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Mechanisms for Enhanced Packaging ,andlor Burn-in Total Dose Scnsitivity in Microelectronics

Ronald L. Pcasc, RLP Rcscarch Marly Shancyfclt, Peter Winokur aiid Dan Fleelwoud. Sandia Nation4 Labs*

Jcrry Corclick and Stcvc McClurc. Hughes Spec iind Communicalion Steva Clark. Naval Surbct: Wirfare Center: Crane Division

Dave Alexander. Mission Research Corprntion L a v Cohn. Defense Special Weapons Agency

*Sandia is a rnulriprogrmi Inbrarory opcratcd by Sand3 Corporation, a Lockhccd Marlin Company, Tor Ihc US Dcpt. OC Energy undcr Contracl DE-ACU4-94ALS5000

htrciductian. ln 1994 [ l ] i t was shown that the tolal dose deyriidxion of both ;1 radiation hiirdcncd (Sondia CMOS 1tTA) and a radialion tolerant (National Seinicoiiductor Corp. NSC. FACT) bulk CMOS kclinology w;1s enhanced by an clcvatcd tcnipraturc burn-in. Thc satic pawcr supply currcnt cxcccdcd the spcciflcation valuc at thc rat& tokil dose lcvcl on pirts which hiid becn SubjLt'Lcd to burn-in, whcrcss prts witliouL burn-in casily passed. In mother s t u d y of the NSC F.l.CT process 121 tlie total dose effects of packaging (ccranric and plastic). in addirion to rhc cffccw ofburn-in. \vc:c charnctcrizcd. For both high and low dose rates, wlicrc tlic failurc incchanisrns wcrc diffcrent (I: chmncl cdgc lcnkagc at high ratc and ncld oxide leakage at low ratc), thc pl3sLic p;ickagc greatly enhancd the el€ect oCburn-in. Thc rncchanisrn for rlic burti-in cffcct ivns studied on the rndiarion hardtxcd technology [I, 31 using both g3tc and ficld oxidc MOSFE-Ts. Charge scpararion analysis pxformcd on tlic garc oxidc transistors showed that burn-in had vcry liltlc cffecr on rlie irmdiarioii induccd incrasi: in oxidc trappcd chargc. ANot, bul it signiticanrly rcduccd the buildup of iiircrfnce traps. ANit. No clmrgc scparntion annlysis was possible in Llic licld oslde transistors becnusc of tlicir dcsign. Howcvcr thc field oside transistors wcre stuciicri for the cffects of temprnturc and bias during burn-in using the irradiation Induced threshold shill at 10 IIA drain curreht [3]. It wus shown that the nlecllanisiii was n hinction of tiiiic and tenipxaiurc, with no bias dcpcndcncc. Thc shift In thc sribrlircsliold rcgion was ncarly parallzl and much largcr in the burncd-in dcviccs: suggcsting that the enhanced eEcect was duc to largcr ANot Thc activa(ion cnergy for the process was dcccrrninccl to bc 0.38 eV. which is siniilnr to chat of hole coinpnsatioii (0.4 I eV) 141 and molecular hydrogen diITusion in bdk fiiscd silica (0.45 eV) 151.

cnllrrnccclby thc plastic package, whereas for tlic non burncd-in paris thcrc was littlc clfect of pachging. Additional tcstlng, previously unpublishcd, showcd that the burn-in effect was not sensitive to bins, hdiciiting rliar rlic samc tncchanism observed in tlie Sandia CMOS IIIA :nay bc 31 work in lhc NSC PACT tcchnology. It Is not known wlicthcr tlic n channcl cdgc or tnc licld oxidc leakage is ;I result of ANOL alonc or ANot compensated by ANit, sincu licld oxidu test structuns were not available. However, sincc tlic plastic alone has little cffcct, ic appcars [hat the plastic iiccclefntes the burn-in effect. Additional lcsts an: pluniied to vary thc tirnc and temperature of tlic plastic molding proccss to scc if grcaicr [imc andlor renipcrarurc causcs more burn-in effect. Also tcsts will bc pcrlbrnicd co isolate potcnlial phstic effects such as mobile ion charging and slrcss.

not bccn rcprtcd in any bipolar technologies. In this pnpx we will show new data dcrnonstrating tlic burn-in clrccr in 3 bipolJr linair circuit. Wc will also prcscnt a summary of a11 of thc studies (to our knowledge) on the burn-in nnd packaging cLTcct on total dose response.

I n rlic packsgingburn-in study on NSC FACL' 121, tlic burn-in cll'cct \vas shown LO bc grcally

Atthough the burn-in cffcct Iras bccn obscrvcd in two CMOS process technologies, to dnte it has

f DlSTRlBUVfON OF VHlS DOCUMEf4T IS UNLIMITED

1

DISCLAIMER

This report was prepared as a n account of work sponsored by an agency of the United States Government, Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liabdi- ty or responsibility for the aawacy, completeness, or usefulness of any information, appa- ratus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, pmess, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessar- ily state or reflect those of the United States Government or any agency thereof.

Exnerimcntiil Dctslls ~ i i t l Dijcusyion. Charackrizallon testing W.IS pxforrnLui on LTIO 14 bipolar liiienr quud operational aeiplifiers ta study the elTect of burn-in on the total dose response in plastlc packaged pnrtu. No coinpison wm ma& to parts in ceramic pck-ges. AI1 pans in thc study were from the snme date code (9603) and no burn-in had k e n performed by the nianur~ctumr. One group of samples was burncd-ln prior to irradiation 3t 125 "C for I60 hours under static dc bias. Eight samples from the burnd-in group and 8 non burncd-in snmplcs wcrc Irradiatui at 90 rad (Sl)/s in a Cod0 source. under sPatIc dc blus, to cunulativc dosc: lcvels of 5 , 10. 15. 20.25, 30, and 40 h a d (SI). AI1 of the specification clcctrical parameters were nreasurcd txforu and dRcr burn-in and utter cadi irradiation level. No significant changcs in prcirdiation parameters werc observed ns u result of the bum-in alonc, Thc total dose response of four scnsilive pmmeters Is sliown in Figures I-.) as ihc average value of tho parnmcicr for op niiip # lin the quad (dl 4 op mips in clic package showed similar response) vs. dose for the 8 bumcd-in (BI) and 8 hon burncd-in (NRI) parts. Dila are not shown in the t'igures pJst thc onset of functional failurc. whcrc puarneter sldls becoiiic largc and crmiic For rhc BI pans this occurrcd between 20 and 25 krads und tbr [lie NBI parts i r occurrcd bctwccn IO and 40 krads. Howcvcr. cvcn rhoogb tlic ET pims failed nt a lowcr dosc Icvcl. m n y of the electrical parameters showed fess dcgrxlnlioii than thc NBI pans at dose lcvcls k low f:iilure ;is discussed below. Figms 1-3 show tlle positivc supply currunt (Tsb), dic posirivc input bias current (lbk) and thc input on:m volugc (Vos), rcspcctively. The ncgative Is and Ib showed the same qualimrivc rcspoiisc ay ihc pusitivc 1s and Ib. For cach of these pormcicrs thc BI pans degradcd substantially lcss t hn the NBI parts. 'l'he mechanism [or this bchavior is rclalcd to the excess b s a currcnt in the critical transistors. For Ihc Ll'l(114. the input transistors arc substrite pnps and thc current sources tisc lotcral pnpls. A rcccnt siudy on the rncchanism for excess bnse current iiu latcral and substrate pnp rransistors lo] shows tlut the domirunt paranieter is an inletface trnp induccd increasc in surhcc rccomblnation velocity. Incrcascs in o.\tdc t rappd chargc, on thu oihcr hand. alT.'.t the effect ofincrascd surfacc rmombinution velocity. rcstdring i l l lcss CXCCSJ base current. Thus the better performance of Is+, lb+ and Vos in the BI parrs m y be tlie rcsuli ofborh 3 rcductron in ANit and an incrcase in ANot. However. cvcn ihoiigh tltcsc parameters showed less c l k t !io111 burn-in. othcr purarnctcrs. c.g. voltagc g i n . showed much inorc dcgradation l iom bum-in. which lei& to eurlier o l w t of fi~nctional failurc of ihc E1 pirts. The vohgc gain rlcpcnds on npn transistor g i n - which is more affi%ted by ANot 171. In npn transistors rlic focal dosc clcpcndcnce on ANot is exponential. wherens the dcpcndence on ANit is linear.

B a d on thc LTlOl4 results. ic appcars that thc mechanisms wllich esplnin the CMOS hum-in effect nre consistcnt with the blplnr lincar r c s p w . Data are currently king taken on NSC LMl11 voll3gc rompr;itors. Rcsulis will bc presented in thc full papcr.

Summary of Data on Piickndnr?/Burii-in F,lTecr on Totnl Dnsc Hc.qimi.sc. In addition Lo the sludles disciisscd abovc, the effeca of packaging andor bum-in on total dose rcsponsc h w e been studied in bipolar transistors (8-111, power MOSFETs [l I ] and additional CMOS microcircuit technologics 1121. Also, pwiously unpublished dntru Iinve bccn rakcn at NSWC Crane on [lie eEccts of both packaging and bum-in on nn NSC LMI 13 bipolar dud voIt3gc comparator. Table I is a list of a11 of thc part rypcs and proccss rcchnologies that hnvc bccn studied to date (to our knowlcdgc) along with whether or not a scnsitivily was obsemd for either packaging, burn-in or bath. %vo 01' the studies looked at discrctc bipolarjunction iransistors, BJTs [%Ill . In rhc morc rccent work by Dowling and Wcst [IO[ thc study was perfornied on a single process lor or matcriol for eucli of two npn BJl' part Lypcs, looking at @in degradation. Dlc wefe packaged in four package types, mcral can (TOS), epoxy potted in metal coli, and both ccramic and plnstic strrfacc mount (SCY113). 'I'ha only rniljor cffect seen for packngc lypc was that Lhc ceramic SOT23 part dcgmded morc rhan thc others for both BJT Ljyes. In all pacbgc i p s tlie effect of bun-in was a 10% greater gain dcgradation. In the ERA study [ I 1 1, lwo npn BJT typcs em chnracclcrixcd ;IS a function of bum-in for both ceramic and plastic packages. Unfortunutely the ceramic i d plastic pans wcrc from different proccss lo&. Considering the spread in the dah, llic only clcar c l k t of burmin was that for one cypc in plastic, the burn-in rcsultcd in significantly Ic.ss &gradation. For the othcr thrcc groups then: was no significant effect. In thc s3mc study [ 1 1 I both n and p clmnel power MQSFETs were clmmclcrcrki for tlie bur-in clTcct in both certimnic and plnstic. No packaging or bum-in affects werc observed. In the NSWC study on the NSC LMl19, the plastic parts dcgrJdcd about a factor

of LWO niorc than tile Ccritmic ports, bur tlierc was only n smnll el&cr of burn-in. However, the burn-in nlonc rcsultcd In ;I signifie~nr chiige in rhc plastic parrs. All dic wcrc from tlic s m c wafcr intended for spcc and millmry pns, wllich did not have a silicon niuidc ovcrco;Ir. Tho nitridc, ovarcoat is always uscd for commercial plastlc puns at NSC. Thus rhc plastic package rcsults arc nor rcprcscntafivc of nvailablc pncbiged producr but may providc insighr into cflcct oT plastic alono on thc tot31 dosc rcspnsu. In a rccent study by Hush, ct al, 1121 four additional CMOS microcircuit tcchnologics wcrc cvaluatcd for lhc burn-In effect. Only one dcmonslralcd a signilicant effccct as sllown in Tablc 1. No dclluls of the proccss arc available. nor arc there tests structurcs lor cvalt~alion.

The effect of packaging on llic total dosc response has been studcd independently of burn-in, but few studics linvc had odcquatc controls to isolate effects to pckige alone. Bccause of the potentidly largc variation in total dose response from process lot to lor and cvcn walcr to wafcr within tho s3mc lot, it is ncccssary LO have die From n single wafer to 3ssurc illat packago is thc main variablc. Anothcr v;intlblc which is introduccd in a packaging study is thc dctcrmination of total dosc in the sensitive diclcctric. Mnny packagc conligurations C ~ U S C si@icant dose enhancciiient in sensitive regions. Only one of the studics citcd [ 101 .show a’significatit pchge effect withour a burn-in clfcct. and his occurrcd in a ccraniic P a c h C .

Cunclualan, Many sludlcs hwe been perfonlied to look at tlic clTcct:; of packagirrg and/or burn-in on total dose rcsponsc. We have presciired a sutniiiary of tlicsc studics to d3tc (to our knowledgc). Only 4 process tcchnologles (3 GMOS and 1 bipolar) show n signiticant burn-in etkct to dnte. ’I’he nieclmiiisms for this effect apprurs to bc coiisistcnt with tlut reprtcd earlier 1 I , 31 €or the Sandia ChlOS IlLA process. Additional tcsling with appropriate test devices und htructures will k ,-onductcd to dctcriiiinc thc imivcrsality of these mcchnnisms.

References 1. M. R. Shaneyfclt. D. M. Flcctwood, J. R, Schwa& T. L. Meisenlicimer. and P. S. Winokur. ”Effccrs of Burn-ln on Rndiadon f-hrdncss”: IEEE ‘l’rans. Nucl. Sci. N $ 1 I , ‘LSSO ( 1994). 2. S. I). Clark. J. P. Rings, M. C. Mahcr, M. K. Williams, D. R. Alcxandcr. and R. I,. h e . ”PliUtk Packaging and Rum-in Effececrs on Ionizing Dosc Rcvponx in CTvIOS MicrociKuits“. IEEE l’rnns. Nucl. Sci. NS 42, 1607 (1995). 3. M. R. Sliancyfclr, P. S. Wlnokur. D. M. Fleerwoo4 J. R. Schwank. and R. A. Rcbcr, Jr., “EEa& of Kcliability Screens on MOS Charge Trapping”, IEEE Trans. Nucl. Sa. NS 43. 865 (L996). 4. J. R. Schivonk, P. S. Winokur. P. I. McWhorter. F. W. Sexton. P V. Dressendorfcr, and U. C. Turpin. “Physicill Mechnnisms Contributing to Device Rebound”, IEEE Trans. Nucl. Sci. NS 3 I , 1474 (1984). 5. D. L. Griscom. “DilJhsloii ofbdiolytic Molccular Hydrogcn as 7 Mcchanism for UIC Postirrndiatlon Buildup oflnlcrfncc Statcs in Si0Z-S; Structurcs“. J. Awl. Phys.. 58 . 2.524 (1985). G. D. M. Schmidt. A. Wii, H. D, Sclirirnpf, D. M. Flmtwood rind R. L. Pease, “Modcling Ionizing bdiation Induced Gain Ucgrahtion of the Lateral B i p l s r Junction Transistor”. IEEE Trans. Nucl. Sci. NS 4 I, 2550 (1994). 7. S. L. Koslur, A. Wei, K. S. Schrimpf, D. M. Fleetwood. M. DeLaus. R. L. Pcasc. and W. E. Combs. “Physically Based Comparison of Hot-Carrier-Induced and Ionizing-Hadiation-Induccd Rcgradation in RJT’s”, IEEE Trans, Elc. Dcv., ED42, 436. (lW5). 8. S. Ihwling, “Comparative Effects of Gamma Tot31 Dosc on Surfricc Mount nnd Non-Surfncc Mount Bipolar ’rrawistors”, Proceedings of RADECS 93. 338 (1993). 9, S. Dowling and R IL WesL “The Effects of Rndiation on ldenticnl Dcviccs with Diffiirent Types of Packaging”, Proceedings d RADECS 95,244 (1 995). 10. S. Dowling, “Thc T o L ~ Dosc Rcspansc of Nl”N Transistors with Diffcrcnt Packogc ‘Typcs to Various [rradiation Condlions”. B E E Radiation Effkcts Data Workshop Record 44 (1996). 11. B. C. Roberts, C. P. Strudwick, and J. W. Billing, “A Study into Increasing the Cost Effectiveness of Future Spaccccaft by thc Use of Plnsric Encapsulatcd Semiconductors. Phase 2”, ERA Tcchnology Report 915-0198, April, 1996. 12. G. L. Hash , M. R. Shancyfclt, F. W. Sexton, and P. S. Winokur, ”Kadiation Hardness Assur.lncc Cnlogorics for COrS Technologies”, submitted to NSREC 97.

~~

Figure 1. Average Is+ vs. Dose

~~

Figure 2. Average Ib+ vs. Dose

0 20 43 0 al rx3

Dome (krada)

- ........ -. ..-..- ..-_.-- . ... L - __.I-...-". -. .. . . .

Daaa (krads)

Flgure 4. Average Gain vs. Dose i Flgure 3. Average Vos vs. Dose

1

0.8 r------ r--W--' -7

I--.. - * . -I -.

Dam (krada)

. . - ... __ _. .

16X SRAM SNL C O I P S N l large

-.. . ..-

-. CDlP

-.-._. - . FACT rad to1 large

CDIP, PDIP NSWC slgnlflcant none

blpofar cornrn CDIP, SOlC (P) ERA small - amall _ _ OMOS j . radtoi i-03,+6247(~) ERA none.. ~ __- none

Ad tot TO3, T&247(Pj;'- - ERA none none none red 101 T- e!.. -. ___ ERA

.- plestlc --.. . HAC - large Herrneilc HAC 1 small

large smell small

- - . .. .. . . - - - bipolar ulmm -- T018, -. . E-llne ERA small amall _-. -- . . . - --..___.

.- . . I. _..._ . - ..... -_

-1.

I