml HO 025 II MoO 7(18 V 06-09 Acm slainless sleel graphite or PI cathode stlmng

Other etches

-ltmmin

05t m mrn

I min

94tmmm

Neplunium

Also usable as electrochem etch usinll stainless cathode al 6 V pholoresisl masks applicable

Photoresist mask can be used

Electrochenca polish

Electrochemical pohsh supenor surface finish

steel [14 1551 5075521

1518]

29]

1553

[29 38 57 554-5561

HCI 1557

5HNO 5CHCOOH 2HSObull HO as desired

IHNO IHCI 3HO

FeCI 42-49B 43-54

4

Igt

3HNO IHSO I HPO 198) 5CHCOOH 85-95

IHNO IHO or 9HPO IHNO or 9OHPO 15HNO 4HCL IHO

IOHSo OHO HPO lt-1 NISO JO ~ltr

Nickel

12 -25 tm min

05-1 min

1-2mmln

Etches Ni and Nimiddotbased alloys at same rale as Cu and (506)

Cumiddotbased alloys

Spray elching recommended 1507] o

Photoresist mask may be used [15507513)

Gives very llood polish 1291

Polishing elchants for eleclrol N-P very undercutllng despile conlacl to noble melah

hllie 1571

For ecclrole N film nu undCrcuttmJL mll r fMlfhnn uc-ful (Of ~ittrnl(H Cu

com I ~S8j

bull ~ 8

~7HSObull 4)H 1 U 0 ~ ALm

Other electrochemical polishegt 2 min mm1n lJellrtKht 1~lil1 rulnh

15~ 5601

129J

NiobIum

2 Lacue acid IHSO bull IHF 15~20 V PI cathode sIllmiddot 5-10 mm nng EleClrochemical polish

129]

7HF 7HNO 26HO 49 12-20 V 20~34 Adrn PI cathode Electrochemical etch 14(9) _

9HSO IHF H-45 50 V 2 Adrn PI Or carbon 5-10 min

cathode Electrochem etch temp nses during use cool bath [29]

~--~-----~----~----~----Osmium

Aqua regia 1557)

Palladium

IHCI 10HNO IOCHCOOH 1000 Aim

Aqua rega 15611

1513) Platinum

SHO 7HCI I HNO 85 400-500 AImln 2 f562 563)Aqua regIa precede etchin by 30 sec ImmersIOn in HF

EtCh tIme mlled because photoreSIst mask demiddot 114 507i strayed

3 M HCI 03-+ 14 V versus SeE modIfied Inangumiddot -1000 Almln lar waveform -600 Hz magneuc slmng Electrochem elch good resolu[lOn either po or neg 15141

photoreslS[ usable

Plutonium

I HPOI981 1 diethlene glvcol 5 V ltAdm lainmiddot L 10 mm less steel carhode Electrochemical pohsh

1291

(Conllnttf d

~--~~- - ~ -_ --__~ ~- h __ ~_

Table XIV (Cotiu~d) ~~------- ~---~----~~-~-~-----

Etch rate or Etchmg conditIOns tch time Remarks Ref

Polonium

Dilute mineral acid [557J

Potassium

CHOH or iCH)CHOH 3 sec (ethanoB or 10 SeC (Ioproshypanol)

Brilliant smooth surface obtained [551]

Praesiodymium

Mineral acid -~-~--~-~----------~~------ -------shy

Rhenium

[557]

Dilute HNO [557]

Rhodium

3 M HC -03- + 14 V versus SCE modified triangumiddot ElectTOchem etch I Im line spacings ofRh films over [514]

lar waveform -600 Hz magnetic stirring 5000 ATi on 5i dearly resolved

Ruthenium --------------------~----------------

Fused alkalis [557]

Samarium

Minual acids (557J

Sdenium

HStl ~( IM tf U undtf CkmCnl1 womtunduton 11 bull ~---~--~~-----

Silver

11 g Fe(NO) 9 ml HO 44-49 20 IJmmm Photoresist mask can be used [14 15 507J

2 5-9HNO1-5HO39-49 12-251Jmmin 11415517J

3 35 g AgCN 37 g KCN 38 g KCO 100 ml HO 25- 10 min Electrochem etch best polishing in region of voltage (29) 30 V 1 Alent Ag cathode 10 stirring and currel1t instability

4 3HNO 19H0 2 V [ainle steel cathode ElectrOChemical etch [507)

5 Kl-I etches listed for Cu and Ag O3-llJmsec Immersion followed by HO rinse [14]

60 Asec Useful for pattern etching with photoresist mask rinse [512] quickly after etching

6 4(HOH INHOH IHO

Sodium-

CHtCH)CHOH (nonyl alcohol) 30 sec Brilliant smooth surface [551)

Stronlium

Liquid ammonia [557]

Tanlalum

2

9NaOH or KOH 00laquo) IHO heal alka to 9(t Ihen add HO

5HSObull 2HNO 2HF

1-2HNO IHF 1-2H0

100(l-~OO(l A min

5-20 sec

4 9HSObull IHf (-4 50 cathgtd

A urn 11 1 carb -1(1 rnln

Metal (eg Au) rna muq be used very httle undermiddot cutting etche TO and Ta- al same rale 3 Ta

116~ 16~J

POlishing elch [29 522 5~~

HO rna) be omllled ftgtr fasler elch espeCially if film coniaim oxygen and reslsh etching fasler etch reshyduce re t al1a(~

(14 5 HI

Eletruchernlal etch temp of solUlion ne dunng ue and 11 rna he nece ar~ tp cool hath

129

- -~-~-=-

-4

2

Tabl Xf (Colltlllud)

Etch ratr or Etching condtion rtch time Remarks Refs

Tellurium

2HND3HO [513]

240 g (NH~So bring to I liter with HO [513J

Terbium

M ine 1 acid~ [557]

Thallium

to

HND or HSO

Thonum

------------~----

[557]

14CHCOOH 4HCIO IHO -1060 Adrn stain- 7-12 sec Electrochemical polish [29] less steel cathode

Tin

FeCI 36-42B 32-54 ~------~-

[15 513)

2 IHNO49CHOH [534] (

j iCIO lt35 5O-W V 40 Adrn AI cathode hold piece vertically and rotate at 50-100 r Imin

420 fLmmin Electrochemical polish on large sunaces orange peel effect may occur

(29]

4 Other electrochemical polishes [29]

Titanium

9H0 IHF 3gt 12 fLmmin Photorist mllsk may be used 114 15 507]

2 7Hli 21iNII IH~ n IImmln PhOI maoa m~ be uWd 114155071

bull - bull bull bull

tllO mllHOH 2U ml middotbutyl hoI t2 II Alll ~ II I-JeC1fochcml41 fKlhh 14m) zne 30-50 V 12 Adm ~Utinle Ied cathode

4 3HCIO 5OCHCOOH 200 30 V 30-40 Adm Ti 2 min E)ectrochem etch anode to cathode distance about 129] cathode 3 cm

5 Other electrochemical etches [29 564 5651

6 See Zirconium etch no [29]

Tungsten ~--~~-----~ -------~-------~----~---~~-----------------~~----~~-~--~~~-~---~--~--~------

34 g KHPO 134 g KOH 33 g KFeICN) HO to 1600 Amin Photoresist mask may be used high resolution (1- (515] make I liter 2 Lml can be achieved

2 5 KOH 5 KFe(CN) 1 sunaclant -2302 --23Lmmin Electrochem etch photoresist mask can be used good [51J Acm PI cathode pauem resolution

5-10 NaOH 6 V 3-6 Adm stainless steel cathode Electrochem etch rotation of anode or agitation of [29 513 566deg) - electrolyte with N is necessary

4 Other etches [5158515 555 567]

Uranium

1-2HClO 2OCHCOOH 5O-W v 5 Adrn stainless 19 fLmmill Electrochemical polish (29) steel cathode

2 Other electrochemical pohshe [29]

VanadIum __----------------___---------__-_

1-2HClO 18-19CHCOOH lt35 50-60 V 16-24 1-2 min Electrocherrucal polish a second polishing ofabout the f29] Adm stainless steel cathode sarne duration ill a fresh soln sometimes necessary

---~-~-----~----~--

Ytlcrbium -----~---------------~-----

lhneraJ aCid 1557j

fCwwj

Tampble IX (Colltillll~d)

No Etchant Substrate etching conditions Application etch rate remarks Refs

19 25HCI0bull 75CHCOOH GaAs electrolytic gently flowing from Thinning specimens for electron microscopy [424J an orifice above sample at 42 V

20 10--40 KOH or NaOH GaAs p type and heavily doped n type Electropolishing to mirror-smooth surfaces [428J

electrolytic 1-5 Acm

21 10 KOH (100) (110) (III) GaAs n type electroshy Anodic dissolution [426J

lytic flowing 10 KOH

22 3 M NaOH (100) GaAs p type spray electrolytic Selective removal of p-type substrate leaving [429J

100 mAcm n-type epi GaAs or GaAsP ~ 23 0025M NaOH-OOOI M EDTA (100) (III) Ga (1111 As GaAs n type Electropolishing (430J

electrolytic illumination

24 HCI-HO GaAs n type electrolytic Controlled thinning [431]

25 001-1 N HNO (100) GaAs n type electrolytic 10-20 Controlled electroetching [432]

mAcm 2-3 V

26 H AsH HC) (900 3 2 (100) (III) GaAs Te Zn Si Cr doped Substrate polishing prior to epitaxy 7-11 (434]

cmmin) vapor phase 9000 Lmmin nonpreferential specular 0 27 IOOCHOHIBr GaAs General etching 8 Lmhr

28 5HSObull IH0 GaAs Polishing 25 Lmhr

29 70HO 20HO 10 fonnic acd GaAs Surface cleanup

30 95CHOH 58r (100) GaAs n-type CVD SiO as etch Preferential etching of (32) Ga plane (416) mak

If r I j t 11 ~_ p bull mbull [ bullbullbull1middot ~~ rlIIJIUII _

Tampble X

Group I- Compound Semiconductors GaP

No Etchant Substrate etching conditions Application etch rate remarks Refs - 1-20 Br 99-80 CHOH GaP (solution

niques) or Pelion cloth techshy Generll etching and polishing (402J

2

4

6

R

9

1 Br 997r- CHOH

2HCI IHNO IHO

2HCI 2H0 I HNO

2HCI 2HO I HNO

Aqua rega

2HCI 2HSObull 2HO IHNO

3HSObull IHO (33(-) IHO

CHOH sal with Br I HPObull freshly mIXed

GaP

III) GaP hot

P (J II) GaP

(III) (ijj) (100) GaP 601-2 min

(ijj) GaP

P III GaP 5 min cold then 50 or 10 sec etching on Pelion cloth

GaP 60 5 min

(II J) GaP chem-mech technrque wafer rotates face down

Polishing highest-quality surface -025 Lmmin

Polishing III surface

Polishing P III surface

Polishing

Groove and pattern etching SiO mask

Polishing P III surface Ga III face pitting etch rate depends on Te carrier conc

Surface etching for saw damage removal I Lm5 min etches p-type preferentially

Work damage remoal prior to no 10 elch

120)

1438)

(439]

[442]

1441]

1440J

[443444)

14364311

10

II

5HSObull IHO IHO

Etchant no 9

( III) GaP 80 mrn

( III ) GaP 50

SunSlrale preparation for ep growth after no 9

and before no II etch 06 Lm mm optimal

Substrate final etch for epi growth Immediatel

after no 10 etch 15 Lmmin optimal

1431)

1437)

-------shy --------shy(ConlinUld I

- -~-~~ ~--~-~- - shy

Table X (Continued

No Etcnant Substrate etcnlng conditions Application etch rate remarklt Rdbull

11 10 M KFe(CN)-O) M KOH (1001 () II) GaP and p-type 60_95 Polishing and mesa etching SiO or Ti mask [445] sllrring

POll) -type 95deg 260 mhr polished Ga(llll Hype SO I J5 mnr smooth textured

P(lOO) -type SO 210 mihr polished

13 Cl-HO sat soln (III) (1001 GaP p epi on n substrate PoliShing -05 mmin [446J

14 HPO (iii) (1111 (1001 GaP 150-200C Groove etching Au mask V grooves result 1442)

15 IHfIHO GaP p type on n substrate Preferential etching of p-type GaP on n type (443) r ~ 16 7NaOCI (525 wt ) IHCI GaP n type on p substrate electrolytic Preferential etching of n-type [443) middottype anode PI cathode

17 16H0 2NaOCI 2HCI III) GaP plii h by chemicaliet etching Polishing lIat smooth surfaces [2(6) Ga(lll) by jet electroetching

18 Cl CHOH (concentration not Ga( III) PI Ill) GaP electrolytic jet Localized Ihinning of specimens for transmission [447)

specified) electron microscopy

n --~3 N NaOH GaO II) P( ii j) GaP 20 electrolytic PI Anodic dissolution and selective etching [448J

cathode

20 01 N HNo (ill) GaP mAlem

Hype electrolytic 20 Anodic dissolution 1250 300 sec (432J

21 2HNOIHCI GaP 1-2 min Polishing of some orientations (437aJ

~ 0 (HOHat soln GaP immer~e sample while (I bubnle Ihroullh 1 onln 20 mtn

Poli_hlnj 40~J

171 lJ r tlrt r r 111[ II NI1I 1 I 11111 bullbullbull 11 IFF HI II 1 illMil 111 4-Table XI

Other Group IIl-V Compound Semiconducfon

~=-terial No Etchant Conditions Application etch rate remarks Rerf ---~

AIN IO laOH or hot HPO 30-80 (NaOH) General etching (449]

BN ~ HPO or HO 0laquo1 Hot General etching of pyrolytic films (450 450a]

BP 3 10 NaOH Electrolytic in dark 01-10 Aem Electrochem etching pmiddottype etches (451J gt IOOx faster than nmiddott ype

J AISb 4 lal IHF IHO IHO I min (a) followed by 2 sec (h) Etching (l ii) face (452J _4

(h) IHC IHNO

Gal 5O7r NaOH L9O General etching [453J 6 01 NaOH Electrolytic jet etching Selective etching of singlemiddotcrystal (454]

vapor-transpon grown films

7 Hf() HOI Etches but develops etch figures (455J

GaSp 8 99-800f CHOH 1-2or Br General polishml [402J 9 9HNOIHF 1-) min General pollhing 402J

10 2HNQ IHF ICHCOOH I) sec Pollshmg develops pits on (I J J I face (452J II IHF lHNn IHO Etching I j j j 1 face 1457] 12 10 citric aCid ()O wI 7r I 1HO pmiddottype 5) photoresist masks Pallern etching (100) face 10 Asec 418J

_--__w-_~ _~_ -~--~ltf

J

Table XI (Continued)

Matenal No Etchant CondItion Application etch rate remarks Reh ~---------- --~-----~-~--~

InAs 13 Etchant no 1 Polishing (II J) and ell il faces (460]

14 5HNo 3HF 3CHCC)()H 006 Br General etching (458J (CP4)

15 75HNO UHF 15CHCOOH 006 Br 55 Etching d i lJ face etch pits on ( II) face [458J

16 HCI 75 General etdng 5 mgcm min 1457 459J

17 04 M Fe -WHCI General etching (452] v 0lt 18 996 ml CHCOOH 04 g Br General polishing 1423J

InP 19 99CHOH IBror9OCHOH IOBr General polishing 40246IJ

20 IHCIIHNO Etching (100) face hillocks on (l j h face [46IJ

inSb 21 I CHOH (concentration not specified) General polishing (402J

22 Etchant no 17 General etching [452]

23 IHF IHNO 2-5 sec Polishing (ii i) and (110) faces no etchshy [423465] 0

ing on (III) or (100) faces ltj

24 5HF 5HNO 2HO 20 sec Etching (100) and (110) faces [8]

25 5HNO bull 3HF 3CHCOOH (CP-4AI 5-30 sec General polishing [463464]

26 IHO ICHCOOH 1 CP4 1 min Etching ( i I) (i Ii) faces etc 1463)

27 2HF IHNO ICHCOOH 5-30 sec Polishing etch pits on (III) face [452J

2X 4HO IHF IHO 5-10 sec Etching (i jj) face [457)

2V Etchanl no 12 311 pholnrt mllk Pallem etchinjl 11001 race 60 Aec 1418)

n II 11 1IUIiI1r Ir PI IF IflTlE 71 bullbull bull bull bull -t

Table XII

Group II-VI Compound Semiconductors

Material No Etchant Conditions Application etch rate remarks Refs

10 KOH General etching 1162468) 2 HCI 120 General etching (467] 3 HPO-HSO boiling General etching at low rate [467468]

CdO 4 Mineral acids or NH salts General etching [4691

CdS 5 100 ml HO 1 mI HSO 008 g CrO 80 10 min Etching of [IOTO) face [471) J Jgt -c

6 16 N HSO-05 M KCrO 955-10 min General etching and polishing etch pits on (jj j) face

[472J

7 300 ml precip sihca 90 ml HNO 10 g AICIlner HO

Chem-mech pOlishing Poromenc disk 240 rlmin 370 gcm

Pohshing (0001) face [475]

8 70HO 30HCI Rotating on Pelion cloth Polishing Cd S and prismatic faces [473J 9 1000 ml HO 137 g KCl 05 ml Hel pH 25 Politegt Pix pad 58 rlmin

025-)40 kgem Polishing Cd face [476J

10 1000 mI HO 131 g KCI 16 ml HC) pH 10 same as no 9 Folishing S face 1476]

CdSe II 30HNO 20HSO IOCHCOOH 40 S sec General etChing thick films forming (472) OIHCI are soluble in HSO

CdTe 12 3HF2HOIHO Polistung (J III and (iii) faces etch 14711 pitgt on (ill) face

(Continued I

---_-_~_~~~IC-Ymiddot

Table XII (Continued)

Malenai --lt--ltshy

Nolt Etchanl Condition Application etch rale remark Reflt

13 2HNO 2HC lHO Polishing [477]

14

15

20 ml HO 10 ml HNO

995 CHOH 05Br

4g KCrO

Slnp deposil 45 min

formed wth Cs

Polishong 10 mirrorlike surface

General etching

[477J

[478]

CdTe 1005)-HgTe (095)

16 6HNOIHCI Rinse in IHCI-ICHOH Polishing 1479]

~

HgSe 17 50HNO 20HSO (18 N) IOCHCOOH IHCI

4010-15 min Polishing 1472]

HgTe 18 6HNO IHC IHO 10-15 min Polishing [472]

ZnO 19 Mineral acids solns

or alkali or NHCI General etching [469

ZnS 20 Elchant nolt 6 95deg 10 min Polishing to high polish etch pits on ( Ill) face

1472J

21 Elchant no 15 Same as nolt 15 General etching etch pits on (Ill)

face (478)

ZnTe 22

23

4HF3HNO

Etchant no 15

Stnpfilm formed with HCI then HO

Same as no 15

General etching and polishing 14721

1478)

p F II I bullbullbull jill bull M U bull bull bull TbW lUll

Orhrr Sritutd Compound gtrmlnmduc(on

Malerial No Elchant Condition Application etch rale remarks Refs

AgSe 5HSO lHO 50 ~ min rinse in EDTA solution then Polishing of some orientations 1479J H 20

2 2KOH sat) 2 ethylene glycol 80 2 min following damage removal Polishing 14791 IHO with etchant no I

Aile ~ 3iHOH2HO Remove film by brushing under water Polishing of some onentaions 1479]

BiSe 4 IHO tHCI Damaged layer following much polshy Polishing and removal of workshy 1470J ishing damaged layers

2HNOIHCI May be diluted with H20 Cleaning and etching 1470 481]

BIltTe 6 Etchant io 5 Cleaning and etching [470 481J

Hg fCdI1e 7 80CHOH20Br Rinse with CHOH Removal of surface 1482483]

InO Sn doped

8

I

HSO

HCI

50-60 Cr film etch mask Pattern etching -05 Amhr

Pattern etching

1484]

14851 10 10 M oxalic acid aqlt soln 50 Shiple~ AZ1350 etch mask Pattern etchmg of annealed films 1486]

InO Sno 14 ltII

II 5~S HI Immerse sample vertically Shipley AZ- 1350H mask postbaked 90 min

Precision pattern etching 25 Asec [4871

I~O

12 2HCI IHO Zn pder Paint Zn powder-HO slurr) on submiddot Rapid etchm~ 150 Asec 1487J trate Immerse hOrlZ IOto HCI-HO 0 mask as 10 nt I(I

In-Je I 19CHCOOH acidlt 1 Br

sat with citric FInish b~ ftooding with CHCOOH sat with cllnc aCid

Polishing 1488]

Inle ISr alh~ shy

14 4 clfn aCld ~uln

~H~() IHF at vlth Bi Polhinf 1488

-~~~-~~-- -----~-~--~

(ConllnUfd i

_~_F-lt--~-_-~__~

4

Table XIII iCollrillutd)

Material 0 Etchant ConditIons Applications etch rate remarks Refs

PbS 15 30HCI 10HNO ICHCOOH 50 few min CHCOOH

then rinse with 10 Polishing [489]

16 HNO 70 Rapid etching [489]

PbSe 17 5KOH (45) 5 ethylene glycol IHO

Electrolytic add HO during etching to maintain rate remove stains with 5()f

CHCOOH

Thinning specimens for electron transmission microscopy

[490]

18 Etchant no 17 403 min Polihino [480]

PbTe 19

20

45 ml HO 35 ml glycerol 20 ml CHOH 20 g KOH

Etchant no 19

Electrolytic 4-6 V 02 Aem

Electrolytic 10 V rinse in CHOH

Thinning specimens for electron transmission microscopy

Polishing

[493]

1492) (494)

~gtb_rSnrSe 21 10 ethylene glycol 10KOH (sat aq soln at 25deg) I HO

Felt covered etch ant

wheel saturated with Polishing [495) [496]

Pb_SnTe 22 Etchant no 19 Electrolytic 10 V rinse in CHOH Polishing [492) [494)

23 95HBr 5Sr 1-2 min rinse many times with CHOH followed with slight etching with no 22

Polishing faster than etchant no 22 [494)

sr 24 3-IOHOIHCI Electrolytic 5-40 mAcm Pattern mask

precision etching SiO used 1600 Almin at 20

[498J

mAcm

25 HCI Zn powder Zn powder in photoresist in Ref 500 Paltern etching 497499

500)

SnO Sb doped

26 HC Zn powder Pattern etchinB 150IJ

E Conductors

Table XI

Elemental Metal

Etch rate or Etching conditions etch time Remarks Refs

Aluminum

4HPO 4CHCOOH lHNO IHO 350 Amm Polishing etch contact to noble metals is possible withshyout increases in etch rate and undercutting

[57504J

2 75 NaCO 35 g NaPO12HO 16 g KFe(CN) bull 05 liter HO

1300 Amin Polishing etch contact to noble metals is possible withshyout increase in etch rate and undercutting

[57]

16-J9HPObull IHNO 0-4HO 40 stirring 1500-2500 Amin Gas evolution OCcurs [14J

4

5

IHCIO ICHCO~O

74IHPO 185HO 73HNO 500

3 mimin

9000 Amin

(29]

[46505]

6

7

8

9

1 HC 4HO 8ltr

2Ok NaOH 60-90

FeCI 12-36degBlt

IOHCI IHSO 9HO 49 25-50 mmm

For fine hne etchmg photoresist masks can be used

Photoresist mask can be used

[507 532J

114507)

[15513J

[15]

10 01 M KB0051 M KOH06M KFe(CNt pH 13tgt

Immm No H j eJlved 158]

II 1 Electngt Glo 100 (Electro Glo Co ChIcago) ~HPO bull 79 7-10 006 Acm PI cathode

ElectrOChemical polish excellent polishing occurs (533J

12 Olher eIlaquoIr(Khemlal etche 291

~( dnlttrlUJ j

~~---~~-~ - --~----~- -----~

- - _H-~~~~~_W __

Table XIV (Continued)

Elch ralr or Etchl ng conditIons etch time Remark Refs

~----

Antimony

Aqua regIa or hot HSO 1469J

2 5ltlt AgNO [5341

3 I g FeCI 3 ml HC 12 ml HO 1534J --~--- ---- shy

Aroenic --------------- --------- --------~

HNO 1469J

Beryllium 5 g HSObull 75 g HPO(98) 7 g crO 13 ml HO 49- JLmmin Passive film formed removable by immersion for 15- [29468)

50 30 sec in 10 HSO

2 HCI 1535J

1 H2SO preset voltage 30 V 2240 Almin Electrochemical etch [468J

4 1 KOH preset voltage 50 V 260 Amin Electrochemical etch [468] f

bull ~middot-ther electrochemical etches 129 536J

Bismuth

Hot HSO 469J

2 5ltlt AgNO [534J

3 lt49 ml sal KI soln I ml HCI 5-7 V 20 Adm stainmiddot Penltxh of 30 sec Electrochemical etch allo brown film formed 10 dismiddot 129] Ic IlrC or cKrhon cathode Ive een elchml period

bull bull bull - - bull I 1 -4 CadmIum

3 fuming HNO (type not specified) IHO

7CHCOOH 3 fuming HNO (type not specified)

I g I 3 g Kl 10 ml HO

olectrochemical etches and polishes

Periods 00-10 sec

30 sec-) min

Etchmg periods stream of H20

are followed by rinsing in a rapid 129)

[291

15341

[29 537 538J

ChromIUm

t 2

3

4

5

6

8

9

1 vol t 1 g NaOH 2 ml HOi 3 vo(J g K[Fe(CN) 3 mlf50IOOOAmin H20J

I g CeISOh2(NH)SOmiddot2HO 5 ml HNO 25 ml 85 Almin HO 28

1645 CeISO)2(NH)SO~H() 43 m HClO HO to make I Iller 25-50

2FeCI47BeIHCI80

HCI

454 g AICImiddot6HO 135 I ZnCl 30 ml HPObull 40() ml HO

9 sat Ce(SO soln IHNO

Dilute HCI or HNO

gt1500 Aimin

800 Amm

IHCIObull 2OCHCOOH4~-~OI-20A dm slammiddot cJ(l~er

Ie steel cathode

Does not require depassivation for etching Cr masks and vacuum-deposited Cr in general photoresist mask can be used

Oxide coating etches at 200 Amin

Recommended for precision patterning ofCr masks on glass substrates

Good for plated Cr photoresist mask can be used

Must depassivate with Zn rod

Photoresist mas~ can be used

Electnxhemlral polh

[14 15507 510J

[519J

1520J

[IS507J

[14516)

(14)

[14517)

[15507513 S17)

[29]

(ConlinLlfd

-- - - --

2

Table XlV (tontid)

Etch rate or Etchmg conditIo etch time Remarkgt Refs

Cobalt

I HC IcHOH 8-9 V 250 AdTn stainless steel 05-15 min Electrochemical polish bluish-green anodic film is sol- [29J uble in HO gIve polished surface WIth slight grain cathode boundary delineatIon

ElectrochemIcal pohsh sohd black film forms which is (29]HPO (98) - 15 V 1-2 Adm Co cathode 5-10 min removed by WIping WIth cotton wool

1539 540JOther electrochemical etc he

Copper ~---~~~-----

0 FeCI 42Be 49 50 Immin Use more dilute solution for slower etching 114 15 50s 509J

2 20-30 HSObull 10-20 crO or KCrO 49 37 Immin (14 15509]

1 g (NH)SO 3 ml HO 32-49 25 Immin Addition of 5 ppm Hg as HgCI activates etehant at [15513 lower temperatures 541-543J

4 5HNO 5CHCOOH 2HSO dilute with HO as Etches Cu and Cumiddotbased alloys at same rate as Ni and (506J

- desired

g KI I g 14 ml H2 0 dip into etch rinse remove

N i-based alloys

Rapid etch but undercutting is limited by formation of [14J

residue with Neutra-clean (Shipley Co Newton an insoluble Cu compound at line edges

Mas)

6 4HNO IIHPO (98) 5CHCOOH 6O-7if 1-2 min Polishing etch (29J

7 2HPOt98I IHO 15-2 V 6-8 Adm Cu cathode 15-30 mm Electrochemical polish [429544 545

()tmiddot~t clflru-hcml1 chhf I~l

fa RIP bull WI1 bull Til bull bull ~-~--~-~-------~-------------~-----~~------------~------

Gallium

Mineral acids or alkali solutions Must be processed below meltmg point (469J

Gold -----~~~~~---~~--~~-~--------~--------------~~------~--------------

)- 4 g KL I g I 40 ml HO 05-1 Immin Better contr~1 of line edges than in more concentnlled [141551 solution solution is opaque so removal from solu tion to observe end point is required

2 3HCL IHNO 32-38 25-50 Immin (IS]

NaCN HO HO mixtures (unspecified composition) [14 15J

4 05 g 12 g NHL 10 ml HO 15 ml cHOH 2if 700 Amin Converts the surface of an underlying Ag layer to the [5101 +shy

iodide thus preventing undercutting -- 04 M KFe(CN) 02 M KCN 01 M KOH 600 Amin Fresh solution must be used no atack on Pd is obshy [58]

served

6 tOO ml HO 05-10 ml HCL 10-JO g NaCl 4-5 V Electrochemical elch which retains bright surface only 1547] 65-2 Adm Mo cathode 20-40 small amount Cl evolved

7 Other electrOChemical etches 129548]

Hafnium

I-cltf HF

lt-6HCIO IOOCHCOOH 18 V Slamle steel cathmiddot ode U several SUCCegtlH dIps with continued agitation

5-10 sec dips

Negative photoreSIst can be ued as mask

ElectrochemICal pohsh -)

[14549J

[29J

See Zircomum etch fltl [291

CConHnurd

--- ---~- --~ -~-------- ~---~ -

Table X (Corllid

Etching condition~

Etch rate or etch lime Remarh Refs

Indium

Mineral acid [469J

IHNO 3CHOH 40-50 V 30 Adm stainless steel cathode cool bath

1-2 min Electrochemical polish [291

Iron

3HNO 7HCI 30H0 6O-7r 2-3 min Dense brown viscous layer forms on surface layer is soluble in solution

[29J

j CgtshyOlt

2

3

4

-I()o( KAI(SOl 12HO

3 liter 1O7c HNO 03 mhr 0 injected 3r

1 HCIO 2OCHCOOH 45-60 V 40-80 Adm stainmiddot less steel cathode

30 mmin

15-30 sec

Slowly soluble

Etches iron plate smoothly 0 removes passive film

Electrochemical polish solid film sometimes forms on the surface during washing removable with dil HF

[469J

[550J

[29J

5 Other electrochemical polishes _

[29J

Lead -----shy----------------------------------------------------------

FeC~ 36-42Be 43-54 [IS 513J -~

9FeCI 42Be IHCI 2rBe 43-49

I HtObull 4CHCOOH Periods 00-10 sec Alternate with immersion in a soln of 10 g molybdic acid and 140 ml NHOH in 240 ml HO to which 60 ml HNO is finally added

[ 15]

(29J

4

5

6

IHNO19HO

35HCIO 63(CHCO)0 20H0 lt3r 50-70 V 9-12 5-10 min A Idm Ph or Cu cathode

()the- k-tdmJ Pbullbulltw

ltlhtum

-------------------

Electrochemical polish

(534J

[291

1191 bull CHOH 30 sec Surface achIeves high luster and is smooth [551]

Magnesium

240-400 g FeCI 330 ml Hel HO to make I liter [469]

1-3HNO 17-19HO [507513 534]

3 fuming HNO type not specifiedl IHO wash imme Periods of 3 sec Reaction rcac Imot explosive violence after -I [29J diately after removal from solution min if allowed to continue it ceases after several

minutes leaving a polished surface

4 7HPO(987cL I3CHOH 1-2V05Admstainle 025 mmin Electrochemical pohsh there is considerable initial [29)

steel or cathode gassing shake anode to remove adhering bubbles

5 5 Other electrochemical etches [29J ~

Manganese

2

IHel IHO

Other dilute mineral acids

1513)

14691

Mercury

Sloght_ diluted HNO

Molybdenum

1469J

5HPO 3HNO 2HO Polishing elch contact to noble metals possible withmiddot OUI mcrcase in etch ratc and undercutling

[57J

IHSO IHNO 1-5H0 ~5-4 J~ 11m imin I~lt I ~ ftm min (~4

Photoresist mask can be used al 25 115507 518

(( OnltnUtJ I

- -~~~ ~ -- --~~-~middotltli0kmiddotmiddot-

Elching condtlons

Tb xrv (Co(Hu~d)

Elch fale or etch tme

Molybdenum (Continuedl

-------shy ~-~---------

Remarh Reh

o

4

6

7

20011 K[Fe(CN))2011 NaOH 3-35 g sodium oxalate add HO 10 make I liter

38HPO 15HNO 3OCHCOOH 75HO

IHSO 7CHOH 80-120 Adm stainless steel cathmiddot ode no agilation

100 ml HPO 20 ml HSObull 40 ml HO 025 II MoO 7(18 V 06-09 Acm slainless sleel graphite or PI cathode stlmng

Other etches

-ltmmin

05t m mrn

I min

94tmmm

Neplunium

Also usable as electrochem etch usinll stainless cathode al 6 V pholoresisl masks applicable

Photoresist mask can be used

Electrochenca polish

Electrochemical pohsh supenor surface finish

steel [14 1551 5075521

1518]

29]

1553

[29 38 57 554-5561

HCI 1557

5HNO 5CHCOOH 2HSObull HO as desired

IHNO IHCI 3HO

FeCI 42-49B 43-54

4

Igt

3HNO IHSO I HPO 198) 5CHCOOH 85-95

IHNO IHO or 9HPO IHNO or 9OHPO 15HNO 4HCL IHO

IOHSo OHO HPO lt-1 NISO JO ~ltr

Nickel

12 -25 tm min

05-1 min

1-2mmln

Etches Ni and Nimiddotbased alloys at same rale as Cu and (506)

Cumiddotbased alloys

Spray elching recommended 1507] o

Photoresist mask may be used [15507513)

Gives very llood polish 1291

Polishing elchants for eleclrol N-P very undercutllng despile conlacl to noble melah

hllie 1571

For ecclrole N film nu undCrcuttmJL mll r fMlfhnn uc-ful (Of ~ittrnl(H Cu

com I ~S8j

bull ~ 8

~7HSObull 4)H 1 U 0 ~ ALm

Other electrochemical polishegt 2 min mm1n lJellrtKht 1~lil1 rulnh

15~ 5601

129J

NiobIum

2 Lacue acid IHSO bull IHF 15~20 V PI cathode sIllmiddot 5-10 mm nng EleClrochemical polish

129]

7HF 7HNO 26HO 49 12-20 V 20~34 Adrn PI cathode Electrochemical etch 14(9) _

9HSO IHF H-45 50 V 2 Adrn PI Or carbon 5-10 min

cathode Electrochem etch temp nses during use cool bath [29]

~--~-----~----~----~----Osmium

Aqua regia 1557)

Palladium

IHCI 10HNO IOCHCOOH 1000 Aim

Aqua rega 15611

1513) Platinum

SHO 7HCI I HNO 85 400-500 AImln 2 f562 563)Aqua regIa precede etchin by 30 sec ImmersIOn in HF

EtCh tIme mlled because photoreSIst mask demiddot 114 507i strayed

3 M HCI 03-+ 14 V versus SeE modIfied Inangumiddot -1000 Almln lar waveform -600 Hz magneuc slmng Electrochem elch good resolu[lOn either po or neg 15141

photoreslS[ usable

Plutonium

I HPOI981 1 diethlene glvcol 5 V ltAdm lainmiddot L 10 mm less steel carhode Electrochemical pohsh

1291

(Conllnttf d

~--~~- - ~ -_ --__~ ~- h __ ~_

Table XIV (Cotiu~d) ~~------- ~---~----~~-~-~-----

Etch rate or Etchmg conditIOns tch time Remarks Ref

Polonium

Dilute mineral acid [557J

Potassium

CHOH or iCH)CHOH 3 sec (ethanoB or 10 SeC (Ioproshypanol)

Brilliant smooth surface obtained [551]

Praesiodymium

Mineral acid -~-~--~-~----------~~------ -------shy

Rhenium

[557]

Dilute HNO [557]

Rhodium

3 M HC -03- + 14 V versus SCE modified triangumiddot ElectTOchem etch I Im line spacings ofRh films over [514]

lar waveform -600 Hz magnetic stirring 5000 ATi on 5i dearly resolved

Ruthenium --------------------~----------------

Fused alkalis [557]

Samarium

Minual acids (557J

Sdenium

HStl ~( IM tf U undtf CkmCnl1 womtunduton 11 bull ~---~--~~-----

Silver

11 g Fe(NO) 9 ml HO 44-49 20 IJmmm Photoresist mask can be used [14 15 507J

2 5-9HNO1-5HO39-49 12-251Jmmin 11415517J

3 35 g AgCN 37 g KCN 38 g KCO 100 ml HO 25- 10 min Electrochem etch best polishing in region of voltage (29) 30 V 1 Alent Ag cathode 10 stirring and currel1t instability

4 3HNO 19H0 2 V [ainle steel cathode ElectrOChemical etch [507)

5 Kl-I etches listed for Cu and Ag O3-llJmsec Immersion followed by HO rinse [14]

60 Asec Useful for pattern etching with photoresist mask rinse [512] quickly after etching

6 4(HOH INHOH IHO

Sodium-

CHtCH)CHOH (nonyl alcohol) 30 sec Brilliant smooth surface [551)

Stronlium

Liquid ammonia [557]

Tanlalum

2

9NaOH or KOH 00laquo) IHO heal alka to 9(t Ihen add HO

5HSObull 2HNO 2HF

1-2HNO IHF 1-2H0

100(l-~OO(l A min

5-20 sec

4 9HSObull IHf (-4 50 cathgtd

A urn 11 1 carb -1(1 rnln

Metal (eg Au) rna muq be used very httle undermiddot cutting etche TO and Ta- al same rale 3 Ta

116~ 16~J

POlishing elch [29 522 5~~

HO rna) be omllled ftgtr fasler elch espeCially if film coniaim oxygen and reslsh etching fasler etch reshyduce re t al1a(~

(14 5 HI

Eletruchernlal etch temp of solUlion ne dunng ue and 11 rna he nece ar~ tp cool hath

129

- -~-~-=-

-4

2

Tabl Xf (Colltlllud)

Etch ratr or Etching condtion rtch time Remarks Refs

Tellurium

2HND3HO [513]

240 g (NH~So bring to I liter with HO [513J

Terbium

M ine 1 acid~ [557]

Thallium

to

HND or HSO

Thonum

------------~----

[557]

14CHCOOH 4HCIO IHO -1060 Adrn stain- 7-12 sec Electrochemical polish [29] less steel cathode

Tin

FeCI 36-42B 32-54 ~------~-

[15 513)

2 IHNO49CHOH [534] (

j iCIO lt35 5O-W V 40 Adrn AI cathode hold piece vertically and rotate at 50-100 r Imin

420 fLmmin Electrochemical polish on large sunaces orange peel effect may occur

(29]

4 Other electrochemical polishes [29]

Titanium

9H0 IHF 3gt 12 fLmmin Photorist mllsk may be used 114 15 507]

2 7Hli 21iNII IH~ n IImmln PhOI maoa m~ be uWd 114155071

bull - bull bull bull

tllO mllHOH 2U ml middotbutyl hoI t2 II Alll ~ II I-JeC1fochcml41 fKlhh 14m) zne 30-50 V 12 Adm ~Utinle Ied cathode

4 3HCIO 5OCHCOOH 200 30 V 30-40 Adm Ti 2 min E)ectrochem etch anode to cathode distance about 129] cathode 3 cm

5 Other electrochemical etches [29 564 5651

6 See Zirconium etch no [29]

Tungsten ~--~~-----~ -------~-------~----~---~~-----------------~~----~~-~--~~~-~---~--~--~------

34 g KHPO 134 g KOH 33 g KFeICN) HO to 1600 Amin Photoresist mask may be used high resolution (1- (515] make I liter 2 Lml can be achieved

2 5 KOH 5 KFe(CN) 1 sunaclant -2302 --23Lmmin Electrochem etch photoresist mask can be used good [51J Acm PI cathode pauem resolution

5-10 NaOH 6 V 3-6 Adm stainless steel cathode Electrochem etch rotation of anode or agitation of [29 513 566deg) - electrolyte with N is necessary

4 Other etches [5158515 555 567]

Uranium

1-2HClO 2OCHCOOH 5O-W v 5 Adrn stainless 19 fLmmill Electrochemical polish (29) steel cathode

2 Other electrochemical pohshe [29]

VanadIum __----------------___---------__-_

1-2HClO 18-19CHCOOH lt35 50-60 V 16-24 1-2 min Electrocherrucal polish a second polishing ofabout the f29] Adm stainless steel cathode sarne duration ill a fresh soln sometimes necessary

---~-~-----~----~--

Ytlcrbium -----~---------------~-----

lhneraJ aCid 1557j

fCwwj

Table X (Continued

No Etcnant Substrate etcnlng conditions Application etch rate remarklt Rdbull

11 10 M KFe(CN)-O) M KOH (1001 () II) GaP and p-type 60_95 Polishing and mesa etching SiO or Ti mask [445] sllrring

POll) -type 95deg 260 mhr polished Ga(llll Hype SO I J5 mnr smooth textured

P(lOO) -type SO 210 mihr polished

13 Cl-HO sat soln (III) (1001 GaP p epi on n substrate PoliShing -05 mmin [446J

14 HPO (iii) (1111 (1001 GaP 150-200C Groove etching Au mask V grooves result 1442)

15 IHfIHO GaP p type on n substrate Preferential etching of p-type GaP on n type (443) r ~ 16 7NaOCI (525 wt ) IHCI GaP n type on p substrate electrolytic Preferential etching of n-type [443) middottype anode PI cathode

17 16H0 2NaOCI 2HCI III) GaP plii h by chemicaliet etching Polishing lIat smooth surfaces [2(6) Ga(lll) by jet electroetching

18 Cl CHOH (concentration not Ga( III) PI Ill) GaP electrolytic jet Localized Ihinning of specimens for transmission [447)

specified) electron microscopy

n --~3 N NaOH GaO II) P( ii j) GaP 20 electrolytic PI Anodic dissolution and selective etching [448J

cathode

20 01 N HNo (ill) GaP mAlem

Hype electrolytic 20 Anodic dissolution 1250 300 sec (432J

21 2HNOIHCI GaP 1-2 min Polishing of some orientations (437aJ

~ 0 (HOHat soln GaP immer~e sample while (I bubnle Ihroullh 1 onln 20 mtn

Poli_hlnj 40~J

171 lJ r tlrt r r 111[ II NI1I 1 I 11111 bullbullbull 11 IFF HI II 1 illMil 111 4-Table XI

Other Group IIl-V Compound Semiconducfon

~=-terial No Etchant Conditions Application etch rate remarks Rerf ---~

AIN IO laOH or hot HPO 30-80 (NaOH) General etching (449]

BN ~ HPO or HO 0laquo1 Hot General etching of pyrolytic films (450 450a]

BP 3 10 NaOH Electrolytic in dark 01-10 Aem Electrochem etching pmiddottype etches (451J gt IOOx faster than nmiddott ype

J AISb 4 lal IHF IHO IHO I min (a) followed by 2 sec (h) Etching (l ii) face (452J _4

(h) IHC IHNO

Gal 5O7r NaOH L9O General etching [453J 6 01 NaOH Electrolytic jet etching Selective etching of singlemiddotcrystal (454]

vapor-transpon grown films

7 Hf() HOI Etches but develops etch figures (455J

GaSp 8 99-800f CHOH 1-2or Br General polishml [402J 9 9HNOIHF 1-) min General pollhing 402J

10 2HNQ IHF ICHCOOH I) sec Pollshmg develops pits on (I J J I face (452J II IHF lHNn IHO Etching I j j j 1 face 1457] 12 10 citric aCid ()O wI 7r I 1HO pmiddottype 5) photoresist masks Pallern etching (100) face 10 Asec 418J

_--__w-_~ _~_ -~--~ltf

J

Table XI (Continued)

Matenal No Etchant CondItion Application etch rate remarks Reh ~---------- --~-----~-~--~

InAs 13 Etchant no 1 Polishing (II J) and ell il faces (460]

14 5HNo 3HF 3CHCC)()H 006 Br General etching (458J (CP4)

15 75HNO UHF 15CHCOOH 006 Br 55 Etching d i lJ face etch pits on ( II) face [458J

16 HCI 75 General etdng 5 mgcm min 1457 459J

17 04 M Fe -WHCI General etching (452] v 0lt 18 996 ml CHCOOH 04 g Br General polishing 1423J

InP 19 99CHOH IBror9OCHOH IOBr General polishing 40246IJ

20 IHCIIHNO Etching (100) face hillocks on (l j h face [46IJ

inSb 21 I CHOH (concentration not specified) General polishing (402J

22 Etchant no 17 General etching [452]

23 IHF IHNO 2-5 sec Polishing (ii i) and (110) faces no etchshy [423465] 0

ing on (III) or (100) faces ltj

24 5HF 5HNO 2HO 20 sec Etching (100) and (110) faces [8]

25 5HNO bull 3HF 3CHCOOH (CP-4AI 5-30 sec General polishing [463464]

26 IHO ICHCOOH 1 CP4 1 min Etching ( i I) (i Ii) faces etc 1463)

27 2HF IHNO ICHCOOH 5-30 sec Polishing etch pits on (III) face [452J

2X 4HO IHF IHO 5-10 sec Etching (i jj) face [457)

2V Etchanl no 12 311 pholnrt mllk Pallem etchinjl 11001 race 60 Aec 1418)

n II 11 1IUIiI1r Ir PI IF IflTlE 71 bullbull bull bull bull -t

Table XII

Group II-VI Compound Semiconductors

Material No Etchant Conditions Application etch rate remarks Refs

10 KOH General etching 1162468) 2 HCI 120 General etching (467] 3 HPO-HSO boiling General etching at low rate [467468]

CdO 4 Mineral acids or NH salts General etching [4691

CdS 5 100 ml HO 1 mI HSO 008 g CrO 80 10 min Etching of [IOTO) face [471) J Jgt -c

6 16 N HSO-05 M KCrO 955-10 min General etching and polishing etch pits on (jj j) face

[472J

7 300 ml precip sihca 90 ml HNO 10 g AICIlner HO

Chem-mech pOlishing Poromenc disk 240 rlmin 370 gcm

Pohshing (0001) face [475]

8 70HO 30HCI Rotating on Pelion cloth Polishing Cd S and prismatic faces [473J 9 1000 ml HO 137 g KCl 05 ml Hel pH 25 Politegt Pix pad 58 rlmin

025-)40 kgem Polishing Cd face [476J

10 1000 mI HO 131 g KCI 16 ml HC) pH 10 same as no 9 Folishing S face 1476]

CdSe II 30HNO 20HSO IOCHCOOH 40 S sec General etChing thick films forming (472) OIHCI are soluble in HSO

CdTe 12 3HF2HOIHO Polistung (J III and (iii) faces etch 14711 pitgt on (ill) face

(Continued I

---_-_~_~~~IC-Ymiddot

Table XII (Continued)

Malenai --lt--ltshy

Nolt Etchanl Condition Application etch rale remark Reflt

13 2HNO 2HC lHO Polishing [477]

14

15

20 ml HO 10 ml HNO

995 CHOH 05Br

4g KCrO

Slnp deposil 45 min

formed wth Cs

Polishong 10 mirrorlike surface

General etching

[477J

[478]

CdTe 1005)-HgTe (095)

16 6HNOIHCI Rinse in IHCI-ICHOH Polishing 1479]

~

HgSe 17 50HNO 20HSO (18 N) IOCHCOOH IHCI

4010-15 min Polishing 1472]

HgTe 18 6HNO IHC IHO 10-15 min Polishing [472]

ZnO 19 Mineral acids solns

or alkali or NHCI General etching [469

ZnS 20 Elchant nolt 6 95deg 10 min Polishing to high polish etch pits on ( Ill) face

1472J

21 Elchant no 15 Same as nolt 15 General etching etch pits on (Ill)

face (478)

ZnTe 22

23

4HF3HNO

Etchant no 15

Stnpfilm formed with HCI then HO

Same as no 15

General etching and polishing 14721

1478)

p F II I bullbullbull jill bull M U bull bull bull TbW lUll

Orhrr Sritutd Compound gtrmlnmduc(on

Malerial No Elchant Condition Application etch rale remarks Refs

AgSe 5HSO lHO 50 ~ min rinse in EDTA solution then Polishing of some orientations 1479J H 20

2 2KOH sat) 2 ethylene glycol 80 2 min following damage removal Polishing 14791 IHO with etchant no I

Aile ~ 3iHOH2HO Remove film by brushing under water Polishing of some onentaions 1479]

BiSe 4 IHO tHCI Damaged layer following much polshy Polishing and removal of workshy 1470J ishing damaged layers

2HNOIHCI May be diluted with H20 Cleaning and etching 1470 481]

BIltTe 6 Etchant io 5 Cleaning and etching [470 481J

Hg fCdI1e 7 80CHOH20Br Rinse with CHOH Removal of surface 1482483]

InO Sn doped

8

I

HSO

HCI

50-60 Cr film etch mask Pattern etching -05 Amhr

Pattern etching

1484]

14851 10 10 M oxalic acid aqlt soln 50 Shiple~ AZ1350 etch mask Pattern etchmg of annealed films 1486]

InO Sno 14 ltII

II 5~S HI Immerse sample vertically Shipley AZ- 1350H mask postbaked 90 min

Precision pattern etching 25 Asec [4871

I~O

12 2HCI IHO Zn pder Paint Zn powder-HO slurr) on submiddot Rapid etchm~ 150 Asec 1487J trate Immerse hOrlZ IOto HCI-HO 0 mask as 10 nt I(I

In-Je I 19CHCOOH acidlt 1 Br

sat with citric FInish b~ ftooding with CHCOOH sat with cllnc aCid

Polishing 1488]

Inle ISr alh~ shy

14 4 clfn aCld ~uln

~H~() IHF at vlth Bi Polhinf 1488

-~~~-~~-- -----~-~--~

(ConllnUfd i

_~_F-lt--~-_-~__~

4

Table XIII iCollrillutd)

Material 0 Etchant ConditIons Applications etch rate remarks Refs

PbS 15 30HCI 10HNO ICHCOOH 50 few min CHCOOH

then rinse with 10 Polishing [489]

16 HNO 70 Rapid etching [489]

PbSe 17 5KOH (45) 5 ethylene glycol IHO

Electrolytic add HO during etching to maintain rate remove stains with 5()f

CHCOOH

Thinning specimens for electron transmission microscopy

[490]

18 Etchant no 17 403 min Polihino [480]

PbTe 19

20

45 ml HO 35 ml glycerol 20 ml CHOH 20 g KOH

Etchant no 19

Electrolytic 4-6 V 02 Aem

Electrolytic 10 V rinse in CHOH

Thinning specimens for electron transmission microscopy

Polishing

[493]

1492) (494)

~gtb_rSnrSe 21 10 ethylene glycol 10KOH (sat aq soln at 25deg) I HO

Felt covered etch ant

wheel saturated with Polishing [495) [496]

Pb_SnTe 22 Etchant no 19 Electrolytic 10 V rinse in CHOH Polishing [492) [494)

23 95HBr 5Sr 1-2 min rinse many times with CHOH followed with slight etching with no 22

Polishing faster than etchant no 22 [494)

sr 24 3-IOHOIHCI Electrolytic 5-40 mAcm Pattern mask

precision etching SiO used 1600 Almin at 20

[498J

mAcm

25 HCI Zn powder Zn powder in photoresist in Ref 500 Paltern etching 497499

500)

SnO Sb doped

26 HC Zn powder Pattern etchinB 150IJ

E Conductors

Table XI

Elemental Metal

Etch rate or Etching conditions etch time Remarks Refs

Aluminum

4HPO 4CHCOOH lHNO IHO 350 Amm Polishing etch contact to noble metals is possible withshyout increases in etch rate and undercutting

[57504J

2 75 NaCO 35 g NaPO12HO 16 g KFe(CN) bull 05 liter HO

1300 Amin Polishing etch contact to noble metals is possible withshyout increase in etch rate and undercutting

[57]

16-J9HPObull IHNO 0-4HO 40 stirring 1500-2500 Amin Gas evolution OCcurs [14J

4

5

IHCIO ICHCO~O

74IHPO 185HO 73HNO 500

3 mimin

9000 Amin

(29]

[46505]

6

7

8

9

1 HC 4HO 8ltr

2Ok NaOH 60-90

FeCI 12-36degBlt

IOHCI IHSO 9HO 49 25-50 mmm

For fine hne etchmg photoresist masks can be used

Photoresist mask can be used

[507 532J

114507)

[15513J

[15]

10 01 M KB0051 M KOH06M KFe(CNt pH 13tgt

Immm No H j eJlved 158]

II 1 Electngt Glo 100 (Electro Glo Co ChIcago) ~HPO bull 79 7-10 006 Acm PI cathode

ElectrOChemical polish excellent polishing occurs (533J

12 Olher eIlaquoIr(Khemlal etche 291

~( dnlttrlUJ j

~~---~~-~ - --~----~- -----~

- - _H-~~~~~_W __

Table XIV (Continued)

Elch ralr or Etchl ng conditIons etch time Remark Refs

~----

Antimony

Aqua regIa or hot HSO 1469J

2 5ltlt AgNO [5341

3 I g FeCI 3 ml HC 12 ml HO 1534J --~--- ---- shy

Aroenic --------------- --------- --------~

HNO 1469J

Beryllium 5 g HSObull 75 g HPO(98) 7 g crO 13 ml HO 49- JLmmin Passive film formed removable by immersion for 15- [29468)

50 30 sec in 10 HSO

2 HCI 1535J

1 H2SO preset voltage 30 V 2240 Almin Electrochemical etch [468J

4 1 KOH preset voltage 50 V 260 Amin Electrochemical etch [468] f

bull ~middot-ther electrochemical etches 129 536J

Bismuth

Hot HSO 469J

2 5ltlt AgNO [534J

3 lt49 ml sal KI soln I ml HCI 5-7 V 20 Adm stainmiddot Penltxh of 30 sec Electrochemical etch allo brown film formed 10 dismiddot 129] Ic IlrC or cKrhon cathode Ive een elchml period

bull bull bull - - bull I 1 -4 CadmIum

3 fuming HNO (type not specified) IHO

7CHCOOH 3 fuming HNO (type not specified)

I g I 3 g Kl 10 ml HO

olectrochemical etches and polishes

Periods 00-10 sec

30 sec-) min

Etchmg periods stream of H20

are followed by rinsing in a rapid 129)

[291

15341

[29 537 538J

ChromIUm

t 2

3

4

5

6

8

9

1 vol t 1 g NaOH 2 ml HOi 3 vo(J g K[Fe(CN) 3 mlf50IOOOAmin H20J

I g CeISOh2(NH)SOmiddot2HO 5 ml HNO 25 ml 85 Almin HO 28

1645 CeISO)2(NH)SO~H() 43 m HClO HO to make I Iller 25-50

2FeCI47BeIHCI80

HCI

454 g AICImiddot6HO 135 I ZnCl 30 ml HPObull 40() ml HO

9 sat Ce(SO soln IHNO

Dilute HCI or HNO

gt1500 Aimin

800 Amm

IHCIObull 2OCHCOOH4~-~OI-20A dm slammiddot cJ(l~er

Ie steel cathode

Does not require depassivation for etching Cr masks and vacuum-deposited Cr in general photoresist mask can be used

Oxide coating etches at 200 Amin

Recommended for precision patterning ofCr masks on glass substrates

Good for plated Cr photoresist mask can be used

Must depassivate with Zn rod

Photoresist mas~ can be used

Electnxhemlral polh

[14 15507 510J

[519J

1520J

[IS507J

[14516)

(14)

[14517)

[15507513 S17)

[29]

(ConlinLlfd

-- - - --

2

Table XlV (tontid)

Etch rate or Etchmg conditIo etch time Remarkgt Refs

Cobalt

I HC IcHOH 8-9 V 250 AdTn stainless steel 05-15 min Electrochemical polish bluish-green anodic film is sol- [29J uble in HO gIve polished surface WIth slight grain cathode boundary delineatIon

ElectrochemIcal pohsh sohd black film forms which is (29]HPO (98) - 15 V 1-2 Adm Co cathode 5-10 min removed by WIping WIth cotton wool

1539 540JOther electrochemical etc he

Copper ~---~~~-----

0 FeCI 42Be 49 50 Immin Use more dilute solution for slower etching 114 15 50s 509J

2 20-30 HSObull 10-20 crO or KCrO 49 37 Immin (14 15509]

1 g (NH)SO 3 ml HO 32-49 25 Immin Addition of 5 ppm Hg as HgCI activates etehant at [15513 lower temperatures 541-543J

4 5HNO 5CHCOOH 2HSO dilute with HO as Etches Cu and Cumiddotbased alloys at same rate as Ni and (506J

- desired

g KI I g 14 ml H2 0 dip into etch rinse remove

N i-based alloys

Rapid etch but undercutting is limited by formation of [14J

residue with Neutra-clean (Shipley Co Newton an insoluble Cu compound at line edges

Mas)

6 4HNO IIHPO (98) 5CHCOOH 6O-7if 1-2 min Polishing etch (29J

7 2HPOt98I IHO 15-2 V 6-8 Adm Cu cathode 15-30 mm Electrochemical polish [429544 545

()tmiddot~t clflru-hcml1 chhf I~l

fa RIP bull WI1 bull Til bull bull ~-~--~-~-------~-------------~-----~~------------~------

Gallium

Mineral acids or alkali solutions Must be processed below meltmg point (469J

Gold -----~~~~~---~~--~~-~--------~--------------~~------~--------------

)- 4 g KL I g I 40 ml HO 05-1 Immin Better contr~1 of line edges than in more concentnlled [141551 solution solution is opaque so removal from solu tion to observe end point is required

2 3HCL IHNO 32-38 25-50 Immin (IS]

NaCN HO HO mixtures (unspecified composition) [14 15J

4 05 g 12 g NHL 10 ml HO 15 ml cHOH 2if 700 Amin Converts the surface of an underlying Ag layer to the [5101 +shy

iodide thus preventing undercutting -- 04 M KFe(CN) 02 M KCN 01 M KOH 600 Amin Fresh solution must be used no atack on Pd is obshy [58]

served

6 tOO ml HO 05-10 ml HCL 10-JO g NaCl 4-5 V Electrochemical elch which retains bright surface only 1547] 65-2 Adm Mo cathode 20-40 small amount Cl evolved

7 Other electrOChemical etches 129548]

Hafnium

I-cltf HF

lt-6HCIO IOOCHCOOH 18 V Slamle steel cathmiddot ode U several SUCCegtlH dIps with continued agitation

5-10 sec dips

Negative photoreSIst can be ued as mask

ElectrochemICal pohsh -)

[14549J

[29J

See Zircomum etch fltl [291

CConHnurd

--- ---~- --~ -~-------- ~---~ -

Table X (Corllid

Etching condition~

Etch rate or etch lime Remarh Refs

Indium

Mineral acid [469J

IHNO 3CHOH 40-50 V 30 Adm stainless steel cathode cool bath

1-2 min Electrochemical polish [291

Iron

3HNO 7HCI 30H0 6O-7r 2-3 min Dense brown viscous layer forms on surface layer is soluble in solution

[29J

j CgtshyOlt

2

3

4

-I()o( KAI(SOl 12HO

3 liter 1O7c HNO 03 mhr 0 injected 3r

1 HCIO 2OCHCOOH 45-60 V 40-80 Adm stainmiddot less steel cathode

30 mmin

15-30 sec

Slowly soluble

Etches iron plate smoothly 0 removes passive film

Electrochemical polish solid film sometimes forms on the surface during washing removable with dil HF

[469J

[550J

[29J

5 Other electrochemical polishes _

[29J

Lead -----shy----------------------------------------------------------

FeC~ 36-42Be 43-54 [IS 513J -~

9FeCI 42Be IHCI 2rBe 43-49

I HtObull 4CHCOOH Periods 00-10 sec Alternate with immersion in a soln of 10 g molybdic acid and 140 ml NHOH in 240 ml HO to which 60 ml HNO is finally added

[ 15]

(29J

4

5

6

IHNO19HO

35HCIO 63(CHCO)0 20H0 lt3r 50-70 V 9-12 5-10 min A Idm Ph or Cu cathode

()the- k-tdmJ Pbullbulltw

ltlhtum

-------------------

Electrochemical polish

(534J

[291

1191 bull CHOH 30 sec Surface achIeves high luster and is smooth [551]

Magnesium

240-400 g FeCI 330 ml Hel HO to make I liter [469]

1-3HNO 17-19HO [507513 534]

3 fuming HNO type not specifiedl IHO wash imme Periods of 3 sec Reaction rcac Imot explosive violence after -I [29J diately after removal from solution min if allowed to continue it ceases after several

minutes leaving a polished surface

4 7HPO(987cL I3CHOH 1-2V05Admstainle 025 mmin Electrochemical pohsh there is considerable initial [29)

steel or cathode gassing shake anode to remove adhering bubbles

5 5 Other electrochemical etches [29J ~

Manganese

2

IHel IHO

Other dilute mineral acids

1513)

14691

Mercury

Sloght_ diluted HNO

Molybdenum

1469J

5HPO 3HNO 2HO Polishing elch contact to noble metals possible withmiddot OUI mcrcase in etch ratc and undercutling

[57J

IHSO IHNO 1-5H0 ~5-4 J~ 11m imin I~lt I ~ ftm min (~4

Photoresist mask can be used al 25 115507 518

(( OnltnUtJ I

- -~~~ ~ -- --~~-~middotltli0kmiddotmiddot-

Elching condtlons

Tb xrv (Co(Hu~d)

Elch fale or etch tme

Molybdenum (Continuedl

-------shy ~-~---------

Remarh Reh

o

4

6

7

20011 K[Fe(CN))2011 NaOH 3-35 g sodium oxalate add HO 10 make I liter

38HPO 15HNO 3OCHCOOH 75HO

IHSO 7CHOH 80-120 Adm stainless steel cathmiddot ode no agilation

100 ml HPO 20 ml HSObull 40 ml HO 025 II MoO 7(18 V 06-09 Acm slainless sleel graphite or PI cathode stlmng

Other etches

-ltmmin

05t m mrn

I min

94tmmm

Neplunium

Also usable as electrochem etch usinll stainless cathode al 6 V pholoresisl masks applicable

Photoresist mask can be used

Electrochenca polish

Electrochemical pohsh supenor surface finish

steel [14 1551 5075521

1518]

29]

1553

[29 38 57 554-5561

HCI 1557

5HNO 5CHCOOH 2HSObull HO as desired

IHNO IHCI 3HO

FeCI 42-49B 43-54

4

Igt

3HNO IHSO I HPO 198) 5CHCOOH 85-95

IHNO IHO or 9HPO IHNO or 9OHPO 15HNO 4HCL IHO

IOHSo OHO HPO lt-1 NISO JO ~ltr

Nickel

12 -25 tm min

05-1 min

1-2mmln

Etches Ni and Nimiddotbased alloys at same rale as Cu and (506)

Cumiddotbased alloys

Spray elching recommended 1507] o

Photoresist mask may be used [15507513)

Gives very llood polish 1291

Polishing elchants for eleclrol N-P very undercutllng despile conlacl to noble melah

hllie 1571

For ecclrole N film nu undCrcuttmJL mll r fMlfhnn uc-ful (Of ~ittrnl(H Cu

com I ~S8j

bull ~ 8

~7HSObull 4)H 1 U 0 ~ ALm

Other electrochemical polishegt 2 min mm1n lJellrtKht 1~lil1 rulnh

15~ 5601

129J

NiobIum

2 Lacue acid IHSO bull IHF 15~20 V PI cathode sIllmiddot 5-10 mm nng EleClrochemical polish

129]

7HF 7HNO 26HO 49 12-20 V 20~34 Adrn PI cathode Electrochemical etch 14(9) _

9HSO IHF H-45 50 V 2 Adrn PI Or carbon 5-10 min

cathode Electrochem etch temp nses during use cool bath [29]

~--~-----~----~----~----Osmium

Aqua regia 1557)

Palladium

IHCI 10HNO IOCHCOOH 1000 Aim

Aqua rega 15611

1513) Platinum

SHO 7HCI I HNO 85 400-500 AImln 2 f562 563)Aqua regIa precede etchin by 30 sec ImmersIOn in HF

EtCh tIme mlled because photoreSIst mask demiddot 114 507i strayed

3 M HCI 03-+ 14 V versus SeE modIfied Inangumiddot -1000 Almln lar waveform -600 Hz magneuc slmng Electrochem elch good resolu[lOn either po or neg 15141

photoreslS[ usable

Plutonium

I HPOI981 1 diethlene glvcol 5 V ltAdm lainmiddot L 10 mm less steel carhode Electrochemical pohsh

1291

(Conllnttf d

~--~~- - ~ -_ --__~ ~- h __ ~_

Table XIV (Cotiu~d) ~~------- ~---~----~~-~-~-----

Etch rate or Etchmg conditIOns tch time Remarks Ref

Polonium

Dilute mineral acid [557J

Potassium

CHOH or iCH)CHOH 3 sec (ethanoB or 10 SeC (Ioproshypanol)

Brilliant smooth surface obtained [551]

Praesiodymium

Mineral acid -~-~--~-~----------~~------ -------shy

Rhenium

[557]

Dilute HNO [557]

Rhodium

3 M HC -03- + 14 V versus SCE modified triangumiddot ElectTOchem etch I Im line spacings ofRh films over [514]

lar waveform -600 Hz magnetic stirring 5000 ATi on 5i dearly resolved

Ruthenium --------------------~----------------

Fused alkalis [557]

Samarium

Minual acids (557J

Sdenium

HStl ~( IM tf U undtf CkmCnl1 womtunduton 11 bull ~---~--~~-----

Silver

11 g Fe(NO) 9 ml HO 44-49 20 IJmmm Photoresist mask can be used [14 15 507J

2 5-9HNO1-5HO39-49 12-251Jmmin 11415517J

3 35 g AgCN 37 g KCN 38 g KCO 100 ml HO 25- 10 min Electrochem etch best polishing in region of voltage (29) 30 V 1 Alent Ag cathode 10 stirring and currel1t instability

4 3HNO 19H0 2 V [ainle steel cathode ElectrOChemical etch [507)

5 Kl-I etches listed for Cu and Ag O3-llJmsec Immersion followed by HO rinse [14]

60 Asec Useful for pattern etching with photoresist mask rinse [512] quickly after etching

6 4(HOH INHOH IHO

Sodium-

CHtCH)CHOH (nonyl alcohol) 30 sec Brilliant smooth surface [551)

Stronlium

Liquid ammonia [557]

Tanlalum

2

9NaOH or KOH 00laquo) IHO heal alka to 9(t Ihen add HO

5HSObull 2HNO 2HF

1-2HNO IHF 1-2H0

100(l-~OO(l A min

5-20 sec

4 9HSObull IHf (-4 50 cathgtd

A urn 11 1 carb -1(1 rnln

Metal (eg Au) rna muq be used very httle undermiddot cutting etche TO and Ta- al same rale 3 Ta

116~ 16~J

POlishing elch [29 522 5~~

HO rna) be omllled ftgtr fasler elch espeCially if film coniaim oxygen and reslsh etching fasler etch reshyduce re t al1a(~

(14 5 HI

Eletruchernlal etch temp of solUlion ne dunng ue and 11 rna he nece ar~ tp cool hath

129

- -~-~-=-

-4

2

Tabl Xf (Colltlllud)

Etch ratr or Etching condtion rtch time Remarks Refs

Tellurium

2HND3HO [513]

240 g (NH~So bring to I liter with HO [513J

Terbium

M ine 1 acid~ [557]

Thallium

to

HND or HSO

Thonum

------------~----

[557]

14CHCOOH 4HCIO IHO -1060 Adrn stain- 7-12 sec Electrochemical polish [29] less steel cathode

Tin

FeCI 36-42B 32-54 ~------~-

[15 513)

2 IHNO49CHOH [534] (

j iCIO lt35 5O-W V 40 Adrn AI cathode hold piece vertically and rotate at 50-100 r Imin

420 fLmmin Electrochemical polish on large sunaces orange peel effect may occur

(29]

4 Other electrochemical polishes [29]

Titanium

9H0 IHF 3gt 12 fLmmin Photorist mllsk may be used 114 15 507]

2 7Hli 21iNII IH~ n IImmln PhOI maoa m~ be uWd 114155071

bull - bull bull bull

tllO mllHOH 2U ml middotbutyl hoI t2 II Alll ~ II I-JeC1fochcml41 fKlhh 14m) zne 30-50 V 12 Adm ~Utinle Ied cathode

4 3HCIO 5OCHCOOH 200 30 V 30-40 Adm Ti 2 min E)ectrochem etch anode to cathode distance about 129] cathode 3 cm

5 Other electrochemical etches [29 564 5651

6 See Zirconium etch no [29]

Tungsten ~--~~-----~ -------~-------~----~---~~-----------------~~----~~-~--~~~-~---~--~--~------

34 g KHPO 134 g KOH 33 g KFeICN) HO to 1600 Amin Photoresist mask may be used high resolution (1- (515] make I liter 2 Lml can be achieved

2 5 KOH 5 KFe(CN) 1 sunaclant -2302 --23Lmmin Electrochem etch photoresist mask can be used good [51J Acm PI cathode pauem resolution

5-10 NaOH 6 V 3-6 Adm stainless steel cathode Electrochem etch rotation of anode or agitation of [29 513 566deg) - electrolyte with N is necessary

4 Other etches [5158515 555 567]

Uranium

1-2HClO 2OCHCOOH 5O-W v 5 Adrn stainless 19 fLmmill Electrochemical polish (29) steel cathode

2 Other electrochemical pohshe [29]

VanadIum __----------------___---------__-_

1-2HClO 18-19CHCOOH lt35 50-60 V 16-24 1-2 min Electrocherrucal polish a second polishing ofabout the f29] Adm stainless steel cathode sarne duration ill a fresh soln sometimes necessary

---~-~-----~----~--

Ytlcrbium -----~---------------~-----

lhneraJ aCid 1557j

fCwwj

Table XI (Continued)

Matenal No Etchant CondItion Application etch rate remarks Reh ~---------- --~-----~-~--~

InAs 13 Etchant no 1 Polishing (II J) and ell il faces (460]

14 5HNo 3HF 3CHCC)()H 006 Br General etching (458J (CP4)

15 75HNO UHF 15CHCOOH 006 Br 55 Etching d i lJ face etch pits on ( II) face [458J

16 HCI 75 General etdng 5 mgcm min 1457 459J

17 04 M Fe -WHCI General etching (452] v 0lt 18 996 ml CHCOOH 04 g Br General polishing 1423J

InP 19 99CHOH IBror9OCHOH IOBr General polishing 40246IJ

20 IHCIIHNO Etching (100) face hillocks on (l j h face [46IJ

inSb 21 I CHOH (concentration not specified) General polishing (402J

22 Etchant no 17 General etching [452]

23 IHF IHNO 2-5 sec Polishing (ii i) and (110) faces no etchshy [423465] 0

ing on (III) or (100) faces ltj

24 5HF 5HNO 2HO 20 sec Etching (100) and (110) faces [8]

25 5HNO bull 3HF 3CHCOOH (CP-4AI 5-30 sec General polishing [463464]

26 IHO ICHCOOH 1 CP4 1 min Etching ( i I) (i Ii) faces etc 1463)

27 2HF IHNO ICHCOOH 5-30 sec Polishing etch pits on (III) face [452J

2X 4HO IHF IHO 5-10 sec Etching (i jj) face [457)

2V Etchanl no 12 311 pholnrt mllk Pallem etchinjl 11001 race 60 Aec 1418)

n II 11 1IUIiI1r Ir PI IF IflTlE 71 bullbull bull bull bull -t

Table XII

Group II-VI Compound Semiconductors

Material No Etchant Conditions Application etch rate remarks Refs

10 KOH General etching 1162468) 2 HCI 120 General etching (467] 3 HPO-HSO boiling General etching at low rate [467468]

CdO 4 Mineral acids or NH salts General etching [4691

CdS 5 100 ml HO 1 mI HSO 008 g CrO 80 10 min Etching of [IOTO) face [471) J Jgt -c

6 16 N HSO-05 M KCrO 955-10 min General etching and polishing etch pits on (jj j) face

[472J

7 300 ml precip sihca 90 ml HNO 10 g AICIlner HO

Chem-mech pOlishing Poromenc disk 240 rlmin 370 gcm

Pohshing (0001) face [475]

8 70HO 30HCI Rotating on Pelion cloth Polishing Cd S and prismatic faces [473J 9 1000 ml HO 137 g KCl 05 ml Hel pH 25 Politegt Pix pad 58 rlmin

025-)40 kgem Polishing Cd face [476J

10 1000 mI HO 131 g KCI 16 ml HC) pH 10 same as no 9 Folishing S face 1476]

CdSe II 30HNO 20HSO IOCHCOOH 40 S sec General etChing thick films forming (472) OIHCI are soluble in HSO

CdTe 12 3HF2HOIHO Polistung (J III and (iii) faces etch 14711 pitgt on (ill) face

(Continued I

---_-_~_~~~IC-Ymiddot

Table XII (Continued)

Malenai --lt--ltshy

Nolt Etchanl Condition Application etch rale remark Reflt

13 2HNO 2HC lHO Polishing [477]

14

15

20 ml HO 10 ml HNO

995 CHOH 05Br

4g KCrO

Slnp deposil 45 min

formed wth Cs

Polishong 10 mirrorlike surface

General etching

[477J

[478]

CdTe 1005)-HgTe (095)

16 6HNOIHCI Rinse in IHCI-ICHOH Polishing 1479]

~

HgSe 17 50HNO 20HSO (18 N) IOCHCOOH IHCI

4010-15 min Polishing 1472]

HgTe 18 6HNO IHC IHO 10-15 min Polishing [472]

ZnO 19 Mineral acids solns

or alkali or NHCI General etching [469

ZnS 20 Elchant nolt 6 95deg 10 min Polishing to high polish etch pits on ( Ill) face

1472J

21 Elchant no 15 Same as nolt 15 General etching etch pits on (Ill)

face (478)

ZnTe 22

23

4HF3HNO

Etchant no 15

Stnpfilm formed with HCI then HO

Same as no 15

General etching and polishing 14721

1478)

p F II I bullbullbull jill bull M U bull bull bull TbW lUll

Orhrr Sritutd Compound gtrmlnmduc(on

Malerial No Elchant Condition Application etch rale remarks Refs

AgSe 5HSO lHO 50 ~ min rinse in EDTA solution then Polishing of some orientations 1479J H 20

2 2KOH sat) 2 ethylene glycol 80 2 min following damage removal Polishing 14791 IHO with etchant no I

Aile ~ 3iHOH2HO Remove film by brushing under water Polishing of some onentaions 1479]

BiSe 4 IHO tHCI Damaged layer following much polshy Polishing and removal of workshy 1470J ishing damaged layers

2HNOIHCI May be diluted with H20 Cleaning and etching 1470 481]

BIltTe 6 Etchant io 5 Cleaning and etching [470 481J

Hg fCdI1e 7 80CHOH20Br Rinse with CHOH Removal of surface 1482483]

InO Sn doped

8

I

HSO

HCI

50-60 Cr film etch mask Pattern etching -05 Amhr

Pattern etching

1484]

14851 10 10 M oxalic acid aqlt soln 50 Shiple~ AZ1350 etch mask Pattern etchmg of annealed films 1486]

InO Sno 14 ltII

II 5~S HI Immerse sample vertically Shipley AZ- 1350H mask postbaked 90 min

Precision pattern etching 25 Asec [4871

I~O

12 2HCI IHO Zn pder Paint Zn powder-HO slurr) on submiddot Rapid etchm~ 150 Asec 1487J trate Immerse hOrlZ IOto HCI-HO 0 mask as 10 nt I(I

In-Je I 19CHCOOH acidlt 1 Br

sat with citric FInish b~ ftooding with CHCOOH sat with cllnc aCid

Polishing 1488]

Inle ISr alh~ shy

14 4 clfn aCld ~uln

~H~() IHF at vlth Bi Polhinf 1488

-~~~-~~-- -----~-~--~

(ConllnUfd i

_~_F-lt--~-_-~__~

4

Table XIII iCollrillutd)

Material 0 Etchant ConditIons Applications etch rate remarks Refs

PbS 15 30HCI 10HNO ICHCOOH 50 few min CHCOOH

then rinse with 10 Polishing [489]

16 HNO 70 Rapid etching [489]

PbSe 17 5KOH (45) 5 ethylene glycol IHO

Electrolytic add HO during etching to maintain rate remove stains with 5()f

CHCOOH

Thinning specimens for electron transmission microscopy

[490]

18 Etchant no 17 403 min Polihino [480]

PbTe 19

20

45 ml HO 35 ml glycerol 20 ml CHOH 20 g KOH

Etchant no 19

Electrolytic 4-6 V 02 Aem

Electrolytic 10 V rinse in CHOH

Thinning specimens for electron transmission microscopy

Polishing

[493]

1492) (494)

~gtb_rSnrSe 21 10 ethylene glycol 10KOH (sat aq soln at 25deg) I HO

Felt covered etch ant

wheel saturated with Polishing [495) [496]

Pb_SnTe 22 Etchant no 19 Electrolytic 10 V rinse in CHOH Polishing [492) [494)

23 95HBr 5Sr 1-2 min rinse many times with CHOH followed with slight etching with no 22

Polishing faster than etchant no 22 [494)

sr 24 3-IOHOIHCI Electrolytic 5-40 mAcm Pattern mask

precision etching SiO used 1600 Almin at 20

[498J

mAcm

25 HCI Zn powder Zn powder in photoresist in Ref 500 Paltern etching 497499

500)

SnO Sb doped

26 HC Zn powder Pattern etchinB 150IJ

E Conductors

Table XI

Elemental Metal

Etch rate or Etching conditions etch time Remarks Refs

Aluminum

4HPO 4CHCOOH lHNO IHO 350 Amm Polishing etch contact to noble metals is possible withshyout increases in etch rate and undercutting

[57504J

2 75 NaCO 35 g NaPO12HO 16 g KFe(CN) bull 05 liter HO

1300 Amin Polishing etch contact to noble metals is possible withshyout increase in etch rate and undercutting

[57]

16-J9HPObull IHNO 0-4HO 40 stirring 1500-2500 Amin Gas evolution OCcurs [14J

4

5

IHCIO ICHCO~O

74IHPO 185HO 73HNO 500

3 mimin

9000 Amin

(29]

[46505]

6

7

8

9

1 HC 4HO 8ltr

2Ok NaOH 60-90

FeCI 12-36degBlt

IOHCI IHSO 9HO 49 25-50 mmm

For fine hne etchmg photoresist masks can be used

Photoresist mask can be used

[507 532J

114507)

[15513J

[15]

10 01 M KB0051 M KOH06M KFe(CNt pH 13tgt

Immm No H j eJlved 158]

II 1 Electngt Glo 100 (Electro Glo Co ChIcago) ~HPO bull 79 7-10 006 Acm PI cathode

ElectrOChemical polish excellent polishing occurs (533J

12 Olher eIlaquoIr(Khemlal etche 291

~( dnlttrlUJ j

~~---~~-~ - --~----~- -----~

- - _H-~~~~~_W __

Table XIV (Continued)

Elch ralr or Etchl ng conditIons etch time Remark Refs

~----

Antimony

Aqua regIa or hot HSO 1469J

2 5ltlt AgNO [5341

3 I g FeCI 3 ml HC 12 ml HO 1534J --~--- ---- shy

Aroenic --------------- --------- --------~

HNO 1469J

Beryllium 5 g HSObull 75 g HPO(98) 7 g crO 13 ml HO 49- JLmmin Passive film formed removable by immersion for 15- [29468)

50 30 sec in 10 HSO

2 HCI 1535J

1 H2SO preset voltage 30 V 2240 Almin Electrochemical etch [468J

4 1 KOH preset voltage 50 V 260 Amin Electrochemical etch [468] f

bull ~middot-ther electrochemical etches 129 536J

Bismuth

Hot HSO 469J

2 5ltlt AgNO [534J

3 lt49 ml sal KI soln I ml HCI 5-7 V 20 Adm stainmiddot Penltxh of 30 sec Electrochemical etch allo brown film formed 10 dismiddot 129] Ic IlrC or cKrhon cathode Ive een elchml period

bull bull bull - - bull I 1 -4 CadmIum

3 fuming HNO (type not specified) IHO

7CHCOOH 3 fuming HNO (type not specified)

I g I 3 g Kl 10 ml HO

olectrochemical etches and polishes

Periods 00-10 sec

30 sec-) min

Etchmg periods stream of H20

are followed by rinsing in a rapid 129)

[291

15341

[29 537 538J

ChromIUm

t 2

3

4

5

6

8

9

1 vol t 1 g NaOH 2 ml HOi 3 vo(J g K[Fe(CN) 3 mlf50IOOOAmin H20J

I g CeISOh2(NH)SOmiddot2HO 5 ml HNO 25 ml 85 Almin HO 28

1645 CeISO)2(NH)SO~H() 43 m HClO HO to make I Iller 25-50

2FeCI47BeIHCI80

HCI

454 g AICImiddot6HO 135 I ZnCl 30 ml HPObull 40() ml HO

9 sat Ce(SO soln IHNO

Dilute HCI or HNO

gt1500 Aimin

800 Amm

IHCIObull 2OCHCOOH4~-~OI-20A dm slammiddot cJ(l~er

Ie steel cathode

Does not require depassivation for etching Cr masks and vacuum-deposited Cr in general photoresist mask can be used

Oxide coating etches at 200 Amin

Recommended for precision patterning ofCr masks on glass substrates

Good for plated Cr photoresist mask can be used

Must depassivate with Zn rod

Photoresist mas~ can be used

Electnxhemlral polh

[14 15507 510J

[519J

1520J

[IS507J

[14516)

(14)

[14517)

[15507513 S17)

[29]

(ConlinLlfd

-- - - --

2

Table XlV (tontid)

Etch rate or Etchmg conditIo etch time Remarkgt Refs

Cobalt

I HC IcHOH 8-9 V 250 AdTn stainless steel 05-15 min Electrochemical polish bluish-green anodic film is sol- [29J uble in HO gIve polished surface WIth slight grain cathode boundary delineatIon

ElectrochemIcal pohsh sohd black film forms which is (29]HPO (98) - 15 V 1-2 Adm Co cathode 5-10 min removed by WIping WIth cotton wool

1539 540JOther electrochemical etc he

Copper ~---~~~-----

0 FeCI 42Be 49 50 Immin Use more dilute solution for slower etching 114 15 50s 509J

2 20-30 HSObull 10-20 crO or KCrO 49 37 Immin (14 15509]

1 g (NH)SO 3 ml HO 32-49 25 Immin Addition of 5 ppm Hg as HgCI activates etehant at [15513 lower temperatures 541-543J

4 5HNO 5CHCOOH 2HSO dilute with HO as Etches Cu and Cumiddotbased alloys at same rate as Ni and (506J

- desired

g KI I g 14 ml H2 0 dip into etch rinse remove

N i-based alloys

Rapid etch but undercutting is limited by formation of [14J

residue with Neutra-clean (Shipley Co Newton an insoluble Cu compound at line edges

Mas)

6 4HNO IIHPO (98) 5CHCOOH 6O-7if 1-2 min Polishing etch (29J

7 2HPOt98I IHO 15-2 V 6-8 Adm Cu cathode 15-30 mm Electrochemical polish [429544 545

()tmiddot~t clflru-hcml1 chhf I~l

fa RIP bull WI1 bull Til bull bull ~-~--~-~-------~-------------~-----~~------------~------

Gallium

Mineral acids or alkali solutions Must be processed below meltmg point (469J

Gold -----~~~~~---~~--~~-~--------~--------------~~------~--------------

)- 4 g KL I g I 40 ml HO 05-1 Immin Better contr~1 of line edges than in more concentnlled [141551 solution solution is opaque so removal from solu tion to observe end point is required

2 3HCL IHNO 32-38 25-50 Immin (IS]

NaCN HO HO mixtures (unspecified composition) [14 15J

4 05 g 12 g NHL 10 ml HO 15 ml cHOH 2if 700 Amin Converts the surface of an underlying Ag layer to the [5101 +shy

iodide thus preventing undercutting -- 04 M KFe(CN) 02 M KCN 01 M KOH 600 Amin Fresh solution must be used no atack on Pd is obshy [58]

served

6 tOO ml HO 05-10 ml HCL 10-JO g NaCl 4-5 V Electrochemical elch which retains bright surface only 1547] 65-2 Adm Mo cathode 20-40 small amount Cl evolved

7 Other electrOChemical etches 129548]

Hafnium

I-cltf HF

lt-6HCIO IOOCHCOOH 18 V Slamle steel cathmiddot ode U several SUCCegtlH dIps with continued agitation

5-10 sec dips

Negative photoreSIst can be ued as mask

ElectrochemICal pohsh -)

[14549J

[29J

See Zircomum etch fltl [291

CConHnurd

--- ---~- --~ -~-------- ~---~ -

Table X (Corllid

Etching condition~

Etch rate or etch lime Remarh Refs

Indium

Mineral acid [469J

IHNO 3CHOH 40-50 V 30 Adm stainless steel cathode cool bath

1-2 min Electrochemical polish [291

Iron

3HNO 7HCI 30H0 6O-7r 2-3 min Dense brown viscous layer forms on surface layer is soluble in solution

[29J

j CgtshyOlt

2

3

4

-I()o( KAI(SOl 12HO

3 liter 1O7c HNO 03 mhr 0 injected 3r

1 HCIO 2OCHCOOH 45-60 V 40-80 Adm stainmiddot less steel cathode

30 mmin

15-30 sec

Slowly soluble

Etches iron plate smoothly 0 removes passive film

Electrochemical polish solid film sometimes forms on the surface during washing removable with dil HF

[469J

[550J

[29J

5 Other electrochemical polishes _

[29J

Lead -----shy----------------------------------------------------------

FeC~ 36-42Be 43-54 [IS 513J -~

9FeCI 42Be IHCI 2rBe 43-49

I HtObull 4CHCOOH Periods 00-10 sec Alternate with immersion in a soln of 10 g molybdic acid and 140 ml NHOH in 240 ml HO to which 60 ml HNO is finally added

[ 15]

(29J

4

5

6

IHNO19HO

35HCIO 63(CHCO)0 20H0 lt3r 50-70 V 9-12 5-10 min A Idm Ph or Cu cathode

()the- k-tdmJ Pbullbulltw

ltlhtum

-------------------

Electrochemical polish

(534J

[291

1191 bull CHOH 30 sec Surface achIeves high luster and is smooth [551]

Magnesium

240-400 g FeCI 330 ml Hel HO to make I liter [469]

1-3HNO 17-19HO [507513 534]

3 fuming HNO type not specifiedl IHO wash imme Periods of 3 sec Reaction rcac Imot explosive violence after -I [29J diately after removal from solution min if allowed to continue it ceases after several

minutes leaving a polished surface

4 7HPO(987cL I3CHOH 1-2V05Admstainle 025 mmin Electrochemical pohsh there is considerable initial [29)

steel or cathode gassing shake anode to remove adhering bubbles

5 5 Other electrochemical etches [29J ~

Manganese

2

IHel IHO

Other dilute mineral acids

1513)

14691

Mercury

Sloght_ diluted HNO

Molybdenum

1469J

5HPO 3HNO 2HO Polishing elch contact to noble metals possible withmiddot OUI mcrcase in etch ratc and undercutling

[57J

IHSO IHNO 1-5H0 ~5-4 J~ 11m imin I~lt I ~ ftm min (~4

Photoresist mask can be used al 25 115507 518

(( OnltnUtJ I

- -~~~ ~ -- --~~-~middotltli0kmiddotmiddot-

Elching condtlons

Tb xrv (Co(Hu~d)

Elch fale or etch tme

Molybdenum (Continuedl

-------shy ~-~---------

Remarh Reh

o

4

6

7

20011 K[Fe(CN))2011 NaOH 3-35 g sodium oxalate add HO 10 make I liter

38HPO 15HNO 3OCHCOOH 75HO

IHSO 7CHOH 80-120 Adm stainless steel cathmiddot ode no agilation

100 ml HPO 20 ml HSObull 40 ml HO 025 II MoO 7(18 V 06-09 Acm slainless sleel graphite or PI cathode stlmng

Other etches

-ltmmin

05t m mrn

I min

94tmmm

Neplunium

Also usable as electrochem etch usinll stainless cathode al 6 V pholoresisl masks applicable

Photoresist mask can be used

Electrochenca polish

Electrochemical pohsh supenor surface finish

steel [14 1551 5075521

1518]

29]

1553

[29 38 57 554-5561

HCI 1557

5HNO 5CHCOOH 2HSObull HO as desired

IHNO IHCI 3HO

FeCI 42-49B 43-54

4

Igt

3HNO IHSO I HPO 198) 5CHCOOH 85-95

IHNO IHO or 9HPO IHNO or 9OHPO 15HNO 4HCL IHO

IOHSo OHO HPO lt-1 NISO JO ~ltr

Nickel

12 -25 tm min

05-1 min

1-2mmln

Etches Ni and Nimiddotbased alloys at same rale as Cu and (506)

Cumiddotbased alloys

Spray elching recommended 1507] o

Photoresist mask may be used [15507513)

Gives very llood polish 1291

Polishing elchants for eleclrol N-P very undercutllng despile conlacl to noble melah

hllie 1571

For ecclrole N film nu undCrcuttmJL mll r fMlfhnn uc-ful (Of ~ittrnl(H Cu

com I ~S8j

bull ~ 8

~7HSObull 4)H 1 U 0 ~ ALm

Other electrochemical polishegt 2 min mm1n lJellrtKht 1~lil1 rulnh

15~ 5601

129J

NiobIum

2 Lacue acid IHSO bull IHF 15~20 V PI cathode sIllmiddot 5-10 mm nng EleClrochemical polish

129]

7HF 7HNO 26HO 49 12-20 V 20~34 Adrn PI cathode Electrochemical etch 14(9) _

9HSO IHF H-45 50 V 2 Adrn PI Or carbon 5-10 min

cathode Electrochem etch temp nses during use cool bath [29]

~--~-----~----~----~----Osmium

Aqua regia 1557)

Palladium

IHCI 10HNO IOCHCOOH 1000 Aim

Aqua rega 15611

1513) Platinum

SHO 7HCI I HNO 85 400-500 AImln 2 f562 563)Aqua regIa precede etchin by 30 sec ImmersIOn in HF

EtCh tIme mlled because photoreSIst mask demiddot 114 507i strayed

3 M HCI 03-+ 14 V versus SeE modIfied Inangumiddot -1000 Almln lar waveform -600 Hz magneuc slmng Electrochem elch good resolu[lOn either po or neg 15141

photoreslS[ usable

Plutonium

I HPOI981 1 diethlene glvcol 5 V ltAdm lainmiddot L 10 mm less steel carhode Electrochemical pohsh

1291

(Conllnttf d

~--~~- - ~ -_ --__~ ~- h __ ~_

Table XIV (Cotiu~d) ~~------- ~---~----~~-~-~-----

Etch rate or Etchmg conditIOns tch time Remarks Ref

Polonium

Dilute mineral acid [557J

Potassium

CHOH or iCH)CHOH 3 sec (ethanoB or 10 SeC (Ioproshypanol)

Brilliant smooth surface obtained [551]

Praesiodymium

Mineral acid -~-~--~-~----------~~------ -------shy

Rhenium

[557]

Dilute HNO [557]

Rhodium

3 M HC -03- + 14 V versus SCE modified triangumiddot ElectTOchem etch I Im line spacings ofRh films over [514]

lar waveform -600 Hz magnetic stirring 5000 ATi on 5i dearly resolved

Ruthenium --------------------~----------------

Fused alkalis [557]

Samarium

Minual acids (557J

Sdenium

HStl ~( IM tf U undtf CkmCnl1 womtunduton 11 bull ~---~--~~-----

Silver

11 g Fe(NO) 9 ml HO 44-49 20 IJmmm Photoresist mask can be used [14 15 507J

2 5-9HNO1-5HO39-49 12-251Jmmin 11415517J

3 35 g AgCN 37 g KCN 38 g KCO 100 ml HO 25- 10 min Electrochem etch best polishing in region of voltage (29) 30 V 1 Alent Ag cathode 10 stirring and currel1t instability

4 3HNO 19H0 2 V [ainle steel cathode ElectrOChemical etch [507)

5 Kl-I etches listed for Cu and Ag O3-llJmsec Immersion followed by HO rinse [14]

60 Asec Useful for pattern etching with photoresist mask rinse [512] quickly after etching

6 4(HOH INHOH IHO

Sodium-

CHtCH)CHOH (nonyl alcohol) 30 sec Brilliant smooth surface [551)

Stronlium

Liquid ammonia [557]

Tanlalum

2

9NaOH or KOH 00laquo) IHO heal alka to 9(t Ihen add HO

5HSObull 2HNO 2HF

1-2HNO IHF 1-2H0

100(l-~OO(l A min

5-20 sec

4 9HSObull IHf (-4 50 cathgtd

A urn 11 1 carb -1(1 rnln

Metal (eg Au) rna muq be used very httle undermiddot cutting etche TO and Ta- al same rale 3 Ta

116~ 16~J

POlishing elch [29 522 5~~

HO rna) be omllled ftgtr fasler elch espeCially if film coniaim oxygen and reslsh etching fasler etch reshyduce re t al1a(~

(14 5 HI

Eletruchernlal etch temp of solUlion ne dunng ue and 11 rna he nece ar~ tp cool hath

129

- -~-~-=-

-4

2

Tabl Xf (Colltlllud)

Etch ratr or Etching condtion rtch time Remarks Refs

Tellurium

2HND3HO [513]

240 g (NH~So bring to I liter with HO [513J

Terbium

M ine 1 acid~ [557]

Thallium

to

HND or HSO

Thonum

------------~----

[557]

14CHCOOH 4HCIO IHO -1060 Adrn stain- 7-12 sec Electrochemical polish [29] less steel cathode

Tin

FeCI 36-42B 32-54 ~------~-

[15 513)

2 IHNO49CHOH [534] (

j iCIO lt35 5O-W V 40 Adrn AI cathode hold piece vertically and rotate at 50-100 r Imin

420 fLmmin Electrochemical polish on large sunaces orange peel effect may occur

(29]

4 Other electrochemical polishes [29]

Titanium

9H0 IHF 3gt 12 fLmmin Photorist mllsk may be used 114 15 507]

2 7Hli 21iNII IH~ n IImmln PhOI maoa m~ be uWd 114155071

bull - bull bull bull

tllO mllHOH 2U ml middotbutyl hoI t2 II Alll ~ II I-JeC1fochcml41 fKlhh 14m) zne 30-50 V 12 Adm ~Utinle Ied cathode

4 3HCIO 5OCHCOOH 200 30 V 30-40 Adm Ti 2 min E)ectrochem etch anode to cathode distance about 129] cathode 3 cm

5 Other electrochemical etches [29 564 5651

6 See Zirconium etch no [29]

Tungsten ~--~~-----~ -------~-------~----~---~~-----------------~~----~~-~--~~~-~---~--~--~------

34 g KHPO 134 g KOH 33 g KFeICN) HO to 1600 Amin Photoresist mask may be used high resolution (1- (515] make I liter 2 Lml can be achieved

2 5 KOH 5 KFe(CN) 1 sunaclant -2302 --23Lmmin Electrochem etch photoresist mask can be used good [51J Acm PI cathode pauem resolution

5-10 NaOH 6 V 3-6 Adm stainless steel cathode Electrochem etch rotation of anode or agitation of [29 513 566deg) - electrolyte with N is necessary

4 Other etches [5158515 555 567]

Uranium

1-2HClO 2OCHCOOH 5O-W v 5 Adrn stainless 19 fLmmill Electrochemical polish (29) steel cathode

2 Other electrochemical pohshe [29]

VanadIum __----------------___---------__-_

1-2HClO 18-19CHCOOH lt35 50-60 V 16-24 1-2 min Electrocherrucal polish a second polishing ofabout the f29] Adm stainless steel cathode sarne duration ill a fresh soln sometimes necessary

---~-~-----~----~--

Ytlcrbium -----~---------------~-----

lhneraJ aCid 1557j

fCwwj

Table XII (Continued)

Malenai --lt--ltshy

Nolt Etchanl Condition Application etch rale remark Reflt

13 2HNO 2HC lHO Polishing [477]

14

15

20 ml HO 10 ml HNO

995 CHOH 05Br

4g KCrO

Slnp deposil 45 min

formed wth Cs

Polishong 10 mirrorlike surface

General etching

[477J

[478]

CdTe 1005)-HgTe (095)

16 6HNOIHCI Rinse in IHCI-ICHOH Polishing 1479]

~

HgSe 17 50HNO 20HSO (18 N) IOCHCOOH IHCI

4010-15 min Polishing 1472]

HgTe 18 6HNO IHC IHO 10-15 min Polishing [472]

ZnO 19 Mineral acids solns

or alkali or NHCI General etching [469

ZnS 20 Elchant nolt 6 95deg 10 min Polishing to high polish etch pits on ( Ill) face

1472J

21 Elchant no 15 Same as nolt 15 General etching etch pits on (Ill)

face (478)

ZnTe 22

23

4HF3HNO

Etchant no 15

Stnpfilm formed with HCI then HO

Same as no 15

General etching and polishing 14721

1478)

p F II I bullbullbull jill bull M U bull bull bull TbW lUll

Orhrr Sritutd Compound gtrmlnmduc(on

Malerial No Elchant Condition Application etch rale remarks Refs

AgSe 5HSO lHO 50 ~ min rinse in EDTA solution then Polishing of some orientations 1479J H 20

2 2KOH sat) 2 ethylene glycol 80 2 min following damage removal Polishing 14791 IHO with etchant no I

Aile ~ 3iHOH2HO Remove film by brushing under water Polishing of some onentaions 1479]

BiSe 4 IHO tHCI Damaged layer following much polshy Polishing and removal of workshy 1470J ishing damaged layers

2HNOIHCI May be diluted with H20 Cleaning and etching 1470 481]

BIltTe 6 Etchant io 5 Cleaning and etching [470 481J

Hg fCdI1e 7 80CHOH20Br Rinse with CHOH Removal of surface 1482483]

InO Sn doped

8

I

HSO

HCI

50-60 Cr film etch mask Pattern etching -05 Amhr

Pattern etching

1484]

14851 10 10 M oxalic acid aqlt soln 50 Shiple~ AZ1350 etch mask Pattern etchmg of annealed films 1486]

InO Sno 14 ltII

II 5~S HI Immerse sample vertically Shipley AZ- 1350H mask postbaked 90 min

Precision pattern etching 25 Asec [4871

I~O

12 2HCI IHO Zn pder Paint Zn powder-HO slurr) on submiddot Rapid etchm~ 150 Asec 1487J trate Immerse hOrlZ IOto HCI-HO 0 mask as 10 nt I(I

In-Je I 19CHCOOH acidlt 1 Br

sat with citric FInish b~ ftooding with CHCOOH sat with cllnc aCid

Polishing 1488]

Inle ISr alh~ shy

14 4 clfn aCld ~uln

~H~() IHF at vlth Bi Polhinf 1488

-~~~-~~-- -----~-~--~

(ConllnUfd i

_~_F-lt--~-_-~__~

4

Table XIII iCollrillutd)

Material 0 Etchant ConditIons Applications etch rate remarks Refs

PbS 15 30HCI 10HNO ICHCOOH 50 few min CHCOOH

then rinse with 10 Polishing [489]

16 HNO 70 Rapid etching [489]

PbSe 17 5KOH (45) 5 ethylene glycol IHO

Electrolytic add HO during etching to maintain rate remove stains with 5()f

CHCOOH

Thinning specimens for electron transmission microscopy

[490]

18 Etchant no 17 403 min Polihino [480]

PbTe 19

20

45 ml HO 35 ml glycerol 20 ml CHOH 20 g KOH

Etchant no 19

Electrolytic 4-6 V 02 Aem

Electrolytic 10 V rinse in CHOH

Thinning specimens for electron transmission microscopy

Polishing

[493]

1492) (494)

~gtb_rSnrSe 21 10 ethylene glycol 10KOH (sat aq soln at 25deg) I HO

Felt covered etch ant

wheel saturated with Polishing [495) [496]

Pb_SnTe 22 Etchant no 19 Electrolytic 10 V rinse in CHOH Polishing [492) [494)

23 95HBr 5Sr 1-2 min rinse many times with CHOH followed with slight etching with no 22

Polishing faster than etchant no 22 [494)

sr 24 3-IOHOIHCI Electrolytic 5-40 mAcm Pattern mask

precision etching SiO used 1600 Almin at 20

[498J

mAcm

25 HCI Zn powder Zn powder in photoresist in Ref 500 Paltern etching 497499

500)

SnO Sb doped

26 HC Zn powder Pattern etchinB 150IJ

E Conductors

Table XI

Elemental Metal

Etch rate or Etching conditions etch time Remarks Refs

Aluminum

4HPO 4CHCOOH lHNO IHO 350 Amm Polishing etch contact to noble metals is possible withshyout increases in etch rate and undercutting

[57504J

2 75 NaCO 35 g NaPO12HO 16 g KFe(CN) bull 05 liter HO

1300 Amin Polishing etch contact to noble metals is possible withshyout increase in etch rate and undercutting

[57]

16-J9HPObull IHNO 0-4HO 40 stirring 1500-2500 Amin Gas evolution OCcurs [14J

4

5

IHCIO ICHCO~O

74IHPO 185HO 73HNO 500

3 mimin

9000 Amin

(29]

[46505]

6

7

8

9

1 HC 4HO 8ltr

2Ok NaOH 60-90

FeCI 12-36degBlt

IOHCI IHSO 9HO 49 25-50 mmm

For fine hne etchmg photoresist masks can be used

Photoresist mask can be used

[507 532J

114507)

[15513J

[15]

10 01 M KB0051 M KOH06M KFe(CNt pH 13tgt

Immm No H j eJlved 158]

II 1 Electngt Glo 100 (Electro Glo Co ChIcago) ~HPO bull 79 7-10 006 Acm PI cathode

ElectrOChemical polish excellent polishing occurs (533J

12 Olher eIlaquoIr(Khemlal etche 291

~( dnlttrlUJ j

~~---~~-~ - --~----~- -----~

- - _H-~~~~~_W __

Table XIV (Continued)

Elch ralr or Etchl ng conditIons etch time Remark Refs

~----

Antimony

Aqua regIa or hot HSO 1469J

2 5ltlt AgNO [5341

3 I g FeCI 3 ml HC 12 ml HO 1534J --~--- ---- shy

Aroenic --------------- --------- --------~

HNO 1469J

Beryllium 5 g HSObull 75 g HPO(98) 7 g crO 13 ml HO 49- JLmmin Passive film formed removable by immersion for 15- [29468)

50 30 sec in 10 HSO

2 HCI 1535J

1 H2SO preset voltage 30 V 2240 Almin Electrochemical etch [468J

4 1 KOH preset voltage 50 V 260 Amin Electrochemical etch [468] f

bull ~middot-ther electrochemical etches 129 536J

Bismuth

Hot HSO 469J

2 5ltlt AgNO [534J

3 lt49 ml sal KI soln I ml HCI 5-7 V 20 Adm stainmiddot Penltxh of 30 sec Electrochemical etch allo brown film formed 10 dismiddot 129] Ic IlrC or cKrhon cathode Ive een elchml period

bull bull bull - - bull I 1 -4 CadmIum

3 fuming HNO (type not specified) IHO

7CHCOOH 3 fuming HNO (type not specified)

I g I 3 g Kl 10 ml HO

olectrochemical etches and polishes

Periods 00-10 sec

30 sec-) min

Etchmg periods stream of H20

are followed by rinsing in a rapid 129)

[291

15341

[29 537 538J

ChromIUm

t 2

3

4

5

6

8

9

1 vol t 1 g NaOH 2 ml HOi 3 vo(J g K[Fe(CN) 3 mlf50IOOOAmin H20J

I g CeISOh2(NH)SOmiddot2HO 5 ml HNO 25 ml 85 Almin HO 28

1645 CeISO)2(NH)SO~H() 43 m HClO HO to make I Iller 25-50

2FeCI47BeIHCI80

HCI

454 g AICImiddot6HO 135 I ZnCl 30 ml HPObull 40() ml HO

9 sat Ce(SO soln IHNO

Dilute HCI or HNO

gt1500 Aimin

800 Amm

IHCIObull 2OCHCOOH4~-~OI-20A dm slammiddot cJ(l~er

Ie steel cathode

Does not require depassivation for etching Cr masks and vacuum-deposited Cr in general photoresist mask can be used

Oxide coating etches at 200 Amin

Recommended for precision patterning ofCr masks on glass substrates

Good for plated Cr photoresist mask can be used

Must depassivate with Zn rod

Photoresist mas~ can be used

Electnxhemlral polh

[14 15507 510J

[519J

1520J

[IS507J

[14516)

(14)

[14517)

[15507513 S17)

[29]

(ConlinLlfd

-- - - --

2

Table XlV (tontid)

Etch rate or Etchmg conditIo etch time Remarkgt Refs

Cobalt

I HC IcHOH 8-9 V 250 AdTn stainless steel 05-15 min Electrochemical polish bluish-green anodic film is sol- [29J uble in HO gIve polished surface WIth slight grain cathode boundary delineatIon

ElectrochemIcal pohsh sohd black film forms which is (29]HPO (98) - 15 V 1-2 Adm Co cathode 5-10 min removed by WIping WIth cotton wool

1539 540JOther electrochemical etc he

Copper ~---~~~-----

0 FeCI 42Be 49 50 Immin Use more dilute solution for slower etching 114 15 50s 509J

2 20-30 HSObull 10-20 crO or KCrO 49 37 Immin (14 15509]

1 g (NH)SO 3 ml HO 32-49 25 Immin Addition of 5 ppm Hg as HgCI activates etehant at [15513 lower temperatures 541-543J

4 5HNO 5CHCOOH 2HSO dilute with HO as Etches Cu and Cumiddotbased alloys at same rate as Ni and (506J

- desired

g KI I g 14 ml H2 0 dip into etch rinse remove

N i-based alloys

Rapid etch but undercutting is limited by formation of [14J

residue with Neutra-clean (Shipley Co Newton an insoluble Cu compound at line edges

Mas)

6 4HNO IIHPO (98) 5CHCOOH 6O-7if 1-2 min Polishing etch (29J

7 2HPOt98I IHO 15-2 V 6-8 Adm Cu cathode 15-30 mm Electrochemical polish [429544 545

()tmiddot~t clflru-hcml1 chhf I~l

fa RIP bull WI1 bull Til bull bull ~-~--~-~-------~-------------~-----~~------------~------

Gallium

Mineral acids or alkali solutions Must be processed below meltmg point (469J

Gold -----~~~~~---~~--~~-~--------~--------------~~------~--------------

)- 4 g KL I g I 40 ml HO 05-1 Immin Better contr~1 of line edges than in more concentnlled [141551 solution solution is opaque so removal from solu tion to observe end point is required

2 3HCL IHNO 32-38 25-50 Immin (IS]

NaCN HO HO mixtures (unspecified composition) [14 15J

4 05 g 12 g NHL 10 ml HO 15 ml cHOH 2if 700 Amin Converts the surface of an underlying Ag layer to the [5101 +shy

iodide thus preventing undercutting -- 04 M KFe(CN) 02 M KCN 01 M KOH 600 Amin Fresh solution must be used no atack on Pd is obshy [58]

served

6 tOO ml HO 05-10 ml HCL 10-JO g NaCl 4-5 V Electrochemical elch which retains bright surface only 1547] 65-2 Adm Mo cathode 20-40 small amount Cl evolved

7 Other electrOChemical etches 129548]

Hafnium

I-cltf HF

lt-6HCIO IOOCHCOOH 18 V Slamle steel cathmiddot ode U several SUCCegtlH dIps with continued agitation

5-10 sec dips

Negative photoreSIst can be ued as mask

ElectrochemICal pohsh -)

[14549J

[29J

See Zircomum etch fltl [291

CConHnurd

--- ---~- --~ -~-------- ~---~ -

Table X (Corllid

Etching condition~

Etch rate or etch lime Remarh Refs

Indium

Mineral acid [469J

IHNO 3CHOH 40-50 V 30 Adm stainless steel cathode cool bath

1-2 min Electrochemical polish [291

Iron

3HNO 7HCI 30H0 6O-7r 2-3 min Dense brown viscous layer forms on surface layer is soluble in solution

[29J

j CgtshyOlt

2

3

4

-I()o( KAI(SOl 12HO

3 liter 1O7c HNO 03 mhr 0 injected 3r

1 HCIO 2OCHCOOH 45-60 V 40-80 Adm stainmiddot less steel cathode

30 mmin

15-30 sec

Slowly soluble

Etches iron plate smoothly 0 removes passive film

Electrochemical polish solid film sometimes forms on the surface during washing removable with dil HF

[469J

[550J

[29J

5 Other electrochemical polishes _

[29J

Lead -----shy----------------------------------------------------------

FeC~ 36-42Be 43-54 [IS 513J -~

9FeCI 42Be IHCI 2rBe 43-49

I HtObull 4CHCOOH Periods 00-10 sec Alternate with immersion in a soln of 10 g molybdic acid and 140 ml NHOH in 240 ml HO to which 60 ml HNO is finally added

[ 15]

(29J

4

5

6

IHNO19HO

35HCIO 63(CHCO)0 20H0 lt3r 50-70 V 9-12 5-10 min A Idm Ph or Cu cathode

()the- k-tdmJ Pbullbulltw

ltlhtum

-------------------

Electrochemical polish

(534J

[291

1191 bull CHOH 30 sec Surface achIeves high luster and is smooth [551]

Magnesium

240-400 g FeCI 330 ml Hel HO to make I liter [469]

1-3HNO 17-19HO [507513 534]

3 fuming HNO type not specifiedl IHO wash imme Periods of 3 sec Reaction rcac Imot explosive violence after -I [29J diately after removal from solution min if allowed to continue it ceases after several

minutes leaving a polished surface

4 7HPO(987cL I3CHOH 1-2V05Admstainle 025 mmin Electrochemical pohsh there is considerable initial [29)

steel or cathode gassing shake anode to remove adhering bubbles

5 5 Other electrochemical etches [29J ~

Manganese

2

IHel IHO

Other dilute mineral acids

1513)

14691

Mercury

Sloght_ diluted HNO

Molybdenum

1469J

5HPO 3HNO 2HO Polishing elch contact to noble metals possible withmiddot OUI mcrcase in etch ratc and undercutling

[57J

IHSO IHNO 1-5H0 ~5-4 J~ 11m imin I~lt I ~ ftm min (~4

Photoresist mask can be used al 25 115507 518

(( OnltnUtJ I

- -~~~ ~ -- --~~-~middotltli0kmiddotmiddot-

Elching condtlons

Tb xrv (Co(Hu~d)

Elch fale or etch tme

Molybdenum (Continuedl

-------shy ~-~---------

Remarh Reh

o

4

6

7

20011 K[Fe(CN))2011 NaOH 3-35 g sodium oxalate add HO 10 make I liter

38HPO 15HNO 3OCHCOOH 75HO

IHSO 7CHOH 80-120 Adm stainless steel cathmiddot ode no agilation

100 ml HPO 20 ml HSObull 40 ml HO 025 II MoO 7(18 V 06-09 Acm slainless sleel graphite or PI cathode stlmng

Other etches

-ltmmin

05t m mrn

I min

94tmmm

Neplunium

Also usable as electrochem etch usinll stainless cathode al 6 V pholoresisl masks applicable

Photoresist mask can be used

Electrochenca polish

Electrochemical pohsh supenor surface finish

steel [14 1551 5075521

1518]

29]

1553

[29 38 57 554-5561

HCI 1557

5HNO 5CHCOOH 2HSObull HO as desired

IHNO IHCI 3HO

FeCI 42-49B 43-54

4

Igt

3HNO IHSO I HPO 198) 5CHCOOH 85-95

IHNO IHO or 9HPO IHNO or 9OHPO 15HNO 4HCL IHO

IOHSo OHO HPO lt-1 NISO JO ~ltr

Nickel

12 -25 tm min

05-1 min

1-2mmln

Etches Ni and Nimiddotbased alloys at same rale as Cu and (506)

Cumiddotbased alloys

Spray elching recommended 1507] o

Photoresist mask may be used [15507513)

Gives very llood polish 1291

Polishing elchants for eleclrol N-P very undercutllng despile conlacl to noble melah

hllie 1571

For ecclrole N film nu undCrcuttmJL mll r fMlfhnn uc-ful (Of ~ittrnl(H Cu

com I ~S8j

bull ~ 8

~7HSObull 4)H 1 U 0 ~ ALm

Other electrochemical polishegt 2 min mm1n lJellrtKht 1~lil1 rulnh

15~ 5601

129J

NiobIum

2 Lacue acid IHSO bull IHF 15~20 V PI cathode sIllmiddot 5-10 mm nng EleClrochemical polish

129]

7HF 7HNO 26HO 49 12-20 V 20~34 Adrn PI cathode Electrochemical etch 14(9) _

9HSO IHF H-45 50 V 2 Adrn PI Or carbon 5-10 min

cathode Electrochem etch temp nses during use cool bath [29]

~--~-----~----~----~----Osmium

Aqua regia 1557)

Palladium

IHCI 10HNO IOCHCOOH 1000 Aim

Aqua rega 15611

1513) Platinum

SHO 7HCI I HNO 85 400-500 AImln 2 f562 563)Aqua regIa precede etchin by 30 sec ImmersIOn in HF

EtCh tIme mlled because photoreSIst mask demiddot 114 507i strayed

3 M HCI 03-+ 14 V versus SeE modIfied Inangumiddot -1000 Almln lar waveform -600 Hz magneuc slmng Electrochem elch good resolu[lOn either po or neg 15141

photoreslS[ usable

Plutonium

I HPOI981 1 diethlene glvcol 5 V ltAdm lainmiddot L 10 mm less steel carhode Electrochemical pohsh

1291

(Conllnttf d

~--~~- - ~ -_ --__~ ~- h __ ~_

Table XIV (Cotiu~d) ~~------- ~---~----~~-~-~-----

Etch rate or Etchmg conditIOns tch time Remarks Ref

Polonium

Dilute mineral acid [557J

Potassium

CHOH or iCH)CHOH 3 sec (ethanoB or 10 SeC (Ioproshypanol)

Brilliant smooth surface obtained [551]

Praesiodymium

Mineral acid -~-~--~-~----------~~------ -------shy

Rhenium

[557]

Dilute HNO [557]

Rhodium

3 M HC -03- + 14 V versus SCE modified triangumiddot ElectTOchem etch I Im line spacings ofRh films over [514]

lar waveform -600 Hz magnetic stirring 5000 ATi on 5i dearly resolved

Ruthenium --------------------~----------------

Fused alkalis [557]

Samarium

Minual acids (557J

Sdenium

HStl ~( IM tf U undtf CkmCnl1 womtunduton 11 bull ~---~--~~-----

Silver

11 g Fe(NO) 9 ml HO 44-49 20 IJmmm Photoresist mask can be used [14 15 507J

2 5-9HNO1-5HO39-49 12-251Jmmin 11415517J

3 35 g AgCN 37 g KCN 38 g KCO 100 ml HO 25- 10 min Electrochem etch best polishing in region of voltage (29) 30 V 1 Alent Ag cathode 10 stirring and currel1t instability

4 3HNO 19H0 2 V [ainle steel cathode ElectrOChemical etch [507)

5 Kl-I etches listed for Cu and Ag O3-llJmsec Immersion followed by HO rinse [14]

60 Asec Useful for pattern etching with photoresist mask rinse [512] quickly after etching

6 4(HOH INHOH IHO

Sodium-

CHtCH)CHOH (nonyl alcohol) 30 sec Brilliant smooth surface [551)

Stronlium

Liquid ammonia [557]

Tanlalum

2

9NaOH or KOH 00laquo) IHO heal alka to 9(t Ihen add HO

5HSObull 2HNO 2HF

1-2HNO IHF 1-2H0

100(l-~OO(l A min

5-20 sec

4 9HSObull IHf (-4 50 cathgtd

A urn 11 1 carb -1(1 rnln

Metal (eg Au) rna muq be used very httle undermiddot cutting etche TO and Ta- al same rale 3 Ta

116~ 16~J

POlishing elch [29 522 5~~

HO rna) be omllled ftgtr fasler elch espeCially if film coniaim oxygen and reslsh etching fasler etch reshyduce re t al1a(~

(14 5 HI

Eletruchernlal etch temp of solUlion ne dunng ue and 11 rna he nece ar~ tp cool hath

129

- -~-~-=-

-4

2

Tabl Xf (Colltlllud)

Etch ratr or Etching condtion rtch time Remarks Refs

Tellurium

2HND3HO [513]

240 g (NH~So bring to I liter with HO [513J

Terbium

M ine 1 acid~ [557]

Thallium

to

HND or HSO

Thonum

------------~----

[557]

14CHCOOH 4HCIO IHO -1060 Adrn stain- 7-12 sec Electrochemical polish [29] less steel cathode

Tin

FeCI 36-42B 32-54 ~------~-

[15 513)

2 IHNO49CHOH [534] (

j iCIO lt35 5O-W V 40 Adrn AI cathode hold piece vertically and rotate at 50-100 r Imin

420 fLmmin Electrochemical polish on large sunaces orange peel effect may occur

(29]

4 Other electrochemical polishes [29]

Titanium

9H0 IHF 3gt 12 fLmmin Photorist mllsk may be used 114 15 507]

2 7Hli 21iNII IH~ n IImmln PhOI maoa m~ be uWd 114155071

bull - bull bull bull

tllO mllHOH 2U ml middotbutyl hoI t2 II Alll ~ II I-JeC1fochcml41 fKlhh 14m) zne 30-50 V 12 Adm ~Utinle Ied cathode

4 3HCIO 5OCHCOOH 200 30 V 30-40 Adm Ti 2 min E)ectrochem etch anode to cathode distance about 129] cathode 3 cm

5 Other electrochemical etches [29 564 5651

6 See Zirconium etch no [29]

Tungsten ~--~~-----~ -------~-------~----~---~~-----------------~~----~~-~--~~~-~---~--~--~------

34 g KHPO 134 g KOH 33 g KFeICN) HO to 1600 Amin Photoresist mask may be used high resolution (1- (515] make I liter 2 Lml can be achieved

2 5 KOH 5 KFe(CN) 1 sunaclant -2302 --23Lmmin Electrochem etch photoresist mask can be used good [51J Acm PI cathode pauem resolution

5-10 NaOH 6 V 3-6 Adm stainless steel cathode Electrochem etch rotation of anode or agitation of [29 513 566deg) - electrolyte with N is necessary

4 Other etches [5158515 555 567]

Uranium

1-2HClO 2OCHCOOH 5O-W v 5 Adrn stainless 19 fLmmill Electrochemical polish (29) steel cathode

2 Other electrochemical pohshe [29]

VanadIum __----------------___---------__-_

1-2HClO 18-19CHCOOH lt35 50-60 V 16-24 1-2 min Electrocherrucal polish a second polishing ofabout the f29] Adm stainless steel cathode sarne duration ill a fresh soln sometimes necessary

---~-~-----~----~--

Ytlcrbium -----~---------------~-----

lhneraJ aCid 1557j

fCwwj

Table XIII iCollrillutd)

Material 0 Etchant ConditIons Applications etch rate remarks Refs

PbS 15 30HCI 10HNO ICHCOOH 50 few min CHCOOH

then rinse with 10 Polishing [489]

16 HNO 70 Rapid etching [489]

PbSe 17 5KOH (45) 5 ethylene glycol IHO

Electrolytic add HO during etching to maintain rate remove stains with 5()f

CHCOOH

Thinning specimens for electron transmission microscopy

[490]

18 Etchant no 17 403 min Polihino [480]

PbTe 19

20

45 ml HO 35 ml glycerol 20 ml CHOH 20 g KOH

Etchant no 19

Electrolytic 4-6 V 02 Aem

Electrolytic 10 V rinse in CHOH

Thinning specimens for electron transmission microscopy

Polishing

[493]

1492) (494)

~gtb_rSnrSe 21 10 ethylene glycol 10KOH (sat aq soln at 25deg) I HO

Felt covered etch ant

wheel saturated with Polishing [495) [496]

Pb_SnTe 22 Etchant no 19 Electrolytic 10 V rinse in CHOH Polishing [492) [494)

23 95HBr 5Sr 1-2 min rinse many times with CHOH followed with slight etching with no 22

Polishing faster than etchant no 22 [494)

sr 24 3-IOHOIHCI Electrolytic 5-40 mAcm Pattern mask

precision etching SiO used 1600 Almin at 20

[498J

mAcm

25 HCI Zn powder Zn powder in photoresist in Ref 500 Paltern etching 497499

500)

SnO Sb doped

26 HC Zn powder Pattern etchinB 150IJ

E Conductors

Table XI

Elemental Metal

Etch rate or Etching conditions etch time Remarks Refs

Aluminum

4HPO 4CHCOOH lHNO IHO 350 Amm Polishing etch contact to noble metals is possible withshyout increases in etch rate and undercutting

[57504J

2 75 NaCO 35 g NaPO12HO 16 g KFe(CN) bull 05 liter HO

1300 Amin Polishing etch contact to noble metals is possible withshyout increase in etch rate and undercutting

[57]

16-J9HPObull IHNO 0-4HO 40 stirring 1500-2500 Amin Gas evolution OCcurs [14J

4

5

IHCIO ICHCO~O

74IHPO 185HO 73HNO 500

3 mimin

9000 Amin

(29]

[46505]

6

7

8

9

1 HC 4HO 8ltr

2Ok NaOH 60-90

FeCI 12-36degBlt

IOHCI IHSO 9HO 49 25-50 mmm

For fine hne etchmg photoresist masks can be used

Photoresist mask can be used

[507 532J

114507)

[15513J

[15]

10 01 M KB0051 M KOH06M KFe(CNt pH 13tgt

Immm No H j eJlved 158]

II 1 Electngt Glo 100 (Electro Glo Co ChIcago) ~HPO bull 79 7-10 006 Acm PI cathode

ElectrOChemical polish excellent polishing occurs (533J

12 Olher eIlaquoIr(Khemlal etche 291

~( dnlttrlUJ j

~~---~~-~ - --~----~- -----~

- - _H-~~~~~_W __

Table XIV (Continued)

Elch ralr or Etchl ng conditIons etch time Remark Refs

~----

Antimony

Aqua regIa or hot HSO 1469J

2 5ltlt AgNO [5341

3 I g FeCI 3 ml HC 12 ml HO 1534J --~--- ---- shy

Aroenic --------------- --------- --------~

HNO 1469J

Beryllium 5 g HSObull 75 g HPO(98) 7 g crO 13 ml HO 49- JLmmin Passive film formed removable by immersion for 15- [29468)

50 30 sec in 10 HSO

2 HCI 1535J

1 H2SO preset voltage 30 V 2240 Almin Electrochemical etch [468J

4 1 KOH preset voltage 50 V 260 Amin Electrochemical etch [468] f

bull ~middot-ther electrochemical etches 129 536J

Bismuth

Hot HSO 469J

2 5ltlt AgNO [534J

3 lt49 ml sal KI soln I ml HCI 5-7 V 20 Adm stainmiddot Penltxh of 30 sec Electrochemical etch allo brown film formed 10 dismiddot 129] Ic IlrC or cKrhon cathode Ive een elchml period

bull bull bull - - bull I 1 -4 CadmIum

3 fuming HNO (type not specified) IHO

7CHCOOH 3 fuming HNO (type not specified)

I g I 3 g Kl 10 ml HO

olectrochemical etches and polishes

Periods 00-10 sec

30 sec-) min

Etchmg periods stream of H20

are followed by rinsing in a rapid 129)

[291

15341

[29 537 538J

ChromIUm

t 2

3

4

5

6

8

9

1 vol t 1 g NaOH 2 ml HOi 3 vo(J g K[Fe(CN) 3 mlf50IOOOAmin H20J

I g CeISOh2(NH)SOmiddot2HO 5 ml HNO 25 ml 85 Almin HO 28

1645 CeISO)2(NH)SO~H() 43 m HClO HO to make I Iller 25-50

2FeCI47BeIHCI80

HCI

454 g AICImiddot6HO 135 I ZnCl 30 ml HPObull 40() ml HO

9 sat Ce(SO soln IHNO

Dilute HCI or HNO

gt1500 Aimin

800 Amm

IHCIObull 2OCHCOOH4~-~OI-20A dm slammiddot cJ(l~er

Ie steel cathode

Does not require depassivation for etching Cr masks and vacuum-deposited Cr in general photoresist mask can be used

Oxide coating etches at 200 Amin

Recommended for precision patterning ofCr masks on glass substrates

Good for plated Cr photoresist mask can be used

Must depassivate with Zn rod

Photoresist mas~ can be used

Electnxhemlral polh

[14 15507 510J

[519J

1520J

[IS507J

[14516)

(14)

[14517)

[15507513 S17)

[29]

(ConlinLlfd

-- - - --

2

Table XlV (tontid)

Etch rate or Etchmg conditIo etch time Remarkgt Refs

Cobalt

I HC IcHOH 8-9 V 250 AdTn stainless steel 05-15 min Electrochemical polish bluish-green anodic film is sol- [29J uble in HO gIve polished surface WIth slight grain cathode boundary delineatIon

ElectrochemIcal pohsh sohd black film forms which is (29]HPO (98) - 15 V 1-2 Adm Co cathode 5-10 min removed by WIping WIth cotton wool

1539 540JOther electrochemical etc he

Copper ~---~~~-----

0 FeCI 42Be 49 50 Immin Use more dilute solution for slower etching 114 15 50s 509J

2 20-30 HSObull 10-20 crO or KCrO 49 37 Immin (14 15509]

1 g (NH)SO 3 ml HO 32-49 25 Immin Addition of 5 ppm Hg as HgCI activates etehant at [15513 lower temperatures 541-543J

4 5HNO 5CHCOOH 2HSO dilute with HO as Etches Cu and Cumiddotbased alloys at same rate as Ni and (506J

- desired

g KI I g 14 ml H2 0 dip into etch rinse remove

N i-based alloys

Rapid etch but undercutting is limited by formation of [14J

residue with Neutra-clean (Shipley Co Newton an insoluble Cu compound at line edges

Mas)

6 4HNO IIHPO (98) 5CHCOOH 6O-7if 1-2 min Polishing etch (29J

7 2HPOt98I IHO 15-2 V 6-8 Adm Cu cathode 15-30 mm Electrochemical polish [429544 545

()tmiddot~t clflru-hcml1 chhf I~l

fa RIP bull WI1 bull Til bull bull ~-~--~-~-------~-------------~-----~~------------~------

Gallium

Mineral acids or alkali solutions Must be processed below meltmg point (469J

Gold -----~~~~~---~~--~~-~--------~--------------~~------~--------------

)- 4 g KL I g I 40 ml HO 05-1 Immin Better contr~1 of line edges than in more concentnlled [141551 solution solution is opaque so removal from solu tion to observe end point is required

2 3HCL IHNO 32-38 25-50 Immin (IS]

NaCN HO HO mixtures (unspecified composition) [14 15J

4 05 g 12 g NHL 10 ml HO 15 ml cHOH 2if 700 Amin Converts the surface of an underlying Ag layer to the [5101 +shy

iodide thus preventing undercutting -- 04 M KFe(CN) 02 M KCN 01 M KOH 600 Amin Fresh solution must be used no atack on Pd is obshy [58]

served

6 tOO ml HO 05-10 ml HCL 10-JO g NaCl 4-5 V Electrochemical elch which retains bright surface only 1547] 65-2 Adm Mo cathode 20-40 small amount Cl evolved

7 Other electrOChemical etches 129548]

Hafnium

I-cltf HF

lt-6HCIO IOOCHCOOH 18 V Slamle steel cathmiddot ode U several SUCCegtlH dIps with continued agitation

5-10 sec dips

Negative photoreSIst can be ued as mask

ElectrochemICal pohsh -)

[14549J

[29J

See Zircomum etch fltl [291

CConHnurd

--- ---~- --~ -~-------- ~---~ -

Table X (Corllid

Etching condition~

Etch rate or etch lime Remarh Refs

Indium

Mineral acid [469J

IHNO 3CHOH 40-50 V 30 Adm stainless steel cathode cool bath

1-2 min Electrochemical polish [291

Iron

3HNO 7HCI 30H0 6O-7r 2-3 min Dense brown viscous layer forms on surface layer is soluble in solution

[29J

j CgtshyOlt

2

3

4

-I()o( KAI(SOl 12HO

3 liter 1O7c HNO 03 mhr 0 injected 3r

1 HCIO 2OCHCOOH 45-60 V 40-80 Adm stainmiddot less steel cathode

30 mmin

15-30 sec

Slowly soluble

Etches iron plate smoothly 0 removes passive film

Electrochemical polish solid film sometimes forms on the surface during washing removable with dil HF

[469J

[550J

[29J

5 Other electrochemical polishes _

[29J

Lead -----shy----------------------------------------------------------

FeC~ 36-42Be 43-54 [IS 513J -~

9FeCI 42Be IHCI 2rBe 43-49

I HtObull 4CHCOOH Periods 00-10 sec Alternate with immersion in a soln of 10 g molybdic acid and 140 ml NHOH in 240 ml HO to which 60 ml HNO is finally added

[ 15]

(29J

4

5

6

IHNO19HO

35HCIO 63(CHCO)0 20H0 lt3r 50-70 V 9-12 5-10 min A Idm Ph or Cu cathode

()the- k-tdmJ Pbullbulltw

ltlhtum

-------------------

Electrochemical polish

(534J

[291

1191 bull CHOH 30 sec Surface achIeves high luster and is smooth [551]

Magnesium

240-400 g FeCI 330 ml Hel HO to make I liter [469]

1-3HNO 17-19HO [507513 534]

3 fuming HNO type not specifiedl IHO wash imme Periods of 3 sec Reaction rcac Imot explosive violence after -I [29J diately after removal from solution min if allowed to continue it ceases after several

minutes leaving a polished surface

4 7HPO(987cL I3CHOH 1-2V05Admstainle 025 mmin Electrochemical pohsh there is considerable initial [29)

steel or cathode gassing shake anode to remove adhering bubbles

5 5 Other electrochemical etches [29J ~

Manganese

2

IHel IHO

Other dilute mineral acids

1513)

14691

Mercury

Sloght_ diluted HNO

Molybdenum

1469J

5HPO 3HNO 2HO Polishing elch contact to noble metals possible withmiddot OUI mcrcase in etch ratc and undercutling

[57J

IHSO IHNO 1-5H0 ~5-4 J~ 11m imin I~lt I ~ ftm min (~4

Photoresist mask can be used al 25 115507 518

(( OnltnUtJ I

- -~~~ ~ -- --~~-~middotltli0kmiddotmiddot-

Elching condtlons

Tb xrv (Co(Hu~d)

Elch fale or etch tme

Molybdenum (Continuedl

-------shy ~-~---------

Remarh Reh

o

4

6

7

20011 K[Fe(CN))2011 NaOH 3-35 g sodium oxalate add HO 10 make I liter

38HPO 15HNO 3OCHCOOH 75HO

IHSO 7CHOH 80-120 Adm stainless steel cathmiddot ode no agilation

100 ml HPO 20 ml HSObull 40 ml HO 025 II MoO 7(18 V 06-09 Acm slainless sleel graphite or PI cathode stlmng

Other etches

-ltmmin

05t m mrn

I min

94tmmm

Neplunium

Also usable as electrochem etch usinll stainless cathode al 6 V pholoresisl masks applicable

Photoresist mask can be used

Electrochenca polish

Electrochemical pohsh supenor surface finish

steel [14 1551 5075521

1518]

29]

1553

[29 38 57 554-5561

HCI 1557

5HNO 5CHCOOH 2HSObull HO as desired

IHNO IHCI 3HO

FeCI 42-49B 43-54

4

Igt

3HNO IHSO I HPO 198) 5CHCOOH 85-95

IHNO IHO or 9HPO IHNO or 9OHPO 15HNO 4HCL IHO

IOHSo OHO HPO lt-1 NISO JO ~ltr

Nickel

12 -25 tm min

05-1 min

1-2mmln

Etches Ni and Nimiddotbased alloys at same rale as Cu and (506)

Cumiddotbased alloys

Spray elching recommended 1507] o

Photoresist mask may be used [15507513)

Gives very llood polish 1291

Polishing elchants for eleclrol N-P very undercutllng despile conlacl to noble melah

hllie 1571

For ecclrole N film nu undCrcuttmJL mll r fMlfhnn uc-ful (Of ~ittrnl(H Cu

com I ~S8j

bull ~ 8

~7HSObull 4)H 1 U 0 ~ ALm

Other electrochemical polishegt 2 min mm1n lJellrtKht 1~lil1 rulnh

15~ 5601

129J

NiobIum

2 Lacue acid IHSO bull IHF 15~20 V PI cathode sIllmiddot 5-10 mm nng EleClrochemical polish

129]

7HF 7HNO 26HO 49 12-20 V 20~34 Adrn PI cathode Electrochemical etch 14(9) _

9HSO IHF H-45 50 V 2 Adrn PI Or carbon 5-10 min

cathode Electrochem etch temp nses during use cool bath [29]

~--~-----~----~----~----Osmium

Aqua regia 1557)

Palladium

IHCI 10HNO IOCHCOOH 1000 Aim

Aqua rega 15611

1513) Platinum

SHO 7HCI I HNO 85 400-500 AImln 2 f562 563)Aqua regIa precede etchin by 30 sec ImmersIOn in HF

EtCh tIme mlled because photoreSIst mask demiddot 114 507i strayed

3 M HCI 03-+ 14 V versus SeE modIfied Inangumiddot -1000 Almln lar waveform -600 Hz magneuc slmng Electrochem elch good resolu[lOn either po or neg 15141

photoreslS[ usable

Plutonium

I HPOI981 1 diethlene glvcol 5 V ltAdm lainmiddot L 10 mm less steel carhode Electrochemical pohsh

1291

(Conllnttf d

~--~~- - ~ -_ --__~ ~- h __ ~_

Table XIV (Cotiu~d) ~~------- ~---~----~~-~-~-----

Etch rate or Etchmg conditIOns tch time Remarks Ref

Polonium

Dilute mineral acid [557J

Potassium

CHOH or iCH)CHOH 3 sec (ethanoB or 10 SeC (Ioproshypanol)

Brilliant smooth surface obtained [551]

Praesiodymium

Mineral acid -~-~--~-~----------~~------ -------shy

Rhenium

[557]

Dilute HNO [557]

Rhodium

3 M HC -03- + 14 V versus SCE modified triangumiddot ElectTOchem etch I Im line spacings ofRh films over [514]

lar waveform -600 Hz magnetic stirring 5000 ATi on 5i dearly resolved

Ruthenium --------------------~----------------

Fused alkalis [557]

Samarium

Minual acids (557J

Sdenium

HStl ~( IM tf U undtf CkmCnl1 womtunduton 11 bull ~---~--~~-----

Silver

11 g Fe(NO) 9 ml HO 44-49 20 IJmmm Photoresist mask can be used [14 15 507J

2 5-9HNO1-5HO39-49 12-251Jmmin 11415517J

3 35 g AgCN 37 g KCN 38 g KCO 100 ml HO 25- 10 min Electrochem etch best polishing in region of voltage (29) 30 V 1 Alent Ag cathode 10 stirring and currel1t instability

4 3HNO 19H0 2 V [ainle steel cathode ElectrOChemical etch [507)

5 Kl-I etches listed for Cu and Ag O3-llJmsec Immersion followed by HO rinse [14]

60 Asec Useful for pattern etching with photoresist mask rinse [512] quickly after etching

6 4(HOH INHOH IHO

Sodium-

CHtCH)CHOH (nonyl alcohol) 30 sec Brilliant smooth surface [551)

Stronlium

Liquid ammonia [557]

Tanlalum

2

9NaOH or KOH 00laquo) IHO heal alka to 9(t Ihen add HO

5HSObull 2HNO 2HF

1-2HNO IHF 1-2H0

100(l-~OO(l A min

5-20 sec

4 9HSObull IHf (-4 50 cathgtd

A urn 11 1 carb -1(1 rnln

Metal (eg Au) rna muq be used very httle undermiddot cutting etche TO and Ta- al same rale 3 Ta

116~ 16~J

POlishing elch [29 522 5~~

HO rna) be omllled ftgtr fasler elch espeCially if film coniaim oxygen and reslsh etching fasler etch reshyduce re t al1a(~

(14 5 HI

Eletruchernlal etch temp of solUlion ne dunng ue and 11 rna he nece ar~ tp cool hath

129

- -~-~-=-

-4

2

Tabl Xf (Colltlllud)

Etch ratr or Etching condtion rtch time Remarks Refs

Tellurium

2HND3HO [513]

240 g (NH~So bring to I liter with HO [513J

Terbium

M ine 1 acid~ [557]

Thallium

to

HND or HSO

Thonum

------------~----

[557]

14CHCOOH 4HCIO IHO -1060 Adrn stain- 7-12 sec Electrochemical polish [29] less steel cathode

Tin

FeCI 36-42B 32-54 ~------~-

[15 513)

2 IHNO49CHOH [534] (

j iCIO lt35 5O-W V 40 Adrn AI cathode hold piece vertically and rotate at 50-100 r Imin

420 fLmmin Electrochemical polish on large sunaces orange peel effect may occur

(29]

4 Other electrochemical polishes [29]

Titanium

9H0 IHF 3gt 12 fLmmin Photorist mllsk may be used 114 15 507]

2 7Hli 21iNII IH~ n IImmln PhOI maoa m~ be uWd 114155071

bull - bull bull bull

tllO mllHOH 2U ml middotbutyl hoI t2 II Alll ~ II I-JeC1fochcml41 fKlhh 14m) zne 30-50 V 12 Adm ~Utinle Ied cathode

4 3HCIO 5OCHCOOH 200 30 V 30-40 Adm Ti 2 min E)ectrochem etch anode to cathode distance about 129] cathode 3 cm

5 Other electrochemical etches [29 564 5651

6 See Zirconium etch no [29]

Tungsten ~--~~-----~ -------~-------~----~---~~-----------------~~----~~-~--~~~-~---~--~--~------

34 g KHPO 134 g KOH 33 g KFeICN) HO to 1600 Amin Photoresist mask may be used high resolution (1- (515] make I liter 2 Lml can be achieved

2 5 KOH 5 KFe(CN) 1 sunaclant -2302 --23Lmmin Electrochem etch photoresist mask can be used good [51J Acm PI cathode pauem resolution

5-10 NaOH 6 V 3-6 Adm stainless steel cathode Electrochem etch rotation of anode or agitation of [29 513 566deg) - electrolyte with N is necessary

4 Other etches [5158515 555 567]

Uranium

1-2HClO 2OCHCOOH 5O-W v 5 Adrn stainless 19 fLmmill Electrochemical polish (29) steel cathode

2 Other electrochemical pohshe [29]

VanadIum __----------------___---------__-_

1-2HClO 18-19CHCOOH lt35 50-60 V 16-24 1-2 min Electrocherrucal polish a second polishing ofabout the f29] Adm stainless steel cathode sarne duration ill a fresh soln sometimes necessary

---~-~-----~----~--

Ytlcrbium -----~---------------~-----

lhneraJ aCid 1557j

fCwwj

Table XIV (Continued)

Elch ralr or Etchl ng conditIons etch time Remark Refs

~----

Antimony

Aqua regIa or hot HSO 1469J

2 5ltlt AgNO [5341

3 I g FeCI 3 ml HC 12 ml HO 1534J --~--- ---- shy

Aroenic --------------- --------- --------~

HNO 1469J

Beryllium 5 g HSObull 75 g HPO(98) 7 g crO 13 ml HO 49- JLmmin Passive film formed removable by immersion for 15- [29468)

50 30 sec in 10 HSO

2 HCI 1535J

1 H2SO preset voltage 30 V 2240 Almin Electrochemical etch [468J

4 1 KOH preset voltage 50 V 260 Amin Electrochemical etch [468] f

bull ~middot-ther electrochemical etches 129 536J

Bismuth

Hot HSO 469J

2 5ltlt AgNO [534J

3 lt49 ml sal KI soln I ml HCI 5-7 V 20 Adm stainmiddot Penltxh of 30 sec Electrochemical etch allo brown film formed 10 dismiddot 129] Ic IlrC or cKrhon cathode Ive een elchml period

bull bull bull - - bull I 1 -4 CadmIum

3 fuming HNO (type not specified) IHO

7CHCOOH 3 fuming HNO (type not specified)

I g I 3 g Kl 10 ml HO

olectrochemical etches and polishes

Periods 00-10 sec

30 sec-) min

Etchmg periods stream of H20

are followed by rinsing in a rapid 129)

[291

15341

[29 537 538J

ChromIUm

t 2

3

4

5

6

8

9

1 vol t 1 g NaOH 2 ml HOi 3 vo(J g K[Fe(CN) 3 mlf50IOOOAmin H20J

I g CeISOh2(NH)SOmiddot2HO 5 ml HNO 25 ml 85 Almin HO 28

1645 CeISO)2(NH)SO~H() 43 m HClO HO to make I Iller 25-50

2FeCI47BeIHCI80

HCI

454 g AICImiddot6HO 135 I ZnCl 30 ml HPObull 40() ml HO

9 sat Ce(SO soln IHNO

Dilute HCI or HNO

gt1500 Aimin

800 Amm

IHCIObull 2OCHCOOH4~-~OI-20A dm slammiddot cJ(l~er

Ie steel cathode

Does not require depassivation for etching Cr masks and vacuum-deposited Cr in general photoresist mask can be used

Oxide coating etches at 200 Amin

Recommended for precision patterning ofCr masks on glass substrates

Good for plated Cr photoresist mask can be used

Must depassivate with Zn rod

Photoresist mas~ can be used

Electnxhemlral polh

[14 15507 510J

[519J

1520J

[IS507J

[14516)

(14)

[14517)

[15507513 S17)

[29]

(ConlinLlfd

-- - - --

2

Table XlV (tontid)

Etch rate or Etchmg conditIo etch time Remarkgt Refs

Cobalt

I HC IcHOH 8-9 V 250 AdTn stainless steel 05-15 min Electrochemical polish bluish-green anodic film is sol- [29J uble in HO gIve polished surface WIth slight grain cathode boundary delineatIon

ElectrochemIcal pohsh sohd black film forms which is (29]HPO (98) - 15 V 1-2 Adm Co cathode 5-10 min removed by WIping WIth cotton wool

1539 540JOther electrochemical etc he

Copper ~---~~~-----

0 FeCI 42Be 49 50 Immin Use more dilute solution for slower etching 114 15 50s 509J

2 20-30 HSObull 10-20 crO or KCrO 49 37 Immin (14 15509]

1 g (NH)SO 3 ml HO 32-49 25 Immin Addition of 5 ppm Hg as HgCI activates etehant at [15513 lower temperatures 541-543J

4 5HNO 5CHCOOH 2HSO dilute with HO as Etches Cu and Cumiddotbased alloys at same rate as Ni and (506J

- desired

g KI I g 14 ml H2 0 dip into etch rinse remove

N i-based alloys

Rapid etch but undercutting is limited by formation of [14J

residue with Neutra-clean (Shipley Co Newton an insoluble Cu compound at line edges

Mas)

6 4HNO IIHPO (98) 5CHCOOH 6O-7if 1-2 min Polishing etch (29J

7 2HPOt98I IHO 15-2 V 6-8 Adm Cu cathode 15-30 mm Electrochemical polish [429544 545

()tmiddot~t clflru-hcml1 chhf I~l

fa RIP bull WI1 bull Til bull bull ~-~--~-~-------~-------------~-----~~------------~------

Gallium

Mineral acids or alkali solutions Must be processed below meltmg point (469J

Gold -----~~~~~---~~--~~-~--------~--------------~~------~--------------

)- 4 g KL I g I 40 ml HO 05-1 Immin Better contr~1 of line edges than in more concentnlled [141551 solution solution is opaque so removal from solu tion to observe end point is required

2 3HCL IHNO 32-38 25-50 Immin (IS]

NaCN HO HO mixtures (unspecified composition) [14 15J

4 05 g 12 g NHL 10 ml HO 15 ml cHOH 2if 700 Amin Converts the surface of an underlying Ag layer to the [5101 +shy

iodide thus preventing undercutting -- 04 M KFe(CN) 02 M KCN 01 M KOH 600 Amin Fresh solution must be used no atack on Pd is obshy [58]

served

6 tOO ml HO 05-10 ml HCL 10-JO g NaCl 4-5 V Electrochemical elch which retains bright surface only 1547] 65-2 Adm Mo cathode 20-40 small amount Cl evolved

7 Other electrOChemical etches 129548]

Hafnium

I-cltf HF

lt-6HCIO IOOCHCOOH 18 V Slamle steel cathmiddot ode U several SUCCegtlH dIps with continued agitation

5-10 sec dips

Negative photoreSIst can be ued as mask

ElectrochemICal pohsh -)

[14549J

[29J

See Zircomum etch fltl [291

CConHnurd

--- ---~- --~ -~-------- ~---~ -

Table X (Corllid

Etching condition~

Etch rate or etch lime Remarh Refs

Indium

Mineral acid [469J

IHNO 3CHOH 40-50 V 30 Adm stainless steel cathode cool bath

1-2 min Electrochemical polish [291

Iron

3HNO 7HCI 30H0 6O-7r 2-3 min Dense brown viscous layer forms on surface layer is soluble in solution

[29J

j CgtshyOlt

2

3

4

-I()o( KAI(SOl 12HO

3 liter 1O7c HNO 03 mhr 0 injected 3r

1 HCIO 2OCHCOOH 45-60 V 40-80 Adm stainmiddot less steel cathode

30 mmin

15-30 sec

Slowly soluble

Etches iron plate smoothly 0 removes passive film

Electrochemical polish solid film sometimes forms on the surface during washing removable with dil HF

[469J

[550J

[29J

5 Other electrochemical polishes _

[29J

Lead -----shy----------------------------------------------------------

FeC~ 36-42Be 43-54 [IS 513J -~

9FeCI 42Be IHCI 2rBe 43-49

I HtObull 4CHCOOH Periods 00-10 sec Alternate with immersion in a soln of 10 g molybdic acid and 140 ml NHOH in 240 ml HO to which 60 ml HNO is finally added

[ 15]

(29J

4

5

6

IHNO19HO

35HCIO 63(CHCO)0 20H0 lt3r 50-70 V 9-12 5-10 min A Idm Ph or Cu cathode

()the- k-tdmJ Pbullbulltw

ltlhtum

-------------------

Electrochemical polish

(534J

[291

1191 bull CHOH 30 sec Surface achIeves high luster and is smooth [551]

Magnesium

240-400 g FeCI 330 ml Hel HO to make I liter [469]

1-3HNO 17-19HO [507513 534]

3 fuming HNO type not specifiedl IHO wash imme Periods of 3 sec Reaction rcac Imot explosive violence after -I [29J diately after removal from solution min if allowed to continue it ceases after several

minutes leaving a polished surface

4 7HPO(987cL I3CHOH 1-2V05Admstainle 025 mmin Electrochemical pohsh there is considerable initial [29)

steel or cathode gassing shake anode to remove adhering bubbles

5 5 Other electrochemical etches [29J ~

Manganese

2

IHel IHO

Other dilute mineral acids

1513)

14691

Mercury

Sloght_ diluted HNO

Molybdenum

1469J

5HPO 3HNO 2HO Polishing elch contact to noble metals possible withmiddot OUI mcrcase in etch ratc and undercutling

[57J

IHSO IHNO 1-5H0 ~5-4 J~ 11m imin I~lt I ~ ftm min (~4

Photoresist mask can be used al 25 115507 518

(( OnltnUtJ I

- -~~~ ~ -- --~~-~middotltli0kmiddotmiddot-

Elching condtlons

Tb xrv (Co(Hu~d)

Elch fale or etch tme

Molybdenum (Continuedl

-------shy ~-~---------

Remarh Reh

o

4

6

7

20011 K[Fe(CN))2011 NaOH 3-35 g sodium oxalate add HO 10 make I liter

38HPO 15HNO 3OCHCOOH 75HO

IHSO 7CHOH 80-120 Adm stainless steel cathmiddot ode no agilation

100 ml HPO 20 ml HSObull 40 ml HO 025 II MoO 7(18 V 06-09 Acm slainless sleel graphite or PI cathode stlmng

Other etches

-ltmmin

05t m mrn

I min

94tmmm

Neplunium

Also usable as electrochem etch usinll stainless cathode al 6 V pholoresisl masks applicable

Photoresist mask can be used

Electrochenca polish

Electrochemical pohsh supenor surface finish

steel [14 1551 5075521

1518]

29]

1553

[29 38 57 554-5561

HCI 1557

5HNO 5CHCOOH 2HSObull HO as desired

IHNO IHCI 3HO

FeCI 42-49B 43-54

4

Igt

3HNO IHSO I HPO 198) 5CHCOOH 85-95

IHNO IHO or 9HPO IHNO or 9OHPO 15HNO 4HCL IHO

IOHSo OHO HPO lt-1 NISO JO ~ltr

Nickel

12 -25 tm min

05-1 min

1-2mmln

Etches Ni and Nimiddotbased alloys at same rale as Cu and (506)

Cumiddotbased alloys

Spray elching recommended 1507] o

Photoresist mask may be used [15507513)

Gives very llood polish 1291

Polishing elchants for eleclrol N-P very undercutllng despile conlacl to noble melah

hllie 1571

For ecclrole N film nu undCrcuttmJL mll r fMlfhnn uc-ful (Of ~ittrnl(H Cu

com I ~S8j

bull ~ 8

~7HSObull 4)H 1 U 0 ~ ALm

Other electrochemical polishegt 2 min mm1n lJellrtKht 1~lil1 rulnh

15~ 5601

129J

NiobIum

2 Lacue acid IHSO bull IHF 15~20 V PI cathode sIllmiddot 5-10 mm nng EleClrochemical polish

129]

7HF 7HNO 26HO 49 12-20 V 20~34 Adrn PI cathode Electrochemical etch 14(9) _

9HSO IHF H-45 50 V 2 Adrn PI Or carbon 5-10 min

cathode Electrochem etch temp nses during use cool bath [29]

~--~-----~----~----~----Osmium

Aqua regia 1557)

Palladium

IHCI 10HNO IOCHCOOH 1000 Aim

Aqua rega 15611

1513) Platinum

SHO 7HCI I HNO 85 400-500 AImln 2 f562 563)Aqua regIa precede etchin by 30 sec ImmersIOn in HF

EtCh tIme mlled because photoreSIst mask demiddot 114 507i strayed

3 M HCI 03-+ 14 V versus SeE modIfied Inangumiddot -1000 Almln lar waveform -600 Hz magneuc slmng Electrochem elch good resolu[lOn either po or neg 15141

photoreslS[ usable

Plutonium

I HPOI981 1 diethlene glvcol 5 V ltAdm lainmiddot L 10 mm less steel carhode Electrochemical pohsh

1291

(Conllnttf d

~--~~- - ~ -_ --__~ ~- h __ ~_

Table XIV (Cotiu~d) ~~------- ~---~----~~-~-~-----

Etch rate or Etchmg conditIOns tch time Remarks Ref

Polonium

Dilute mineral acid [557J

Potassium

CHOH or iCH)CHOH 3 sec (ethanoB or 10 SeC (Ioproshypanol)

Brilliant smooth surface obtained [551]

Praesiodymium

Mineral acid -~-~--~-~----------~~------ -------shy

Rhenium

[557]

Dilute HNO [557]

Rhodium

3 M HC -03- + 14 V versus SCE modified triangumiddot ElectTOchem etch I Im line spacings ofRh films over [514]

lar waveform -600 Hz magnetic stirring 5000 ATi on 5i dearly resolved

Ruthenium --------------------~----------------

Fused alkalis [557]

Samarium

Minual acids (557J

Sdenium

HStl ~( IM tf U undtf CkmCnl1 womtunduton 11 bull ~---~--~~-----

Silver

11 g Fe(NO) 9 ml HO 44-49 20 IJmmm Photoresist mask can be used [14 15 507J

2 5-9HNO1-5HO39-49 12-251Jmmin 11415517J

3 35 g AgCN 37 g KCN 38 g KCO 100 ml HO 25- 10 min Electrochem etch best polishing in region of voltage (29) 30 V 1 Alent Ag cathode 10 stirring and currel1t instability

4 3HNO 19H0 2 V [ainle steel cathode ElectrOChemical etch [507)

5 Kl-I etches listed for Cu and Ag O3-llJmsec Immersion followed by HO rinse [14]

60 Asec Useful for pattern etching with photoresist mask rinse [512] quickly after etching

6 4(HOH INHOH IHO

Sodium-

CHtCH)CHOH (nonyl alcohol) 30 sec Brilliant smooth surface [551)

Stronlium

Liquid ammonia [557]

Tanlalum

2

9NaOH or KOH 00laquo) IHO heal alka to 9(t Ihen add HO

5HSObull 2HNO 2HF

1-2HNO IHF 1-2H0

100(l-~OO(l A min

5-20 sec

4 9HSObull IHf (-4 50 cathgtd

A urn 11 1 carb -1(1 rnln

Metal (eg Au) rna muq be used very httle undermiddot cutting etche TO and Ta- al same rale 3 Ta

116~ 16~J

POlishing elch [29 522 5~~

HO rna) be omllled ftgtr fasler elch espeCially if film coniaim oxygen and reslsh etching fasler etch reshyduce re t al1a(~

(14 5 HI

Eletruchernlal etch temp of solUlion ne dunng ue and 11 rna he nece ar~ tp cool hath

129

- -~-~-=-

-4

2

Tabl Xf (Colltlllud)

Etch ratr or Etching condtion rtch time Remarks Refs

Tellurium

2HND3HO [513]

240 g (NH~So bring to I liter with HO [513J

Terbium

M ine 1 acid~ [557]

Thallium

to

HND or HSO

Thonum

------------~----

[557]

14CHCOOH 4HCIO IHO -1060 Adrn stain- 7-12 sec Electrochemical polish [29] less steel cathode

Tin

FeCI 36-42B 32-54 ~------~-

[15 513)

2 IHNO49CHOH [534] (

j iCIO lt35 5O-W V 40 Adrn AI cathode hold piece vertically and rotate at 50-100 r Imin

420 fLmmin Electrochemical polish on large sunaces orange peel effect may occur

(29]

4 Other electrochemical polishes [29]

Titanium

9H0 IHF 3gt 12 fLmmin Photorist mllsk may be used 114 15 507]

2 7Hli 21iNII IH~ n IImmln PhOI maoa m~ be uWd 114155071

bull - bull bull bull

tllO mllHOH 2U ml middotbutyl hoI t2 II Alll ~ II I-JeC1fochcml41 fKlhh 14m) zne 30-50 V 12 Adm ~Utinle Ied cathode

4 3HCIO 5OCHCOOH 200 30 V 30-40 Adm Ti 2 min E)ectrochem etch anode to cathode distance about 129] cathode 3 cm

5 Other electrochemical etches [29 564 5651

6 See Zirconium etch no [29]

Tungsten ~--~~-----~ -------~-------~----~---~~-----------------~~----~~-~--~~~-~---~--~--~------

34 g KHPO 134 g KOH 33 g KFeICN) HO to 1600 Amin Photoresist mask may be used high resolution (1- (515] make I liter 2 Lml can be achieved

2 5 KOH 5 KFe(CN) 1 sunaclant -2302 --23Lmmin Electrochem etch photoresist mask can be used good [51J Acm PI cathode pauem resolution

5-10 NaOH 6 V 3-6 Adm stainless steel cathode Electrochem etch rotation of anode or agitation of [29 513 566deg) - electrolyte with N is necessary

4 Other etches [5158515 555 567]

Uranium

1-2HClO 2OCHCOOH 5O-W v 5 Adrn stainless 19 fLmmill Electrochemical polish (29) steel cathode

2 Other electrochemical pohshe [29]

VanadIum __----------------___---------__-_

1-2HClO 18-19CHCOOH lt35 50-60 V 16-24 1-2 min Electrocherrucal polish a second polishing ofabout the f29] Adm stainless steel cathode sarne duration ill a fresh soln sometimes necessary

---~-~-----~----~--

Ytlcrbium -----~---------------~-----

lhneraJ aCid 1557j

fCwwj

-- - - --

2

Table XlV (tontid)

Etch rate or Etchmg conditIo etch time Remarkgt Refs

Cobalt

I HC IcHOH 8-9 V 250 AdTn stainless steel 05-15 min Electrochemical polish bluish-green anodic film is sol- [29J uble in HO gIve polished surface WIth slight grain cathode boundary delineatIon

ElectrochemIcal pohsh sohd black film forms which is (29]HPO (98) - 15 V 1-2 Adm Co cathode 5-10 min removed by WIping WIth cotton wool

1539 540JOther electrochemical etc he

Copper ~---~~~-----

0 FeCI 42Be 49 50 Immin Use more dilute solution for slower etching 114 15 50s 509J

2 20-30 HSObull 10-20 crO or KCrO 49 37 Immin (14 15509]

1 g (NH)SO 3 ml HO 32-49 25 Immin Addition of 5 ppm Hg as HgCI activates etehant at [15513 lower temperatures 541-543J

4 5HNO 5CHCOOH 2HSO dilute with HO as Etches Cu and Cumiddotbased alloys at same rate as Ni and (506J

- desired

g KI I g 14 ml H2 0 dip into etch rinse remove

N i-based alloys

Rapid etch but undercutting is limited by formation of [14J

residue with Neutra-clean (Shipley Co Newton an insoluble Cu compound at line edges

Mas)

6 4HNO IIHPO (98) 5CHCOOH 6O-7if 1-2 min Polishing etch (29J

7 2HPOt98I IHO 15-2 V 6-8 Adm Cu cathode 15-30 mm Electrochemical polish [429544 545

()tmiddot~t clflru-hcml1 chhf I~l

fa RIP bull WI1 bull Til bull bull ~-~--~-~-------~-------------~-----~~------------~------

Gallium

Mineral acids or alkali solutions Must be processed below meltmg point (469J

Gold -----~~~~~---~~--~~-~--------~--------------~~------~--------------

)- 4 g KL I g I 40 ml HO 05-1 Immin Better contr~1 of line edges than in more concentnlled [141551 solution solution is opaque so removal from solu tion to observe end point is required

2 3HCL IHNO 32-38 25-50 Immin (IS]

NaCN HO HO mixtures (unspecified composition) [14 15J

4 05 g 12 g NHL 10 ml HO 15 ml cHOH 2if 700 Amin Converts the surface of an underlying Ag layer to the [5101 +shy

iodide thus preventing undercutting -- 04 M KFe(CN) 02 M KCN 01 M KOH 600 Amin Fresh solution must be used no atack on Pd is obshy [58]

served

6 tOO ml HO 05-10 ml HCL 10-JO g NaCl 4-5 V Electrochemical elch which retains bright surface only 1547] 65-2 Adm Mo cathode 20-40 small amount Cl evolved

7 Other electrOChemical etches 129548]

Hafnium

I-cltf HF

lt-6HCIO IOOCHCOOH 18 V Slamle steel cathmiddot ode U several SUCCegtlH dIps with continued agitation

5-10 sec dips

Negative photoreSIst can be ued as mask

ElectrochemICal pohsh -)

[14549J

[29J

See Zircomum etch fltl [291

CConHnurd

--- ---~- --~ -~-------- ~---~ -

Table X (Corllid

Etching condition~

Etch rate or etch lime Remarh Refs

Indium

Mineral acid [469J

IHNO 3CHOH 40-50 V 30 Adm stainless steel cathode cool bath

1-2 min Electrochemical polish [291

Iron

3HNO 7HCI 30H0 6O-7r 2-3 min Dense brown viscous layer forms on surface layer is soluble in solution

[29J

j CgtshyOlt

2

3

4

-I()o( KAI(SOl 12HO

3 liter 1O7c HNO 03 mhr 0 injected 3r

1 HCIO 2OCHCOOH 45-60 V 40-80 Adm stainmiddot less steel cathode

30 mmin

15-30 sec

Slowly soluble

Etches iron plate smoothly 0 removes passive film

Electrochemical polish solid film sometimes forms on the surface during washing removable with dil HF

[469J

[550J

[29J

5 Other electrochemical polishes _

[29J

Lead -----shy----------------------------------------------------------

FeC~ 36-42Be 43-54 [IS 513J -~

9FeCI 42Be IHCI 2rBe 43-49

I HtObull 4CHCOOH Periods 00-10 sec Alternate with immersion in a soln of 10 g molybdic acid and 140 ml NHOH in 240 ml HO to which 60 ml HNO is finally added

[ 15]

(29J

4

5

6

IHNO19HO

35HCIO 63(CHCO)0 20H0 lt3r 50-70 V 9-12 5-10 min A Idm Ph or Cu cathode

()the- k-tdmJ Pbullbulltw

ltlhtum

-------------------

Electrochemical polish

(534J

[291

1191 bull CHOH 30 sec Surface achIeves high luster and is smooth [551]

Magnesium

240-400 g FeCI 330 ml Hel HO to make I liter [469]

1-3HNO 17-19HO [507513 534]

3 fuming HNO type not specifiedl IHO wash imme Periods of 3 sec Reaction rcac Imot explosive violence after -I [29J diately after removal from solution min if allowed to continue it ceases after several

minutes leaving a polished surface

4 7HPO(987cL I3CHOH 1-2V05Admstainle 025 mmin Electrochemical pohsh there is considerable initial [29)

steel or cathode gassing shake anode to remove adhering bubbles

5 5 Other electrochemical etches [29J ~

Manganese

2

IHel IHO

Other dilute mineral acids

1513)

14691

Mercury

Sloght_ diluted HNO

Molybdenum

1469J

5HPO 3HNO 2HO Polishing elch contact to noble metals possible withmiddot OUI mcrcase in etch ratc and undercutling

[57J

IHSO IHNO 1-5H0 ~5-4 J~ 11m imin I~lt I ~ ftm min (~4

Photoresist mask can be used al 25 115507 518

(( OnltnUtJ I

- -~~~ ~ -- --~~-~middotltli0kmiddotmiddot-

Elching condtlons

Tb xrv (Co(Hu~d)

Elch fale or etch tme

Molybdenum (Continuedl

-------shy ~-~---------

Remarh Reh

o

4

6

7

20011 K[Fe(CN))2011 NaOH 3-35 g sodium oxalate add HO 10 make I liter

38HPO 15HNO 3OCHCOOH 75HO

IHSO 7CHOH 80-120 Adm stainless steel cathmiddot ode no agilation

100 ml HPO 20 ml HSObull 40 ml HO 025 II MoO 7(18 V 06-09 Acm slainless sleel graphite or PI cathode stlmng

Other etches

-ltmmin

05t m mrn

I min

94tmmm

Neplunium

Also usable as electrochem etch usinll stainless cathode al 6 V pholoresisl masks applicable

Photoresist mask can be used

Electrochenca polish

Electrochemical pohsh supenor surface finish

steel [14 1551 5075521

1518]

29]

1553

[29 38 57 554-5561

HCI 1557

5HNO 5CHCOOH 2HSObull HO as desired

IHNO IHCI 3HO

FeCI 42-49B 43-54

4

Igt

3HNO IHSO I HPO 198) 5CHCOOH 85-95

IHNO IHO or 9HPO IHNO or 9OHPO 15HNO 4HCL IHO

IOHSo OHO HPO lt-1 NISO JO ~ltr

Nickel

12 -25 tm min

05-1 min

1-2mmln

Etches Ni and Nimiddotbased alloys at same rale as Cu and (506)

Cumiddotbased alloys

Spray elching recommended 1507] o

Photoresist mask may be used [15507513)

Gives very llood polish 1291

Polishing elchants for eleclrol N-P very undercutllng despile conlacl to noble melah

hllie 1571

For ecclrole N film nu undCrcuttmJL mll r fMlfhnn uc-ful (Of ~ittrnl(H Cu

com I ~S8j

bull ~ 8

~7HSObull 4)H 1 U 0 ~ ALm

Other electrochemical polishegt 2 min mm1n lJellrtKht 1~lil1 rulnh

15~ 5601

129J

NiobIum

2 Lacue acid IHSO bull IHF 15~20 V PI cathode sIllmiddot 5-10 mm nng EleClrochemical polish

129]

7HF 7HNO 26HO 49 12-20 V 20~34 Adrn PI cathode Electrochemical etch 14(9) _

9HSO IHF H-45 50 V 2 Adrn PI Or carbon 5-10 min

cathode Electrochem etch temp nses during use cool bath [29]

~--~-----~----~----~----Osmium

Aqua regia 1557)

Palladium

IHCI 10HNO IOCHCOOH 1000 Aim

Aqua rega 15611

1513) Platinum

SHO 7HCI I HNO 85 400-500 AImln 2 f562 563)Aqua regIa precede etchin by 30 sec ImmersIOn in HF

EtCh tIme mlled because photoreSIst mask demiddot 114 507i strayed

3 M HCI 03-+ 14 V versus SeE modIfied Inangumiddot -1000 Almln lar waveform -600 Hz magneuc slmng Electrochem elch good resolu[lOn either po or neg 15141

photoreslS[ usable

Plutonium

I HPOI981 1 diethlene glvcol 5 V ltAdm lainmiddot L 10 mm less steel carhode Electrochemical pohsh

1291

(Conllnttf d

~--~~- - ~ -_ --__~ ~- h __ ~_

Table XIV (Cotiu~d) ~~------- ~---~----~~-~-~-----

Etch rate or Etchmg conditIOns tch time Remarks Ref

Polonium

Dilute mineral acid [557J

Potassium

CHOH or iCH)CHOH 3 sec (ethanoB or 10 SeC (Ioproshypanol)

Brilliant smooth surface obtained [551]

Praesiodymium

Mineral acid -~-~--~-~----------~~------ -------shy

Rhenium

[557]

Dilute HNO [557]

Rhodium

3 M HC -03- + 14 V versus SCE modified triangumiddot ElectTOchem etch I Im line spacings ofRh films over [514]

lar waveform -600 Hz magnetic stirring 5000 ATi on 5i dearly resolved

Ruthenium --------------------~----------------

Fused alkalis [557]

Samarium

Minual acids (557J

Sdenium

HStl ~( IM tf U undtf CkmCnl1 womtunduton 11 bull ~---~--~~-----

Silver

11 g Fe(NO) 9 ml HO 44-49 20 IJmmm Photoresist mask can be used [14 15 507J

2 5-9HNO1-5HO39-49 12-251Jmmin 11415517J

3 35 g AgCN 37 g KCN 38 g KCO 100 ml HO 25- 10 min Electrochem etch best polishing in region of voltage (29) 30 V 1 Alent Ag cathode 10 stirring and currel1t instability

4 3HNO 19H0 2 V [ainle steel cathode ElectrOChemical etch [507)

5 Kl-I etches listed for Cu and Ag O3-llJmsec Immersion followed by HO rinse [14]

60 Asec Useful for pattern etching with photoresist mask rinse [512] quickly after etching

6 4(HOH INHOH IHO

Sodium-

CHtCH)CHOH (nonyl alcohol) 30 sec Brilliant smooth surface [551)

Stronlium

Liquid ammonia [557]

Tanlalum

2

9NaOH or KOH 00laquo) IHO heal alka to 9(t Ihen add HO

5HSObull 2HNO 2HF

1-2HNO IHF 1-2H0

100(l-~OO(l A min

5-20 sec

4 9HSObull IHf (-4 50 cathgtd

A urn 11 1 carb -1(1 rnln

Metal (eg Au) rna muq be used very httle undermiddot cutting etche TO and Ta- al same rale 3 Ta

116~ 16~J

POlishing elch [29 522 5~~

HO rna) be omllled ftgtr fasler elch espeCially if film coniaim oxygen and reslsh etching fasler etch reshyduce re t al1a(~

(14 5 HI

Eletruchernlal etch temp of solUlion ne dunng ue and 11 rna he nece ar~ tp cool hath

129

- -~-~-=-

-4

2

Tabl Xf (Colltlllud)

Etch ratr or Etching condtion rtch time Remarks Refs

Tellurium

2HND3HO [513]

240 g (NH~So bring to I liter with HO [513J

Terbium

M ine 1 acid~ [557]

Thallium

to

HND or HSO

Thonum

------------~----

[557]

14CHCOOH 4HCIO IHO -1060 Adrn stain- 7-12 sec Electrochemical polish [29] less steel cathode

Tin

FeCI 36-42B 32-54 ~------~-

[15 513)

2 IHNO49CHOH [534] (

j iCIO lt35 5O-W V 40 Adrn AI cathode hold piece vertically and rotate at 50-100 r Imin

420 fLmmin Electrochemical polish on large sunaces orange peel effect may occur

(29]

4 Other electrochemical polishes [29]

Titanium

9H0 IHF 3gt 12 fLmmin Photorist mllsk may be used 114 15 507]

2 7Hli 21iNII IH~ n IImmln PhOI maoa m~ be uWd 114155071

bull - bull bull bull

tllO mllHOH 2U ml middotbutyl hoI t2 II Alll ~ II I-JeC1fochcml41 fKlhh 14m) zne 30-50 V 12 Adm ~Utinle Ied cathode

4 3HCIO 5OCHCOOH 200 30 V 30-40 Adm Ti 2 min E)ectrochem etch anode to cathode distance about 129] cathode 3 cm

5 Other electrochemical etches [29 564 5651

6 See Zirconium etch no [29]

Tungsten ~--~~-----~ -------~-------~----~---~~-----------------~~----~~-~--~~~-~---~--~--~------

34 g KHPO 134 g KOH 33 g KFeICN) HO to 1600 Amin Photoresist mask may be used high resolution (1- (515] make I liter 2 Lml can be achieved

2 5 KOH 5 KFe(CN) 1 sunaclant -2302 --23Lmmin Electrochem etch photoresist mask can be used good [51J Acm PI cathode pauem resolution

5-10 NaOH 6 V 3-6 Adm stainless steel cathode Electrochem etch rotation of anode or agitation of [29 513 566deg) - electrolyte with N is necessary

4 Other etches [5158515 555 567]

Uranium

1-2HClO 2OCHCOOH 5O-W v 5 Adrn stainless 19 fLmmill Electrochemical polish (29) steel cathode

2 Other electrochemical pohshe [29]

VanadIum __----------------___---------__-_

1-2HClO 18-19CHCOOH lt35 50-60 V 16-24 1-2 min Electrocherrucal polish a second polishing ofabout the f29] Adm stainless steel cathode sarne duration ill a fresh soln sometimes necessary

---~-~-----~----~--

Ytlcrbium -----~---------------~-----

lhneraJ aCid 1557j

fCwwj

Table X (Corllid

Etching condition~

Etch rate or etch lime Remarh Refs

Indium

Mineral acid [469J

IHNO 3CHOH 40-50 V 30 Adm stainless steel cathode cool bath

1-2 min Electrochemical polish [291

Iron

3HNO 7HCI 30H0 6O-7r 2-3 min Dense brown viscous layer forms on surface layer is soluble in solution

[29J

j CgtshyOlt

2

3

4

-I()o( KAI(SOl 12HO

3 liter 1O7c HNO 03 mhr 0 injected 3r

1 HCIO 2OCHCOOH 45-60 V 40-80 Adm stainmiddot less steel cathode

30 mmin

15-30 sec

Slowly soluble

Etches iron plate smoothly 0 removes passive film

Electrochemical polish solid film sometimes forms on the surface during washing removable with dil HF

[469J

[550J

[29J

5 Other electrochemical polishes _

[29J

Lead -----shy----------------------------------------------------------

FeC~ 36-42Be 43-54 [IS 513J -~

9FeCI 42Be IHCI 2rBe 43-49

I HtObull 4CHCOOH Periods 00-10 sec Alternate with immersion in a soln of 10 g molybdic acid and 140 ml NHOH in 240 ml HO to which 60 ml HNO is finally added

[ 15]

(29J

4

5

6

IHNO19HO

35HCIO 63(CHCO)0 20H0 lt3r 50-70 V 9-12 5-10 min A Idm Ph or Cu cathode

()the- k-tdmJ Pbullbulltw

ltlhtum

-------------------

Electrochemical polish

(534J

[291

1191 bull CHOH 30 sec Surface achIeves high luster and is smooth [551]

Magnesium

240-400 g FeCI 330 ml Hel HO to make I liter [469]

1-3HNO 17-19HO [507513 534]

3 fuming HNO type not specifiedl IHO wash imme Periods of 3 sec Reaction rcac Imot explosive violence after -I [29J diately after removal from solution min if allowed to continue it ceases after several

minutes leaving a polished surface

4 7HPO(987cL I3CHOH 1-2V05Admstainle 025 mmin Electrochemical pohsh there is considerable initial [29)

steel or cathode gassing shake anode to remove adhering bubbles

5 5 Other electrochemical etches [29J ~

Manganese

2

IHel IHO

Other dilute mineral acids

1513)

14691

Mercury

Sloght_ diluted HNO

Molybdenum

1469J

5HPO 3HNO 2HO Polishing elch contact to noble metals possible withmiddot OUI mcrcase in etch ratc and undercutling

[57J

IHSO IHNO 1-5H0 ~5-4 J~ 11m imin I~lt I ~ ftm min (~4

Photoresist mask can be used al 25 115507 518

(( OnltnUtJ I

- -~~~ ~ -- --~~-~middotltli0kmiddotmiddot-

Elching condtlons

Tb xrv (Co(Hu~d)

Elch fale or etch tme

Molybdenum (Continuedl

-------shy ~-~---------

Remarh Reh

o

4

6

7

20011 K[Fe(CN))2011 NaOH 3-35 g sodium oxalate add HO 10 make I liter

38HPO 15HNO 3OCHCOOH 75HO

IHSO 7CHOH 80-120 Adm stainless steel cathmiddot ode no agilation

100 ml HPO 20 ml HSObull 40 ml HO 025 II MoO 7(18 V 06-09 Acm slainless sleel graphite or PI cathode stlmng

Other etches

-ltmmin

05t m mrn

I min

94tmmm

Neplunium

Also usable as electrochem etch usinll stainless cathode al 6 V pholoresisl masks applicable

Photoresist mask can be used

Electrochenca polish

Electrochemical pohsh supenor surface finish

steel [14 1551 5075521

1518]

29]

1553

[29 38 57 554-5561

HCI 1557

5HNO 5CHCOOH 2HSObull HO as desired

IHNO IHCI 3HO

FeCI 42-49B 43-54

4

Igt

3HNO IHSO I HPO 198) 5CHCOOH 85-95

IHNO IHO or 9HPO IHNO or 9OHPO 15HNO 4HCL IHO

IOHSo OHO HPO lt-1 NISO JO ~ltr

Nickel

12 -25 tm min

05-1 min

1-2mmln

Etches Ni and Nimiddotbased alloys at same rale as Cu and (506)

Cumiddotbased alloys

Spray elching recommended 1507] o

Photoresist mask may be used [15507513)

Gives very llood polish 1291

Polishing elchants for eleclrol N-P very undercutllng despile conlacl to noble melah

hllie 1571

For ecclrole N film nu undCrcuttmJL mll r fMlfhnn uc-ful (Of ~ittrnl(H Cu

com I ~S8j

bull ~ 8

~7HSObull 4)H 1 U 0 ~ ALm

Other electrochemical polishegt 2 min mm1n lJellrtKht 1~lil1 rulnh

15~ 5601

129J

NiobIum

2 Lacue acid IHSO bull IHF 15~20 V PI cathode sIllmiddot 5-10 mm nng EleClrochemical polish

129]

7HF 7HNO 26HO 49 12-20 V 20~34 Adrn PI cathode Electrochemical etch 14(9) _

9HSO IHF H-45 50 V 2 Adrn PI Or carbon 5-10 min

cathode Electrochem etch temp nses during use cool bath [29]

~--~-----~----~----~----Osmium

Aqua regia 1557)

Palladium

IHCI 10HNO IOCHCOOH 1000 Aim

Aqua rega 15611

1513) Platinum

SHO 7HCI I HNO 85 400-500 AImln 2 f562 563)Aqua regIa precede etchin by 30 sec ImmersIOn in HF

EtCh tIme mlled because photoreSIst mask demiddot 114 507i strayed

3 M HCI 03-+ 14 V versus SeE modIfied Inangumiddot -1000 Almln lar waveform -600 Hz magneuc slmng Electrochem elch good resolu[lOn either po or neg 15141

photoreslS[ usable

Plutonium

I HPOI981 1 diethlene glvcol 5 V ltAdm lainmiddot L 10 mm less steel carhode Electrochemical pohsh

1291

(Conllnttf d

~--~~- - ~ -_ --__~ ~- h __ ~_

Table XIV (Cotiu~d) ~~------- ~---~----~~-~-~-----

Etch rate or Etchmg conditIOns tch time Remarks Ref

Polonium

Dilute mineral acid [557J

Potassium

CHOH or iCH)CHOH 3 sec (ethanoB or 10 SeC (Ioproshypanol)

Brilliant smooth surface obtained [551]

Praesiodymium

Mineral acid -~-~--~-~----------~~------ -------shy

Rhenium

[557]

Dilute HNO [557]

Rhodium

3 M HC -03- + 14 V versus SCE modified triangumiddot ElectTOchem etch I Im line spacings ofRh films over [514]

lar waveform -600 Hz magnetic stirring 5000 ATi on 5i dearly resolved

Ruthenium --------------------~----------------

Fused alkalis [557]

Samarium

Minual acids (557J

Sdenium

HStl ~( IM tf U undtf CkmCnl1 womtunduton 11 bull ~---~--~~-----

Silver

11 g Fe(NO) 9 ml HO 44-49 20 IJmmm Photoresist mask can be used [14 15 507J

2 5-9HNO1-5HO39-49 12-251Jmmin 11415517J

3 35 g AgCN 37 g KCN 38 g KCO 100 ml HO 25- 10 min Electrochem etch best polishing in region of voltage (29) 30 V 1 Alent Ag cathode 10 stirring and currel1t instability

4 3HNO 19H0 2 V [ainle steel cathode ElectrOChemical etch [507)

5 Kl-I etches listed for Cu and Ag O3-llJmsec Immersion followed by HO rinse [14]

60 Asec Useful for pattern etching with photoresist mask rinse [512] quickly after etching

6 4(HOH INHOH IHO

Sodium-

CHtCH)CHOH (nonyl alcohol) 30 sec Brilliant smooth surface [551)

Stronlium

Liquid ammonia [557]

Tanlalum

2

9NaOH or KOH 00laquo) IHO heal alka to 9(t Ihen add HO

5HSObull 2HNO 2HF

1-2HNO IHF 1-2H0

100(l-~OO(l A min

5-20 sec

4 9HSObull IHf (-4 50 cathgtd

A urn 11 1 carb -1(1 rnln

Metal (eg Au) rna muq be used very httle undermiddot cutting etche TO and Ta- al same rale 3 Ta

116~ 16~J

POlishing elch [29 522 5~~

HO rna) be omllled ftgtr fasler elch espeCially if film coniaim oxygen and reslsh etching fasler etch reshyduce re t al1a(~

(14 5 HI

Eletruchernlal etch temp of solUlion ne dunng ue and 11 rna he nece ar~ tp cool hath

129

- -~-~-=-

-4

2

Tabl Xf (Colltlllud)

Etch ratr or Etching condtion rtch time Remarks Refs

Tellurium

2HND3HO [513]

240 g (NH~So bring to I liter with HO [513J

Terbium

M ine 1 acid~ [557]

Thallium

to

HND or HSO

Thonum

------------~----

[557]

14CHCOOH 4HCIO IHO -1060 Adrn stain- 7-12 sec Electrochemical polish [29] less steel cathode

Tin

FeCI 36-42B 32-54 ~------~-

[15 513)

2 IHNO49CHOH [534] (

j iCIO lt35 5O-W V 40 Adrn AI cathode hold piece vertically and rotate at 50-100 r Imin

420 fLmmin Electrochemical polish on large sunaces orange peel effect may occur

(29]

4 Other electrochemical polishes [29]

Titanium

9H0 IHF 3gt 12 fLmmin Photorist mllsk may be used 114 15 507]

2 7Hli 21iNII IH~ n IImmln PhOI maoa m~ be uWd 114155071

bull - bull bull bull

tllO mllHOH 2U ml middotbutyl hoI t2 II Alll ~ II I-JeC1fochcml41 fKlhh 14m) zne 30-50 V 12 Adm ~Utinle Ied cathode

4 3HCIO 5OCHCOOH 200 30 V 30-40 Adm Ti 2 min E)ectrochem etch anode to cathode distance about 129] cathode 3 cm

5 Other electrochemical etches [29 564 5651

6 See Zirconium etch no [29]

Tungsten ~--~~-----~ -------~-------~----~---~~-----------------~~----~~-~--~~~-~---~--~--~------

34 g KHPO 134 g KOH 33 g KFeICN) HO to 1600 Amin Photoresist mask may be used high resolution (1- (515] make I liter 2 Lml can be achieved

2 5 KOH 5 KFe(CN) 1 sunaclant -2302 --23Lmmin Electrochem etch photoresist mask can be used good [51J Acm PI cathode pauem resolution

5-10 NaOH 6 V 3-6 Adm stainless steel cathode Electrochem etch rotation of anode or agitation of [29 513 566deg) - electrolyte with N is necessary

4 Other etches [5158515 555 567]

Uranium

1-2HClO 2OCHCOOH 5O-W v 5 Adrn stainless 19 fLmmill Electrochemical polish (29) steel cathode

2 Other electrochemical pohshe [29]

VanadIum __----------------___---------__-_

1-2HClO 18-19CHCOOH lt35 50-60 V 16-24 1-2 min Electrocherrucal polish a second polishing ofabout the f29] Adm stainless steel cathode sarne duration ill a fresh soln sometimes necessary

---~-~-----~----~--

Ytlcrbium -----~---------------~-----

lhneraJ aCid 1557j

fCwwj

Elching condtlons

Tb xrv (Co(Hu~d)

Elch fale or etch tme

Molybdenum (Continuedl

-------shy ~-~---------

Remarh Reh

o

4

6

7

20011 K[Fe(CN))2011 NaOH 3-35 g sodium oxalate add HO 10 make I liter

38HPO 15HNO 3OCHCOOH 75HO

IHSO 7CHOH 80-120 Adm stainless steel cathmiddot ode no agilation

100 ml HPO 20 ml HSObull 40 ml HO 025 II MoO 7(18 V 06-09 Acm slainless sleel graphite or PI cathode stlmng

Other etches

-ltmmin

05t m mrn

I min

94tmmm

Neplunium

Also usable as electrochem etch usinll stainless cathode al 6 V pholoresisl masks applicable

Photoresist mask can be used

Electrochenca polish

Electrochemical pohsh supenor surface finish

steel [14 1551 5075521

1518]

29]

1553

[29 38 57 554-5561

HCI 1557

5HNO 5CHCOOH 2HSObull HO as desired

IHNO IHCI 3HO

FeCI 42-49B 43-54

4

Igt

3HNO IHSO I HPO 198) 5CHCOOH 85-95

IHNO IHO or 9HPO IHNO or 9OHPO 15HNO 4HCL IHO

IOHSo OHO HPO lt-1 NISO JO ~ltr

Nickel

12 -25 tm min

05-1 min

1-2mmln

Etches Ni and Nimiddotbased alloys at same rale as Cu and (506)

Cumiddotbased alloys

Spray elching recommended 1507] o

Photoresist mask may be used [15507513)

Gives very llood polish 1291

Polishing elchants for eleclrol N-P very undercutllng despile conlacl to noble melah

hllie 1571

For ecclrole N film nu undCrcuttmJL mll r fMlfhnn uc-ful (Of ~ittrnl(H Cu

com I ~S8j

bull ~ 8

~7HSObull 4)H 1 U 0 ~ ALm

Other electrochemical polishegt 2 min mm1n lJellrtKht 1~lil1 rulnh

15~ 5601

129J

NiobIum

2 Lacue acid IHSO bull IHF 15~20 V PI cathode sIllmiddot 5-10 mm nng EleClrochemical polish

129]

7HF 7HNO 26HO 49 12-20 V 20~34 Adrn PI cathode Electrochemical etch 14(9) _

9HSO IHF H-45 50 V 2 Adrn PI Or carbon 5-10 min

cathode Electrochem etch temp nses during use cool bath [29]

~--~-----~----~----~----Osmium

Aqua regia 1557)

Palladium

IHCI 10HNO IOCHCOOH 1000 Aim

Aqua rega 15611

1513) Platinum

SHO 7HCI I HNO 85 400-500 AImln 2 f562 563)Aqua regIa precede etchin by 30 sec ImmersIOn in HF

EtCh tIme mlled because photoreSIst mask demiddot 114 507i strayed

3 M HCI 03-+ 14 V versus SeE modIfied Inangumiddot -1000 Almln lar waveform -600 Hz magneuc slmng Electrochem elch good resolu[lOn either po or neg 15141

photoreslS[ usable

Plutonium

I HPOI981 1 diethlene glvcol 5 V ltAdm lainmiddot L 10 mm less steel carhode Electrochemical pohsh

1291

(Conllnttf d

~--~~- - ~ -_ --__~ ~- h __ ~_

Table XIV (Cotiu~d) ~~------- ~---~----~~-~-~-----

Etch rate or Etchmg conditIOns tch time Remarks Ref

Polonium

Dilute mineral acid [557J

Potassium

CHOH or iCH)CHOH 3 sec (ethanoB or 10 SeC (Ioproshypanol)

Brilliant smooth surface obtained [551]

Praesiodymium

Mineral acid -~-~--~-~----------~~------ -------shy

Rhenium

[557]

Dilute HNO [557]

Rhodium

3 M HC -03- + 14 V versus SCE modified triangumiddot ElectTOchem etch I Im line spacings ofRh films over [514]

lar waveform -600 Hz magnetic stirring 5000 ATi on 5i dearly resolved

Ruthenium --------------------~----------------

Fused alkalis [557]

Samarium

Minual acids (557J

Sdenium

HStl ~( IM tf U undtf CkmCnl1 womtunduton 11 bull ~---~--~~-----

Silver

11 g Fe(NO) 9 ml HO 44-49 20 IJmmm Photoresist mask can be used [14 15 507J

2 5-9HNO1-5HO39-49 12-251Jmmin 11415517J

3 35 g AgCN 37 g KCN 38 g KCO 100 ml HO 25- 10 min Electrochem etch best polishing in region of voltage (29) 30 V 1 Alent Ag cathode 10 stirring and currel1t instability

4 3HNO 19H0 2 V [ainle steel cathode ElectrOChemical etch [507)

5 Kl-I etches listed for Cu and Ag O3-llJmsec Immersion followed by HO rinse [14]

60 Asec Useful for pattern etching with photoresist mask rinse [512] quickly after etching

6 4(HOH INHOH IHO

Sodium-

CHtCH)CHOH (nonyl alcohol) 30 sec Brilliant smooth surface [551)

Stronlium

Liquid ammonia [557]

Tanlalum

2

9NaOH or KOH 00laquo) IHO heal alka to 9(t Ihen add HO

5HSObull 2HNO 2HF

1-2HNO IHF 1-2H0

100(l-~OO(l A min

5-20 sec

4 9HSObull IHf (-4 50 cathgtd

A urn 11 1 carb -1(1 rnln

Metal (eg Au) rna muq be used very httle undermiddot cutting etche TO and Ta- al same rale 3 Ta

116~ 16~J

POlishing elch [29 522 5~~

HO rna) be omllled ftgtr fasler elch espeCially if film coniaim oxygen and reslsh etching fasler etch reshyduce re t al1a(~

(14 5 HI

Eletruchernlal etch temp of solUlion ne dunng ue and 11 rna he nece ar~ tp cool hath

129

- -~-~-=-

-4

2

Tabl Xf (Colltlllud)

Etch ratr or Etching condtion rtch time Remarks Refs

Tellurium

2HND3HO [513]

240 g (NH~So bring to I liter with HO [513J

Terbium

M ine 1 acid~ [557]

Thallium

to

HND or HSO

Thonum

------------~----

[557]

14CHCOOH 4HCIO IHO -1060 Adrn stain- 7-12 sec Electrochemical polish [29] less steel cathode

Tin

FeCI 36-42B 32-54 ~------~-

[15 513)

2 IHNO49CHOH [534] (

j iCIO lt35 5O-W V 40 Adrn AI cathode hold piece vertically and rotate at 50-100 r Imin

420 fLmmin Electrochemical polish on large sunaces orange peel effect may occur

(29]

4 Other electrochemical polishes [29]

Titanium

9H0 IHF 3gt 12 fLmmin Photorist mllsk may be used 114 15 507]

2 7Hli 21iNII IH~ n IImmln PhOI maoa m~ be uWd 114155071

bull - bull bull bull

tllO mllHOH 2U ml middotbutyl hoI t2 II Alll ~ II I-JeC1fochcml41 fKlhh 14m) zne 30-50 V 12 Adm ~Utinle Ied cathode

4 3HCIO 5OCHCOOH 200 30 V 30-40 Adm Ti 2 min E)ectrochem etch anode to cathode distance about 129] cathode 3 cm

5 Other electrochemical etches [29 564 5651

6 See Zirconium etch no [29]

Tungsten ~--~~-----~ -------~-------~----~---~~-----------------~~----~~-~--~~~-~---~--~--~------

34 g KHPO 134 g KOH 33 g KFeICN) HO to 1600 Amin Photoresist mask may be used high resolution (1- (515] make I liter 2 Lml can be achieved

2 5 KOH 5 KFe(CN) 1 sunaclant -2302 --23Lmmin Electrochem etch photoresist mask can be used good [51J Acm PI cathode pauem resolution

5-10 NaOH 6 V 3-6 Adm stainless steel cathode Electrochem etch rotation of anode or agitation of [29 513 566deg) - electrolyte with N is necessary

4 Other etches [5158515 555 567]

Uranium

1-2HClO 2OCHCOOH 5O-W v 5 Adrn stainless 19 fLmmill Electrochemical polish (29) steel cathode

2 Other electrochemical pohshe [29]

VanadIum __----------------___---------__-_

1-2HClO 18-19CHCOOH lt35 50-60 V 16-24 1-2 min Electrocherrucal polish a second polishing ofabout the f29] Adm stainless steel cathode sarne duration ill a fresh soln sometimes necessary

---~-~-----~----~--

Ytlcrbium -----~---------------~-----

lhneraJ aCid 1557j

fCwwj

Table XIV (Cotiu~d) ~~------- ~---~----~~-~-~-----

Etch rate or Etchmg conditIOns tch time Remarks Ref

Polonium

Dilute mineral acid [557J

Potassium

CHOH or iCH)CHOH 3 sec (ethanoB or 10 SeC (Ioproshypanol)

Brilliant smooth surface obtained [551]

Praesiodymium

Mineral acid -~-~--~-~----------~~------ -------shy

Rhenium

[557]

Dilute HNO [557]

Rhodium

3 M HC -03- + 14 V versus SCE modified triangumiddot ElectTOchem etch I Im line spacings ofRh films over [514]

lar waveform -600 Hz magnetic stirring 5000 ATi on 5i dearly resolved

Ruthenium --------------------~----------------

Fused alkalis [557]

Samarium

Minual acids (557J

Sdenium

HStl ~( IM tf U undtf CkmCnl1 womtunduton 11 bull ~---~--~~-----

Silver

11 g Fe(NO) 9 ml HO 44-49 20 IJmmm Photoresist mask can be used [14 15 507J

2 5-9HNO1-5HO39-49 12-251Jmmin 11415517J

3 35 g AgCN 37 g KCN 38 g KCO 100 ml HO 25- 10 min Electrochem etch best polishing in region of voltage (29) 30 V 1 Alent Ag cathode 10 stirring and currel1t instability

4 3HNO 19H0 2 V [ainle steel cathode ElectrOChemical etch [507)

5 Kl-I etches listed for Cu and Ag O3-llJmsec Immersion followed by HO rinse [14]

60 Asec Useful for pattern etching with photoresist mask rinse [512] quickly after etching

6 4(HOH INHOH IHO

Sodium-

CHtCH)CHOH (nonyl alcohol) 30 sec Brilliant smooth surface [551)

Stronlium

Liquid ammonia [557]

Tanlalum

2

9NaOH or KOH 00laquo) IHO heal alka to 9(t Ihen add HO

5HSObull 2HNO 2HF

1-2HNO IHF 1-2H0

100(l-~OO(l A min

5-20 sec

4 9HSObull IHf (-4 50 cathgtd

A urn 11 1 carb -1(1 rnln

Metal (eg Au) rna muq be used very httle undermiddot cutting etche TO and Ta- al same rale 3 Ta

116~ 16~J

POlishing elch [29 522 5~~

HO rna) be omllled ftgtr fasler elch espeCially if film coniaim oxygen and reslsh etching fasler etch reshyduce re t al1a(~

(14 5 HI

Eletruchernlal etch temp of solUlion ne dunng ue and 11 rna he nece ar~ tp cool hath

129

- -~-~-=-

-4

2

Tabl Xf (Colltlllud)

Etch ratr or Etching condtion rtch time Remarks Refs

Tellurium

2HND3HO [513]

240 g (NH~So bring to I liter with HO [513J

Terbium

M ine 1 acid~ [557]

Thallium

to

HND or HSO

Thonum

------------~----

[557]

14CHCOOH 4HCIO IHO -1060 Adrn stain- 7-12 sec Electrochemical polish [29] less steel cathode

Tin

FeCI 36-42B 32-54 ~------~-

[15 513)

2 IHNO49CHOH [534] (

j iCIO lt35 5O-W V 40 Adrn AI cathode hold piece vertically and rotate at 50-100 r Imin

420 fLmmin Electrochemical polish on large sunaces orange peel effect may occur

(29]

4 Other electrochemical polishes [29]

Titanium

9H0 IHF 3gt 12 fLmmin Photorist mllsk may be used 114 15 507]

2 7Hli 21iNII IH~ n IImmln PhOI maoa m~ be uWd 114155071

bull - bull bull bull

tllO mllHOH 2U ml middotbutyl hoI t2 II Alll ~ II I-JeC1fochcml41 fKlhh 14m) zne 30-50 V 12 Adm ~Utinle Ied cathode

4 3HCIO 5OCHCOOH 200 30 V 30-40 Adm Ti 2 min E)ectrochem etch anode to cathode distance about 129] cathode 3 cm

5 Other electrochemical etches [29 564 5651

6 See Zirconium etch no [29]

Tungsten ~--~~-----~ -------~-------~----~---~~-----------------~~----~~-~--~~~-~---~--~--~------

34 g KHPO 134 g KOH 33 g KFeICN) HO to 1600 Amin Photoresist mask may be used high resolution (1- (515] make I liter 2 Lml can be achieved

2 5 KOH 5 KFe(CN) 1 sunaclant -2302 --23Lmmin Electrochem etch photoresist mask can be used good [51J Acm PI cathode pauem resolution

5-10 NaOH 6 V 3-6 Adm stainless steel cathode Electrochem etch rotation of anode or agitation of [29 513 566deg) - electrolyte with N is necessary

4 Other etches [5158515 555 567]

Uranium

1-2HClO 2OCHCOOH 5O-W v 5 Adrn stainless 19 fLmmill Electrochemical polish (29) steel cathode

2 Other electrochemical pohshe [29]

VanadIum __----------------___---------__-_

1-2HClO 18-19CHCOOH lt35 50-60 V 16-24 1-2 min Electrocherrucal polish a second polishing ofabout the f29] Adm stainless steel cathode sarne duration ill a fresh soln sometimes necessary

---~-~-----~----~--

Ytlcrbium -----~---------------~-----

lhneraJ aCid 1557j

fCwwj

2

Tabl Xf (Colltlllud)

Etch ratr or Etching condtion rtch time Remarks Refs

Tellurium

2HND3HO [513]

240 g (NH~So bring to I liter with HO [513J

Terbium

M ine 1 acid~ [557]

Thallium

to

HND or HSO

Thonum

------------~----

[557]

14CHCOOH 4HCIO IHO -1060 Adrn stain- 7-12 sec Electrochemical polish [29] less steel cathode

Tin

FeCI 36-42B 32-54 ~------~-

[15 513)

2 IHNO49CHOH [534] (

j iCIO lt35 5O-W V 40 Adrn AI cathode hold piece vertically and rotate at 50-100 r Imin

420 fLmmin Electrochemical polish on large sunaces orange peel effect may occur

(29]

4 Other electrochemical polishes [29]

Titanium

9H0 IHF 3gt 12 fLmmin Photorist mllsk may be used 114 15 507]

2 7Hli 21iNII IH~ n IImmln PhOI maoa m~ be uWd 114155071

bull - bull bull bull

tllO mllHOH 2U ml middotbutyl hoI t2 II Alll ~ II I-JeC1fochcml41 fKlhh 14m) zne 30-50 V 12 Adm ~Utinle Ied cathode

4 3HCIO 5OCHCOOH 200 30 V 30-40 Adm Ti 2 min E)ectrochem etch anode to cathode distance about 129] cathode 3 cm

5 Other electrochemical etches [29 564 5651

6 See Zirconium etch no [29]

Tungsten ~--~~-----~ -------~-------~----~---~~-----------------~~----~~-~--~~~-~---~--~--~------

34 g KHPO 134 g KOH 33 g KFeICN) HO to 1600 Amin Photoresist mask may be used high resolution (1- (515] make I liter 2 Lml can be achieved

2 5 KOH 5 KFe(CN) 1 sunaclant -2302 --23Lmmin Electrochem etch photoresist mask can be used good [51J Acm PI cathode pauem resolution

5-10 NaOH 6 V 3-6 Adm stainless steel cathode Electrochem etch rotation of anode or agitation of [29 513 566deg) - electrolyte with N is necessary

4 Other etches [5158515 555 567]

Uranium

1-2HClO 2OCHCOOH 5O-W v 5 Adrn stainless 19 fLmmill Electrochemical polish (29) steel cathode

2 Other electrochemical pohshe [29]

VanadIum __----------------___---------__-_

1-2HClO 18-19CHCOOH lt35 50-60 V 16-24 1-2 min Electrocherrucal polish a second polishing ofabout the f29] Adm stainless steel cathode sarne duration ill a fresh soln sometimes necessary

---~-~-----~----~--

Ytlcrbium -----~---------------~-----

lhneraJ aCid 1557j

fCwwj

Table X[V (Colltid)

Etch rate or Etching conditions etch time Remarks Refs

Yttrium

Dilule mineral acids or hot KOH solutions

Zinc

[557J

j

2

3

4

5

2-3HNO _ J7-18H0 38-49

40 g CrO 3 g NaSObull 10 ml HND 190 ml HO

1 g crO5 mI H20 60 V 250-350Adm Pt Ni orZn cathode

20-45 KOH 0-50 interrupted dc or sine wave method

Other electrochemical etches

251mmin

71mmin

40-45 sec

Dense layer formed during treatment is soluble in water

Electrochem polish tendency for a passive film forshymatlon

Electrochem etch Zn is amalgamated first by dipping in a soln of 50 gliter HgCI for 30 sec

[15513]

[29J

129J

I568J

[29569shy571]

Zirconium

45HNO 8-IOHf 45H0 or HO swab for 5-10 sec rinse in running H20

5-10 sec Brownish-yellow vapor is evolved similar solution can be used for Ti and H f

[29]

- JClO 7CHCOOH 4 ethylene glycol gt 100 Adm stainless steel cathode

30-50 V 20-30 seC Electrochemical polish [29J

Other electrochemical etches 29]

4 Chemical polish elch 1572J

bull Starred () rcference numbers refer to secondary numbers bull In acids der8ivation of Cr mu be Induced h til phySIcal contact with declroJgtOllve mela tAl wire Zn rod or rellets) (2) Cr ions in

aqutou olutlon nl CH arrhcalJon of c-alhimiddotdlmiddot fllrnhaJ Thrn (r dI(lht Idl~ tn 0laquo-(1) aU mlOtud aCid

bull - Iibull ~

Table XV

Metal All and Superconductor

Etch rate Etching condition or etch lime Remarks Refgt ---~---~----~----~~~ ~-----~-------~---~-------------------------~-~~----- - -

Inconel

FeCI 36-411-1lt 43_54deg 115513)

Invar -J

CBCOOH 2HNO 2HCI IHO [469J

~ FeCl 36-4~ Be Photoreit mak can he used 1507]

KovarJ -------~--~----~------------------------------------ ------~--~~-~

400cHCOOK 200HNO 75HO 9HCI rine in running HO 15-20 Sec POlishmg etch heav~ oxide i first removed in 6 M HCI 14(9)after clchmg

----~-----~--~---------------~--- -~--~---------~--~------- --------~-------~-----

Monel

5HN() 5CHCOOH 2HSO dilute wnh H) a dcred (5061

(Conlinuni)

Table XV (CQtiu~d)

Etch rate Etching condlIofi or etch time Remarks Refs

Nichrome

FeCI 36degBe 43deg Photoresist mask may be used [5075I3J

2 IHNoIHCl3HO Photoresist mask rna) be used [507J

3 4HCI HO [513) )C

4 7HPO IHSO 2H0 II V Cu cathode Electrochemical polish [469)

Permalloy

39 M HSO 112 M HO 04-4 M HF 4 mmin Edges can be beveled using a Ti overcoat [54]

NbSn

bullbull ISO 4HNO IHF 12 V graphite electrode Electrochem polish rinse immediatel) in HO [469]

bull Trade name of Westinghouse Electric Corp bull Trade name of Driver-Harris Co

-F Miscellaneoua Matelals

- bull

Table XVI

Miscellaneous Materials

-t

rate or Etching conditions etch time Remarks Refs

-z

p

S

AgO

crO

erO-

CuO

FeO or

FeO

MoO

PbO

WO

CHOH (abs)

CS CH alkalis ether CHCI toluene

Cs or toluene

INHOH 4H~O

1Ok KCN

2gCe(NH)(SOk2H0lOmlHNO 50ml H028c

1645 g Ce(NH~(NO)bull 90 ml HNO- HO to make I liter

IHel 2H0 hot

Dilute HF

10lr ammonium citrate warm

IHClIHO

9NHOH IHO nnse In runmn HO and dr~

2Y7 KOH rinse with HO dip in 6 M HCI rine With HO then CHOH and d~

H NO followed by HO rinse then CHOH nnse and dl)

~(lY NaO ho

200 Amin

Red pho~h gtrus

Yellow (wi ) phosphorus

Cr itself etches at 85 Amin

Used for removing CrO contamination from gold surshyfaces

Little loss of Cu

Little or nt )Ss of Fe

No loss of h

Used for pattern etching

Electrochemical polish

Do not expose piece to air during treatment

[557J

[557]

[557J

[469]

[469J

[519J

[573]

14(9)

[469J

[469J

1526]

1469)

1469]

1469J

1469

-

t( onltnur d )

4_gt~ ~~~-- __ -o_~O~~_~______~

~--~~$~gt ~ lt

CI

c v

0 N v

v

~ - v

v v

~

ltt_ ~- ~ ~

v

g ~ ~

~ ~

0

~ OJ c

v-I CHEMICAL ITCHING 4K

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u

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u Vl ~ ~ ~ t c c -if Ishy 0 U IQ

S ~~ ~ ~= ~ ~

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~ ] lt

c E

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shy U cshy c ~ ~ 0

0 0J t OJ

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b- ov

() pound o Vl

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c E

-lt sect

~ I

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~ Z

u

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u

E J bull

g E u 0 iii

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amp 0

u ~

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U ~ c u

gt o Vl cf Z

shyo 6 Z I ()

~ ~ i G ~ I

~ t Z

v U U IJ

o o iii

i zIilt t sect

N

e Ii 6 iii ~ u E c

6 c

0 1 00

e ~ 0 E ~ ~ ~ 6

fill 1 0shylt

IJ I

6 Z I i oo u i ~

~

C ~

iii

1 o 0

e Ii c ~ o l i o N

9 0

~ u OJ ull C CI

c E

-lt sect N

-~ -IJ X Z 0

u

6 -pound gtampgt

vi

o =j o U U

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is lt2 ]

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~

u E c

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c E

N

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o -pound E 8 -8

ulaquoi~- c58E~ ~ 8 ~-

N E I~ltilt z8 N

~ 2 shyo c

~ o c

i 0

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=jv t u

8 ]

1 9

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u

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1 co

E Ii Vi ~ c o

~ ~

~ u

8 OJ ]

V SUMMARY AND CONCLUSIONS

Fundamental principles of chemicdl etching reaction~ prO(c~~c~ and techniques have been brietly outlined Con~idcrations in paltern delincashytion etching of thin films have been di~cued and the importance of surmiddot face contamination before and after etching prOle~e~ ha been noted

Chemical etching of specific material of technical importance ha been discussed and referenced Extensiv tahle summniLing etchanh condition and applications have been presented for imulatllrs dielecshytrics semiconductors conductors and miscellaneous nlitteriab to failimiddot tate the selection of suitable system Most of the inforillation has been retrieved from the literature which contain widely dispersed data It is obviously impossible to include all etchlI1h for all rnateriab in a brief summary but an attempt has been made III present signiticant and repremiddot sentative information covering the literature through 1177

ACKNOWI LllliM1N 1 S

We wh to lhank C E Tracy for h help 10 laruJtlOg Ihe huill cichg ddli K Il Vlorunck for clrrying out many of the gla~~ Il(hing IIHdUlcmCIH~ anti ( I S~hnahll 11I1 offering many ggelion and for ailically rccic Ihc lIltnUnpl

REFERENtLS

1 J W Fau Jr in Solid Slale Phyic Pan A Peparatlun Stlueurc Mechac1 and Thermal Propcnie lK LarkmiddotHorol and V A Johnon clh) Melhod of lmiddotx penmenlal Phyiegt Vol 6 Ch 2H AcademIC Prc New Y~ 1~5~ J W Faut Jr ill The Surfe Chemlry oi Melalgt and SCJJlIlonuucl (II

(iaIO cd) pp 151-173 Wiley New 101110 3 N Haderlllan in The Suface Chemblry of Mctuh and Scmiconuutlor 111 (

Gatos ed) pp 313-325 Wiley New York I()

4 P Lacombe in The Surface Chemistry or Meidlgt anu Semiconduclllr III t Galo ed) pp 244-284 Wiley New York 10

5 P J Holme in The Elcclrochemistry of Semiconductor (P 1 Holme cd) (h

B Academic Press New York 1962 6 B A Irving in The Electrochemitry 1)1 Scmiconuuclors II

256-2B8 AcademiC Pre New York JZ

llolmes cd) PI

7 J W Faust in Semiconducting Compound IK K WlilurulIl and H I (illlIlg cdS) Vol I pp 445-468 Reinhold New YOlk 12

B H C Gatos and M C Lavine Prol SItIjlunJ 9 1-46 (I~) i Integraleu Circuit Silicon Device Technology XmiddotChemlcal Meldllugcal PrOperll

of Silicon ASD-TDR-63-316 Vol X AD 625 ~B5 Rcscanh Triangle Int Research Triangle Park North Carolina (1965)

U E u

iii U

Vi 8

o iii iiiU U

iii i

iii 6

~

u is

E Vl

IU M Aven and J S lrener The Physic and Chcllllgtlry of Itmiddot V I Compound pp 14

155733 NorthmiddotHolland Puhl Amtertlum J7 J l C V King in I Suriace Chemilry or Meta and Semiconductor IH C (jal

ed) pr 357-38L Wiley New York 1960

tHO

482 WERNER KERN AND CHERYL A DECKERT

12 S K Ghandhi The Theory and Practice of Microelectronics Ch 7 Wiley Ne10lt York 1968

13 C D Dobson in Gallium Arsenide Lasers (e H Gooch ed) pp )93-222 Wiley (interscience) New York 1969

I~ R Giang and L V Gregor in Handbook of Thin Film Technology (L 1 Mah~1 and R Giang cds) Ch 7 McGrawmiddotHill New York 1970

15 R J Ryan E B Dayidson and H O HooK in Handbook of Materials and Proshycesses For Electronics Ie A Harper ed) Ch 14 McGrawmiddotHill New York 1970

16 W A Pliskin and S J Zanin In Handbook of ThinmiddotFilm Technology (L L Mais~1 and R Giang eds) Ch 11 McGraw-Hili New York 1970

17 P F Kane and G B Larrabee Chlracterization of Semiconductor Material bull McGraw-Hili New York 1970 t

18 H F Wolf Semiconductors pp 130-136 Wiley (Interscielce) New York 197L 19 T C Harman and I Melngailis Appl Solid 51011 Sci 41-94 (1974) 20 B Tuck J Motu Sci 10 321 (1975) 21 W R Runyan Semiconductor Measurements and Instrumentation Chs 127

and 9 McGraw-Hili New York 1975 22 R Tijburg Phys Technol September p 202 (1976) 23 D J Stirland and B W Slraughan Thin Solid Films 31139 (1976) 24 M J Pryor and R W Staehle in Trealise on Solid Stale Chemistry (N B Hanllity

ed) Vol 4 Ch 9 Plenum New York 1976 25 Metals Reference Book (e J Smilhells ed) 5th Ed Butterworth London 1971gt 26 Etching for Pattern Definition (H G Hughes and M J Rand eds) Electrochem

Socbull Princeton New Jersey 1976 27 W Kern ref 26 pp 1-ISd 27a W Kern RCA Rey 39278 (1918) 28 J S Judge ref 26 pp 19-36 29 W Tegert The Electrolytic and Chemical Poli~hing of Metals 2nd Ed Pergamon

Oxford 1959 30 J F Dewald in Semiconductors IN B Hannay ed) pp 727-752 Reinhold N~

York 1959 31 The Surface Chemi5lry of Metal and Semicondu~tor~ (H C GalO ed) Wile)

New York 1960 32 The Electrochemistry of SemiconduclOrs (P J Holmes ed) Aademic Pres Nc

York 1962 33 J L Pankoye ref 32 Ch 7 34 E A Eomoy and I G Erualimchik Electrochemistry of Germanium and Silicon

(A Peiperl ed and transl) Sigma Press Wa5hington DC 1963 35 P J Boddy J Elf(rollnul (hem 10 199 (1965) 36 V A Myamlin and Y V Pleskoy Electrochemistry of Semiconductors Plenum

New York 1967 37 H Gerischer in Electrochemistry Part A (W Jost ed) Physical Chemislry Vol

9 pp 463-542 Academic Press New York 1970 3S P V Shchigolev Electrolylic and Chemical Polishing of Metals Freund Publ

House Holon Israel 1910 39 Y V Pleskoy Prog Surf Mmbr Sci 751-9311913) 40 A K Vijh Electrochemistry of Metalgt and Semiconduclors Dekker New Yor bull

1973 41 G L Schnable and P F Schmid J EItClrochem Soc 123 310C (1976) 42 Corrosion (L L Shreir ed) 2nd Ed Newne-Bullerworth London 1976

v-I CIiIMICAL L I CHING 4X

43 A H AgaJnian Solid SIallt Techllul 16( 121 73 (19731 18(4) 61 I lJ 112011136 11177 43d C W Wilmsen and S Szpak Thin Solid Filmgt 47 17 (19771 44 L Romankiy ref 26 pp 161-193 45 P R Camp 1 t1-lroch-m Suc 102 5t6 (1155) 46 W Kern J 1 Vossen and G L Schnable Anna Pro Rdwh 1ltvI IIliI 1214

(973) 47 Il A Irving ref 32 Ch 6 4~ J L Vossen G L Schnable and W Kern 1 ~w S i Tecllol 110011174) 49 V F Dorfman SUY Mitro(rull 5 (2) N (IY76)

50 W S DeForest Photoreist Materialgt and ProCc M( lIill NeW York 1975

51 W Kern and J M Shaw 1 Eleclrohelil Su 118 lo~~ (1~71) 52 CA Deckert and D A Pelers Proc KodA M rllleclroll 11111 hlgtllIIan KoJak

Co Rochester New York pp 3-25 il97MI 53 C A Deckert ill Adhesion Measurement of nlln hlnh Thtk hit (fI1 Hulk Co1

ng IK 1 Mitta ed) pp 327-341 ASTM Iluladclphla lelltl~ltlHt 1I7M S4 J J Kelly and G J Koe 1 EIuroclwm SO 125 HIgtO (J17~1

55 Anonymous Ifld Regt 19 (2) 19 (1977) 56 S Somekh 1 Vae Sci r hllul 13 1003 (197fl) 57 J J Kelly and C H de Minjer1 tleclrodltlIJ Su 122 131 111l1 5K D MacArthur ref 26 pp 7b-90 59 P J Holme and K C Newman Proc 11111 Elcclr tng 11111 ull 15 HI

(1959) W J W Faul Jr NUll Bur Slund (US I Spcc Pu Nu137 PI j ()-l4 1191111 61 W Kern RCA R- 31207 (19701 b~ W Kern RCA RImiddot 31 23411970) 03 W Kern RCA R-I 32 b4 (1971) 1gt4 W Kern Solid Sulmiddot Tecllflol 15(1)34(1172 15(2) 3Y (11721 05 W Kern and D Puolinen RCA Regtlt 31 IM7 11170) 06 A Mayer and D A Puulinen NUll Bur gtwlld 11431-43 (U 1 )1 Ill N

337 (1I7U) 67 R C Hendel)un 1 tJedro hem So 11977211172) 6 K L Meek T M Huck anJ e F Gibbon 1 1ln Ir ilOIl 1 IlU 141 11)7 0) D A Kielt I J [YHaellens and J A KOlh I Un II 111 111110 IIIil4 69a D A Pelers and C A Deckert Electro 111111 Imiddotp i-I(Ih 04[1 7Hmiddotl on (197X 70 P KaimiddotChoudhury ill ScrnlCllnduclor Silicoll 1173 111 K Hull)d K KlhHe

ed) pp 243-257 Elcctrochcm Soc Pnel(lll Nev Jeq 1117 71 D K (hwuld 1 tleltlrocilI So 12353111176 72 J A Amick Solid S[al iJlJo 19111) 4711no 73 D Tolliver Solid Sldl Techllol 18(11)33 111751 74 M G Yang K M Kohwad and G E McUultmiddote1 Un Iro 11lt111 ) 1120711117)1 75 R Seltzer elllill M( 15111) SI 1117) 76 R A Geckk Ekclrllll p(( A) Prod lSI I~7 1111

77 G L Schnable W Kern unci K Il Corniah1 U 11 11lt111 ) 122101211171 7~ R L Meek 1 tlc troellllII Soc 121 172 (IY74) 79 W Kern unpubllgthed obcrvation KO W Kern Sem((ond Prod Sold SflIlc nlIIl1l 611111 n 11 ) 6 II 2 111011 81 Clean Surfaces Their Prepalation and CharaclcIIlatiun fUI IllIelllal Slucit

(G Goldfinger ed) Dekker New York 170 82 Ref I~ pp 4445541559-611

Table XV (CQtiu~d)

Etch rate Etching condlIofi or etch time Remarks Refs

Nichrome

FeCI 36degBe 43deg Photoresist mask may be used [5075I3J

2 IHNoIHCl3HO Photoresist mask rna) be used [507J

3 4HCI HO [513) )C

4 7HPO IHSO 2H0 II V Cu cathode Electrochemical polish [469)

Permalloy

39 M HSO 112 M HO 04-4 M HF 4 mmin Edges can be beveled using a Ti overcoat [54]

NbSn

bullbull ISO 4HNO IHF 12 V graphite electrode Electrochem polish rinse immediatel) in HO [469]

bull Trade name of Westinghouse Electric Corp bull Trade name of Driver-Harris Co

-F Miscellaneoua Matelals

- bull

Table XVI

Miscellaneous Materials

-t

rate or Etching conditions etch time Remarks Refs

-z

p

S

AgO

crO

erO-

CuO

FeO or

FeO

MoO

PbO

WO

CHOH (abs)

CS CH alkalis ether CHCI toluene

Cs or toluene

INHOH 4H~O

1Ok KCN

2gCe(NH)(SOk2H0lOmlHNO 50ml H028c

1645 g Ce(NH~(NO)bull 90 ml HNO- HO to make I liter

IHel 2H0 hot

Dilute HF

10lr ammonium citrate warm

IHClIHO

9NHOH IHO nnse In runmn HO and dr~

2Y7 KOH rinse with HO dip in 6 M HCI rine With HO then CHOH and d~

H NO followed by HO rinse then CHOH nnse and dl)

~(lY NaO ho

200 Amin

Red pho~h gtrus

Yellow (wi ) phosphorus

Cr itself etches at 85 Amin

Used for removing CrO contamination from gold surshyfaces

Little loss of Cu

Little or nt )Ss of Fe

No loss of h

Used for pattern etching

Electrochemical polish

Do not expose piece to air during treatment

[557J

[557]

[557J

[469]

[469J

[519J

[573]

14(9)

[469J

[469J

1526]

1469)

1469]

1469J

1469

-

t( onltnur d )

4_gt~ ~~~-- __ -o_~O~~_~______~

~--~~$~gt ~ lt

CI

c v

0 N v

v

~ - v

v v

~

ltt_ ~- ~ ~

v

g ~ ~

~ ~

0

~ OJ c

v-I CHEMICAL ITCHING 4K

1 ~ is Ishy

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V SUMMARY AND CONCLUSIONS

Fundamental principles of chemicdl etching reaction~ prO(c~~c~ and techniques have been brietly outlined Con~idcrations in paltern delincashytion etching of thin films have been di~cued and the importance of surmiddot face contamination before and after etching prOle~e~ ha been noted

Chemical etching of specific material of technical importance ha been discussed and referenced Extensiv tahle summniLing etchanh condition and applications have been presented for imulatllrs dielecshytrics semiconductors conductors and miscellaneous nlitteriab to failimiddot tate the selection of suitable system Most of the inforillation has been retrieved from the literature which contain widely dispersed data It is obviously impossible to include all etchlI1h for all rnateriab in a brief summary but an attempt has been made III present signiticant and repremiddot sentative information covering the literature through 1177

ACKNOWI LllliM1N 1 S

We wh to lhank C E Tracy for h help 10 laruJtlOg Ihe huill cichg ddli K Il Vlorunck for clrrying out many of the gla~~ Il(hing IIHdUlcmCIH~ anti ( I S~hnahll 11I1 offering many ggelion and for ailically rccic Ihc lIltnUnpl

REFERENtLS

1 J W Fau Jr in Solid Slale Phyic Pan A Peparatlun Stlueurc Mechac1 and Thermal Propcnie lK LarkmiddotHorol and V A Johnon clh) Melhod of lmiddotx penmenlal Phyiegt Vol 6 Ch 2H AcademIC Prc New Y~ 1~5~ J W Faut Jr ill The Surfe Chemlry oi Melalgt and SCJJlIlonuucl (II

(iaIO cd) pp 151-173 Wiley New 101110 3 N Haderlllan in The Suface Chemblry of Mctuh and Scmiconuutlor 111 (

Gatos ed) pp 313-325 Wiley New York I()

4 P Lacombe in The Surface Chemistry or Meidlgt anu Semiconduclllr III t Galo ed) pp 244-284 Wiley New York 10

5 P J Holme in The Elcclrochemistry of Semiconductor (P 1 Holme cd) (h

B Academic Press New York 1962 6 B A Irving in The Electrochemitry 1)1 Scmiconuuclors II

256-2B8 AcademiC Pre New York JZ

llolmes cd) PI

7 J W Faust in Semiconducting Compound IK K WlilurulIl and H I (illlIlg cdS) Vol I pp 445-468 Reinhold New YOlk 12

B H C Gatos and M C Lavine Prol SItIjlunJ 9 1-46 (I~) i Integraleu Circuit Silicon Device Technology XmiddotChemlcal Meldllugcal PrOperll

of Silicon ASD-TDR-63-316 Vol X AD 625 ~B5 Rcscanh Triangle Int Research Triangle Park North Carolina (1965)

U E u

iii U

Vi 8

o iii iiiU U

iii i

iii 6

~

u is

E Vl

IU M Aven and J S lrener The Physic and Chcllllgtlry of Itmiddot V I Compound pp 14

155733 NorthmiddotHolland Puhl Amtertlum J7 J l C V King in I Suriace Chemilry or Meta and Semiconductor IH C (jal

ed) pr 357-38L Wiley New York 1960

tHO

482 WERNER KERN AND CHERYL A DECKERT

12 S K Ghandhi The Theory and Practice of Microelectronics Ch 7 Wiley Ne10lt York 1968

13 C D Dobson in Gallium Arsenide Lasers (e H Gooch ed) pp )93-222 Wiley (interscience) New York 1969

I~ R Giang and L V Gregor in Handbook of Thin Film Technology (L 1 Mah~1 and R Giang cds) Ch 7 McGrawmiddotHill New York 1970

15 R J Ryan E B Dayidson and H O HooK in Handbook of Materials and Proshycesses For Electronics Ie A Harper ed) Ch 14 McGrawmiddotHill New York 1970

16 W A Pliskin and S J Zanin In Handbook of ThinmiddotFilm Technology (L L Mais~1 and R Giang eds) Ch 11 McGraw-Hili New York 1970

17 P F Kane and G B Larrabee Chlracterization of Semiconductor Material bull McGraw-Hili New York 1970 t

18 H F Wolf Semiconductors pp 130-136 Wiley (Interscielce) New York 197L 19 T C Harman and I Melngailis Appl Solid 51011 Sci 41-94 (1974) 20 B Tuck J Motu Sci 10 321 (1975) 21 W R Runyan Semiconductor Measurements and Instrumentation Chs 127

and 9 McGraw-Hili New York 1975 22 R Tijburg Phys Technol September p 202 (1976) 23 D J Stirland and B W Slraughan Thin Solid Films 31139 (1976) 24 M J Pryor and R W Staehle in Trealise on Solid Stale Chemistry (N B Hanllity

ed) Vol 4 Ch 9 Plenum New York 1976 25 Metals Reference Book (e J Smilhells ed) 5th Ed Butterworth London 1971gt 26 Etching for Pattern Definition (H G Hughes and M J Rand eds) Electrochem

Socbull Princeton New Jersey 1976 27 W Kern ref 26 pp 1-ISd 27a W Kern RCA Rey 39278 (1918) 28 J S Judge ref 26 pp 19-36 29 W Tegert The Electrolytic and Chemical Poli~hing of Metals 2nd Ed Pergamon

Oxford 1959 30 J F Dewald in Semiconductors IN B Hannay ed) pp 727-752 Reinhold N~

York 1959 31 The Surface Chemi5lry of Metal and Semicondu~tor~ (H C GalO ed) Wile)

New York 1960 32 The Electrochemistry of SemiconduclOrs (P J Holmes ed) Aademic Pres Nc

York 1962 33 J L Pankoye ref 32 Ch 7 34 E A Eomoy and I G Erualimchik Electrochemistry of Germanium and Silicon

(A Peiperl ed and transl) Sigma Press Wa5hington DC 1963 35 P J Boddy J Elf(rollnul (hem 10 199 (1965) 36 V A Myamlin and Y V Pleskoy Electrochemistry of Semiconductors Plenum

New York 1967 37 H Gerischer in Electrochemistry Part A (W Jost ed) Physical Chemislry Vol

9 pp 463-542 Academic Press New York 1970 3S P V Shchigolev Electrolylic and Chemical Polishing of Metals Freund Publ

House Holon Israel 1910 39 Y V Pleskoy Prog Surf Mmbr Sci 751-9311913) 40 A K Vijh Electrochemistry of Metalgt and Semiconduclors Dekker New Yor bull

1973 41 G L Schnable and P F Schmid J EItClrochem Soc 123 310C (1976) 42 Corrosion (L L Shreir ed) 2nd Ed Newne-Bullerworth London 1976

v-I CIiIMICAL L I CHING 4X

43 A H AgaJnian Solid SIallt Techllul 16( 121 73 (19731 18(4) 61 I lJ 112011136 11177 43d C W Wilmsen and S Szpak Thin Solid Filmgt 47 17 (19771 44 L Romankiy ref 26 pp 161-193 45 P R Camp 1 t1-lroch-m Suc 102 5t6 (1155) 46 W Kern J 1 Vossen and G L Schnable Anna Pro Rdwh 1ltvI IIliI 1214

(973) 47 Il A Irving ref 32 Ch 6 4~ J L Vossen G L Schnable and W Kern 1 ~w S i Tecllol 110011174) 49 V F Dorfman SUY Mitro(rull 5 (2) N (IY76)

50 W S DeForest Photoreist Materialgt and ProCc M( lIill NeW York 1975

51 W Kern and J M Shaw 1 Eleclrohelil Su 118 lo~~ (1~71) 52 CA Deckert and D A Pelers Proc KodA M rllleclroll 11111 hlgtllIIan KoJak

Co Rochester New York pp 3-25 il97MI 53 C A Deckert ill Adhesion Measurement of nlln hlnh Thtk hit (fI1 Hulk Co1

ng IK 1 Mitta ed) pp 327-341 ASTM Iluladclphla lelltl~ltlHt 1I7M S4 J J Kelly and G J Koe 1 EIuroclwm SO 125 HIgtO (J17~1

55 Anonymous Ifld Regt 19 (2) 19 (1977) 56 S Somekh 1 Vae Sci r hllul 13 1003 (197fl) 57 J J Kelly and C H de Minjer1 tleclrodltlIJ Su 122 131 111l1 5K D MacArthur ref 26 pp 7b-90 59 P J Holme and K C Newman Proc 11111 Elcclr tng 11111 ull 15 HI

(1959) W J W Faul Jr NUll Bur Slund (US I Spcc Pu Nu137 PI j ()-l4 1191111 61 W Kern RCA R- 31207 (19701 b~ W Kern RCA RImiddot 31 23411970) 03 W Kern RCA R-I 32 b4 (1971) 1gt4 W Kern Solid Sulmiddot Tecllflol 15(1)34(1172 15(2) 3Y (11721 05 W Kern and D Puolinen RCA Regtlt 31 IM7 11170) 06 A Mayer and D A Puulinen NUll Bur gtwlld 11431-43 (U 1 )1 Ill N

337 (1I7U) 67 R C Hendel)un 1 tJedro hem So 11977211172) 6 K L Meek T M Huck anJ e F Gibbon 1 1ln Ir ilOIl 1 IlU 141 11)7 0) D A Kielt I J [YHaellens and J A KOlh I Un II 111 111110 IIIil4 69a D A Pelers and C A Deckert Electro 111111 Imiddotp i-I(Ih 04[1 7Hmiddotl on (197X 70 P KaimiddotChoudhury ill ScrnlCllnduclor Silicoll 1173 111 K Hull)d K KlhHe

ed) pp 243-257 Elcctrochcm Soc Pnel(lll Nev Jeq 1117 71 D K (hwuld 1 tleltlrocilI So 12353111176 72 J A Amick Solid S[al iJlJo 19111) 4711no 73 D Tolliver Solid Sldl Techllol 18(11)33 111751 74 M G Yang K M Kohwad and G E McUultmiddote1 Un Iro 11lt111 ) 1120711117)1 75 R Seltzer elllill M( 15111) SI 1117) 76 R A Geckk Ekclrllll p(( A) Prod lSI I~7 1111

77 G L Schnable W Kern unci K Il Corniah1 U 11 11lt111 ) 122101211171 7~ R L Meek 1 tlc troellllII Soc 121 172 (IY74) 79 W Kern unpubllgthed obcrvation KO W Kern Sem((ond Prod Sold SflIlc nlIIl1l 611111 n 11 ) 6 II 2 111011 81 Clean Surfaces Their Prepalation and CharaclcIIlatiun fUI IllIelllal Slucit

(G Goldfinger ed) Dekker New York 170 82 Ref I~ pp 4445541559-611

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V SUMMARY AND CONCLUSIONS

Fundamental principles of chemicdl etching reaction~ prO(c~~c~ and techniques have been brietly outlined Con~idcrations in paltern delincashytion etching of thin films have been di~cued and the importance of surmiddot face contamination before and after etching prOle~e~ ha been noted

Chemical etching of specific material of technical importance ha been discussed and referenced Extensiv tahle summniLing etchanh condition and applications have been presented for imulatllrs dielecshytrics semiconductors conductors and miscellaneous nlitteriab to failimiddot tate the selection of suitable system Most of the inforillation has been retrieved from the literature which contain widely dispersed data It is obviously impossible to include all etchlI1h for all rnateriab in a brief summary but an attempt has been made III present signiticant and repremiddot sentative information covering the literature through 1177

ACKNOWI LllliM1N 1 S

We wh to lhank C E Tracy for h help 10 laruJtlOg Ihe huill cichg ddli K Il Vlorunck for clrrying out many of the gla~~ Il(hing IIHdUlcmCIH~ anti ( I S~hnahll 11I1 offering many ggelion and for ailically rccic Ihc lIltnUnpl

REFERENtLS

1 J W Fau Jr in Solid Slale Phyic Pan A Peparatlun Stlueurc Mechac1 and Thermal Propcnie lK LarkmiddotHorol and V A Johnon clh) Melhod of lmiddotx penmenlal Phyiegt Vol 6 Ch 2H AcademIC Prc New Y~ 1~5~ J W Faut Jr ill The Surfe Chemlry oi Melalgt and SCJJlIlonuucl (II

(iaIO cd) pp 151-173 Wiley New 101110 3 N Haderlllan in The Suface Chemblry of Mctuh and Scmiconuutlor 111 (

Gatos ed) pp 313-325 Wiley New York I()

4 P Lacombe in The Surface Chemistry or Meidlgt anu Semiconduclllr III t Galo ed) pp 244-284 Wiley New York 10

5 P J Holme in The Elcclrochemistry of Semiconductor (P 1 Holme cd) (h

B Academic Press New York 1962 6 B A Irving in The Electrochemitry 1)1 Scmiconuuclors II

256-2B8 AcademiC Pre New York JZ

llolmes cd) PI

7 J W Faust in Semiconducting Compound IK K WlilurulIl and H I (illlIlg cdS) Vol I pp 445-468 Reinhold New YOlk 12

B H C Gatos and M C Lavine Prol SItIjlunJ 9 1-46 (I~) i Integraleu Circuit Silicon Device Technology XmiddotChemlcal Meldllugcal PrOperll

of Silicon ASD-TDR-63-316 Vol X AD 625 ~B5 Rcscanh Triangle Int Research Triangle Park North Carolina (1965)

U E u

iii U

Vi 8

o iii iiiU U

iii i

iii 6

~

u is

E Vl

IU M Aven and J S lrener The Physic and Chcllllgtlry of Itmiddot V I Compound pp 14

155733 NorthmiddotHolland Puhl Amtertlum J7 J l C V King in I Suriace Chemilry or Meta and Semiconductor IH C (jal

ed) pr 357-38L Wiley New York 1960

tHO

482 WERNER KERN AND CHERYL A DECKERT

12 S K Ghandhi The Theory and Practice of Microelectronics Ch 7 Wiley Ne10lt York 1968

13 C D Dobson in Gallium Arsenide Lasers (e H Gooch ed) pp )93-222 Wiley (interscience) New York 1969

I~ R Giang and L V Gregor in Handbook of Thin Film Technology (L 1 Mah~1 and R Giang cds) Ch 7 McGrawmiddotHill New York 1970

15 R J Ryan E B Dayidson and H O HooK in Handbook of Materials and Proshycesses For Electronics Ie A Harper ed) Ch 14 McGrawmiddotHill New York 1970

16 W A Pliskin and S J Zanin In Handbook of ThinmiddotFilm Technology (L L Mais~1 and R Giang eds) Ch 11 McGraw-Hili New York 1970

17 P F Kane and G B Larrabee Chlracterization of Semiconductor Material bull McGraw-Hili New York 1970 t

18 H F Wolf Semiconductors pp 130-136 Wiley (Interscielce) New York 197L 19 T C Harman and I Melngailis Appl Solid 51011 Sci 41-94 (1974) 20 B Tuck J Motu Sci 10 321 (1975) 21 W R Runyan Semiconductor Measurements and Instrumentation Chs 127

and 9 McGraw-Hili New York 1975 22 R Tijburg Phys Technol September p 202 (1976) 23 D J Stirland and B W Slraughan Thin Solid Films 31139 (1976) 24 M J Pryor and R W Staehle in Trealise on Solid Stale Chemistry (N B Hanllity

ed) Vol 4 Ch 9 Plenum New York 1976 25 Metals Reference Book (e J Smilhells ed) 5th Ed Butterworth London 1971gt 26 Etching for Pattern Definition (H G Hughes and M J Rand eds) Electrochem

Socbull Princeton New Jersey 1976 27 W Kern ref 26 pp 1-ISd 27a W Kern RCA Rey 39278 (1918) 28 J S Judge ref 26 pp 19-36 29 W Tegert The Electrolytic and Chemical Poli~hing of Metals 2nd Ed Pergamon

Oxford 1959 30 J F Dewald in Semiconductors IN B Hannay ed) pp 727-752 Reinhold N~

York 1959 31 The Surface Chemi5lry of Metal and Semicondu~tor~ (H C GalO ed) Wile)

New York 1960 32 The Electrochemistry of SemiconduclOrs (P J Holmes ed) Aademic Pres Nc

York 1962 33 J L Pankoye ref 32 Ch 7 34 E A Eomoy and I G Erualimchik Electrochemistry of Germanium and Silicon

(A Peiperl ed and transl) Sigma Press Wa5hington DC 1963 35 P J Boddy J Elf(rollnul (hem 10 199 (1965) 36 V A Myamlin and Y V Pleskoy Electrochemistry of Semiconductors Plenum

New York 1967 37 H Gerischer in Electrochemistry Part A (W Jost ed) Physical Chemislry Vol

9 pp 463-542 Academic Press New York 1970 3S P V Shchigolev Electrolylic and Chemical Polishing of Metals Freund Publ

House Holon Israel 1910 39 Y V Pleskoy Prog Surf Mmbr Sci 751-9311913) 40 A K Vijh Electrochemistry of Metalgt and Semiconduclors Dekker New Yor bull

1973 41 G L Schnable and P F Schmid J EItClrochem Soc 123 310C (1976) 42 Corrosion (L L Shreir ed) 2nd Ed Newne-Bullerworth London 1976

v-I CIiIMICAL L I CHING 4X

43 A H AgaJnian Solid SIallt Techllul 16( 121 73 (19731 18(4) 61 I lJ 112011136 11177 43d C W Wilmsen and S Szpak Thin Solid Filmgt 47 17 (19771 44 L Romankiy ref 26 pp 161-193 45 P R Camp 1 t1-lroch-m Suc 102 5t6 (1155) 46 W Kern J 1 Vossen and G L Schnable Anna Pro Rdwh 1ltvI IIliI 1214

(973) 47 Il A Irving ref 32 Ch 6 4~ J L Vossen G L Schnable and W Kern 1 ~w S i Tecllol 110011174) 49 V F Dorfman SUY Mitro(rull 5 (2) N (IY76)

50 W S DeForest Photoreist Materialgt and ProCc M( lIill NeW York 1975

51 W Kern and J M Shaw 1 Eleclrohelil Su 118 lo~~ (1~71) 52 CA Deckert and D A Pelers Proc KodA M rllleclroll 11111 hlgtllIIan KoJak

Co Rochester New York pp 3-25 il97MI 53 C A Deckert ill Adhesion Measurement of nlln hlnh Thtk hit (fI1 Hulk Co1

ng IK 1 Mitta ed) pp 327-341 ASTM Iluladclphla lelltl~ltlHt 1I7M S4 J J Kelly and G J Koe 1 EIuroclwm SO 125 HIgtO (J17~1

55 Anonymous Ifld Regt 19 (2) 19 (1977) 56 S Somekh 1 Vae Sci r hllul 13 1003 (197fl) 57 J J Kelly and C H de Minjer1 tleclrodltlIJ Su 122 131 111l1 5K D MacArthur ref 26 pp 7b-90 59 P J Holme and K C Newman Proc 11111 Elcclr tng 11111 ull 15 HI

(1959) W J W Faul Jr NUll Bur Slund (US I Spcc Pu Nu137 PI j ()-l4 1191111 61 W Kern RCA R- 31207 (19701 b~ W Kern RCA RImiddot 31 23411970) 03 W Kern RCA R-I 32 b4 (1971) 1gt4 W Kern Solid Sulmiddot Tecllflol 15(1)34(1172 15(2) 3Y (11721 05 W Kern and D Puolinen RCA Regtlt 31 IM7 11170) 06 A Mayer and D A Puulinen NUll Bur gtwlld 11431-43 (U 1 )1 Ill N

337 (1I7U) 67 R C Hendel)un 1 tJedro hem So 11977211172) 6 K L Meek T M Huck anJ e F Gibbon 1 1ln Ir ilOIl 1 IlU 141 11)7 0) D A Kielt I J [YHaellens and J A KOlh I Un II 111 111110 IIIil4 69a D A Pelers and C A Deckert Electro 111111 Imiddotp i-I(Ih 04[1 7Hmiddotl on (197X 70 P KaimiddotChoudhury ill ScrnlCllnduclor Silicoll 1173 111 K Hull)d K KlhHe

ed) pp 243-257 Elcctrochcm Soc Pnel(lll Nev Jeq 1117 71 D K (hwuld 1 tleltlrocilI So 12353111176 72 J A Amick Solid S[al iJlJo 19111) 4711no 73 D Tolliver Solid Sldl Techllol 18(11)33 111751 74 M G Yang K M Kohwad and G E McUultmiddote1 Un Iro 11lt111 ) 1120711117)1 75 R Seltzer elllill M( 15111) SI 1117) 76 R A Geckk Ekclrllll p(( A) Prod lSI I~7 1111

77 G L Schnable W Kern unci K Il Corniah1 U 11 11lt111 ) 122101211171 7~ R L Meek 1 tlc troellllII Soc 121 172 (IY74) 79 W Kern unpubllgthed obcrvation KO W Kern Sem((ond Prod Sold SflIlc nlIIl1l 611111 n 11 ) 6 II 2 111011 81 Clean Surfaces Their Prepalation and CharaclcIIlatiun fUI IllIelllal Slucit

(G Goldfinger ed) Dekker New York 170 82 Ref I~ pp 4445541559-611

482 WERNER KERN AND CHERYL A DECKERT

12 S K Ghandhi The Theory and Practice of Microelectronics Ch 7 Wiley Ne10lt York 1968

13 C D Dobson in Gallium Arsenide Lasers (e H Gooch ed) pp )93-222 Wiley (interscience) New York 1969

I~ R Giang and L V Gregor in Handbook of Thin Film Technology (L 1 Mah~1 and R Giang cds) Ch 7 McGrawmiddotHill New York 1970

15 R J Ryan E B Dayidson and H O HooK in Handbook of Materials and Proshycesses For Electronics Ie A Harper ed) Ch 14 McGrawmiddotHill New York 1970

16 W A Pliskin and S J Zanin In Handbook of ThinmiddotFilm Technology (L L Mais~1 and R Giang eds) Ch 11 McGraw-Hili New York 1970

17 P F Kane and G B Larrabee Chlracterization of Semiconductor Material bull McGraw-Hili New York 1970 t

18 H F Wolf Semiconductors pp 130-136 Wiley (Interscielce) New York 197L 19 T C Harman and I Melngailis Appl Solid 51011 Sci 41-94 (1974) 20 B Tuck J Motu Sci 10 321 (1975) 21 W R Runyan Semiconductor Measurements and Instrumentation Chs 127

and 9 McGraw-Hili New York 1975 22 R Tijburg Phys Technol September p 202 (1976) 23 D J Stirland and B W Slraughan Thin Solid Films 31139 (1976) 24 M J Pryor and R W Staehle in Trealise on Solid Stale Chemistry (N B Hanllity

ed) Vol 4 Ch 9 Plenum New York 1976 25 Metals Reference Book (e J Smilhells ed) 5th Ed Butterworth London 1971gt 26 Etching for Pattern Definition (H G Hughes and M J Rand eds) Electrochem

Socbull Princeton New Jersey 1976 27 W Kern ref 26 pp 1-ISd 27a W Kern RCA Rey 39278 (1918) 28 J S Judge ref 26 pp 19-36 29 W Tegert The Electrolytic and Chemical Poli~hing of Metals 2nd Ed Pergamon

Oxford 1959 30 J F Dewald in Semiconductors IN B Hannay ed) pp 727-752 Reinhold N~

York 1959 31 The Surface Chemi5lry of Metal and Semicondu~tor~ (H C GalO ed) Wile)

New York 1960 32 The Electrochemistry of SemiconduclOrs (P J Holmes ed) Aademic Pres Nc

York 1962 33 J L Pankoye ref 32 Ch 7 34 E A Eomoy and I G Erualimchik Electrochemistry of Germanium and Silicon

(A Peiperl ed and transl) Sigma Press Wa5hington DC 1963 35 P J Boddy J Elf(rollnul (hem 10 199 (1965) 36 V A Myamlin and Y V Pleskoy Electrochemistry of Semiconductors Plenum

New York 1967 37 H Gerischer in Electrochemistry Part A (W Jost ed) Physical Chemislry Vol

9 pp 463-542 Academic Press New York 1970 3S P V Shchigolev Electrolylic and Chemical Polishing of Metals Freund Publ

House Holon Israel 1910 39 Y V Pleskoy Prog Surf Mmbr Sci 751-9311913) 40 A K Vijh Electrochemistry of Metalgt and Semiconduclors Dekker New Yor bull

1973 41 G L Schnable and P F Schmid J EItClrochem Soc 123 310C (1976) 42 Corrosion (L L Shreir ed) 2nd Ed Newne-Bullerworth London 1976

v-I CIiIMICAL L I CHING 4X

43 A H AgaJnian Solid SIallt Techllul 16( 121 73 (19731 18(4) 61 I lJ 112011136 11177 43d C W Wilmsen and S Szpak Thin Solid Filmgt 47 17 (19771 44 L Romankiy ref 26 pp 161-193 45 P R Camp 1 t1-lroch-m Suc 102 5t6 (1155) 46 W Kern J 1 Vossen and G L Schnable Anna Pro Rdwh 1ltvI IIliI 1214

(973) 47 Il A Irving ref 32 Ch 6 4~ J L Vossen G L Schnable and W Kern 1 ~w S i Tecllol 110011174) 49 V F Dorfman SUY Mitro(rull 5 (2) N (IY76)

50 W S DeForest Photoreist Materialgt and ProCc M( lIill NeW York 1975

51 W Kern and J M Shaw 1 Eleclrohelil Su 118 lo~~ (1~71) 52 CA Deckert and D A Pelers Proc KodA M rllleclroll 11111 hlgtllIIan KoJak

Co Rochester New York pp 3-25 il97MI 53 C A Deckert ill Adhesion Measurement of nlln hlnh Thtk hit (fI1 Hulk Co1

ng IK 1 Mitta ed) pp 327-341 ASTM Iluladclphla lelltl~ltlHt 1I7M S4 J J Kelly and G J Koe 1 EIuroclwm SO 125 HIgtO (J17~1

55 Anonymous Ifld Regt 19 (2) 19 (1977) 56 S Somekh 1 Vae Sci r hllul 13 1003 (197fl) 57 J J Kelly and C H de Minjer1 tleclrodltlIJ Su 122 131 111l1 5K D MacArthur ref 26 pp 7b-90 59 P J Holme and K C Newman Proc 11111 Elcclr tng 11111 ull 15 HI

(1959) W J W Faul Jr NUll Bur Slund (US I Spcc Pu Nu137 PI j ()-l4 1191111 61 W Kern RCA R- 31207 (19701 b~ W Kern RCA RImiddot 31 23411970) 03 W Kern RCA R-I 32 b4 (1971) 1gt4 W Kern Solid Sulmiddot Tecllflol 15(1)34(1172 15(2) 3Y (11721 05 W Kern and D Puolinen RCA Regtlt 31 IM7 11170) 06 A Mayer and D A Puulinen NUll Bur gtwlld 11431-43 (U 1 )1 Ill N

337 (1I7U) 67 R C Hendel)un 1 tJedro hem So 11977211172) 6 K L Meek T M Huck anJ e F Gibbon 1 1ln Ir ilOIl 1 IlU 141 11)7 0) D A Kielt I J [YHaellens and J A KOlh I Un II 111 111110 IIIil4 69a D A Pelers and C A Deckert Electro 111111 Imiddotp i-I(Ih 04[1 7Hmiddotl on (197X 70 P KaimiddotChoudhury ill ScrnlCllnduclor Silicoll 1173 111 K Hull)d K KlhHe

ed) pp 243-257 Elcctrochcm Soc Pnel(lll Nev Jeq 1117 71 D K (hwuld 1 tleltlrocilI So 12353111176 72 J A Amick Solid S[al iJlJo 19111) 4711no 73 D Tolliver Solid Sldl Techllol 18(11)33 111751 74 M G Yang K M Kohwad and G E McUultmiddote1 Un Iro 11lt111 ) 1120711117)1 75 R Seltzer elllill M( 15111) SI 1117) 76 R A Geckk Ekclrllll p(( A) Prod lSI I~7 1111

77 G L Schnable W Kern unci K Il Corniah1 U 11 11lt111 ) 122101211171 7~ R L Meek 1 tlc troellllII Soc 121 172 (IY74) 79 W Kern unpubllgthed obcrvation KO W Kern Sem((ond Prod Sold SflIlc nlIIl1l 611111 n 11 ) 6 II 2 111011 81 Clean Surfaces Their Prepalation and CharaclcIIlatiun fUI IllIelllal Slucit

(G Goldfinger ed) Dekker New York 170 82 Ref I~ pp 4445541559-611

----shy4H4 WERNER KERN AND CHERYL A DECKERl

83 Ref 50 Chs 3 and 7 84 L Holland The Propenie ofGla Surface Ch 5 Wiley New York 1964 S5 R Brown in Hallllbook oCThin Film Technology (L I Maissel and R Giang elk

Ch 6 pp 37-42 McGraw-Hili New York 1970

86 D M Mattox Surface Cleaning in Thin Film Technology AVS Monogr Am Va Soc bull New York 1975

87 R R Sowell R E Cuthrell 0 M Mattox and R D Bland 1 Vae Sci 1chllol II 474 (1974)

8S J R Vig C F Cook N Schmidtal l W LeBus and E Hafner Surface Studie for Quanz Resonator RampD Tech Rep ECOMmiddot 4251 US Anny Electron Command Fort Monmouth New Jersey (1974)

89 D A Bolon and C O Kunz 1(1)111 tllg Sci 12 109 (1972) 90 P H Holloway and D W Buhmire Annu Proc Rehab Phy- 12th p ISO (1974) 91 R C Snogren Handbook of Surface Preparation Palmenon New York 1974 92 J L VossenJ Appl Ph)l 47)44 (1976) 93 L Holland J VaL Sci 1-hllol 14 5 (1977) 94 R B Gillette J R Hollahan and G L Carlson 1 Vue Sci l~(hll() 1534 (1970) 95 J L Vossen J J OmiddotNeill Jr K M Finlayon and L J Royer RCA Rei 31 213

(1970) 96 C C Chang P Petroff G Qumtana and J Sosniak Surf Sci 38341 (1973) 97 D V McCaughan and R A Kuhner Thin Solid Films 22 359 (1974) 98 G J Kominiak and J E Uhl Rep SAND 75-0455 Sandia Labbull Albuquerque New

Mexico (1975) 99 RefSICh5

1001 Smith Surf Sci 2745 (1171) 101 A M Morgan and l Dhn1 VOl Sri Techno 10523 1Il731 102 R W Kirk in Techniques and Application of Plasma Chemistry tJ R Hollahan

and A T Bell ed~l Ch 9 Wiley New York 1974 103 G J Kominiak and D M Maltobull Rp SAND 75-6110 Sandia Lab Albuquerque

New Mexico (l97b) Thin Solid Filml 40 141 (1977) 104 Plama Etching and Depoition Technology Program Allant (ja Meet 1 111middot

chern Sue 124 252C -324C (1177) 105 J S Judge J EItclrochem SOL 11K 1772 (1971) 106 E F Duffek and D Pilling cmiddotlerIWehem Sue blend AbJlr No III p 244 Spnng

Meeting 09(5) 107 S A Harrell and J R People Jr Elecrvchem Soc Exlend Abm No 112 p 247

Spling Meeting (1965) 108 C C Mai and J C Looney -emicond Prod Solid Siule fechllOl 9(1)19 (16)

109 J Lawrence Eleclmchem Soc Extend Abtr 12-2466 (1972) 110 V Harrapin SemiconductorSilicun 1973 (H R Huff and R R Burgess edbull ) pp

354-362 Electrochem Soc Princeton New Jersey 1973 III R Herring and J B Price Eleltlffmiddothem Soc Extend Absr 73-2410 (1973) 112 0 S Herman M A Schuster and H G Oehler Eleetrochem Soc txtelld AbJtr

71-1167 (1971) I U J J Gajda Annu Proc R liub Ph)l 12th p 30 (1974) 114 P J Holme and J E Snell fiavelmiddotclmn Relib S 337 (Ib) 115 T W OKeeffe and R M Hardy Solid-SlUle Elecrrn 11 261 1111) lib R A Moline R R Buckley S E Hazko and A U MacRaeIltt frtls llntr

Onicel ED-ZO 840 (1973) 117 G Bell and J Hoepfner ref 26 pp 47-55

v-I CHEMICAL ETCHINlj -lli

118 W A Pliskin lftill Solid hlm1 2 I (IS)

119 L A Murray and N ullldmith1IJecocilclJ So 113 1~J7IIJhh) 120 Il Swaroop ill Thin Film Dleicctrk IF VaIIlY dl p 407 IIcciucilcIIL ~()I

New York 1161 121 W A Phl-in and R P Unall 1 Ieto h II III S7~ 11) 122 D M Brown W E Engla M Garfinc a11 K HCllmI 1 I 111

114 73U 117)

In W Kern RCA RIgt 29 557 (16~)

124 W A Plikin and H S Lhmml LcctriIII So 1121(1111)

125 D II Gralllham and J Swindal 1111 M III [ 111 p I tX Ilil Soc flytllid Microclctron Montgomery Alabama 11J71

126 T Kublna 11111 AIII Plry II 141 1lt)7~1

127 P C Huang and P M Schaible EiccthltttI -IIltIld 1 1tJ-l 74 (Inh) 12~ M J RanI 1 tledrochtltl Soc 114274 (171 121 S Krongclh Inlro(II(III htII 6 21 11I6K) I3U W Kern and J P White RCA RI 31 I 1117111

I Y AVlg l Bingk and M Schieber J 1middot II III Ill 110 I I 114 132 N Goldsmith and W Kern RCA RCI 211 1 (1h7J 133 B I Deal P J Fl-mlHg and 1 L ltatlo 1 -I I hl11 115 HIO IlloK I

114 M L Barry It1 Chcnllal Vpnr DCPhI LI M Illoh I ltIId J ( Wlh lb) pp 59-bI7 EIclrochem So New YOlk lnO

135 E L MalKcnna [)ro ~(mi( ondjJC PrO( Plod (tll pp 71 X lild ~I (PH

Manage Chicago IlIioi Ilnl) 110 L Hall I Lin I hettl SO 1111 1500 1197 37 W KClii RC-I R(I 37 7K 11170) lJ~ W Kern RCA Rn 37 ) 11lt170) Illti M l llmmoIHI lid (i M IlI)IN 1ml lt1lt11 -11- 14 41 11h~) 14U T L (hll J R SICltl and ( A Urubc 1(1111 illl ) 11 211 12 I tKI 141 W J KIIIII JI R I Illl and J B Waglle I 1 11Ii Ill 11

11175) 142~ A K (junltl ( K AdCIlIalH V J 111 111 I BIlIlcl Iltl h

1 122 7 1197)) 141 J Kildllllan and J (J1llih J Lint h(lll II~ 411 11l 144 H ( 1bull1111 and W I u Ihill Solid Fillll ~I -ll I tJ771 145 J Krullthman I -1111 1 I bull14)23 (17)

140 J 1 Alexander R J Juce lOd H F Sillilllg III 111111 Jlck llk

(F Vralny ed) pp 140-21lX F1eclrohcm Su New yok 1) 147 Ref IU2 pp 3b2-374 147a A G Revc anltl K H Zainingcr RCA RII 2922 (IXI r I (1111 I

l~(hll()l 6 25 (I 1)

14~ J Dey M Lundgren and S Hurd middotlIl1 Ihlo(IIII 01111 VII 2 P 4 (PII2middot1l1 i-aslman Kodak (II bull Rllcheter New Yurk IIX)

14J H 1 Wolf ref I~ p 372 ISO W A Phkin and R P beh leI 26 pp 7-41gt III L E Katl and W ( ElJmanl tntr hlm 123 124~ 11171 In S C H Llfi anltl I J PugIlmiddotMUlakICWICl J A)I 1 43 II IIfl2) 153 L J PugaclmiddotMurakicwll and H R IlanrmlmJ 1 ~Ilt ) I 11lt1 14 41 11177) 14 E T Fitzgibbon K J SlaJ 111lt1 W II 111115 1 UnllllIII II~ ii

11972)

l54a M Yokozawa H Iwa anJ I 1 cramoto 1 1 -III 1lI 7 Jio I IX I

486

~ WERNER KERN AND CHERYL A DECKERT

IS4b D R Harbison and H L Taylor in Thin Film Dielectrics IF Vratny cd) pp 254-218 Electrochem Soc bull New York 1969

155 M Balog M Schieber S Patai and M Michman J Cryst Growlh 17298 (19721 156 Y W Hsueh and H C Lin Anna Rep COll Electr Insul Dieleelr Phnwm p SIS

( 1974) 157 E Kaplan M Balog and D frohman-Bentchkowsky J ElectrociJem Soc 123 1570

I 976) 158_ W H Knauenberger and R N Tauber J Eleclrochem Soc 120927 (1973) 159 JPS Pringle J EItClrochtm Soc 119482 (1972) 160 P W Wyatt J EleClrochem Soc 122 1660 (1975) 161 B H HillJ ElecfOlmiddothtm 50(115668 (1969) 162 J Grossman and D S Herman J Eleclrochem Soc 116674 (1969) 163 H M_ Day A Christou W H Weisenberger and J K HcrvonenJ Eleclro-hem

Soc Ill 769 (1975) 164 R N Tauber A C Dumbri and R E CaffreyJ Electrochem Soc 118747 (1971) 165 J A Abaaf J Electrochem Soc 114948 (1967) 166 N Hashimoto Y Koga and E Yamada in Thin Film Dielectrics (F Vralny

cd) pp 327-331 Eleclrochem Soc bull New York 1969 167 Y Koga M Malsushita K Kobayashi Y Nakaido and S Toyoshima in Thin

Film Dieleclrics (F Vramy ed) pp 355-377 Electrochem Soc New York 1969 168 M T Duffy and W Kern RCA Rn 31754 (1970) 169 M MUlOh Y Mizokami H Malsui S Haampiwara and M Ino J Eltclrochem Soc

Ill 987 (1975) 170 H Kallo and Y Koga J Eltcfochem Soc 118 1619 (1971) 171 A J Learn J Appl Phy bull 44 1251 (1973) 172 K lidaJ Elutrochem Soc 124614 (1977) M Hirayama and K ShohnoJ Elenshy

chem Soc Ill 1671 (1975) 173 E Ferrieu and B PruniauxJ EI((middotlmchtm Soc 1161008 (1969) 174 H Harada S Saloh and M Yoshida IEEE Trans Rehab R25 290 (1976) 175 R G Friescr J Ele-Irochem Soc 113357 (1966) 176 T N Kennedy Electron Packag Prod 14(12) 136(1974) 177 R S Nowiclri J Vae Sci Techno 14 127 (1977) 178 S K Tung and RmiddotE CaffreYJ Eleclrochem Soc 1l4 257C Abstr RNP-24 (19(

179 V Y Doo and P J Tsang EleclfOchem Soc Exend Abslr No 16 p 33 Spnng

Meeting (1969) 180 P J Tsang R M Ander~on and S Cvikevich J EleClrochmiddotm Soc 12357 (19761 181 K M Schlesier J M Shaw and C W Benyon Jrbull RCA Rev 37358 (1976) 182 G C Schwartz and V Plauer J Eleclrochem Soc 122 1508 (1975) 183 A Reisman M Berlrcnblit J Cuomo and S A Chan J Eleclrochem Soc III

1653 (1971) 184 M F Ehman J Electrochem Soc III 1240 (1974) 18j H M Manasevit J Electrochem Soc Ill 293 (1974) 186 J M Green J Eleetrochtm Soc 119 1765 (1972) 187 M Safdar G H Frischal and H Salge J Am Ceram Soc 57 106 (1974) 188 B Siesmayer R Heimann and W Franke J Cryst Grolh lB 157 (l975) 189 I I Baram Zh Prikl Khim 38 2181 (1965) 189- M Balog M Schieber M Michman and S Palai Thin Solid Films 41 24711~77)

190 W Kern and R C Heim Electrochem Soc EXltnd Abstr No 92 p 234 Spnn

Meelinllll9(8) 191 W Kern and R C Heim J Eltclrochem Soc 117 562 (1970)

v-I CHEMICAL ETCHING -lX

192 W Kern G L Schnablc and A W Fhcl R( A Rn 17 11176 193 J M Eldridge and P Balk Trans Mellll ~ AIMJ 242 IIIHI

194 E H Snow and B E Deal J tledmchefl Ioc 11326 1111gt1gt

195 W Kern Eleltrochlt1I1 SJ(middot Exend Abltr 76-1 111 (19761 196 A S Tenney and M Uhazo J Eltctruchelll Soc 1l0 UNI 1111 I) 197 S Nihimatsu and T Tokuyama EItClrociltlII SOl Extend 111111 No 170 p ~

Fall Meeting (1967) 198 T Tokuyuma T MiyalaJi and M Iloriulhi in Thin Film lldLI middotmiddot II VIIII)

ed pp 297-326 Elellochem Soc New York 1969 199 W Kern and R C HClmJ Ekelrochon Su 117568 (7() 200 K Jinno H Kinoshila and Y Matsumoto J Un ImclII ~u 124 12iX 1I7 201 K Chow and L G Ganic J EIclrociJelli Smiddot 124 1133 (1l77l 202 P F Shmidt W Van Gelder and J Dmbck J IrIIi So 1157) IIX 203 P BalJ and J M [eldridge Prtle 111 57 15iK 1196) 204 K Sugawara T Y chhirni and U Sakai 11 Chemic11 Vapo Dermlll -11th IlIIel

national Conference(J M Blocher Jr and H E HilHcrmall cJ I PI 407middot412 lice trochem Soc Princeton New Jerey 1975

2il5 W Kern and A W Fiher RCA Rnmiddot 3171 i 1l70) 206 A H EI-Hoshy leeradllIIL Soc 117 ISH (1970)

207 D M Brown and R P Kcnni(ottJ tIclrocilnll Soc lUI 2~ 11171) 2011 L Rankel Plauger J tIt1lrocilem SOl 1l0 14211 (1973) 209 F N Schwettmann R J De~ter and D F Cole J 1((1011lt111 Sa 120 I toto

1973) 210 R O Schwenker J 1I(lrodmL Soc 11M 3 IJ 11171 211 S S Chang US Palent I7H4424 (1174) 212 W KernJ Eleclroctellt Suc 116251( (19691 213 J Wong J Eleclrott1L Soc 119 1071 (1972) 214 M GhclloanJ D M BrownJ EleclrvcilllIl Soc 120 IlUllill 215 R B fair J EleclfochII Soc 119 13119 (19721 216 F C Everslcijn Philip Rel Rep 21379 (1906) ~17 S K Tung and R E Caffrey J EIlmciJem So 1179111)7111 218 P J Tsang R M Anderon and S Crikcvich J Ell( In( h11 ~ lB IIlih)

219 S M Spiller B Schwartz and G D Weigle J Iclruch(f~ 122197 I

220 T Sugano and Y Mari J Iedrochtm Solt 121 113 (19741 221 G W Morey The PropertIes llfGlass 2nd Ed Ch 4 RltlI1hold New YJ 114 222 L Holland The Properti of Glass Surface Ch J and 5 WIIy New YlH~ 11(gt4 223 T Yoshida and M Koyama US Patenl 3~J113 (1974) 124 M Dumesnil und R Hewitt J Electrocil Sue 117 Ill() Ilnlll 225 F M Ernsberger J Alii Caun Suc 42175 (159) 126 W A Plikin J Ele(lro(h~m Soc 114620 (1967) 227 D M Mattox and G J Kominiak J EItmiddot Iwchem Soc 120 I 114711 228 W A Pliskin P D Davidse H S Lehman and L I Maicl fiAt J RI On II

461 (1967) 229 H N farrer and F J C ROSSOlli Jlllmg Nac 011111 26 IW) (llJtIl

230 J T Milek Silicon Nitnde for Microeieciloillc Appiuallltll PIf I 11 eplI III and Properties pp -II~IFIPlenum New Yorio 1971

231 C A DeckertJ EItCrodlenl Soc 124 32U (197M) 232 W van Gelder and V E Hauser J ElecrodmiddotIII Soc 144 Xbi 11167) 233 D C Miller J Eleclrochtffl Soc 120 1771 (19731 234 C A Deckert unpublished observations (1975)

4~~ WERNER KERN AND CHERYL A DECKERI

235 W Kern and R S Rosier J Vac Sci Technol 14 1082 (1977) 236 E A Taft J EleClTchem Soc 118 1341 (1971) 237 R Gereth and W Scherber J tJ~cchlm Soc n9 1248 (1972) 238 Y Kuwano JpII J Appl Phybull 8 876 (1969) 239 M J Rand Ellcrochem Suc Exend Abslr 77-2419 (1977) 240 W A Lanford and M J Rand ElaCh~m Soc Exfelld Ablr 772421 (1977) 241 V D Wohlheiter and R A Whitner J Ele(f)chem Sac 119945 (1972)

242 H J SteinJ Ellcroll Multr 5 161 0976) 243 V D Wohlheiter J Elecrrochem Soc 122 1736 (1975) 244 G J KominiakJ ElecfOchml Soc 122 1272 (1975) 245 C J Mogab P M Petroff and T T Sheng J Elecfrochem Soc 122815 (1975) 246 A W Stephens J L Vossen and W KernJ ElectroLmiddothem Soc 113303 (1976) 247 C J DeIlOca J EItClflchefll SOL 121 1225 (1973) 248 D M Brown P V Gray F K Herrmann H R Philipp and E A TaftJ Ulclro

chem Soc ISS 311 (1968) 249 M J Rand and J F Robenbull J Elenwchem Soc 120446 (1973) 250 H Nagai and T Niimi J 11((1(11lt111 Soc 115671 (1968) 250a T Yashiro J Elecrochem Soc 119780 (1972) 251 D R Turner J Eluf)chetn Soc 107810 (1960) 252 D L Klein and D J DmiddotStefan J EltClrochem Sac 109 37 (19621 253 H Robbins and B Schwartz J Eecrochem Soc 106505 1020 (1959) 254 H Robbins and B Schwartz J Elalrochem Sac 107 108 (1960) 255 B Schwaru and H Robbins J EleClf)chem Soc 108365 (1961) 256 B Schwartz and H RobbinsJ Eltcfruchem Soc 113 1903 (1976) 257 A F Bogenschutz W Krucmark K H LOcherer and W Mussingcr J EI I

chem Soc 114970 (1967) 258 S M Hu and D R Kerr J Ilnlrochtm Sac 114414 (1967) 259 W Hoffmeister Int J Appi Rudia 11 2 139 (1969) 260 E Cave RCA Solid State Di bull personal communication (1972) 261 G R Booker and R Stickler 8r J Appl Phys 13446 (1962) 262 G Das and N A OmiddotNeil IBM J Rlts Dv 1876 (1974) yb

f263 c J Schmidt P V Lenzo andE G Spencer J Appl PhYL)Mt 4080 (In5) 264 A I Stoller R F Speers and S Opresko RCA Rev 31 265 (1970)

265 J Freyer J EltClr()Chem Soc 122 1238 (1975) 266 B A UnvaJa D B Holt and A SanJ EieclfVchem Soc 119 311i (I72)

267 R E Blaha and W R FahrnerJ EleCrochem Soc 113 515 (1~76) 261 C Raetzel S Schild and H Schlotterer Eleclrachem Soc EXInd Abgtlr 74-2

336 (1974) 269 M J J Theunissen J A Apples and W H C G Verkuylen J Eleclrochtm Sot

117 959 (970) 270 Ref 21 p 199 Table 73 271 R R Stead US Patent 2973253 (1961) 272 Ref 5 p 370 273 Book of ASTM Standards ASTM Philadelphia Pennsylvania 1967 274 P J Holmes Prof InSi Elecl Eng Illrl B Suppl 17861 (1959) 275 Telefunken AG Brit Patent 962335 (1964)

276 M Chappey and P Merilel Fr Patent 1266612 (1961) 277 R J Jacodine J Appl Phys 36 2811 0965) 278 M V Sullivan and R M FinneElecrochem Soc Meet Absr No 156 Fail Meetln~

(1960) 279 B A Irving 8T J Appi Phys Il 92 (1961)

v l (HlMICAL ElCHIN( fK)

2MO B Shwartz and H Robbin J It-elroeitllll () III 1 (14 2MI B A Irving 1 J-ietlmcliltf1I SOC 109 120 (I~)

2S2 D R Turner ref 32 Ch 4

2S3 J W Faut Jr in Reactivity of Solid iJ W Mitchdl R ( Ilc V HC R W R berts and P Cannon cd) pp 337-343 Wiley NcI York 1)

2l14 M F Ehman J W Faut Jr Hnd W B While I nOl IIH144 11971)

2M5 B Schwartz 1 lJetlnllhtlIl Sc 114 21ii 171

2M6 W Pnmak R Kampwirth anu Y Dayal J 1 II h011 1 114 HI 1)gt7J 2M7 P R Camp J EIICIclllII Soc 102 5~b (111) ~gM J P McKelvey anu R l Longjm 1 ApI 1 251114 (1)1 ~gy B W Ballerman J Appl Phygt 28 Inb 11J~71 290 Ref 3~ p J69

2)1 F L Vogei WG PlannH E Corey and I 111101111( 90 4XI I Ih)

~l R D Heiuenreich US PatenI26194141I15~1 lY3 Ref 32 p 3M 2lt)4 P Wang SYullia Tecol II 50 (1158) 2S G A Geach B A Irving anu R Phillipgt Rnl h 1101110111 HI ~II 11)7) 2 W W Harvey anu H C Galos J ElecrocmiddotIIJ So 105654 II 2J7 H C Gal and M C Lavine J tcclro11IJ SOl 10743 I I hIli

211 W K Zwicker and S K Kurtl Semiconductor Silicon lI7l III R lIuli uti k k Burge elb) pp 315-326 Electrochemical SOl Princeton Ncv kC) I7l

~ I J Pugacl MufUlkicicl and B R Hammond J Va 11111 14 41 ( 11771

300 H A Waggener R C Kragne and A [ Tyler 1111 Nnuoll 1 nlmiddotI AI NolllpampH(I9671

301 A 1 Stoller RCA Re 31271 (19]0) JU2 H A Waggener R C Kragne and A l 11ltbull FIe lrullll 14012) 27middot 117 JUl H A Waggcnerand J V Dalton EIurohllll I 0041 72 25H711)72 304 J B Price ill Semlcondutor Silicon 1971 ill R Huff amI R R IllIg Ih

pp 331-353 Elcclrochem Soc Princeton Ne Jcy 117

l) P Clemenbull EIClrOIIII Soc fbull ImiddotII Alnll 73240711) 306 D F Weirrauch 1 Allpl P) 46 1478 (1)71 307 K E Bean R L Yeakley and T K Pdl 1 1I0eh(l I Ifd 1111 74 1

68(1174)

JOI M J Declenq J P DcMoor and J P Ifhell In 11o hOf 1111111

752446 (1971) JOJ D B Lee J App Phygt 4U 4561119) 310 M J Dedcrcq L Gelberg and J D Melnul J 1 100 hnl 122 4 11)1) 311 R M Finne and D L Klein 1 1leclroehtlll S 114 ~ 1171 312 M Aano T Cho and B Muraoka 11-1( ItIIIl So 111 AJlI 76 2

( 1916)

313 I Basuu H N Yu and V Maniscalco 1 Ie lrutllCfII 123172111)])1 J14 K E Bean and W R Runyan J Ellctr- So 1245amp 11177 315 T R Payne and H R Plumlee IfLE 1 Soidmiddot11I1lt (in uill S( H n 111711 J 16 K E Bean and J R 1awon IEEE J SodShllmiddot Circuill S(middot III 111)4 I 317 W Tsang and S Wang J AII Phlgt 462164 111751 J18 C R Hamona and H W Branuhot Ifrtlwlonolui 1( ( I I gtlaquo11

dale AZ pp 44-48 (1915)

319 F Restrepo and C E Bakubull IEtmiddottmiddot middot[rUIlI Uee On n bull ) 21 11)111))laquo1 310 R K Smdtur J EIclrIIIII1 0 122 IlJho 111751

-----_

490 WERNER KERN AND CHERYL A DECKERT

321 R C Ellis Jr J Appl Phys 15 1497 (1954) 18 1068 (1957) 322 A Uhlir Bell Sysi Tech J lS 333 (1956) 323 G L Schnable and W M Lilker EleClrQchem Techllol 1203 (1963) 324 Ref 33 pp 297-308 325 G R Booker and R Stickler 1 Eleclroehfm Soc lOll 1167 (1962) 326 M V Sullivan D L Klein R M Finne L A Pompliano and G A Kolb J Ele(middot

lroehem Soc 1l0 412 (1963) 327 C E HaJlas Solid Slale Technol 14(1) 30 (1971) 328 R L MeekJ Elecfoehem Soc 118437 (1971) 329 H J A van Dijk and J de Jonge J Eleelmchem Soc 1l7 553 (1970) 330 R L Meek J Eleefochem Soc 118 1240 (1971) 331 M J J Theunissen J Eleclrochem Soc 119351 (1972) 332 M J Hill J Eleclroehem Soc 120 142 (1973) 333 C P Wen and K P Weller J EleClruehem Soc 119547 (1972) 334 T I Kamins Proc IEEE 60 915 (1972) 335bull l Kamins J Eleclrocmiddothem S bullbull 1286 (1974) 336 T I Kamins SolidSIaI Elecrn 17667 (1974) 337 H A Waggener Bell Sy-I Tech J 49473 (1970)

338 H A Waggener and J V Dahon Eleclmehem Sue EXlend Absl 70-2 450 (1970)

339 A Manara A Ostidich G Pedroli and G Restelli Thill Solid Films 8 359 (1971) 3w H D Baroer H B Lo and J E Jones J Eleclrmhem Soc Ill 1404 (1976) 341 J Sanada K Furuno K Shima and T Momoi Jpn J Appl Phys 16299 (1977)

342 R Memming and G Schwandt Surf Sci 4 109 (1966) 343 P H Bellin and W K Zwicker J Appl Ph)s 411216 (1971) 344 Y Walanabe y Arita T Yokoyama and y Igaraschi J EleCirochelll Soc 112

1351 (1975) 345 y Arila and y Sunohara J Eleerochem Soc 114285 (1977) 346 Y Yashiro K Sailo and T Suzuki Eleltlrochem SoC Exelld Absr 74-2 351

(1974) 347 J B Price and W C Roman Eleclrochem Soc Exend Absir 72middot2584 (1972)

348 G L Kuhn and C J RhecJ Elecrochem Soc 120 1563 (1973)

349 J P While RCA Solid Slate Division unpublished observalions (104) 150 A Bohg J Elurochem Sot 118401 (1971) 351 H Muraoka T Ohhashi and y Sumilomo ill Semiconduclor Silicon 1973 (H R

Huftand R R Burgess eds) pp 327- 338 Electrochem Soc Princellln New Jermiddot sey 1973

352 Y Yasuda and T Moriya in Semiconduclor Silicon 1973 (H R Huff and R R Burgess cds) pp 271-284 Eleclrochem Soc Princelon New Jersey 1973

353 R E Chappclow and P T Lin J Eleclmchtm Sul Ill 913 (1976) 354 J Lawrence Can Palenl 903650 (1972) 355 Y Sumilomo K Niwa H Sawazaki and K Sakai ill Semiconduclor Silicon

1973 (H R Huff and R R Burgess cds) pp 893-904 Electrochem Soc Princmiddot Ion New Jersey 1973

356 Y Sumitomo T Yasui H Nakatsuka T Oohashi H Tsulsumi and H Mumola EItClrochem So Exeld Abgtr 72-174 (1972)

357 K E Peterson Appl Phys Lm ll 521 (1977) 358 H Guckel S Larsen M G Lagally G Moore J S Miller and J 0 Wiley Appl

Phys Let ll 618 (1977) 359 y S Chiang lind G Looney RCA Laboratories unpublished observalions (1970) 360 P Rai-Choudhury J EI~clroch(m Soc 118266 (1971)

v-I CHEMICAL ETCHING j ) I

361 S E Mayer and D E Shea J EleClmchulI 1 111550 (1-1) 362 L J StinsonJ A Howard and R C NevilleJ tIIdrochem So 12J 551 (1~7tl)

363 G A Lang and T Slavish RCA Rev 24 4~H (13) 364 W H ShepherdJ Eleclrohem Soc Ill IHM (15)

365 L V Gregor P Balk and F J Campagnil IBM J He [)n I n7 (116)

366 W Runyan Silicon Semiconductor Technology pp 72-71 MdirawmiddotHtll Nv York 15

367 K E Bean and p S Gleim Proc IEEE 57 14b~ I I lilY)

368 K Sugawara Y Naklawa and Y Sugila iJeClrochelll Tn 1 b ~) (196M) 36~ K Sugawara J tJtcroehllII Soc 1111 II() (I~71)

370 M Drumimki and R Gssner J (rnl GrowllI 31 312 I~7))

371 A Reiman and M Berk~nblit J EI((I ltIII Soc 112 KI2 l~M) 372 L D Dyer AlChE J 18 nil (1972)

373 J p Di~muke and R UlmerJ EIt(m(hIII S 118634 (19711

374 P Ru-Choudhury and A J NorcikaJ EIClnnhllfI 10 lib f) I IIn)

375 J p Dimuke and E R Levin ill Chcnucal Iocng 01 ~1I(ldcllC Ita teriab IL D Uker and J Childrc ~dJ p 131 Am ) Ckm Ig Nv York 1~70

376 E R Levin J P Djmukc and M D CUlI(h J 1IltiI hu I liN 1171 (II

377 T LOw G A Gruber and R SticklcrJ 1 111111 1111 Ih 11(1 378 W O Oldham and R H)lmtrom J EITIO CIIl SO 114 IX I (19hl) 379 J A Amick E A Ruth and H Go~cnbcrgcl HCA Hn 24 -17 11)

3KO T L Chu and R W Keirn J Ut(IOCtlIl 10 lib 12td II

381 R J Walsh and A H Herwg US Palen 1702731131

382 E Mendel Selllicod Pod Solid Sue Inilll 10 7 (171

383 T M Buck and R L Meek Na Bur Sand (US ) ~fle 1101 No 17 pp 41 I

430 (InO)

384 J T Law Solid Iale 1111101 1411)25 ((i7I) 385 R B Herring Solhl SaI lechllol 19(5137 (1~761 386 E L Kern G L Gill and P Rioux in Semiconductor Slicun IJ77 III K lIull n)

E Sirtl d~I pp 182~ IK6 Eletlrochem Soc Princdun Nev ky 1~77 387 F Mendel and K Yang Prc [IEE 57 1476 (19(9) 388 L H Blllke and E Mendel Solid Sale feci1 UII) 4~ 1117111

3S~ A Ieiman ltlnd R Rllhl J filtlImciltlli III 1-12- 1116-0

3IIJ V L Ridco~t J Ehelr 11 Soc 119 177~ (11721

391 H Hartnagcl and B L Wels J Mua d 8 lOll I (1973) 312 T M Buk ill The Suliae Chemistry or Melagt al1d SCl1l1UlI 1gt( II ( (

cd) pp 107~1J Wiky New York IU

393 R BSperNalfJIISlIlId (US)Sp Pllb No1np 41 -1IXII170

394 A C Bonora ill Semiconductor Silicon 1~77 If R Hull dud I ~I cd I PI 154-161 Ekltllllchem Soc Prindon Ncv Jcry 1177

3~5 J W Faut ill Sil)1 (albide (J R 0(0111101 allJ J Smillell cd r 4(H 1 gamon Oxford 1960

396 R W Barllel1 and M Blllow J Emiddotccrtwi1t1l1I 117 1-1Il llJIIiI 317 W V Muench and I Pflltrencder Thill Solid Fillll1 31li (1~7~1

3~ R C Smith tleClruchem Soc Exelld Ablr No 11 Fall MCCllIIg (11)

391 T l Chu and R B Campbell J Eleu 11 Soc 112 11

400 R W Brander and A L Boughey Br J App Phn 18 )(1 (171 401 M V Sullivan and G A Kolb J Eilturudmll Soc 110 X 1)(0 402 C S Fuller and H W Allr~onJ 11110 Ii Soc 1098XIII21

492 WERNeR KERN AND CHERYL A DECKERT

403 Y Tacui Y Komiya and Y HaradaJ IJectrochem Suc U8 118 (1971) 404 J C Dymem and G A Rozgonyi J Electrochem Soc U8 1346 (1971) 405 D W Shaw J Electr()chem Soc 113958 (1966) 406 I Shiota K Motoya T Ohmi N Miyamoto and J Nishizawa J Elercrochem Soc

124 155 (1977) 407 M V Sullivan and L A Pompliano J Eleclroehem Soc 108 60C (1961) 408 S ida and K Ito J Electrochem Soc 118768 (1971) 4091 J Gannon and C J Nuese J Eiecmchem Soc Ill 1215 (1974) 410 R D PackardJ Electrochem SUI 112871 (1965) 411 R W Bicknell J Phys D 6 1991 (l973) 412 E W Jensen Solid SIGte Thnol 16(8)49 (1973) 43 O Wada S Yanaghawa and H Takanashi J EleClrothem Soc 123 1546(1976) 414 W T Tsang and A Y Cho Appl Phys LeII 30293 (1977) 415 J L Merz and R A LoganJ Appl Phybull 47 3503 (1976) 416 L A Koszi and D L Rode J Electrochem Soc 1221676 (1975) 417 J G Grabmaier and C B Watson Phys Status Solidi 32 K13 (1969) 418 M Otsubo T Oda H Kumabe and H Miki J EIltClrochem Soc 123676 (1976) 419 J L Richards and A J Croltka J Appl Phy 31611 (1960) 420 1 G White and W C Roth J App Ph)s 30946 (1959) 421 D N Nasledov A Y Palrakovd and B V Tsatvenkov Zh Tekh Fiz 28779

(1958) 422 E Biedermann and K Brack J Electruchem Soc 113 1088 (16)

423 Ref 21 p 199 Table 74 424 E S Meieran J Appl Ph) 362544 (1965) 425 G H Olson and V S Ban Alpl Ph) Letl 28734 (1976) 426 T Ambridge C R Elliot anJ M M FaklOr J App Eleuwchem 3 1 (1973) 4 135

tl974) 427 M M Faklor D G FiJdyment and M R Taylor J JJeclrochf1 Soc 122 ISOtgt

(1975)

428 Y V Pleskov Dokl Akld Nuuk SSSR 143 1399 (I962L 429 C J Nuese and J J Gannon J Eeclflt)(hem Soe 117 1094 (1970) 430 A Yamamoto and S Yan J Eieltlrochtm Sot 122260 (1975) 431 D L Rode B Schwartz and J V DiLorenzo Solid-SlUle Il((tron 171119 (1974) 432 B Schwartz F Ermani and B H Bratad J Elaquotru(h~m SoC 123 IOMI (1970) 433 C Lin L Chow and K Miller J Ufclochtlll Suc 117 407 (170) 434 R Bhat D J Baliga and S K Ghandhi J Eleclrochem SOL 121 1378 (1975) 434a R Bhal and S K Ghandhi J ElulfJchem SOL 124 1447 (1977) 435 R P Tijburj and T van Dongen I EClmchem So( 123687 (1976) 436 W G Oldham Elttochelll Technol 357 (15) 437 A G Sigai C J Nue~e R E Enlrom and T ZamernkiJ Eleufltmiddothem Sot 120

947 (1973) 437a Ref 8 p 38 438 M I VaJkov~kaya and Y S Boyankaya Sov Phys-Sid Slale 8 1976 (19671 439 R H Saul J Eectrmhem SO 115 1185 (1968) 440 E HaJkova and R rremunt Ph) bull Statu Solidi A 10 K35 (1972) 441 N E Schumaker M Kuhn and R A Furnage JtEE ]mns Eleccron Delice ED-III

627 (1972) 442 T Uragaki H Yamanaka and M Inoue J Elecrochem Suc 123580 (1976) 443 W H Hackel Jr T E McGahan R W Dixon and G W Karnrnlotl J LImiddottmiddot

hem Sot 1111973 (1972)

v-I CHEMICAL ETCHING j )

444 N E SchurnakerandG S Rozgnnyi1 fitImiddotIII ~ 119IlIllJI1 445 L Ronkel Ploucr 1 1lccrhem Soc 1214 (1))]4) 446 A Mikh J fl~ctrohtlll Sot 123 1256 (11761 447 B [J Chc D H Hllt and H A Unvala 1 Un 11 11tlL p 119 11011lt)721 44S R L Meek and N E Schllmaker1 tecro 111 119 1141 111721 449 1 L Chu and R W Kelm Jr J 1le(rltlchIII 122915 i lnl 450 M J Rand anJ J F Rober 1 Iieuruchu Su liS 4~) (IIOX) 450a M Hirayamo anJ K Shomo J clrochnl So 122 1671 1171 451 T L Chu M Gill and S S Chu 1 How helll S IB2I1161 452 H C Galo and M C LavincI lilccIOh lII So 107 4n 1111 41 L L (hu J IinrrociJtIII Sot 118 2(JO (1171) 454 J L Pan~ove 1 1Ittr helll )1( 119 IIIH (11721

455 A Shinlani and S Minag I ElatrocIf) 123706 (llllgtl

450 A T Churchman G A Gcach and J Winton Prot II SP 2JI 114 (lIhl 457 J W Fiuht and A Sag 1 ApI Phys 31 331 111001 458 E P WarckUlgt anJ PH Mctlgcr1 AIlI Plln 0 0 (1911 459 L 13erntcin 1 1-1( lrgtdHlII Soe 109270 (12) 460 B L Sharma oliis(tI Iedmll 9 12K (IIMI 461 B Tuck and J Baker I Mlltcr Sd 8 1559 i 1I73) 462 V Wrick G J Scilla I I Eaiman R I Henry aoJ L 11 ggnd 11 1111

Lcll 12 314 111761 463 J W AllcnIII Mog 21455 (1157) 464 J F Dewaldl 1I(lr1I1 oe 104244111571 465 1 D Venable and R M HrolJltJy I AIII 11 I 29 1025 IIltJXI ee Ii Ill

commUIliCatIon cilcJ III D ll Hoi J Alpl Ihn 1122311101 466 A Rcmall M 13erkenblil J Cuomo and S A Chan I I I I n 1111 16

11171 I 467 M F Ehmanl licclI hIII S 121 1240 i ln4) 46M MmiddotI Shehata and R KellyI flcuro hltlII So 122 1gt1 IIJi1

46~ E A Jame RCA Laboratorie pconal 0Illn(IU 11 I 470~ J W Fau 1 Flnlro hltII SUl 10S( 121252( (1IlI

471 J Wood Hr 1 API Phl 11296 (1960)

472 E P Wankoi M C Lavine A N Mariallo and II ( (ill 111 1 I 1111111 (12)

473 M V Sullivan anJ W R IIrlaquoht1 1(110)lt111 11421 (IhI 474 W H SIf~hlowI AIpl Phyl 40 292M (11)

475 V Y Pikhardt anJ D L South J tkorh I 1211(11071174) 476 A A PrillharJ and S Wagner 1 IJIClr hOI 124 1 IIJJ71

477 Mlnouel 1ermolo anJ S Takyanagi1 111111 1- c7X 112) 478 A Sagar W Lehman and J W Falll 1 AIII Phll 39 lIl IIXI 479 Ref S p 41 4lO Ref ii p 42 481 L Teramoto alld S Takayanagi 14111 11111 12 II) 11 II 482 S G Parker and J E Pinllcl 1 EIclrrwhmiddot1I1 Su 11K IX6i1 117 4S Ref 11 p 43

484 J C C Fan and F Hahncr1 fJcctnhtlll 11221711) IIIhl 4S5 J Kane W Kern anJ H P ShweiLcr fiJi -gt11 Fillll 29 I 1111 4lb J A Thornton and V L HeJgcnlh 1 I 1lt1 tI1iI 13 1I111l7hl 4S7 G Bradhaw anJ A J Hughe lhin lid hllII B U Ilnt1 4liI Ref 6 pp 256 261-2112

492 WERNeR KERN AND CHERYL A DECKERT

403 Y Tacui Y Komiya and Y HaradaJ IJectrochem Suc U8 118 (1971) 404 J C Dymem and G A Rozgonyi J Electrochem Soc U8 1346 (1971) 405 D W Shaw J Electr()chem Soc 113958 (1966) 406 I Shiota K Motoya T Ohmi N Miyamoto and J Nishizawa J Elercrochem Soc

124 155 (1977) 407 M V Sullivan and L A Pompliano J Eleclroehem Soc 108 60C (1961) 408 S ida and K Ito J Electrochem Soc 118768 (1971) 4091 J Gannon and C J Nuese J Eiecmchem Soc Ill 1215 (1974) 410 R D PackardJ Electrochem SUI 112871 (1965) 411 R W Bicknell J Phys D 6 1991 (l973) 412 E W Jensen Solid SIGte Thnol 16(8)49 (1973) 43 O Wada S Yanaghawa and H Takanashi J EleClrothem Soc 123 1546(1976) 414 W T Tsang and A Y Cho Appl Phys LeII 30293 (1977) 415 J L Merz and R A LoganJ Appl Phybull 47 3503 (1976) 416 L A Koszi and D L Rode J Electrochem Soc 1221676 (1975) 417 J G Grabmaier and C B Watson Phys Status Solidi 32 K13 (1969) 418 M Otsubo T Oda H Kumabe and H Miki J EIltClrochem Soc 123676 (1976) 419 J L Richards and A J Croltka J Appl Phy 31611 (1960) 420 1 G White and W C Roth J App Ph)s 30946 (1959) 421 D N Nasledov A Y Palrakovd and B V Tsatvenkov Zh Tekh Fiz 28779

(1958) 422 E Biedermann and K Brack J Electruchem Soc 113 1088 (16)

423 Ref 21 p 199 Table 74 424 E S Meieran J Appl Ph) 362544 (1965) 425 G H Olson and V S Ban Alpl Ph) Letl 28734 (1976) 426 T Ambridge C R Elliot anJ M M FaklOr J App Eleuwchem 3 1 (1973) 4 135

tl974) 427 M M Faklor D G FiJdyment and M R Taylor J JJeclrochf1 Soc 122 ISOtgt

(1975)

428 Y V Pleskov Dokl Akld Nuuk SSSR 143 1399 (I962L 429 C J Nuese and J J Gannon J Eeclflt)(hem Soe 117 1094 (1970) 430 A Yamamoto and S Yan J Eieltlrochtm Sot 122260 (1975) 431 D L Rode B Schwartz and J V DiLorenzo Solid-SlUle Il((tron 171119 (1974) 432 B Schwartz F Ermani and B H Bratad J Elaquotru(h~m SoC 123 IOMI (1970) 433 C Lin L Chow and K Miller J Ufclochtlll Suc 117 407 (170) 434 R Bhat D J Baliga and S K Ghandhi J Eleclrochem SOL 121 1378 (1975) 434a R Bhal and S K Ghandhi J ElulfJchem SOL 124 1447 (1977) 435 R P Tijburj and T van Dongen I EClmchem So( 123687 (1976) 436 W G Oldham Elttochelll Technol 357 (15) 437 A G Sigai C J Nue~e R E Enlrom and T ZamernkiJ Eleufltmiddothem Sot 120

947 (1973) 437a Ref 8 p 38 438 M I VaJkov~kaya and Y S Boyankaya Sov Phys-Sid Slale 8 1976 (19671 439 R H Saul J Eectrmhem SO 115 1185 (1968) 440 E HaJkova and R rremunt Ph) bull Statu Solidi A 10 K35 (1972) 441 N E Schumaker M Kuhn and R A Furnage JtEE ]mns Eleccron Delice ED-III

627 (1972) 442 T Uragaki H Yamanaka and M Inoue J Elecrochem Suc 123580 (1976) 443 W H Hackel Jr T E McGahan R W Dixon and G W Karnrnlotl J LImiddottmiddot

hem Sot 1111973 (1972)

v-I CHEMICAL ETCHING j )

444 N E SchurnakerandG S Rozgnnyi1 fitImiddotIII ~ 119IlIllJI1 445 L Ronkel Ploucr 1 1lccrhem Soc 1214 (1))]4) 446 A Mikh J fl~ctrohtlll Sot 123 1256 (11761 447 B [J Chc D H Hllt and H A Unvala 1 Un 11 11tlL p 119 11011lt)721 44S R L Meek and N E Schllmaker1 tecro 111 119 1141 111721 449 1 L Chu and R W Kelm Jr J 1le(rltlchIII 122915 i lnl 450 M J Rand anJ J F Rober 1 Iieuruchu Su liS 4~) (IIOX) 450a M Hirayamo anJ K Shomo J clrochnl So 122 1671 1171 451 T L Chu M Gill and S S Chu 1 How helll S IB2I1161 452 H C Galo and M C LavincI lilccIOh lII So 107 4n 1111 41 L L (hu J IinrrociJtIII Sot 118 2(JO (1171) 454 J L Pan~ove 1 1Ittr helll )1( 119 IIIH (11721

455 A Shinlani and S Minag I ElatrocIf) 123706 (llllgtl

450 A T Churchman G A Gcach and J Winton Prot II SP 2JI 114 (lIhl 457 J W Fiuht and A Sag 1 ApI Phys 31 331 111001 458 E P WarckUlgt anJ PH Mctlgcr1 AIlI Plln 0 0 (1911 459 L 13erntcin 1 1-1( lrgtdHlII Soe 109270 (12) 460 B L Sharma oliis(tI Iedmll 9 12K (IIMI 461 B Tuck and J Baker I Mlltcr Sd 8 1559 i 1I73) 462 V Wrick G J Scilla I I Eaiman R I Henry aoJ L 11 ggnd 11 1111

Lcll 12 314 111761 463 J W AllcnIII Mog 21455 (1157) 464 J F Dewaldl 1I(lr1I1 oe 104244111571 465 1 D Venable and R M HrolJltJy I AIII 11 I 29 1025 IIltJXI ee Ii Ill

commUIliCatIon cilcJ III D ll Hoi J Alpl Ihn 1122311101 466 A Rcmall M 13erkenblil J Cuomo and S A Chan I I I I n 1111 16

11171 I 467 M F Ehmanl licclI hIII S 121 1240 i ln4) 46M MmiddotI Shehata and R KellyI flcuro hltlII So 122 1gt1 IIJi1

46~ E A Jame RCA Laboratorie pconal 0Illn(IU 11 I 470~ J W Fau 1 Flnlro hltII SUl 10S( 121252( (1IlI

471 J Wood Hr 1 API Phl 11296 (1960)

472 E P Wankoi M C Lavine A N Mariallo and II ( (ill 111 1 I 1111111 (12)

473 M V Sullivan anJ W R IIrlaquoht1 1(110)lt111 11421 (IhI 474 W H SIf~hlowI AIpl Phyl 40 292M (11)

475 V Y Pikhardt anJ D L South J tkorh I 1211(11071174) 476 A A PrillharJ and S Wagner 1 IJIClr hOI 124 1 IIJJ71

477 Mlnouel 1ermolo anJ S Takyanagi1 111111 1- c7X 112) 478 A Sagar W Lehman and J W Falll 1 AIII Phll 39 lIl IIXI 479 Ref S p 41 4lO Ref ii p 42 481 L Teramoto alld S Takayanagi 14111 11111 12 II) 11 II 482 S G Parker and J E Pinllcl 1 EIclrrwhmiddot1I1 Su 11K IX6i1 117 4S Ref 11 p 43

484 J C C Fan and F Hahncr1 fJcctnhtlll 11221711) IIIhl 4S5 J Kane W Kern anJ H P ShweiLcr fiJi -gt11 Fillll 29 I 1111 4lb J A Thornton and V L HeJgcnlh 1 I 1lt1 tI1iI 13 1I111l7hl 4S7 G Bradhaw anJ A J Hughe lhin lid hllII B U Ilnt1 4liI Ref 6 pp 256 261-2112

494 WERNER KERN AND CHERYL A DECKERT

489 R F Brebrick and W W ScanlonJ Chem Phys Z7 607 (1957) 490 H Abrams and R N TauberJ Elenruchem Soc 116 103 (1969) 491 B B Houston and M K NOrT J Appl Phys 31 615 (1960) 492 M K NOrT J Eleclrochlm Soc 109433 (1962) 493 E Levine and R N Tauber J Eleclrochem Soc liS 107 (1968) 494 Ref 19 p 35 495 A R Calawa T C Harman M Finn and P Youtz Trans AlME 142 374 (1968) 496 Ref 19 pp 38-39 497 R MulO and S Furuuchi Asahi Garusu Kenkyu Hokoku lJ 27 (1973) 498 D J Daliga and S K Ghandhi J Eleclrochem Soc 114 1059 (1977) 499 H B Bullinger US Patent 3615465 (1971) 500 H Kusakawa T Yata and W Fujinaga Jpn Patent 75 85895 (1975) 501 J Kane W Kern and H P Schweizer J Eleclrochem Soc IlJ 270 (1976) 502 D A Vermilyea Annu Rev Maler Sci 1373 (1971) 503 R Weiner MtlolioberJliiche 27 441 (1973) 504 T Agatsuma A Kikuchi K Nabada and A Tomozawa J DeCmehem Soc IlZ

825 (1975) 505 W Kern and R B Cominoli J Vac Sci Technol 1432 (1977l 506 H K Johnston and T L Larson US Paten 3702273 (1972) 507 Applications Data for Kodak Photosensitive Resists Pamphlet poll Eagtlman

Kodak Cobull Rochester New York (1966 5011 W N Greer Plating (EaS Orange NJ) 48 1095 (1961) 509 J R Sayers and J Smit Plaling (East Orange NJ) 48789 (1961) 510 K Nanwlra and M Maeda Jpn Patent 73 08706 (1973) 511 M C Zyetz and A M Despres Am Val Soc Symp Jlh EXlend ADslr p 169

(1966) 512 F Okamato Jpn J Appl Phys 13383 (1974) 513 Dynachem Tech Dala Elchants for Melals and Thin Films Lithoplale Covina

California 514 R F Frankenthal and D H Eaton J Eleclrochem So( IlJ 703 (1976) 515 T A Shankoff and E A Chandros J Electrochem Soc 122294 (1975) 516 A Rogel Rev Sci Instrum 37 1416 (1966) 517 F WoilSch Solid State Technol 11(1)29 (1968) 518 D M Brown W R Cad~ J W Sprague and P J SaivagniIDE Trans Electron

Devices ED-18 931 (1971) 519 A R Janus J Eleclrochem Suc 1111392 (1972) 520 Anon~mous ncidentiallntelligence About Kodak Resists Vol 7 No I p 4 Eastmiddot

man Kodalr Cobull Rochesler New York (1969) 521 G S KelseyJ Eleclrochem Soc 114927 (1977) 522 V H Choo and 0 F Devereux J Eleclrochem Soc IlJ 1868 (1976) 523 T Talramura and H Kihara-Morishita J fmiddotleclrochem So( 122386 (1975) 524 C W Halsted and M W Haller Eleclrochem Soc Extend Abslr 76-1748 (1976) 525 J W Dilile in Oxides and Oxide Films (1 W Diggle ed) Vol 2 Ch 4 Dekker

New York 1971 526 J D MacChesne) P B OConnor and M V Sullivan J Electrochem Soc 111776

(1971) 527 W Sinclair D L Rousseau and J J Stancavish J Eleclrochem Sot 1ZI925

(1974) 528 G W Kammloll and W Sinclair J Eleclroehem Soc 111929 (1974)

v-I CHEMICAL OllNG -lJ~

529 S J Licht J Electroll Mala 4757 (1~75) 530 T Kasai Jpn J Appl Phy 14 1421 (IY751 531 D C Miller 1 E-lnlrO( hem Soc 120 1771 (IY73) 532 I Haller M Hatlakis and R Srinivasan IBM 1 (n 0(12 I (IS) 533 M Zamin P Mayer and M K Murthy J tkerOthem Se 123 IJ77 (1176) 534 Langes Handbook ofChemitry (N A Lange edl IOlh Ed Mdilw-BIJI Ncv

York 1967 535 J B Mooney and J O M~Caldin J EICelrdm Suc 114625111771 536 J W Johnson S C Chen J S Chang and W J James Com I In 17 Mil (1I77l 537 Y OkinakaJ Ekelmchnn Soc 117281 (1170) 538 R D Arll1slfllng (mH Su 11601) (11711 539 R D Cowling and A C Riddiford tClrolilll 110 I~ )81 (111 540 W K Behi and J E roni J Eleclrow(I Chnn 3163 (Inl) 541 Becc Bulletin No Y7 Beco Chern Oiv UuffI Ncv Y nrk 542 Becco Bulletin No N Bcccu Chern Div Uuffaitr Ncv York 543 Becco Bulletin Nil 102 Becco Chern DV Uullalo New Ylk 544 R J Schaefer anti J A Blodgett 1 Ekelrochol Soc 12 17Ut (Ino) 545 P Jacquet Rev Metall (Paris) 42 133 (1945) 546 D Landolt R H Mulier and C W TobiasJ tItflrociltIIL p 1111 4U (IIII) 547 K Umeda Jpn Patent 750131 I (1975) 54~ R P Frankenthal and O E Thompson 1 rllro h lII So 1237) 1171l) 549 F Huber W Witt and I Hlt Prall PIlt Valroll COUlIOtlttJI (un p 66 t 17 550 Y Ohno T Matsuoka and K Miyaji Jpn Patenl 74111737 t1Y74) 551 R N CaMe llano and P H SchmidtJ tmiddotleclnrchtfn iolt 11110)- 111711 552 Ref 14 pp 7-38 553 M Zamin P Mayer and M K MurthYJ flmiddot lromiddot1I So 12-1 IX 11~77) 554 L A Colom and H A LeVine US Patenl 3631IH5 IIns) 555 G D Barnet[ and A Miller US latenI32121I01 (16) 556 R de Uernardy and L F Oonaghcy tmiddotcllllo (If blII1 1111 76-2 (gt-1M

(11J76) 557~ Handbook llf Chembtry and PhYSICS (R C Weasl and S M Sdhy cd I 4l1l J

Chern Rubber Pub Co Cleveland Ohio 1167 19611 558 K Baba Jpn Palent 74 47225 (19741 559 M J Graham G I Sproule D Caplan and M CohenJ Icr hnl 1 1J9l8

(1972) 500 B MacDougall and M Cohen 1 Ueelroilelll Soc 123 Ill i 1i761 561 M S Shivaraman and C M Svensson J IeclroItm Soc lB I ill 111761 562 M J Rand J Eleeroehlm Soc 122811 (10175) 563 M J Rand and J F Rllbenslppl Phylt L(I 24 4Y (19741 564 E J Kelly Pro Inl CcHlgr Mel Corml 51h Tokyo IY72 p 117 11~7j1 565 E J Kelly J EleelrochmiddotIII Soc IlJ 162 (1976 566 J W Johmon and C L Wu J Ele([mchm Soc 118 JiU911i71 i 567 G S Kelsey J EIClrocilelli Soc 124814110177 568 T P Dirkse D DeWit and R Shoemaker J lInllochtlIi So 1154-1211IMI 569 M Eisenberg H F Bauman and D M UrcHner J Icdro hem Soc 108 )11

(1961)

570 R D Armstrong and G M l3ulman1 EleCrtlltuwl Ch 25 121 11~7tl) 571 R W Powers and M W Breiler J Elalrocll m Soc 116 719 (1)1 572 F M Cain Zirconium and its Alloys Am Sll~ Met Column Ohu 1953

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