Electrodeposition for Synthesis of Microsystems

7/31/2019 Electrodeposition for Synthesis of Microsystems

1/8

Electrodeposition for the synthesis of microsystems

This article has been downloaded from IOPscience. Please scroll down to see the full text article.

2000 J. Micromech. Microeng. 10 101

(http://iopscience.iop.org/0960-1317/10/2/301)

Download details:

IP Address: 131.175.28.130

The article was downloaded on 06/06/2012 at 16:13

Please note that terms and conditions apply.

View the table of contents for this issue, or go to thejournal homepage for more

ome Search Collections Journals About Contact us My IOPscience
http://iopscience.iop.org/page/termshttp://iopscience.iop.org/0960-1317/10/2http://iopscience.iop.org/0960-1317http://iopscience.iop.org/http://iopscience.iop.org/searchhttp://iopscience.iop.org/collectionshttp://iopscience.iop.org/journalshttp://iopscience.iop.org/page/aboutioppublishinghttp://iopscience.iop.org/contacthttp://iopscience.iop.org/myiopsciencehttp://iopscience.iop.org/myiopsciencehttp://iopscience.iop.org/contacthttp://iopscience.iop.org/page/aboutioppublishinghttp://iopscience.iop.org/journalshttp://iopscience.iop.org/collectionshttp://iopscience.iop.org/searchhttp://iopscience.iop.org/http://iopscience.iop.org/0960-1317http://iopscience.iop.org/0960-1317/10/2http://iopscience.iop.org/page/terms


2/8

J. Micromech. Microeng. 10 (2000) 101107. Printed in the UK PII: S0960-1317(00)09306-2

Electrodeposition for the synthesis ofmicrosystems

W Ruythooren, K Attenborough, S Beerten, P Merken,J Fransaer, E Beyne, C Van Hoof, J De Boeck and J P Celis

Katholieke Universiteit Leuven, Dept. Metaalkunde en Toegepaste Materiaalkunde (MTM),de Croylaan 2, B-3001 Leuven, Belgium IMEC, Dept. Microsystems, Components and Packaging (MCP), Kapeldreef 75,B-3001 Leuven, Belgium RMA, Avenue de la Renaissance 30, B-1000 Bruxelles, Belgium

Received 10 December 1999

Abstract. Electroplating is an emerging technique for the production of microsystems. Thisis due to advantages such as high rate of deposition, high resolution, high shape fidelity,simple scalability, and good compatibility with existing processes in microelectronics.Materials ranging from high-conductivity metals over soldering connections to ferromagnetscan be deposited. In this paper the basics of electroplating are reviewed and examples ofrecent applications of electroplating in the processing of microsystems are presented.

(Some figures in this article are in colour only in the electronic version; see www.iop.org)

1. Introduction

In recent years, electrodeposition has become a mature

technology for materials deposition in microelectronics

fabrication and for related applications. Whereas1015 years ago, electrodeposition was looked upon as a

dirty, low-cost method, it is now considered to be a cleantechnique while it has maintained its cost advantage over

more traditional methods such as sputtering or evaporation.

Various materials with widely diverse properties such

as composition, crystallographic orientation and grain size

can be obtained through electroplating. High-conductivitycopper or gold for interconnects and multi-chip applications,

soldering materials based on indium or tinlead required for

flip-chip, and even soft or hard magnetic materials based on

nickel, iron and cobalt are possible. In the following section,

the basic aspects of electrochemistry will be introducedfirst. Thereafter, an overview of current applications ofelectrodeposition in microelectronics production will be

given.

2. Electrodeposition process

2.1. General description

In electrodeposition, metal ions present in a solution, the

electrolyte, are reduced at the surface of an electrode to forma metal layer. This process essentially consists of:

an electrically conducting substrate such as a wafer

or another substrate; on insulating or highly-resistivesubstrates, a thin metal film (i.e. several tens of

nanometers) deposited by sputtering or other means has

to be applied first;

an electrolyte solution containing the metal ions that will

be depositedin theform of salts (e.g. CuSO4), supporting

chemicalssuch as acids or salts (e.g. H2SO4 or NaCl) and

additives (e.g. saccharine);

a counter electrode either consisting of an insolublemetal (mostly Pt, but stainless-steel is used in some

instances) or of a soluble metal with a composition

similar to the deposited material;

an electric current or voltage source for controlling the

deposition;

various peripherals for contacting the electrodes, stirring

and heating the solution, etc.

For more precise control of the deposition process, a

reference electrode can be employed.

The electrodeposition process and the most important

components are schematically represented in figure 1. Theactual geometry of the electrochemical cell used in a

practical situation can be very different depending on the

application. Cells with horizontal, vertical or slanted

substrate positioning, with stirring or pumping of the

electrolyte, with or without bubbling of air or nitrogen can

all be used.

Theefficiency of thedeposition process canbe definedas

the ratio ofthe current usedfor the reduction ofthe ionsfor the

intended deposit to the total current passed through the cell.

From thermodynamics it follows that only copper and more

noble metals can be expected to deposit with 100% efficiency

from a water-based electrolyte. For all other elements, at

least a part of the current will be consumed in the formationof hydrogen gas. Usually one wants to reduce this effect

as much as possible, not only to increase the deposition

efficiency and hence the deposition rate but also because

0960-1317/00/020101+07$30.00 2000 IOP Publishing Ltd 101


3/8

W Ruythooren et al

Conduct ingsubstrate

Counterelectrode

Reference

electrode

Electrical control circuitry

Solut ion recycl ing andcondit ioning equipmentElectrolyte containing

metal and other ions

R

Figure 1. Schematic representation of a set-up forelectrochemical deposition.

the formed gas bubbles can be difficult to remove from the

sample surface and can locally hinder further deposition.

Most practical electroplating systems operate at an efficiency

of 90% or higher although in some cases it can be as low as

20%.

The deposition rate in electroplating can be determined

from Faradays law:

m = ItM

nF(1)

orh

t=

IM

nFA=

iM

nF(2)

withm themassof depositedmaterial, thecurrentefficiency

defined earlier, I the total current, t the duration of the

deposition, n the charge of the deposited ions, F Faradays

constant, h and A the thickness and area of the deposit,

the density of the deposit, M the molar mass and i the

current density. For metal deposition under typical operation

conditions, this amounts to a deposition rate of the order of

1 m min1.

Other electrochemical processes based on similar

principles as the electroplating of metals are also employed

in microelectronics fabrication. Electroless deposition of

metals, for example nickelphosphorous alloy, is mainlyused to obtain thin layers for protection of contacts.

Some materials such as aluminum and tantalum are

electrochemically oxidized in order to obtain electrically

insulating layers. These methods are outside the scope

of the present overview as is electrodeposition from non-

aqueous solutions. For some metals, e.g. aluminum [1], the

use of these types of electrolytes is the only option and the

applicability of the techniqueseems currentlyverylimited. A

further detailed description of the electrodeposition process

can be found in many text books, reference works or

dedicated papers, for example [2, 3].

2.2. Advantages of electrodeposition

Similar to more classical evaporation or sputtering

techniques, electroplating allows oneto deposit a broad range

of materials on various substrates (wafer, polymer, etc either

with a seed layer or directly on semiconductor [46]).

For microelectronics related applications, electrochem-

ical deposition has the following advantages over vacuum

techniques:

room-temperature process, thus reducing problems with

thermal stress;

low cost of equipment, no vacuum required;

high rate of deposition;

artificial material structuring such as multilayers;

conformaldeposition or depositionthrough resist masks;

great reliability for high aspect ratio structures and

excellent shape fidelity.

2.3. Possible materials and their uses

Many materials can be obtained through electroplating. The

most commonly used processes for microelectronics are

limited to deposition of metals from aqueous electrolytes.Pure metals, can usually be deposited from rather

simple plating baths. Copper is probably the easiest,

most widely used and most thoroughly studied material for

electrodeposition. Its main use in microelectronics is as low-

resistivity electrical connections. Gold and silver are used

for similar applications whereas indium is deposited as a

soldering material.

Not only single-element deposits are achievable; alloys

are also possible. Alloys are obtained from electrolytes

containing salts of the individual constituents such as in

the case of tinlead soldering materials or the soft magnetic

material Permalloy, consisting of nickel and iron.

Non-metallic elementssuchas phosphorous or boroncan

be co-deposited together with metals from baths containing

specific acids (e.g. hypo-phosphoric acid for phosphorous).

Typically, this type of deposition process has a relatively low

current efficiency, i.e. it is accompanied by a considerable

formation of hydrogen gas.

Electrodeposition allows a precise control of the

material, including its composition, its crystallographic

structure, texture and grainsize. Artificial material structures

such as multi-layers, i.e. a stacking of thin layers with

different compositions, can be obtained with relative ease.

Although metals are the most easy to obtain and by far

the most widely applied, some semiconductor materials canalso be deposited, for example gallium arsenide [7]. These

techniques maybecomeimportantfor thefabrication of opto-

electronic devices, but will not be treated here as they are of

minor relevance to microelectromechanical systems.

3. Examples

3.1. Copper for interconnects

In recent years, a new process has been introduced by IBM

to reduce the electrical resistance of the interconnects in

their chip to one-third of the values possible with aluminum

and at the same time increasing the resistance againstelectromigration [8,9]. This was achieved by implementing

electrodeposition of copper in a Damascene process. The

processing flow is presented in figure 2.

102


4/8


De pos i t ion o f se e d l a ye r

D e pos i t ion o f se e d l a ye r

Pat te rning of d ie lec t r ic

Pa t t e rn ing o f r e s i s t

E l e c t rode pos i t i on

Re m ova l o f re s i s tE t c h ing o f se e d l a ye r

E le c t rode pos i t i on

Planar iza t ion

D a m as cen e T h ro u g h -m a sk

Figure 2. Comparison of processing sequence for the Damasceneprocess and through-mask plating for copper interconnects.

Figure 3. Optical micrograph of microwave inductor with anelectroplated copper spiral.

Copper is deposited on a thin seed layer on top of an

oxide layer which contains trenches and vias that connect to

lower levels. Material is deposited to a thickness of about

1 m, both inside the features and on the rest of surface.

After theplating, thewafer is polished using CMP(chemical-

mechanical polishing) to remove the excess copper.

In this application, an electrodeposition process was

introduced rather than a sputtering or evaporation step since

with these latter techniques, it would be impossible to obtain

properly filled features of only a few tenths of micrometer

across andaspect ratiosof oneormore. Theelectrodeposition

process starts at the seed layer and through the use of well

chosen additives in the electrolyte, the plating process can

be adjusted to super-fill the cavities, i.e. the growth at the

bottom of the trenchesand vias proceeds more rapidly than at

the topor theedges. Such control is notpossible in sputtering

or evaporationwhere thedepositswouldsoon start to obstruct

the features and make further filling unachievable, whichwould result in voids within the interconnects.

An alternateapproach is used for interconnects on multi-

chip modules (MCM) or microwave circuitry such as the

S h a p e & w i d t h d e t e rm i n e db y r es i s t p ro cess

Dep o s i t io n w i thu n i fo rm th ick n ess

Wid th d e te rmin edb y r es i s t p ro cess Elec t ro d ep o s i t io n

Rep ro d u c t io n o f res is t l imitat ions

M in o r in c rease d u e toseed lay er e tch

Etch u n t i l su b s t r a tee x p o s e d

M ajo r in c r ease insep ara t io n w id th

S u b tra c tiv e T h ro u g h -m ask

Figure 4. Comparison of minimal feature separation for asubtractive technique and electrodeposition.

Figure 5. SEM picture of copper mushroom structures grown ontop of nanowires (height 700 nm, diameter 130 nm).

example in figure 3. In this case, the electrodeposition is

limited to the actual conductor geometry only. The required

process flow is quite different from the Damascene-based

procedure as can be seen in figure 2. Through the application

of a resist layer, only selected areas of the seed layer are

exposed to the plating solution. The thickness of the resist

should be at least equal to the final thickness that has to be

obtained for the conductors. Since the deposition process

requires electrical conductivity of the surface, it will only

take place at these uncovered places. A fairly thick copper

layer (typically 320 m) is deposited. The resist is then

removed and the seed layer etched away. Although the

electrodeposited structures are usually also exposed duringthis etching, this is of little importance since their dimensions

(some micrometers in all directions) are many times larger

than the thickness of the seed layer (typically 30100 nm).

103


5/8

W Ruythooren et al

In addition to the general advantages of electroplating

given earlier, its application in this instance is preferable over

sputtering due to the subtractive nature of a process based on

the latter. Thecontrol over lateral dimensions andthedensity

of features that canbe obtainedbyelectrodeposition aremuch

better thanthatachievable by thenon-selectivedeposition of a

thick layer followed by an etching step (figure 4). In a similarfashion to the copper deposited for MCM interconnects,even smaller structures can be obtained. Figure 5 shows

an example of 130 nm wires deposited in resist. In this

case the deposition wasallowed to continue after the patterns

had completely filled, creating a mushroom shaped structure.This example very clearly shows the scalability of the

electrodeposition process using resist masks. Except for the

resist itself, the process is identical for both the100m sized

features forMCMapplications andfor the100 nm nanowires.

3.2. Gold

Electrodeposited goldlayers areusedon electricalconnectorsto ensure low-resistive connections and corrosion resistance

[10]. In microelectronics it is applied to bonding pads for the

same reasons. Gold can be deposited in resist patterns in a

similar fashion as copper [11].

As a related application, gold is also used as the absorber

metal in x-ray masks. Using the high shape fidelity of theplating process, masks with minimal feature sizes of 0.25m

have been demonstrated [12].

3.3. Tinlead solder

Tin-lead alloys are widely used for soldering purposes, both

for printed circuit boards and recently increasingly on thechip level. The most frequently used alloys are those close

to the eutectic composition of 40% Pb and the 95% Pb alloy

with higher melting temperature.

In microelectronics, soldering bumps are used for flip-chip bonding of circuitry integrated on wafer substrates. The

main steps of this process are briefly schematized in figure 6.Contrary to the deposition of copper discussed earlier,

the material thickness in this case is not limited to the resist

height. This can be understood by looking at the rest of

the processing sequence: the shape is not determined by the

plating step itself but by reflow of the material to ensure thespherical profile of the bumps (figure 6). Also, since quite

large volumes of material are required, the resist would haveto be impracticably thick to contain all plated material.

Vapor deposition of the tinlead material system hasbeen demonstrated by IBM and others [13] for use in the

C4 (controlled collapse chip connection) process. This

deposition is however quite difficult due to the largedifference in vapor pressures of tin and lead.

Lead can be electrodeposited quite easily, but tin needs

special care since its ions show a tendency of oxidizing

from a 2+ to a 3+ state in the solution. These Sn3+

ions are an obstacle to the plating. SnPb therefore has

traditionally been deposited from fluoroborate solutions(containing Pb(BF4)2 and Sn(BF4)2) in the printed circuit

board industry [14]. Because of environmental and safety

concerns, these fluoroborate solutions are being replaced byother types of solutions [15]. An example of the outcome of

such a successfully adopted procedure is shown in figure 7.

S u b s t r a te w i th B L Mand re s i s t mask

E lec t rop l a t ing so lde rma te r i a l

R e f l o w o f s o l d e r

Fl ip ch ip on o the rc i rcui t

F ina l geome t ry

Figure 6. Flip-chip process using electroplated soldering bumpson chip. The ball limiting metallurgy (BLM) is a specific layerstack that contains the solder material during reflow.

Figure 7. Tinlead soldering bump on a silicon substrate afterreflow.

3.4. Indium solder

Instead of a tinlead alloy, indium metal can be used as asoldering material. Actually, for certain low-temperature

applications indium is the only option since the pure

metal shows less tendency for brittle fracture and thus

improves reliability. Indium solder bumps are employed

for the flip-chip bonding of infrared detectors (embedded

in GaAs substrates) to their control circuitry (in silicon

technology). The processing sequence includes resist

patterning, electrodeposition and reflowing of the bumps

and is very similar to that presented in figure 6 for tinlead

connections.

However, as can be seen from the SEM images shown

in figure 8, the dimensions of the bumps are much smaller.

When state of the art processes are applied, the diameter forthe soldering bumps can be as small as 1025 m. Also,

since individual detectors are connected to individual parts

on the silicon chip, the density of the structures is very high

104


6/8


Figure 8. Indium solder bumps after reflow (top) and afterflip-chip bonding (bottom).

with the distance between the bumps being of the same order

as their sizes. As discussed earlier, such a density is not

possible with a subtractive technique (see figure 4).

3.5. Nickel-iron and other soft magnets

Soft magnetic micro-actuators or inductive components

(most notably tape or disk read-heads) can be deposited

electrochemically. Most of these applications require large

volumes of magnetic material and therefore electroplatingis the technique of choice because of its high deposition

rate and efficiency. The most widely employed material in

this class is the nickeliron alloy Permalloy (19% Fe, 81%

Ni). Controlling the deposition of this system to obtain

sufficiently narrow distribution of the composition is not

trivial (less then 1% deviation can change the magnetic

properties quite dramatically). Due to the interaction of

nickeland iron, the systemshows anomalous co-deposition

[16,17] characterized by the preferential deposition of the

less noble metal (in this case iron) over the more noble one

(nickel). Thus, even thoughtheelectrolyte contains ten times

less iron ions than it containsnickel ions, themain constituentof the deposit will still be iron. This makes monitoring of

the iron content very important, but also rather difficult due

to the relatively small quantities involved. However, good

results have been obtained and structures and inductances

withmagneticmaterial permeability of severalhundredshave

been demonstrated [1820].

Other soft magnetic materials based on nickel, iron or

cobalt or on any combination of these are also possible.

Amorphous soft magnetic alloys can also be obtained

through electrodeposition, for example cobalt containing

over 12% phosphorous. Although the current efficiency

of such a deposition system is typically rather low due to

the formation of hydrogen gas, (e.g. 3050%), the rate ofdeposition can still be high, since high current densities are

used [2123]. Very high relative permeabilities are reported

for the as-deposited material (e.g. 10 000 [24]).

102

103

104

lo

g

(co

un

ts/se

c)

4746454443424140

2theta

coni22 [5/6]*50

Figure 9. X-ray diffraction scan of a sample containing 50bilayers of 4 nm Co and 5 nm Cu. The two orders of satellitepeaks (indicated by the arrows) either side of the main CoCusuperlattice peak indicate a good compositional layering structurewithin the material.

3.6. Hard magnetic material

Recent publications indicate the possibility of achieving

hard magnetic material by electroplating. An ongoing

Brite/Euram project (a novel method for the synthesis of

microsize permanent magnets, BE97-4130) investigates a

system based on cobalt, platinum and tungsten. Another

electrodeposited permanent magnet material is CoNiMnP

[25].

As with the previous electrodeposition processes, these

materials can be deposited in structures and to substantial

thickness such that they can be used in micromechanical

systems or, for example, to introduce a biasing field in

sensors.

3.7. Multilayers

On top of the possibilities in simple metals or alloys, elec-

trodepositionallows oneto obtain synthetic microstructures

suchas multilayers [26]. Electrodeposited multilayerscan be

created by alternatingly exposing the substrate to the two (or

more) individual plating solutions (double-bath technique)or

by combining the two deposition systems into a single elec-

trolyte and choosing proper deposition conditions (single-

bath technique). Using the first method in which either the

sample is physically moved from one solution to the other

or the area to be plated is periodically contacted by the sep-arate solutions, virtually any combination of the materials

discussed earlier can be obtained: NiPSn [27], CoCu [28]

and CuNi [29].

For the single-bath method, the materials involved

have to have behaviors that are sufficiently distinct from

an electrochemical point of view. More precisely, their

deposition potential should be far enough apart; this is the

case for CoCu [5,28], AgCu [30], AuCo [30], CoPt

[31]. High-quality multilayers can be obtained through this

technique, as testified by the x-ray diffraction spectrum of

figure 9.

Most of these multilayers are used for their specific

electro-magnetic properties such as giant magneto resistance[32,33], with applications as magnetic field sensors [5]

while others find application as wear-resistant over-layers

(NiPSn).

105


7/8

W Ruythooren et al

Figure 10. Calculated height distribution for a pattern of 28 28small circular features.

4. Remaining challenges

Although electrochemical deposition is in principle a simple

process and electroplating for micromechanical systems has

been studied extensively in the last decade, quite a few

problems remain to be tackled.

The uniformity of deposits, i.e. their thickness and,

for alloys, their composition, can be difficult to

obtain as it is influenced not only by the electrolyte

composition but also by the pattern configuration[34] (figure 10), the electrode geometry [35] and the

electrolyte hydrodynamics [11,36, 37]. Efforts to obtain

reliable numerical models are required.

During the plating process, some components of the

solution are consumed. Of course, metal ions are

deposited but also organic additives are oxidized at the

counter electrode or incorporated in the deposit. Since

theseadditives are in some instancescrucial to theproper

operation of the plating process [8, 38], it is of prime

importance to monitor their evolution. This monitoring

is a difficult task and needs further study because the

concentrations involved are very small.

The properties of electrodeposited material can differ

from those of similar material, i.e. with the same

composition, deposited by other means or manufactured

in bulk. For example, plated copper is preferable for the

Damascene process since room-temperature annealing

decreases its electrical resistance. This effect does not

occur in sputtered structures. On the other hand, for

other materials, most notably themagnetic materials, the

properties obtained are generally worse. Improvements

are certainly possible since, as stated earlier, material

characteristics such as grain size or preferred crystal

orientation can be steered through the electrodeposition

process parameters. However, for some materials this isnot yet fully understood.

While electroplating generally is a high-efficiency

process, recyclingof theelectrolyte componentsneeds to

be further investigated to further reduce the techniques

impact on theenvironment. Recycling in a closed system

can lead to an additional cost advantage over vacuum

deposition techniques.

5. Conclusions

At present, electroplating is used in the field of

microelectronics and in the production of MEMS. Most ofthe activity is generated by the replacement of the CVD

process of AlCu with the electroplating process of Cu for

low-resistivity interconnects on chips. Another important

application is the deposition of solder bumps. Soft magnetic

materials are deposited for use in inductive components and

magnetic field sensors, while the deposition of permanent

magnets is being developed. The frequency with which

new applications for the electroplating process are surfacing,

proves that the technique is very viable, and is gaining a

foothold beside PVD and CVD techniques in the productionof microelectronics and microcomponents.

References

[1] Frazier A B and Allen M G 1997 Uses of electroplatedaluminum for the development of microstructures andmicromachining processes J. Microelectromech. Syst. 6918

[2] Roos J R, Celis J P and De Bonte M 1991 Electrodepositionof metals and alloys Processing of Metals and Alloys(Materials Science and Technology vol 15) ed R W Cahn(Weinheim: VCH) ch 11, pp 481537

[3] Celis J P, De Bonte M and Roos J R 1994 Electroplating

technology Trans. Inst. Met. Finish. 72 8993[4] Gao L J, Ma P, Novogradecz K M and Norton P R 1997Characterization of Permalloy thin films electrodepositedon Si(111) surfaces J. Appl. Phys. 81 75959

[5] Attenborough K, Boeve H, De Boeck J, Borghs G and Celis JP 1999 Electrodeposited spin valves on n-type GaAs Appl.Phys. Lett. 74 22068

[6] Cerisier M, Attenborough K, Fransaer J, Van Haesendonck Cand Celis J P 1999 Growth mode of copper filmselectrodeposited on silicon from sulfate andpyrophosphate solutions J. Electrochem. Soc. 146 2156

[7] Yang M C, Landau U and Angus J C 1992 Electrodepositionof GaAs from aqueous electrolytes J. Electrochem. Soc.139 34808

[8] Andricacos P C 1999 Copper on-chip interconnections

Interface (The Electrochemical Society) Spring 327[9] Andricacos P C, Uzoh C, Dukovic J O, Horkans J andDeligianni H 1998 Damascene copper electroplating forchip interconnections IBM J. Res. Dev. 42 56774

[10] Roos J R, Celis J P, Van Vooren W and Buelens C 1987Electroplating of hard gold structural characteristics vs.deposition parameters Proc. 11th Int. Precious MetalsInstitute Conf. (Brussels, Belgium, 1987)

[11] Kondo K, Miyazaki T and Tamura Y 1994 Shape formationof electrodeposited gold bumps J. Electrochem. Soc. 14116448

[12] Lochel B, Maciossek A, Trube J and Huber H L 1990 Pulseplating of quarter micron gold patterns on silicon x-raymasks Microelectron. Eng. 11 27982

[13] Haji-Sheikh M J, Ulz D and Campbell M 1997 The effect of

varying the Cu/Au ratio on the thermal-cycle fatigue lifeof 95/5 PbSn bumps IEEE Trans. Components, Packag.Manufact. Technol. A 20 491

[14] Celis J P, Roos J R and Pierkaska A 1990 Electrodepositedcomposite tin-lead coatings Trans. Inst. Met. Finish. 681248

[15] Datta M et al 1995 Electrochemical fabrication ofmechanically robust PbSn C4 interconnectionsJ. Electrochem. Soc. 142 377985

[16] Matlosz M 1993 Competitive adsorption effects in theelectrodeposition of ironnickel alloys J. Electrochem.Soc. 140 22729

[17] Sasaki K Y and Talbot J B 1995 Electrodeposition of binaryiron-group alloys J. Electrochem. Soc. 142 77582

[18] Lochel B and Maciossek A 1996 Electrodeposited magnetic

alloys for surface micromachining J. Electrochem. Soc.143 33438

[19] Ahn C H and Allen M G 1994 A new toroidal-meander typeintegrated inductor with a multilevel meander magneticcore IEEE Trans. Magn. 30 739

106


8/8


[20] Park J Y and Allen M G 1997 High current integratedmicroinductors and microtransformers using lowtemperature fabrication processes Microelectron. Int. 14 8

[21] Brenner A 1950 Electrodeposition of alloys of phosphoruswith nickel or cobalt J. Res. NBS 44 10922

[22] Riveiro J M and Rivero G 1981 Multilayered magneticamorphous CoP films IEEE Trans. Magn. 17 30824

[23] Fukunaka Y, Aikawa S and Asaki Z 1994 Fundamental studyon electrodeposition of Co and CoP films J. Electrochem.Soc. 141 178391

[24] Lanotte L, Matteazzi P and Tagliaferri V 1990 Structuralorder and magnetism of CoP alloys produced byelectrochemical deposition Mater. Sci. Technol. 6 14650

[25] Liakopoulos T M, Wenjin Z and Ahn C H 1996Micromachined thick permanent magnet arrays on siliconwafers IEEE Trans. Magn. 32 51546

[26] Haseeb A, Blanpain B, Wouters G, Celis J P and Roos J R1993 Electrochemical deposition: a method for theproduction of artificially structured materials Mater. Sci.Eng. A 168 13740

[27] Milis S and Celis J P 1996 Investigation of the properties ofNiP/Sn multilayers using a mechanical microprobe ThinSolid Films 288 20211

[28] Blondel A, Doudin B and Ansermet J P 1997 Comparativestudy of the magnetoresistance of electrodeposited Co/Cumultilayered nanowires made by single and dual bathtechniques J. Magn. Magn. Mater. 165 347

[29] Celis J P, Haseeb A and Roos J R 1992 Electrodeposition ofCu/Ni compositionally modulated multilayers by thedual-plating bath technique Trans. Inst. Met. Finish. 701238

[30] Celis J P, Cavallotti P, Machado da Silva J and Zielonka A1998 The future for electroplating electromagneticmaterials in microelectronics Trans. Inst. Met. Finish. 7616370

[31] Jyoko Y, Kashiwabara S, Hayashi Y and Schwarzacher W1999 Preparation of perpendicular magnetization Co/Ptnanostructures by electrodeposition Electrochem. SolidState Lett. 2 679

[32] Lenczowski S K J, Schoenenberger C, Gijs M A M and deJonge W J M 1995 Giant magnetoresistance ofelectrodeposited Co/Cu multilayers J. Magn. Magn.Mater. 148 45565

[33] Schwarzacher W and Lashmore D S 1996 Giantmagnetoresistance in electrodeposited films IEEE Trans.Magn. 32 313353

[34] Dukovic J O 1993 Feature-scale simulation ofresist-patterned electrodeposition IBM J. Res. Dev. 3712541

[35] Mehdizadeh S, Dukovic J, Andricacos P C, Romankiw L Tand Cheh H Y 1990 Optimization of electrodeposituniformity by the use of auxiliary electrodesJ. Electrochem. Soc. 137 11017

[36] Kondo K, Fukui K, Yokoyama M and Shinohara K 1997Shape evolution of electrodeposited copper bumps withhigh Peclet numbers J. Electrochem. Soc. 144 46670

[37] Pozrikidis C 1994 Shear flow over a plane wall with anaxisymmetric cavity or a circular orifice offinite thicknessPhys. Fluids 6 6879

[38] Kelly J J 1998 Copper deposition in the presence ofpolyethylene glycol. II. Electrochemical impedancespectroscopy J. Electrochem. Soc. 145 347781

107

Documents

Electrodeposition for Synthesis of Microsystems