Electrodeposition Science and Technology in the Last Quarter of the Twentieth Century

Journal of The Electrochemical Society, 149 (3) S9-S20 (2002) S9

D

Electrodeposition Science and Technology in the Last Quarter ofthe Twentieth CenturyD. Landolt*

Materials Department, LMCH, Swiss Federal Institute of Technology Lausanne, CH-1015 Lausanne EPFL, Switzerland

© 2002 The Electrochemical Society. All rights reserved.

An ECS Centennial Series Article

On the occasion of the fiftieth anniversary of the ElectrochemicalSociety in 1952, William Blum published a review on electrodepo-sition in which he regretted that its theoretical basis was largelyinsufficient and “the great advances that have been made in elec-trodeposition are therefore largely empirical”.1 Twenty-five yearslater, Mc Kinney and Faust2 published a follow up report in whichthey presented a detailed account of many technological advancesachieved during that period. From today’s perspective, it is interest-ing to note that the authors mentioned electronics applications justbriefly, and they devoted only a single paragraph to fundamentals.Apparently, electrodeposition was still perceived as a mostly empir-ical technology serving primarily for surface finishing and corrosionprotection. Of course, electrochemists and electrochemical engi-neers had studied the scientific principles governing plating process-es for many years before, and an impressive amount of knowledgewas available. However, it would seem that this knowledge had notyet made a decisive industrial impact. At present, the situation hasdramatically changed. Some of the most advanced experimental andtheoretical modeling work in electrochemical metal deposition anddissolution is performed in industrial research laboratories and elec-trodeposition and dissolution processes have found a firm place inelectronic device fabrication.3

Electrodeposition as an industrial activity has been practiced forover 150 years, one of the first applications having been the electro-forming of printing plates.4 Subsequently, electroplating gainedmajor importance as a cheap and versatile surface finishing processfor decorative applications and for corrosion and wear protection.Typical examples include chromium plated automobile trimmings,gold plated brass jewelry, nickel-plated steel, gold plated electricalcontacts or hard chromium plated bearings. Traditionally, the auto-motive industry has been a big user of electroplating (Fig. 1).5 Whilethis industry used large integrated plating facilities, much of the plat-ing for other applications was performed by specialized shops of rel-atively small size. Indeed, a characteristic of the traditional platingindustry has been its fragmentation to which several factors mayhave contributed. On one hand, before strict environmental regula-tions came into effect, the investment needed to start a commercial

* Electrochemical Society Fellow.

address. Redistribution subject to EC177.20.132.35ownloaded on 2014-04-24 to IP

plating activity was relatively modest. Furthermore, the availabilityof fully formulated commercial plating electrolytes reduced thedevelopment efforts needed to start production. Success of a platingoperation then depended mostly on the skill and ingenuity of theelectroplater. Because electroplating depended largely on empiricalknow-how and involved handling of aggressive chemicals and solu-tions, it did not fit well into mechanical production lines and manymanufacturing industries preferred to subcontract plating operationsto specialists. At the end of the twentieth century though, the elec-troplating industry is undergoing fundamental changes, which arelikely to continue in the future.

On one hand, due to ever more severe regulations concerning theemission and final disposal of heavy metal ions and chemicals, theelectroplating industry today needs advanced water recycling andpurification schemes that drastically increase investment cost.Environmental pressures also require that certain established platingprocesses be substituted by more environment friendly technologiesthat often require closer control and better scientific understanding.A well-known example is the replacement of cadmium coatings forcorrosion protection by other metal or alloy coatings. Hexavalentchromium widely used for chromatation of zinc and in chromiumplating has come under attack, as well as lead containing electro-plated solder alloys. On objects that enter into contact with thehuman skin, notably jewelry and watches, traditional nickel barriercoatings must be replaced, because nickel causes allergic reactionsin some people. A second driving force for change is the emergenceof electrodeposition as a large scale manufacturing process involv-ing fully automated high throughput installations. Examples arefound in the steel industry and in the electronics manufacturingindustry. In these and other applications electrochemical processescompete with dry processes and to be competitive they must exhib-it the same degree of reliability and control. Interestingly, the prin-ciples governing scale up and scale down of electrodepositionprocesses are perhaps better understood at present than those ofcompeting plasma deposition processes. Finally, the general trendtowards globalization modifies the market conditions for the elec-troplating industry and creates new types of partnerships betweenthe manufacturing companies and their subcontractors with everhigher demands on technical competence, cost effectiveness andproduct reliabilitiy.

Figure 1. Corrosion of autobody panelshas been drastically reduced by the use ofzinc and zinc alloy coated steel. Fullyautomated plating lines have beendesigned to produce coated steel sheet ina fast, continuous process. The figureshows a high throughput reel-to-reel zincplating installation where the steel stripmoves at a speed of up to 137 m/min.10

) unless CC License in place (see abstract). ecsdl.org/site/terms_useS terms of use (see

http://ecsdl.org/site/terms_use

S10 Journal of The Electrochemical Society, 149 (3) S9-S20 (2002)

D

The period covered by this report coincides with the emergenceof information technology, the first personal computers appearing onthe market in the late 1970s and early 1980s. They were made pos-sible by the invention of cheap and powerful microprocessors basedon integrated circuit technology and of low cost data storage andretrieval systems. The dramatic pace of progress in information tech-nology and its enormous impact on human society is commonknowledge. Perhaps not so well known is the fact that electrodepo-sition and related electrochemical processes have had a decisiveimpact on the development of computer technology.6 The presentreview will retrace significant scientific and technical achievementsin electrodeposition science and technology made during the lastpart of the twentieth century, without any claim to completeness.During this period electroplating, historically considered a “blackart”.7 has evolved into an exciting field of high technology withnumerous new applications and challenges in micro and nanotech-nology. Fundamental research carried out by electrochemists, elec-trochemical engineers and materials scientists made this develop-ment possible. Continuing research will permit to sustain it in thefuture.

Electrodeposition Technology Decorative and functional coatings.—Traditional applications of

electrodeposition include decorative and functional coatings, elec-troforming of three-dimensional objects and plating of printed cir-cuit boards. Many metal winning and refining processes are basedon electrodeposition. These and other applications were thoroughlyreviewed by McKinney and Faust.2 The fourth edition of “ModernElectroplating” published recently under the auspices of theElectrodeposition Division of ECS gives a comprehensive overviewof the current practice of electrodeposition and electroless deposi-tion of different metals and alloys.8

Decorative chromium coatings have been produced by electrode-position for many years. Traditionally, the automobile industry hasbeen the largest user, but due to changing fashion trends the impor-tance of decorative chromium plating has diminished in this indus-try.5 On the other hand, electroplating has found new applications inthe field of corrosion protection of automobile bodies. Starting in the1970s, the automobile industry introduced zinc coated steel sheetsfor body panels replacing plain steel. In response to the new demand,the steel industry developed high throughput continuous reel to reelplating installations for the production of coated steel sheet.9,10

Metallic Zn or Zn-Ni alloys are plated on one or on both sides of thesteel sheet.5 Apparently, the introduction of Zn coated steel wasdelayed somewhat by the fact that the salt spray corrosion test whichhas been widely used in industrial corrosion testing, initially indi-cated poorer performance of Zn coated than untreated steel.11 Morerealistic tests had to be developed to get better agreement with fieldexperience which showed that the use of zinc coated steel panelsdrastically reduced perforation of automobile body panels by rust.

Hard chromium coatings plated from chromic acid electrolytesare extensively used for wear protection of bearings and othermachine elements. Since hexavalent chromium is believed to be car-cinogenic, alternatives have been sought in recent years. Sputterdeposited ceramic coatings are a possible alternative for many tribo-logical applications. Electroless nickel-phosphorous coatings arealso widely used for corrosion and wear protection. Electroplatednickel-tungsten alloys or chromium plated from trivalent chromiumelectrolytes have been investigated as alternatives to hard chromium,but as of now have not had a major commercial impact. The auto-mobile industry uses electroplated Ni/SiC dispersion coatings forwear protection of cylinder linings and piston rings in car engines.These materials were originally developed in Germany for theWankel motor and they were introduced in car engines between1978 and 1980 in Europe and Japan.12 Electroless Ni-P/SiC com-posite coatings find many applications in different kinds of machinessimilarly as electroplated Ni/SiC coatings. Self-lubricating metal


matrix composite coatings such as Ni-P/PTFE fabricated by electro-less plating are used in the mechanical and process industries forvalves, injection molds or sliding contacts.13

Electrodeposited noble metal coatings made of gold, silver, plat-inum, rhodium and their alloys are extensively used for decorativepurposes in the watch and jewelry industries. Gold and gold alloycoatings also serve to avoid corrosion and oxidation of electricalcontacts. In the late 1970s and early 1980s the price of goldincreased manifold. This led to great efforts to reduce the thicknessof gold coatings in electrical contacts or to replace gold by othermaterials such as silver-palladium and nickel-palladium alloys. Inrecent years, the price of gold has substantially decreased while thatof palladium went up and is now almost twice that of gold. Not sur-prisingly, the economic motivation for replacing gold with palladi-um alloys has vanished.

It is well known that only a limited number of metals and alloyscan be plated from aqueous solution. The use of organic solvents ormolten salts, in principle, should permit to plate a larger number ofmetals. In Europe a process for fabricating aluminum coatings byelectrodeposition from aluminum alkyl complexes in toluene hasbeen brought to an industrial scale.14 Because of technological dif-ficulties and safety issues the process has not found wider applica-tion so far. To the authors knowledge no other processes for elec-trodeposition of coatings from organic solvents or molten salts havegained industrial importance.

Electronics manufacturing.—One of the first applications ofelectroplating and electroless plating in the electronics industryinvolved the fabrication of printed circuit boards and electrical con-tacts. Impressive progress recently achieved in these fields includefast speed (several meters per minute) reel to reel plating of electri-cal contacts and high throughput processing of lead frames. In the1980s and 1990s electrodeposition and related technologies havefound new applications in electronics manufacturing, notably inpackaging and magnetic recording. Several recent overviews discussspecific aspects of electrochemical technology in electronics andmicrosystems manufacturing and the reader is referred to these formore detailed information.3,6,15-23 Progress in the field is also docu-mented in several ECS Proceedings Volumes.24-26 Compared tocompeting vapor phase technologies, electrodeposition and electro-less deposition offer several advantages for device fabrication. Firstof all, electrochemical processes are relatively cheap and they are

Figure 2. Magnetic recording heads fabricated by through mask electrode-position were introduced in the late 1970s. Continuing miniaturization ofelectrodeposited magnetic heads has permitted an astonishing increase instorage density. The figure shows an inductive head fabricated by electrode-position comprising a Permalloy horseshoe magnet and a copper coil. Thesize of the entire head is comparable to the diameter of the human hair shownschematically for comparison.6




D

Figure 3. Interconnects are multilevel structures which carry electrical sig-nals between chips in multichip modules. Copper plating is an importanttechnology for the fabrication of interconnects in electronic packaging. TheSEM shows a via stack with 11 levels. The experimental structure was fabri-cated by through mask plating of copper in a number of subsequent steps. Forbetter visibility the dielectric was removed prior to taking the picture.27

highly selective in that metal is deposited only on those places whereit is needed. Electrodeposition has a better throwing power thanphysical vapor deposition (PVD) and it allows one to produce highaspect ratio structures with good precision. Also, the laws governingscaling up and scaling down of electrochemical processes are rela-tively well understood. While electrodeposition requires water treat-ment and recycling installations, the cost of these is not a critical fac-tor for high-throughput production plants.

Of the many applications electroplating has found in electronics,through mask plating of thin film magnetic heads has perhaps hadthe highest impact. Development of electroplated thin film magnet-ic heads started at IBM in the 1960s. The process, which included anelectroplated permalloy (81Ni-19Fe) horse shoe magnet and electro-plated copper coils was introduced into production in 1979 (Fig.2).6,17 Continuing progress achieved in through mask plating tech-nology has led to an increase in the magnetic storage density by oneorder of magnitude every eight years.6 Lately, the rate of growth hasaccelerated even further due to the development of new magneticalloys and electroplated combined inductive-resistive heads.21

Progress in through mask plating of magnetic heads has significant-ly contributed to the fast paced improvement of the performance ofmodern computers.16

Packaging of advanced electronic systems constitutes anotherimportant application of electroplating. Packaging serves for signaland power transmission, heat dissipation and for protection againstmechanical or chemical damage. A typical packaging hierarchy mayinclude chips, chip modules and printed circuit boards. Advancedcomputers contain multilevel chip modules, which are connected by


fine wiring located on the top of the transistor circuitry of logic ormemory chips (Fig. 3).27 In 1997 IBM announced that it would useelectroplated copper wiring in advanced IC chips, replacing thevapor deposited aluminum used previously. Compared to aluminum,copper has a higher conductivity and a better resistance to deteriora-tion by electric migration at high current densities. An additionaladvantage is the easier scalability of electroplating. The electro-chemical manufacturing process relies on the so-called damasceneplating technology.28,29 Contrary to through mask plating, wheremetal is selectively deposited into the features of a patterned pho-toresist, in damascene plating pattern generation precedes the appli-cation of a conducting seed layer. Plating is performed on the entiresurface and unwanted metal is subsequently removed by chemicalmechanical planarization (CMP). Damascene plating permits one toplate simultaneously the via holes and the overlying line trenches(dual damascene plating), making it well suited for interconnect fab-rication on an industrial scale. Barrier layer between the seed layerand the insulator prevent unwanted interactions.

Chips must be attached to a substrate. Different technologiescompete in this field such as wire bonding, tape bonding or con-trolled collapse chip connection (4C). The latter technology uses sol-der bumps, which permit short interconnection distances for fastsignal response and low inductance. In the mid 1990s an electro-chemical route for producing lead-tin alloy solder bumps for inter-connects was developed.30 The process also includes electroplatingof tin-lead alloys as well as a controlled etching step of the seed lay-ers in order to achieve the desired shape of the bumps. Compared tothe earlier PVD technology, electroplating presents not only eco-nomic advantages but it is also considered to be a more environmentfriendly technology.28 The reason is that in sputter deposition metalsdeposit indiscriminately on the reactor walls, whereas in electrode-position metals deposit only on those spots where they are needed.This reduces the need for cleaning and waste material disposal.

Microelectromechanical systems.—Electroforming of three-dimensional structures has been one of the oldest applications ofelectrodeposition.4 Recent years have seen the emergence of elec-trochemical fabrication technologies for micro-electromechanicalsystems (MEMS). For these applications electrochemical throughmask plating offers high precision and the possibility to achieve highaspect ratios. The technology has been pioneered in Germany start-ing in the early 1980s and has become known under the name LIGA,which stands for the German “Lithography, Galvanoformung undAbformung” (Fig. 4). LIGA is a through mask plating process usingthick resist masks with high aspect ratio features. Originally, theresists were patterned by X-ray lithography. Through mask platingwas performed to produce metallic masters for use in injectionmolding of precision polymer parts. More recently, high aspect ratiothrough mask electroplating has been applied to the fabrication of X-ray masks, sensors and tiny turbines among other. Overviews of theLIGA process and similar processes are available,31,32 as well as adiscussion of early experimental work on X-Ray lithography per-formed in the U.S.6 At the time of this writing the indistrial impactof the LIGA process is still limited, but as the technology maturesone may expect that many uses will rapidly develop. Resists haverecently been developed for LIGA applications, which permit theirradiation with much cheaper UV instead of synchrotron radiation.They allow fabrication of high aspect ratio structures by several sub-sequent irradiation steps.32 At present, predominantly nickel is usedin the LIGA process, but Ni-Fe alloys and copper have also beenplated. In the US a complete thin film magnetic micro motor wasrecently built by through mask electroplating with the aim to demon-strate the outstanding capabilities of this technology.6

Electrochemical Phase Formation The kinetics and mechanisms of single metal deposition were

studied extensively in the 1950s and 1960s and reaction paths formany systems were established.33,34 Most metal deposition and dis-




solution reactions proceed through several consecutive steps involv-ing adsorbed reaction intermediates that are often partiallyhydrolyzed. Complexing species play an important role for the dis-charge mechanism because they change the thermodynamic equilib-rium and the rate determining step of the charge transfer reaction atthe electrode surface.33,35 These early investigations laid the foun-dations for later modeling studies of alloy deposition and additiveeffects and they provide a solid basis for current studies of electro-chemical phase formation using scanning probe techniques. The sci-entific study of electrochemical phase formation developed inEurope some 50 years ago.36 Of particular interest was the develop-ment of a method for the fabrication of almost defect free singlecrystal electrodes by electrodeposition. It permitted to perform ele-gant experiments on the energetics of 2D nucleation and to study therole of crystal defects.37 Many authors studied three dimensionalnucleation using potentiostatic transient techniques. Formation andgrowth of three dimensional nuclei on a foreign substrate producecharacteristic overshoots in the current transients and their shape canbe compared to predictions of theoretical nucleation models. Arecent summary of results obtained with this approach is found inRef. 38. Underpotential deposition (UPD) is another important topicin electrochemical phase formation that has found much attention.UPD implies the formation of a metal monolayer on a foreign sub-strate at potentials positive to the reversible potential calculatedfrom the Nernst equation. Typically, UPD is observed when thebinding energy between the depositing atoms and the substrateexceeds that between the atoms of the deposit material. The phe-nomenon was observed for the first time in the 1960s.39 The studyof UPD became quite popular in the 1970s and 1980s, when severalgroups used single crystal substrates in combination with linearsweep voltammetry and other techniques for quantifying UPD phe-nomena. The use of single crystal substrates led to the discovery ofthe formation of UPD superlattice structures.40 Furthermore, it wasfound that the nature of the UPD layers depended on the anions pre-sent. For more details the reader is referred to recent reviews.41,42

Electrochemical phase formation has been most widely studied onmetal substrates, but electrodeposition on semiconductors, notablysilicon, is also of great interest, both from a theoretical and from anindustrial point of view. The subject has recently been reviewed andthree charge transfer mechanisms have been identified, which canlead to electrodeposition of a metal on an n-type semiconductor.43

They involve an electron transfer from the conduction band to themetal ions in solution, the injection of holes into the valence band oran electron transfer from surface states. For a given metal deposit thedominating mechanism depends among other on the prevailingredox potential which can be adjusted by complexing ions.

The invention of the scanning tunneling microscope (STM)44

and of the atomic force microscope (AFM)45 in the early 1980smarked a decisive step forward in the study and understanding of theinitial steps of electrochemical phase formation. The STM openedup entirely new possibilities for the observation of the structure ofmetal-electrolyte interfaces on the microscopic and atomic scales(Fig. 5). The first in situ STM studies of electrode surfaces werepublished in 1986-1988.46-48 In subsequent years scanning probetechniques became important tools for the investigation of adsorp-tion on metal surfaces and for electrochemical phase formation.49-51

Using single crystals, reconstruction of metal surfaces in solutioncould be imaged in situ with atomic resolution. For example, theatomic structure of a gold single crystal electrode was found todepend on the applied potential and on the type of anions present.52

The STM also confirmed the existence of super lattice structuresdeduced previously from indirect techniques. The STM and AFMprovided new insight into the role of step and kink sites for electro-chemical phase formation and growth. For example, it was foundthat after formation of an initial UPD layer copper atoms depositpreferentially on monatomic steps of a gold single crystal surface,

address. Redistribution subject to EC177.20.132.35Downloaded on 2014-04-24 to IP

whereas deposition of silver on the same gold crystal led to a Frank-van der Merve type epitaxial growth up to 10 monolayers.52 The dif-ference was attributed to the fact that the lattice mismatch betweencopper and gold is much larger than between silver and gold. It hasbeen known for many years that step and kink sites as well as bulkcrystal defects, notably screw dislocations, play an important rolefor nucleation and growth of electrodeposits at small overvoltage.53

Using the AFM, copper deposition on a screw dislocation on a (111)single crystal substrate could be followed in situ.54 The literature onthe study of metal electrodes using the STM has been reviewed cov-ering publications up to 1998.55 Other in situ methods for character-izing electrode surfaces are described in Ref. 56. The scanning probetechniques in conjunction with other in situ methods have led to animpressive amount of knowledge concerning adsorption phenomenaand electrochemical phase formation on the nanometer scale.

To produce an image by STM or AFM the surface viewed mustbe scanned and this is a relatively slow process. For this reason theSTM and AFM techniques are suitable only for studying relativelyslow electrodeposition phenomena. In spite of this limitation, inter-esting information on step motion and surface diffusion has beenobtained recently, by analyzing the fuzziness of growth steps inSTM pictures.57 The STM can also serve as a tool for the local ini-tiation of electrochemical phase formation. Local metal depositioncan for example be initiated by producing a surface defect with theSTM.58 In another method metal atoms are first deposited on anSTM tip, then the tip is approached to the polarized substrate surfacein order to initiate a transfer of atoms from the tip to the substratesurface. Using this technique arrays of well-defined copper or palla-dium clusters were produced.59,60 Similarly, cobalt clusters wereproduced by anodically dissolving the metal from an STM tip posi-tioned close to the substrate.61

Several groups used the STM or the AFM to study the effect ofadditives on the formation and movement of atomic steps during thegrowth of electrodeposits. In an early study with copper it was foundthat benzotriazole (BTA) did not affect the nucleation, but inhibitedgrowth of certain planes.62 The observed influence of BTA andthiourea on the growth morphology of copper deposits was attrib-uted to their effect on surface diffusion.51,63 The role of substratestructure was also investigated and it was found that inhibiting addi-tives adsorbed preferentially at defect sites.64 Most commercial plat-

Figure 4. The LIGA process for microelectroforming of metallic componentsby electrodeposition was developed in the 1980s. Originally, synchrotronradiation was used to irradiate PMMA masks suitable for the fabrication ofhigh aspect ratio structures. More recently, UV sensitive resist materials havebecome available, which permit similar results without the need for synchro-tron radiation. The figure shows an microturbine made by electrodepositionof nickel using the LIGA process. The diameter of the turbine is ~0.25 mm.Also shown is a glass fiber speed monitor.31




ing electrolytes contain not one but several additives. For example,many copper plating solutions contain small quantities of chlorideion together with two or three organic additives having differentfunctions.51,65,66 These additives act in conjunction through adsorp-tion processes that inhibit or accelerate electrochemical reactionsteps. A strong synergistic effect between polyethylene glycol andchloride ion was recently reported, copper deposition being inhibit-ed only when both additives were present.66 Similarly, during pulseplating of copper-cobalt alloys it was found that a surfactant (SDS)added alone had a very different effect on the deposit morphologyand the current efficiency than when it was added together with sac-charin, a stress relieving agent.67 Different mechanisms by whichadditives may influence the electrochemical reactions at the elec-trode-solution interface have been discussed in a recent review froma chemical point of view.68 The author distinguishes blocking addi-tives, complex-forming additives, ion pairing additives, surfactantsand insoluble film forming additives. Acid-base concepts have alsobeen considered.69 Using scanning probe techniques the evolution ofdeposit morphology in presence and absence of additives was stud-ied with the aim to find scaling laws permitting to relate atomisticgrowth mechanisms to macroscopic models.51,63,70 Only a limitednumber of additives have been studied so far with scanning probetechniques and the different interaction mechanisms between addi-tives are not yet well understood. As scanning probe and other sen-sitive in situ techniques become more widely used, one may expectthat the scientific understanding of how synergistic and antagonisticeffects of additives influence electrochemical phase formation willsignificantly improve. This could open the prospect of formulatingplating electrolytes on a more rational basis in the future.

Electrochemical Engineering Aspects of Electrodeposition Electrochemical engineering concerns the application of the prin-

ciples of thermodynamics, kinetics, mass transport and current dis-tribution to the scaling, optimization and control of electrochemical

Figure 5. The invention of the scanning tunneling microscope in the 1980sopened exciting new possibilities for observation on an atomic scale of elec-trode surfaces and electrodeposition phenomena. The figure shows coppernuclei on a gold [111] surface obtained by electrodeposition from an acid sul-fate solution by stepping the potential. The figure suggests that, under theconditions of the experiment, copper nuclei are formed exclusively at themonoatomic height steps on the substrate surface.52


processes. Mastering these subjects has been crucial for the success-ful introduction of electrodeposition technology in electronics man-ufacturing. The theoretical foundations of current distribution andmass transport in electrochemical systems were laid in the 1940s and1950s. Since then electrochemical engineering has developed into arecognized branch of electrochemistry71 and excellent textesdescribing the underlying principles are available.72,73 In the yearscovered by this report a large number of studies adressed problemsof current distribution and mass transport in electrodeposition.

Current distribution is of critical importance for the design ofplating cells and for the operation of industrial plating processes. Itdetermines the thickness and uniformity of an electrodeposited coat-ing and the shape evolution of the cathode in electroforming, level-ing and superfilling. In alloy plating the distribution of the partialcurrent densities on the cathode determines the uniformity of thechemical composition of the deposits. The current distribution pre-vailing on the cathode during an electrodeposition process is theresult of several parameters such as cell geometry (primary currentdistribution), charge transfer kinetics (secondary current distribu-tion) and mass transport conditions (tertiary current distribution).Numerical simulations involving all these effects are quite involvedand require a detailed knowledge of prevailing hydrodynamic con-ditions. For this reason complete current distribution calculationshave been performed for a limited number of electrochemical sys-tems only, the rotating disk electrode being the classical example.74

For cell design purposes it is often sufficient to consider the limitingcases of primary current distribution or entirely mass transport con-trolled current distribution. Using these principles, a number of newdesigns for electroplating cells were developed in recent years. Theyinclude the rotating cylinder Hull cell,75 the uniform injection cell,76

the recessed rotating disk electrode77 and different types of jet cellswith submersed or emerged electrolyte jets.78-81 The paddle cell82,83

developed for through mask plating of wafers on a laboratory orindustrial scale offers a uniform current distribution over the entiresurface. Mass transport conditions are fairly uniform although themass transport rate may vary periodically with time as the paddlemoves back and forth.84 Through hole plating poses difficult currentdistribution problems because the metal must be deposited uniform-ly into a high aspect ratio geometry. The current distribution inthrough hole plating using direct current85,86 and pulse current87,88

has been studied extensively. Another current distribution problemin electronics concerns the terminal effect that may occur when plat-ing seed layers on an insulating substrate. In these applications theelectrode resistance is not always negligible and potential gradientsmay develop in the cathode parallel to the metal-electrolyte inter-face. As a consequence, more material is plated in the vicinity of theelectrical contact to the cathode than far from it. Dimensionless cri-teria have been proposed for estimating the importance of thiseffect.89

In through mask plating different scales must be taken intoaccount with respect to current distribution and mass transport; theworkpiece scale, the pattern scale and the feature scale.90 At theworkpiece scale the primary current distribution depends essentiallyon the overall cell geometry. In some cases it can be improved byusing auxiliary electrodes.91 On the pattern scale, the current distri-bution between the individual features forming the pattern dependsstrongly on their spacing and their geometry.92,93 Generally, the cur-rent density on a given feature tends to be higher when it is spacedfarther away from a neighboring feature. The “active area density”which is the ratio between the area of the features and the geometri-cal area of the wafer has been found a useful concept for describingthe current distribution on patterned surfaces.92 On the feature scale,the current distribution determines the shape of the growth front inthrough mask and in damascene plating and the shape of the disso-lution front in electrochemical micromachining.90,94-96 Dependingon experimental conditions, the current distribution on the feature




D

scale is governed by the concentration field of the reacting speciesand/or by the potential field in the feature. Convection in cavitiesexposed to fluid flow has been theoretically modeled and it wasshown that it can lead to asymetric concentration fields.97,98 In elec-troplating one controls the current distribution on the feature scalemost often by using suitable additives.90

The effect of additives on the current distribution on micropro-files and the mechanism of cathodic leveling has been studied by anumber of authors as early as the 1950s.97,98 The topic has foundrenewed interest in the 1990s because of its importance in electro-chemical microfabrication and because numerical methods such asfinite element and finite boundary element methods became avail-able that facilitated quantitative modeling of shape changes. A quiteunique feature of electroplating is that under certain conditions moremetal is deposited into recesses than on protruding parts of a micro-profile. This permits to achieve leveling of rough surfaces bycathodic metal deposition. The same behavior can be used to selec-tively fill small cavities on a patterned surface in Damascene plating(Fig. 6). It is generally accepted that leveling requires an inhibitingadditive which is consumed at the cathode under mass transport con-trol. Since recesses in a surface are less accessible than protrusions,metal deposition is less inhibited there and as a consequence the local deposition rate is higher than on the rest of the surface. Several groups have proposed quantitative models based on thisconcept.99-101 Leveling experiments with nickel using model pro-files agreed well with theoretical predictions and confiremd that therate of leveling depends on three dimensionless quantities, whichcharacterize the ratio between mass transport and reaction rate of theadditive, its reaction kinetics and its adsorption properties.102 Theshape evolution during electrodeposition of copper bumps has beenstudied both theoretically and an experimentally.103,104 The Pecletnumber and the resist angle were found to be the most critical quan-tities determining the resulting shape. Superfilling in Damasceneplating has been modeled assuming that the additive reacts underdiffusion control and that the metal deposition is activation con-trolled.90,105 By optimizing the reaction conditions in presence ofadditives it was possible to achieve a flat growth front in the fea-tures. More recently, a different model for superfilling of narrowdeep cavities was proposed, which includes not only inhibition butalso an accelerating effect of additives, the extent of which wasassumed to depend on curvature.106,107

The use of pulse current or pulse reverse current provides an ele-gant way to influence the current distribution in electrodeposi-tion.108 In the absence of significant mass transport effects, the cur-rent distribution in pulse plating is less uniform than in dc platingbecause of the lower Wagner number. On the other hand, platingunder conditions where nonsteady state mass transport controls therate of deposition can lead to a more uniform current distributioncompared to dc plating.109 Using a rotating disk electrode it wasshown that with pulse reverse current a more homogenous currentdistribution can be achieved than with simple pulse current, becauseconditions can be chosen such that during the anodic cycle the metaldissolves preferentially from the outer part of the disk.110 By thesame mechanism, pulse-reverse current was found to be a viablemethod for improving the deposit uniformity in through hole plat-ing.86,111

Electrodeposited Materials Structure and properties of electrodeposits.—Materials science

deals with the relationships between processing, structure and prop-erties of materials. Materials science aspects of electrodepositionhave been the subject of several recent ECS symposia.112-114 Indeed,a wide range of metals and alloys with different structure and com-position can be electrodeposited. Electrodeposition normally takesplace far from equilibrium, and therefore microstructures and alloycompositions can be achieved that are not accessible by convention-al metallurgical means (Fig. 7). For example, X-ray amorphous


alloys115-117 or nanocrystalline metals and alloys118-120 have beenobtained by electrodeposition. Another particularity of electrodepo-sition is that small changes in process conditions, for example thepresence or not of tiny amounts of additives or of complexingagents, can have enormous consequences for the resultingmicrostructure and composition of the deposited materials and hencefor their properties. If not controlled, this behavior can lead to repro-ducibility problems in laboratory experiments and in production.Careful monitoring of electrolyte composition therefore is a criticalfactor for success in industrial electrodeposition.121 On the otherhand, if processing conditions are rigorously controlled electrodepo-sition offers the possibility to fabricate materials with tailor madestructure and properties.113 Frequently, internal stress develops inelectrodeposits. Several factors may contribute to this, such as mis-match between substrate and deposit, grain coalescence duringgrowth and incorporation of electrolyte species or of hydrogen.122-

125 Internal stress can cause cracking of deposits or loss of adhesion.A good review of different methods for measuring stress in elec-trodeposits has been published in the early 1970s.126 Several morerecent papers discuss methods for in situ measurement of internalstress during electrodeposition including X-ray diffraction,127,128

bending of thin film substrates,129,130 strain gauge,131 and the use ofthe electrochemical quartz crystal microbalance.132

Copper is probably the most widely studied metal in electrode-position, because of its industrial importance and because its nobleequilibrium potential makes it well suited for fundamental studieswithout interference of hydrogen formation. The 1990s saw an enor-mous increase in the number of studies on copper electrodepositionstimulated by its use in electronics packaging. Much knowledgetherefore is available on the mechanism of copper deposition andhow deposition conditions affect deposit structure and properties. Asurvey of early work on the electrocrystallization of copper can befound in Ref. 133. Most of the research in the 1960s focussed on thestudy of interfacial kinetics and transient phenomena. An importantresult was the establishment of the reaction mechanism of the cop-per electrode.134 Copper deposition and dissolution in sulfate solu-tion was shown to involve two consecutive charge transfer steps, thecopper(I)-copper(II) step being rate-limiting. More recent studiesdeal with the interactions of additives with the monovalent copperintermediate.135,136 The role of inhibition and of applied currentdensity on deposit morphology has been studied extensively.Increasing inhibition and/or increasing current density was found to

Figure 6. Electrodeposition is unique in that it permits, under certain condi-tions, the preferential deposition of material into the recesses of a surface.The behavior is used to achieve leveling in plating of coatings and superfill-ing in damascene plating. The figure illustrates filling of a hemisphericalgroove by electrodeposition of nickel in the presence of a leveling agent. Across section of the actual deposit is shown together with numerical simula-tions of the shape change for increasing amounts of charge passed. The cal-culation takes into account mass transport and adsorption of the levelingagent.102




favor formation of fine grained deposits. The microstructuresobserved with copper have been summarized in a schematic diagramhaving as its y-axis the degree of inhibition and as the x-axis theapplied current density divided by the copper ion concentra-tion.133,137 It has been known for some time that electrodepositionunder limiting current conditions leads to dendritic or powderydeposits.138 Therefore, the value of applied current density withrespect to the mass transport limited current density is a critical para-meter for deposit morphology. Similarly, the degree of inhibition canbe expressed as the ratio of applied current density to exchange cur-rent density.139,140 Several papers discuss various aspects of therelationship between deposit microstructure and electrochemicalconditions for deposition of copper and other metals.43,122,139-141

Quite generally, kinetically limited growth tends to favor compactcolumnar or equiaxed copper deposits while mass transport limitedgrowth favors formation of loose dendritic deposits.

Additives, typically small amounts of chloride in conjunctionwith two to three organic compounds, are widely used in industrialcopper plating from acid sulfate solutions.51,101 The additives arenot only needed for leveling and superfilling, but they also affect thestructure and roughness of the deposits. Inhibiting additives tend topromote the formation of small equiaxed grains142 which may leadto increased internal stress. Many additives are incorporated into thedeposit.143 The incorporation of additives was found to change themicrostructure of copper deposits and to lower their electrical con-ductivity.144 Copper deposition from sulfate solutions can lead to theformation of nonequilibrium grain structures, which spontaneouslyrecristallize even at room temperature. As a consequence, structuredependent materials properties such as electrical conductivity orinternal stress may change slowly with time after deposition.145

Pulse plating is an interesting method for controlling themicrostructure of electrodeposits.146 Early studies on copper, goldand cadmium suggested that pulse plating leads to refinement of the

Figure 7. Most electrodeposition processes take place far from equilibriumand for this reason materials not readily obtained by classical metallurgicalmethods can be made, including nanocrystalline and amorphous materials.Generally, the structure and properties of electrodeposited metals and alloysvary strongly with the deposition conditions. The figure shows in a ternarydiagram the fcc-bcc phase boundaries of CoNiFe alloys electrodepositedfrom solutions containing different additives, namely (A) saccharine, (B)thiourea, and (C) a nonsulfur containing compound. The data show that thephase boundary and therefore the magnetic properties of the alloys arestrongly affected by the nature of the additive.21


grain structure of copper, which was attributed to the high instanta-neous current densities favoring nucleation.147 A later study of theeffect of pulse current parameters on the microstructure of copperdeposited from sulfate electrolytes indicated that nonsteady state andsteady state mass transport conditions are the most crucial parame-ters.148 Well below the pulse limiting current and the steady statelimiting current the deposit structure was not affected by the appliedpulse parameters, because copper atoms were apparently added atstep and kink sites rather than forming 3D nuclei. Several studiesfound that for nickel deposition the use of pulse plating leads todeposits of finer grain size119,120,149 and increases their hardness andtheir corrosion resistance.120,149 In another study, pulse plating wasfound to affect the crystal structure of chromium deposits because ofdifferent hydrogen charging.150 It would appear from the mentionedliterature that the deposit structure in pulse plating depends on thenucleation mechanism and adsorption phenomena as well as onmass transport conditions, but a general theory in this field is stilllacking.

Fundamentals of alloy deposition.—A comprehensive compila-tion of electrolytes and electrochemical conditions for alloy deposi-tion has been published in the early 1960s.151 Most of the practicalinformation given therein remains of interest today. More recentoverviews on electrodeposition of different metals and alloys arefound in the fourth edition of Modern Electroplating publishedunder the auspices of ECS.8 Reviews covering fundamental aspectsof alloy deposition152,153 or electrodeposition of functional alloysfor magnetic applications16,20 are also available. During the last thir-ty years research on alloy deposition was stimulated greatly by theneeds of the electronics industry for functional alloys and by thesearch for new coatings for corrosion protection. The availability ofnew tools and methods for electrochemical experimentation, materi-als characterization and theoretical simulation provided a furtherstimulus. From a fundamental point of view, alloy deposition can beunderstood by considering the thermodynamics and kinetics of thepartial electrode reactions in a system involving multiple reac-tions.153 Often, the partial electrode reactions do not proceed inde-pendently but are coupled through adsorption processes or solutionequilibria. The quantitative investigation of codeposition phenome-na therefore usually requires numerical modeling. The mechanismof so called anomalous codeposition, has been extensively studied,because of the industrial importance of iron group alloys for mag-netic heads and of zinc alloys for corrosion protection. In anomalouscodeposition a higher proportion of the less noble metal is found inthe deposit than in the solution,151 a behavior typically observedwith iron group metals and with zinc. Different groups studied theanomalous codeposition of Fe-Ni alloys and proposed models forexplaining the codeposition mechanism and for predicting alloycomposition as a function of different variables such as potential orconvection conditions.154-160 Originally, the anomalous effect wasattributed to the formation of an oxide-hydroxide layer at the cath-ode surface.154 A later model considered mostly the effect of solu-tion equilibria in the cathodic diffusion layer.155 More recent papersexplained anomalous codeposition of Fe-Ni alloys by the competi-tive adsorption of reaction intermediates, which leads to inhibitionof nickel deposition.156,160 Of late, it was observed that in additionthe codepositing nickel enhances the rate of codeposition ofiron158,159 and a theoretical model was proposed that takes intoaccount both inhibiting and accelerating effects.157

Certain metals like tungsten or molybdenum, which can not bedeposited from an aqueous solution, readily codeposit with irongroup metals forming an alloy. The phenomenon known as inducedcodeposition151 has recently been theoretically modeled by postulat-ing a mechanism that involves an adsorbed mixed reaction interme-diate of the codepositing metals.161 Alloy formation during codepo-sition of small amounts of Pb and Sn with copper162 as well as of Niwith Al in a molten salt electrolyte163 has been attributed to under-




D

potential deposition. Since no underpotential deposition of molyb-denum on iron group metals has been observed such a mechanismcan not explain induced codeposition of these metals. Quite general-ly, significant progress in the theoretical understanding of alloydeposition has been achieved in recent years thanks to theoreticalmodeling based on numerical simulation. Theoretical models forcodeposition typically take into account mass transport and chemi-cal equilibria, competitive adsorption and charge transfer kinetics.They permit to simulate how experimental parameters such asapplied potential or convection conditions affect the composition ofelectrodeposited alloys and many such predictions were successful-ly tested by experiment. However, most alloy deposition modelsproposed in the literature require knowledge of rate constantsderived from codeposition experiments under similar conditions andin addition they usually involve assumptions as to the nature ofadsorbed species.157 At this time, codeposition phenomena involv-ing coupled partial reactions can not be quantitatively predictedfrom the electrochemical properties of the participating metalsalone.

Pulse plating provides additional means to influence compositionand structure of electroplated alloys.146,153,165,166 In the 1980s and1990s several groups used numerical modeling for the study of pulseplating of alloys.167-171 These models usually consider steady stateand nonsteady state mass transport as well as interfacial kinetics. Ithas been found that displacement reactions during the off time canhave an important effect on resulting alloy composition.171

Theoretical models were proposed which take into account thiseffect and they were successfully tested with copper-nickel and cop-per-cobalt alloys.172

Alloys for magnetic applications.—Electroplated alloys are wide-ly used in magnetic read and write heads. Several Proceedings ofECS symposia provide evidence for the impressive progressachieved in regard to processing technology and properties of elec-trodeposited magnetic alloys.112,173 A recent review presents adetailed discussion of materials requirements and deposition condi-tions of promising alloys.16 Magnetic writing requires magneticallysoft materials with high saturation magnetization, low coercivity andlow magnetostriction.174 Originally, permalloy was used, which is aNi-Fe alloy containing 19 % Fe with a saturation magnetization ofabout 1 Tesla. Much research over the years was carried out to devel-op alloys with higher saturation magnetization. Increasing the Fecontent of Ni-Fe alloy or replacing nickel by cobalt can be usedtowards this end. Still higher values of saturation magnetization areachieved with electroplated ternary alloys.16 The magnetic proper-ties of electrodeposited CoNiFe alloys were found to depend on theircomposition and microstructure.21 Among other, they are modifiedby the presence of sulfur containing additives such as saccharin orthiourea.175 The line separating the bcc and fcc phases in the ternarydiagram Fe-Ni-Co is shifted depending on the additive used. Sulfurcontaining additives lead to incorporation of sulfur into the deposit.While this permits to influence phase formation and grain size, itmay negatively affect the corrosion properties.176 By careful opti-mization of deposition parameters nanocrystalline ternary alloyswith a grain size on the order of 10 nm were produced that exhibit-ed saturation values of 2 Tesla or more.21

Multilayer alloys have been an important field of research duringthe last 20 years. The first electrodeposited multilayer alloy films(also referred to as composition modulated alloys or CMA in the lit-erature) were reported in 1983.177 By periodically varying the poten-tial, well-defined Ag-Pd multilayers could be produced from an elec-trolyte containing both silver and palladium salts. The films wereintended for electrical contacts having a good corrosion resistanceand good electrical conductivity. The same technique was applied inthe mid 1980s to the deposition of Ni-Cu multilayer alloys178 tostudy their mechanical properties. Decreasing the layer thickness tobelow 0.4 micrometer resulted in a strong increase in tensile


strength. A few years later the potential interest of Cu-Ni and Co-Nimultilayer alloys for magnetic applications was discovered.179 Thisled to a considerable number of studies on structure and propertiesof multilayer alloys and to the investigation of how the structure andspacing of the layers influence the magnetic properties, especiallythe magnitude of the giant magnetoresistance (GMR) effect (Fig. 8).A comprehensive review of the literature on electrodeposited mag-netic multilayer alloys was published in 1996.180 The same potentialmodulation technique used for fabricating multilayer alloys can alsobe applied to fabricate composition modulated nanowires using aporous polymer membrane or a porous aluminum oxide as a tem-plate.181 Three-dimensional nanostructuring of pulse plated Cu-Comultilayers was recently achieved due to columnar growth of copperrich and cobalt rich phases.182

Materials for corrosion and wear protection.—Electrodepositedand electroless coatings find a wide range of industrial applicationsfor corrosion and wear protection. In particular, zinc and Zn-Ni alloycoatings with about 15 to 20% Ni are extensively used in the auto-mobile industry for corrosion protection of steel. Codeposition ofzinc with iron group metals involves anomalous codeposition, thedeposition of the iron group element being inhibited by the code-positing zinc in chloride as well as sulfate electrolytes.152,183 A num-ber of papers deal with the mechanism of electrodeposition of Zn-Nialloys and different sometimes contradictory models have been pro-posed.184-187 In one paper impedance data are interpreted in terms ofa mixed adsorbed reaction intermediate.184 Another study found thatthe polarization curve for deposition of Zn-Ni alloys exhibits aninversion before the onset of anomalous codeposition. To accountfor this behavior and for observed impedance data a reaction modelwith twenty-five parameters was developed.185 A different theoreti-cal model considering transport by convective diffusion and migra-

Figure 8. Multilayer alloys with alternating layers of magnetic and a non-magnetic materials, each layer just a few nanometers thick, exhibit the so-called giant magnetoresistance effect, meaning that their resistance changesmarkedly when a magnetic field is applied. These materials are used in a newgeneration of magnetic heads for high density magnetic storage. Multilayeralloys can be electrodeposited from a suitable electrolyte by periodicallyvarying the current or the potential. The figure shows a TEM micrograph ofa nanomodulated Co-Cu multilayer alloy electrodeposited on a silicon [100]substrate. The deposits exhibit columnar growth mode as confirmed by elec-tron diffraction.229




tion at a rotating disk electrode attributed the anomalous codeposi-tion behavior to an increased exchange current density of Zn.186

Codeposition of hydrogen was thought to enhance nickel depositionduring the first stages of Zn-Ni alloy formation which apparentlyinvolved discrete nuclei of zinc and nickel.187 The phase structure ofelectrodeposited zinc alloy coatings differs from that of thermallyproduced alloys and it strongly depends on deposition conditions.188

Similarly, the phase structure and composition of pulse plated Zn-Nialloys varies with the applied pulse parameters.165 Generally, thecorrosion resistance of Zn-Ni alloy coatings is superior to that ofzinc metal coatings, permitting to apply a smaller coating thick-ness.5,184 Electroplated Zn-Fe alloys are less corrosion resistant thanZn-Ni alloys unless they are subjected to a chromate treatment.189

Electroplated and electroless composite materials can be fabri-cated by codeposition of a metal and a powder suspended in the elec-trolyte. Ni/SiC composite coatings obtained by electrochemicalcodeposition of SiC powders with nickel are used for cylinder lin-ings in the automobile industry.12 During the 1970s electroless Ni-

Figure 9. In electroless plating a reducing agent supplies the electrons forreduction of metal ions. The process exhibits a high throwing power and itcan also be used for plating on insulators. Electroless nickel-phosphorousalloys and nickel-phosphorous composite materials containing hard or softphases are widely used for corrosion and wear protection. In recent years,electroless plating has become an important technology in the electronicsindustry. The figure shows the cross section of a circuit board with a highaspect ratio through-hole plated with electroless copper. The thickness of theboard is 4 mm, the hole diameter 0.25 mm] corresponding to an aspect ratioof 16. The figure demonstrates the excellent uniformity of the deposit thick-ness over the entire length of the through hole.210


P/SiC composite alloy coatings were developed for various tribo-logical applications. Generally, the incorporation of hard particlessuch as carbides, oxides, borides or diamond leads to dispersionhardening and thus permits to improve wear resistance of the matrixmaterial.190 The mechanism of codeposition has been studied by anumber of groups and theoretical models of varying degree of com-plexity and sophistication have been proposed.191,192 It is generallyagreed that codeposition of SiC involves transport processes193 andadsorption.194,195 However, many phenomena associated with parti-cle codeposition are not yet well understood. For certain tribologicalapplications such as self-lubricating bearings, it is advantageous toincorporate soft rather than hard particles into metal deposits. Thesoft particles act as solid lubricants that reduce friction. Electrolessor electrodeposited metal matrix composite coatings containingMoS2 196 or PTFE13,197exhibit self-lubricationg properties.Electroless Ni-P/PTFE coatings are well established in industry.Interestingly, they exhibit satisfactory friction and wear behavioronly under oxidizing conditions, which permit the formation of apassive oxide film on the surface.198 Recently, nontribological prop-erties of electrodeposited composite coatings have become of inter-est. Among other, the catalytic properties and electrochromism ofelectroplated metal-oxide and similar materials have been studied199

and the suitability of electrodeposited Ni/PTFE coatings ashydrophobic electrodes for organic reduction and oxidation reac-tions has been explored.200 Nontribological applications of elec-trodeposited composite coatings could well become more importantin the future.199

Electrodeposited semiconductor materials.—Electrodepositionof chalcogenide semiconductor compounds from aqueous solution isa potentially simple and cheap process. An inherent problem, how-ever, is the comparatively low purity of electrodeposited semicon-ductors compared to those produced by vapor phase deposition,especially molecular beam epitaxy. The most promising applicationof electrodeposited semiconductor compounds is thought to be inlarge area solar cells where economy of scale is more important thanuttermost control of purity. Electrodeposition of CdTe was reportedin 1978 and theoretical aspects of codeposition leading to compoundformation were discussed.201 Since then a number of differentselenides, sulfides and tellurides have been electrodeposited such asZnSe, CdSe, PbSe, CuSe, In2Se3, ZnS, CdS, ZnTe, and mixed com-pounds such as Cd(Hg)Te, (CdZn)S, CuInSe2, and CuInTe2.202 Thedeposition mechanism of CdTe is typical for the cathodic reactionsleading to semiconductor compound formation by electrodeposition.Reduction is thought to proceed in two steps. In a first step the tel-lurium is formed by reduction of telluric acid. In a second step theCd undergoes underpotential deposition on tellurium sites on thesurface.202 A similar mechanism apparently applies to electrodepo-sition of zinc oxide in presence of oxygen or hydrogen peroxide.203

The electrodeposition mechanism of ternary compounds such asCuInSe2 involves several reaction steps, but the deposit compositiondepends to a large extent on the relative magnitude of the diffusionfluxes of the codepositing species.204,205 Electrodeposition has alsobeen used to produce epitaxial deposits of semiconductors. The tech-nique involves the use of two electrolytes, which are alternativelyadmitted to the deposition cell.206,207 The potential of the cathode ischosen such that alternatively each element of the compound semi-conductor undergoes a UPD reaction forming a single atomic layer.At the time of this writing the practical applicability of this proce-dure for device fabrication appears to be limited, however.

Related Electrochemical ProcessesThe interests of the Electrodeposition Division of ECS include

not only electrodeposition and its different applications but alsorelated processes such as electroless plating (Fig. 9) and anodic dis-solution applied to electropolishing, electrochemical machining andelectrochemical etching. To keep this review within a reasonablelength these processes will be mentioned only briefly and the reader




D

is referred to the indicated literature for more information.Electroless plating uses chemical reducing agents such as hypophos-phite or formaldehyde as a source of electrons in place of a cathod-ic current. The process, which can be considered a corrosion processin reverse, is best described by mixed potential theory.208 Recentoverviews of the theory and applications of electroless plating aregiven in Ref. 209 and 210. Electroless plating of nickel-phosphorousalloys is widely used to produce coatings for corrosion and wear pro-tection. More recently, electroless plating has found many newapplications in electronics manufacturing, especially for packagingand for producing diffusion barriers.211,212 Electroless platingrequires a more elaborate bath control than electroplating, but on theother hand, it provides better throwing power and it does not requireconducting substrates.

Electropolishing finds numerous applications in the manufactur-ing industry for polishing of metallic objects of complex shape.Fundamental aspects of the process have been reviewed covering theliterature up to 1987.213 More recent studies of electropolishing arefound in Ref. 214-219. Electrochemical machining (ECM) wasdeveloped in the 1960s for machining of complex shapes in hard tomachine alloys used mostly by the aerospace industry.220 Currentdensities applied in ECM are two to three orders of magnitude high-er than in electrodeposition and therefore the process requiresintense electrolyte flow for evacuating reaction products and heatgenerated in the inter electrode gap. For most metals and alloysanodic dissolution under these conditions takes place in the transpas-sive potential region.221 During the 1980s and 1990s electric dis-charge machining has taken over many tasks of ECM, because it iseasier to control and does not need elaborate electrolyte pumpingand filtering installations. On the other hand, during this period elec-trochemical micromachining (EMM) has emerged as a new manu-facturing technology for micromechanics and electronics.3,222-227

EMM is based on controlled anodic dissolution through masks. Theprocess does not require heavy installations and permits precisionfabrication of microstructures using well established photolitho-graphic techniques. Recently, a mask free electrochemical microma-chining process has been described, which uses laser irradiation forforming a pattern on an anodically grown oxide film that acts as amask during anodic dissolution.228

Concluding RemarksThis review describes significant developments in electrodeposi-

tion science and technology that took place during the last part of thetwentieth century. Electrodeposition has become a broad field withmany ramifications making it extremely difficult for a single personto be aware of all important developments. The selection of topicsand references in this review therefore necessarily contains somesubjectivity, reflecting the authors own experience and limitations.Readers are kindly asked to forgive unavoidable shortcomings andomissions. According to W. Blum,1 “a historian must in some degreealso be a prophet”. Keeping in mind the popular wisdom “predic-tions are always difficult, especially when they concern the future”let us therefore conclude this review with a short glance at whatcould be future trends and developments.

Sustained environmental pressures, emerging nanotechnologyand the need for tailor made functional materials for microsystemswill be strong driving forces for future research, innovation andprocess development in the field of electrodeposition and relatedprocesses. The economic importance of electrochemical microfabri-cation technology will likely continue to grow in the coming years,including not only electrodeposition but also electroless depositionand electrochemical micromachining. Continuing miniaturization ininformation technology and the emerging nanotechnology, will leadto an increasing need for understanding the kinetics of electrochem-ical phase formation and electrochemical reaction mechanisms on anatomic scale. This will further increase the importance of in situexperimental methods capable of providing information on phenom-


ena at solid-liquid interfaces on a nanometer scale, including power-ful physical and spectroscopic methods and new types of scanningprobe techniques. Such research should eventually lead to a betterunderstanding and control of electrodeposition processes with andwithout additives, and it may offer new opportunities to electrode-posit not only metals and alloys, but also nonmetallic materials suchas compound semiconductors or functional oxides on a variety ofsubstrates. The importance of numerical modeling will furtherincrease, including ever more realistic assumptions concerningchemical and physical mechanisms involved in metal and alloydeposition and an ever wider range of length scales. This shouldeventually permit to link atomic scale phenomena with macroscopicprocess models and materials properties. Powerful and user friendlysoftware for simulating metal and alloy deposition kinetics willincreasingly become available. As a consequence the plating indus-try will be in a position to routinely apply numerical modeling forelectrolyte development and process optimization. This should facil-itate the development of new environment friendly processes andfunctional materials for specific applications.

During the last part of the twentieth century, electrodepositionscience and technology contributed significantly to the emergence ofour modern information society. There are many reasons to believethat in the twenty first century electrodeposition and related tech-nologies will have an equally important or even more importantimpact. The Electrochemical Society through its symposia and pub-lications has contributed to the development of electrodepositionscience and technology in the past and it is expected that it will con-tinue to stimulate advancements in the field also in the future.

References 1. W. Blum, J. Electrochem. Soc., 99, 31C (1952). 2. B. L. McKinney and C. L. Faust, J. Electrochem. Soc., 124, 379C (1977). 3. M. Datta and D. Landolt, Electrochim. Acta, 45, 2535 (2000). 4. W. H. Safranek, The Properties of Electrodeposited Metals and Alloys, 2nd ed.,

p. 1, AESF, Orlando, FL (1986). 5. J. H. Lindsay and D. D. Snyder, Electrodeposition Technology, Theory and

Practice, L. T. Romankiw and D. R. Turner, Editors, PV 87-17, p. 43, The Electrochemical Society Pennington, NJ (1987).

6. L. T. Romankiw, Electrochim. Acta, 42, 2985 (1997). 7. K. Sheppard, Electrochem. Soc. Interface, 4(2), 25 (1995). 8. M. Schlesinger and M. Paunovic, Modern Electroplating, 4th ed., Wiley

Interscience, New York 2000. 9. M. S. Blaser and E. T. Nowak, Plat. Surf. Finish., 81, 12 (1994).

10. T. R. Heckard and E. A. Williams, Plat. Surf. Finish., 81, 20 (1994). 11. H. E. Townsend, Corrosion (Houston), 55, 547 (1999). 12. J. P. Celis and J. R. Roos, Oberfläche (Berlin), 24, 352 (1983). 13. E. Steiger, Oberfläche (Berlin), 31, 15 (1990). 14. S. Birkle, in Electrodeposition Technology, Theory and Practice, L. T. Romankiw

and D. R. Turner, Editors, PV 87-17, p. 69, The Electrochemical Society Proceedings Series, Pennington NJ (1987).

15. P. C. Andricacos, C. Uzoh, J. O. Dukovic, J. Horkans, and H. Deligianni, IBM J. Res. Dev., 42, 567 (1998)

16. P. C. Andricacos and L. T. Romankiw, in Advances in Electrochemical Science and Engineering, Vol. 3, H. Gerischer and C. W. Tobias, Editors,p. 227, VCH Weinheim (1994).

17. L. T. Romankiw, Plat. Surf. Finish., 84(1), 10 (1997). 18. M. Datta and L. T. Romankiw, J. Electrochem. Soc., 136, 285C (1989). 19. T. Osaka, Electrochim. Acta, 37, 989 (1992). 20. T. Osaka, Electrochim. Acta, 44, 3885 (1999). 21. T. Osaka, Electrochim. Acta, 45, 3311 (2000). 22. Electrochemical Technology, M. Masuko, T. Osaka, and Y. Ito, Editors,

Kodansha, Tokyo (1996). 23. H. Honma, Electrochim. Acta, 47, 75 (2001). 24. Electrodeposition Technology, Theory and Practice, L. T. Romankiw and D. R.

Turner, Editors, PV 87-17, The Electrochemical Society Proceedings Series, Pennington, NJ (1987).

25. Electrochemical Technology in Electronics, L. T. Romankiw and T. Osaka, Editors, PV 88-23, The Electrochemical Society Proceedings Series, Pennington, NJ (1988).

26. Electrochemical Microfabrication, M. Datta, K. Sheppard, and J. O. Dukovic, Editors, PV 94-32, The Electrochemical Society Proceedings Series, Pennington, NJ (1995).

27. S. Krongelb, L. T. Romankiw, and J. A. Tonello, IBM J. Res. Dev., 42, 575 (1998). 28. P. C. Andricacos, Electrochem. Soc. Interface, 8(1), 32 (1998). 29. P. C. Andricacos, C. Uzoh, J. O. Dukovic, J. Horkans, and H. Delgianni, IBM

J. Res. Dev., 42, 567 (1998).




D

30. M. Datta, R. V. Shenoy, C. Jahnes, P. C. Andricacos, J. Horkans, J. O. Dukovic, L. T. Romankiw, J. Roeder, H. Deligianni, H. Nye, B. Agarwalla, H. M. Tong, and P. A. Totta, J. Electrochem. Soc., 142, 3379 (1995).

31. W. Bracher, W. Menz, and J. Mohr, IEEE Trans. Ind. Electron., 42, 431 (1995). 32. B. Löchel and A. Maciossek, J. Electrochem. Soc., 143, 3343 (1996). 33. K. Vetter, Electrochemical Kinetics, Academic Press, New York (1967). 34. J. O’M Bockris and A. K. N. Reddy, Modern Electrochemistry, Vol. 2, Plenum

Press, New York (1970). 35. H. Gerischer, Chem. Ing. Tech., 36, 666 (1964). 36. E. Budevski, G. Staikov, and W. J. Lorenz, Electrochim. Acta, 45, 2559 (2000). 37. R. Kaischew and E. Budevski, Contemp. Phys., 8, 489 (1967). 38. Y. Cao, P. C. Searson, and A. C. West, J. Electrochem. Soc., 148, C376 (2001). 39. E. Schmidt and H. R. Gygax, J. Electroanal. Chem., 12, 300 (1966). 40. F. Hilbert, C. Mayer, and W. J. Lorenz, J. Electroanal. Chem., 47, 167 (1973). 41. C. Sanchez and E. P. M. Leiva, Electrochim. Acta, 45, 690 (1999). 42. E. Budevski, G. Staikov, and W. J. Lorenz, Electrochemical Phase Formation and

Growth, Wiley-VCH, Weinheim (1996). 43. G. Oskam, J. G. Long, A. Natarajan, and P. C. Searson, J. Phys. D: Appl. Phys.,

31, 1927 (1998). 44. G. Binnig and H. Rohrer, Helv. Phys. Acta, 55, 726 (1982). 45. G. Binnig, C. F. Quate, and Ch. Gerber, Phys. Rev. Lett., 56, 930 (1986). 46. R. Sonnenfeld and P. K. Hansma, Science, 232, 211 (1986). 47. P. Lustenberger, H. Rohrer, R. Christoph, and H. Siegenthaler, J. Electroanal.

Chem., 243, 225 (1988). 48. J. Wiechers, T. Twomey, D. M. Kolb, and R. J. Behm, J. Electroanal. Chem., 248,

451 (1988). 49. Scanning Tunneling Microscopy and Related Methods, H. Siegenthaler,

R. Christoph, and R. J. Behm, Editors, p. 315, Kluwer Academic Publishers, The Netherlands (1990).

50. A. A. Gewirth, P. C. Andricacos, J. A. Switzer, and J. O. Dukovic, Electrochem. Soc. Interface, 5(1), 22 (1998).

51. T. Y. B. Leung, M. C. Kang, B. F. Corry, and A. A. Gewirth, J. Electrochem. Soc., 147, 3326 (2000).

52. D. M. Kolb, Electrochim. Acta, 45, 2387 (2000). 53. H. Seiter and H. Fischer, Z. Elektrochemie, 63, 249 (1959). 54. Q. Wu and D. Barkey, J. Electrochem. Soc., 144, L 261 (1997). 55. T. P. Moffat, in Electroanalytical Chemistry, Vol. 21, A. J. Bard, I. Rubinstein,

Editors, p. 211, Marcel Dekker, New York (1999). 56. A. J. Bard, H. D. Abruna, C. E. Chidsey, L. R. Faulkner, S. W. Feldberg, K. Itaya,

O. Melroy, R. W. Murray, M. D. Porter, M. D. Soriaga, and H. S. White, J. Phys. Chem., 97, 7147 (1993).

57. M. Giesen, R. Randler, S. Baier, H. Ibach, and D. Kolb, Electrochim. Acta, 45, 527 (1999).

58. W. Li, J. A. Virtanen, and R. M. Penner, Appl. Phys. Lett., 60, 1181 (1992). 59. D. M. Kolb, R. Ullmann, and J. C. Ziegler, Electrochim. Acta, 43, 2751 (1998 ). 60. G. E. Engelmann, J. C. Ziegler, and D. M. Kolb, J. Electrochem. Soc., 145, L33

(1998). 61. W. Schindler, D. Hofmann, and J. Kirschner, J. Electrochem. Soc., 148, C124

(2001). 62. M. J. Armstrong and R. H. Muller, J. Electrochem. Soc., 138, 2303 (1991). 63. W. U. Schmidt, R. C. Alkire, and A. A. Gewirth, J. Electrochem. Soc., 143, 3122

(1996). 64. R. J. Nichols, D. Schroer, and H. Meyer, Electrochim. Acta, 40, 1479 (1995). 65. J. P. Healy, D. Pletcher, and M. Goodenough, J. Electroanal. Chem., 338,155

(1992). 66. P. Taephaisitphongse, Y. Cao, and A. C. West, J. Electrochem. Soc., 148, C492

(2001). 67. J. J. Kelly, P. Kern, and D. Landolt, J. Electrochem. Soc., 147, 3725 (2000). 68. T. Franklin, Plat. Surf. Finish., 8, 62 (1994). 69. W. Plieth, Electrochim. Acta, 37, 2115 (1992). 70. R. Alkire and M. Verhoff, Electrochim. Acta, 43, 2733 (1998). 71. C. W. Tobias, Electrochem. Soc. Interface, 3(3), 17 (1994). 72. J. Newman, Electrochemical Systems, 2nd ed., Prentice Hall, Englewood Cliffs ,

NJ (1991). 73. N. Ibl, in Comprehensive Treatise of Electrochemistry, E. Yeager, J. O’M Bockris,

and B. Conway, Editors, Vol 6, p. 1, 133, 239, Plenum Press New York (1982). 74. J. Newman, J. Electrochem. Soc., 113, 1235 (1966). 75. C. Madore and D. Landolt, Plat. Surf. Finish., 80, 73 (1993). 76. J. A. Medina, D. L. Sexton, and D. T. Schwarz, J. Electrochem. Soc., 142, 451,

457 (1995). 77. T. E. Dinan, M. Matlosz, and D. Landolt, J. Electrochem. Soc., 138, 2947 (1991). 78. A. A. Sonin, J. Electrochem. Soc., 130, 1501 (1983). 79. R. Alkire and J-B. Ju, J. Electrochem. Soc., 134, 294 (1987). 80. C. Karakus and D. T. Chin, J. Electrochem. Soc., 141, 691 (1994). 81. R. Chalupa, M. Chen, V. Modi, and A. C. West, J. Electrochem. Soc., 148, E92

(2001). 82. J. V. Powers and L. T. Romankiw, U.S. Pat. 3,652,442 (1972). 83. E. E. Castellani, J. V. Powers, and L. T. Romankiw, U.S. Pat. 4,102,756 (1978). 84. D. T. Schwartz, B. G. Higgins, P. Stroeve, and D. Borowski, J. Electrochem. Soc.,

134, 1639 (1987). 85. E. K. Yung, L. T. Romankiw, and R. C. Alkire, J. Electrochem. Soc., 136, 206

(1989). 86. J. W. E. Chern and H. Y. Cheh, J. Electrochem. Soc., 143, 3139 (1996).


87. A. M. Pesco and H. Y. Cheh, J. Electrochem. Soc., 136, 399, 408 (1989). 88. H. H. Wan, R. Y. Chang, and W. L. Yang, J. Electrochem. Soc., 140, 1380 (1993). 89. M. Matlosz, P. H. Vallotton, A. C. West, and D. Landolt, J. Electrochem. Soc.,

139, 752 (1992). 90. J. O. Dukovic, in Advances in Electrochemical Science and Engineering,

H. Gerischer, C. W. Tobias, Editors, Vol 3, VCH Weinheim 1994, p. 117. 91. S. Mehdizadeh, J. O. Dukovic, P. C. Andricacos, L. T. Romankiw, and H. Y. Cheh,

J. Electrochem. Soc., 137, 110 (1990). 92. S. Mehdizadeh, J. O. Dukovic, P. C. Andricacos, L. T. Romankiw, and H. Y. Cheh,

J. Electrochem. Soc., 140, 3497 (1993). 93. A. C. West, M. Matlosz, and D. Landolt, J. Electrochem. Soc., 138, 728 (1991). 94. A. C. West, C. Madore, M. Matlosz, and D. Landolt, J. Electrochem. Soc., 139,

499 (1992). 95. R. C. Alkire and D. B. Reiser, and R. L. Sani, J. Electrochem. Soc., 131, 2795

(1984). 96. M. Georgiadou and R. C. Alkire, J. Electrochem. Soc., 141, 679 (1994). 97. S. S. Kruglikov, N. T. Kudriavtsev, G. F. Vorobiova, and A. Ya. Antonov,

Electrochim. Acta, 10, 253 (1965). 98. O. Kardos, Plating, 61, 129, 229, 316 (1974). 99. K. G. Jordan and C. W. Tobias, J. Electrochem. Soc., 138, 3581 (1991).

100. C. Madore, M. Matlosz, and D. Landolt, J. Electrochem. Soc., 143, 3927 (1996). 101. J. J. Kelly, C. Tian, and A. C. West, J. Electrochem. Soc., 146, 2540 (1999). 102. C. Madore and D. Landolt, J. Electrochem. Soc., 143, 3936 (1996). 103. K. Kondo, K. Fukui, K. Uno, and K. Shinohara, J. Electrochem. Soc., 143, 1880

(1996). 104. K. Kondo, K. Fukui, M. Yokoyama, and K. Shinohara, J. Electrochem. Soc., 144,

466 (1997). 105. J. O. Dukovic, IBM. J. Res. Dev., 37, 125 (1993). 106. T. P. Moffat, J. E. Bonewich, W. H. Huber, A. Stanishevsky, D. R. Kelly, G. R.

Stafford, and D. Josell, J. Electrochem. Soc., 147, 4524 (2000).107. T. P. Moffat, D. Wheeler, W. H. Huber, and D. Josell, Electrochem. Solid-State

Lett., 4, C26 (2001).108. O. Dossenbach, in Theory and Practice of Pulse-Plating, J. C. Puippe and

F. Leaman, Editors, p. 73, AESF, Orlando FL (1986). 109. H. H. Wan and H. Y. Cheh, J. Electrochem. Soc., 135, 643 (1988). 110. K. M. Jeong, K. C. Lee, and H. J. Sohn, J. Electrochem. Soc., 139, 1927 (1992). 111. T. Kobayashi, J. Kawasaki, K. Mihara, and H. Honma, Electrochim. Acta, 47, 85

(2001); T. Kobayashi, J. Kawasaki, K. Mihara, and H. Honma, Electrochim. Acta, 47, 85 (2001).

112. Magnetic Materials, Processes and Devices, L. T. Romankiw and D. A. Herman, Editors, PV 90-8, The Electrochemical Society Proceedings Series, Pennington, NJ (1990); Magnetic Materials, Processes and Devices, L. T. Romankiw and D. A. Herman, Editors, PV 92-10, The Electrochemical Society Proceedings Series, Pennington, NJ (1992); Magnetic Materials, Processes and Devices, L. T. Romankiw and D. A. Herman, Editors, PV 94-6, The Electrochemical Society Proceedings Series, Pennington, NJ (1994.

113. Electrochemical Processing of Tailor Made Materials, R. Alkire, N. Masuko, and D. R. Sadoway, Editors, PV 93-12, The Electrochemical Society Proceedings Series, Princeton, NJ (1993).

114. Electrochemically Deposited Thin Films, M. Paunovic and D. A. Scherson, Editors, PV 96-19, The Electrochemical Society Proceedings Series, Pennington,NJ (1997).

115. M. Matsuoka, S. Imanishi, and T. Hayashi, Plat. Surf. Finish., 76, 54 (1989). 116. E. Bredael, B. Blanpain, J. P. Celis, and J. R. Roos, J. Electrochem. Soc., 141, 294

(1994). 117. M. Donten, Z. Stijek, and J. G. Osteryoung, J. Electrochem. Soc., 140, 3417

(1993). 118. F. Czerwinski, Electrochim. Acta, 44, 667 (1999). 119. R. T. C. Choo, J. M. Toguri, A. M. El-Sherik, and U. Erb, J. Appl. Electrochem.,

25, 384 (1995). 120. P. T. Tang, T. Watanabe, J. E. T. Andersen, and G. Bech-Nielsen, J. Appl.

Electrochem., 25, 347 (1995). 121. T. Taylor, T. Ritzdorf, F. Lindberg, B. Carpenter, and M. LeFebvre, Solid State

Technol., 41, 47 (1998). 122. R. Weil, Annu. Rev. Mater. Sci., 19, 165 (1989). 123. F. Czerwinski, J. Electrochem. Soc., 143, 3327 (1996). 124. H. Feigenbaum, S. T. Rao, and R. Weil, in Electrocrystallization, R. Weil and

R. G. Barradas, Editors, PV 81-6, p. 249, The Electrochemical Society Proceedings Series, Pennington, NJ (1991).

125. S. Armyanov and G. Sotirova-Chakarova, J. Electrochem. Soc., 139, 3454 (1992). 126. R. Weil and R. Sard, in Properties of Electrodeposits: Their Measurement and

Significance, R. Sard, H. Leidheiser Jr, and F. Ogburn, Editors, p. 319, The Electrochemical Society Proceedings Series, Princeton, NJ (1975).

127. J. P. Celis, K. Van Acker, K. Callewaert, and P. Van Houtte, J. Electrochem. Soc., 142, 70 (1995).

128. T. Hara and K. Sakata, Electrochem. Solid-State Lett., 4, G77 (2001). 129. S. Armyanov, in Defect Structure, Morphology and Propeties of Electrodeposits,

H. D Merchant, Editor, p. 273, TMS (1995). 130. H. Feigenbaum and R. Weil, J. Electrochem. Soc., 126, 2085 (1979). 131. Y. Tsuru, M. Nomura, and F. R. Foulkes, J. Appl. Electrochem., 30, 231 (2000). 132. E. Chassaing, J. Electrochem. Soc., 144, L329 (1997). 133. H. Fischer, Elektrolytische Abscheidung und Elektrokristallisation von Metallen,

Springer Verlag Berlin 1954.




134. E. Matsson and J. O’M. Bockris, Trans. Faraday Soc., 55, 1586 (1959). 135. G. Fabricius, Electrochim. Acta, 39, 611 (1994). 136. G. Fabricius, K. Kontturi, and G. Sundholm, J. Appl. Electrochem., 26, 1179

(1996). 137. R. Winand, Trans. Inst. Min. Metall., Sect. C, 84, 67 (1975). 138. N. Ibl, in Advances in Electrochemistry and Electrochemical Engineering, Vol 2,

P. Delahay, C. Tobias, Editors, Wiley New York 1962 p. 49. 139. R. Winand, Electrochim. Acta, 39, 1091 (1994). 140. D. Landolt, in Electrochemically Deposited Thin Films III, M. Paunovic and

D. Shearson, Editors, PV 96-19, p. 160, The Electrochemical Society Proceedings Series, Pennington, NJ (1997).

141. R. Winand, J. Appl. Electrochem., 21, 377 (1991). 142. R. Rashkov and C. Nanev, J. Appl. Electrochem., 25, 603 (1995). 143. G. A. Hope, G. M. Brown, D. P. Schweinsberg, K. Shimizu, and K. Kobayashi,

J. Appl. Electrochem., 25, 890 (1995). 144. V. S. Donepudi, R. Venkatachalapathy, P. O. Ozemoyah, C. S. Johnson, and

J. Prakash, Electrochem. Solid-State Lett., 4, C13 (2001). 145. J. M. E. Harper, C. Cabral, P. C. Andricacos, L. Gignac, I. C. Noyan, K. P.

Rodbell, and C. K. Hu, J. Appl. Phys., 86, 2516 (1999). 146. Theory and Practice of Pulse-Plating, J. C. Puippe and F. Leaman, Editors, AESF,

Orlando, FL (1986). 147. J. Cl. Puippe and N. Ibl, Plat. Surf. Finish., 67, 68 (1980). 148. O. Chène and D. Landolt, J. Appl. Electrochem., 19, 188 (1989). 149. K. P. Wong, K. C. Chan, and T. M. Yue, J. Appl. Electrochem., 31, 25 (2001). 150. R. W. Tsai and S. T. Wu, J. Electrochem. Soc., 138, 2622 (1991). 151. A. Brenner, Electrodeposition of Alloys, Vol. I and II, Academic Press, New York

(1963). 152. D. Landolt, Electrochim. Acta, 39, 1075 (1994). 153. D. Landolt, Plat. Surf. Finish., 88, 70 (2001). 154. H. Dahms and I. M. Croll, J. Electrochem. Soc., 112, 771 (1965). 155. S. Hessami and C. W. Tobias, J. Electrochem. Soc., 136, 3611 (1989). 156. M. Matlosz, J. Electrochem. Soc., 140, 2272 (1993). 157. N. Zech, E. J. Podlaha, and D. Landolt, J. Electrochem. Soc., 146, 2886, 2892

(1999). 158. K. S. Sasaki and J. B. Talbot, J. Electrochem. Soc., 145, 981 (1998). 159. N. Zech, E. J. Podlaha, and D. Landolt, J. Appl. Electrochem., 28, 1251 (1998). 160. B. C. Baker and A. C. West, J. Electrochem. Soc., 144, 169 (1997). 161. E. J. Podlaha and D. Landolt, J. Electrochem. Soc., 143, 893 (1996). 162. J. Horkans, I. H. Chang, P. C. Andricacos, and H. Deligianni, J. Electrochem.

Soc., 142, 2244 (1995). 163. T. P. Moffat, J. Electrochem. Soc., 141, 3059 (1994). 164. D. Landolt, E. J. Podlaha, and N. Zech, Z. Phys. Chem. (Munich), 208, 167

(1999). 165. K. Kondo, M. Yokoyama, and K. Shinohara, J. Electrochem. Soc., 142, 2256

(1995). 166. T. Nakanishi, M. Ozaki, T. Yokoshima, and T. Osaka, J. Electrochem. Soc., 148,

C627 (2001). 167. M. W. Verbrugge and C. W. Tobias, J. Electrochem. Soc., 132, 1298 (1985). 168. K. Viswanathan, M. A. F. Epstein, and H. Y. Cheh, J. Electrochem. Soc., 127,

2383 (1980). 169. A. M. Pesco and H. Y. Cheh, J. Electrochem. Soc., 135, 1722 (1988). 170. A. Ruffoni and D. Landolt, Oberfläche (Berlin), 29, 8 (1988). 171. S. Roy, M. Matlosz, and D. Landolt, J. Electrochem. Soc., 141, 1509 (1994). 172. P. E. Bradley and D. Landolt, Electrochim. Acta, 45, 1077 (1999). 173. Magnetic Materials, Processes and Devices, L. T. Romankiw, S. Krongelb, and

C. H. Kahn, Editors, PV 98-20, The Electrochemical Society Proceedings Series, Pennington NJ (1998).

174. R. E. Jones Jr, Acta Mater., 46, 3805 (1998) . 175. T. Osaka, T Sawaguchi, F. Mizutani, T. Yokoshima, M. Takai, and Y. Okinaka,

J. Electrochem. Soc., 146, 3295 (1999). 176. M. Saito, K. Yamada, K. Ohashi, Y. Yasue, Y. Sogawa, and T. Osaka,

J. Electrochem. Soc., 146, 2845 (1999). 177. U. Cohen, F. B. Koch, and R. Sard, J. Electrochem. Soc., 130, 1987 (1983). 178. D. Tench and J. White, Metall. Trans. A, 15, 2039 (1984). 179. L. H. Bennet, D. S. Lashmore, M. P. Dariel, J. Kaufman, M. Rubinstein, P. Lubitz,

O. Zadok, and J. Yahalom, J. Magn. Magn. Mater., 67, 239 (1987). 180. W. Schwarzacher and D. S. Lashmore, IEEE Trans. Magn., 32, 3133 (1996). 181. B. Doudin and J. P. Ansermet, Nanostruct. Mater., 6, 521 (1995). 182. J. J. Kelly, M. Cantoni, and D. Landolt, J. Electrochem. Soc., 148, C620 (2001). 183. G. Roventi, R. Fratesi, R. A. Della Guardia, and G. Barucca, J. Appl.

Electrochem., 30, 173 (2000).

address. Redistribution subject to E177.20.132.35Downloaded on 2014-04-24 to IP

184. E. Chassaing and R. Wiart, Electrochim. Acta, 37, 454 (1992). 185. F. J. F. Miranda, O. E. Barcia, O. R. Mattos, and R. Wiart, J. Electrochem. Soc.,

144, 3441, 3449 (1997). 186. M. F. Mathias and T. W. Chapman, J. Electrochem. Soc., 137, 102 (1990). 187. Y. P. Lin and J. R. Selman, J. Electrochem. Soc., 140, 1299, 1304 (1993). 188. D. E. Hall, Plat. Surf. Finish., 70, 59 (1983). 189. G. W. Loar, K. R. Romer, and T. J. Aoe, Plat. Surf. Finish., 78, 74 (1991). 190. B. Bozzini, G, Giovannelli, M. Boniardi, and P. L. Cavallotti, Compos. Sci.

Technol., 59, 1579 (1999). 191. A. Hovestad and L. J. J. Janssen, J. Appl. Electrochem., 25, 519 (1995). 192. J. P. Celis, J. R. Roos, C. Buelens, and J. Fransaer, Trans. Inst. Metal Finish., 69,

133 (1991). 193. J. Fransaer, J. P. Celis, and J. R. Roos, J. Electrochem. Soc., 139, 413 (1992 ). 194. N. Guglielmi, J. Electrochem. Soc., 119, 1009 (1972). 195. S. W. Watson, J. Electrochem. Soc., 140, 2235 (1993). 196. Y. C. Chang, Y. Y. Chang, and C. L. Lin, Electrochim. Acta, 43, 315 (1998). 197. P. R. Ebdon, Plat. Surf. Finish., 75, 65 (1988). 198. E. Rosset, S. Mischler, and D. Landolt, in Thin Films in Tribology, D. Dowson,

C. M. Taylor, T. H. C. Childs, and M. Godard, Editors, p. 101, Elsevier, Amsterdam (1993).

199. M. Musiani, Electrochim. Acta, 45, 3397 (2000). 200. Y. Kunugi, P. C. Chen, T. Nonaka, Y. B. Chong, and N. Watanabe, J. Electrochem.

Soc., 140, 2833 (1993). 201. F. A. Kröger, J. Electrochem. Soc., 125, 2028 (1978). 202. T. Pauporté and D. Lincot, Electrochim. Acta, 45, 3345 (2000). 203. T. Pauporte and D. Lincot, J. Electrochem. Soc., 148, C310 (2001). 204. L Thouin and J. Vedel, J. Electrochem. Soc., 142, 2996 (1995). 205. A. Marlot and J. Vedel, J. Electrochem. Soc., 146, 177 (1999). 206. B. M. Huang, L. P. Colletti, B. W. Gregory, J. L. Anderson, and J. L. Stickney,

J. Electrochem. Soc., 142, 3007 (1995). 207. J. Stickney, in Electroanalytical Chemistry, Vol. 21, A. J. Bard and I. Rubinstein,

Editors, p. 75, Marcel Dekker, New York (1999). 208. M. Paunovic and M. Schlesinger, Fundamentals of Electrochemical Depositon,

p. 133, Wiley InterScience, New York (1998). 209. Y. Okinaka and T. Osaka, in Advances in Electrochemical Science and

Engineering, Vol 3, H. Gerischer, and C. W. Tobias, Editors, p. 55, VCH Weinheim(1994).

210. C. J. Sambucetti, in Electrochemical Technology, N. Masuko, T. Osaka, and Y. Ito, Editors, Kodansha Tokyo 1996, p. 69.

211. E. J. O’Sullivan, A. G. Schrott, M. Paunovic, C. J. Sambucetti, J. R. Marino, P. J. Bailey, S. Kaja, and K. W. Semkow, IBM J. Res. Dev., 42, 607 (1998).

212. M. Paunovic, P. Bailey R. Schad, and D. Smith, J. Electrochem. Soc., 141,1843 (1994).

213. D. Landolt, Electrochim. Acta, 32, 1 (1987).214. K. Kontturi and D. J. Schiffrin, J. Appl. Electrochem., 19, 76 (1989).215. M. Matlosz and D. Landolt, J. Electrochem. Soc., 136, 919 (1989).216. M. Datta, L. F. Vega, L. T. Romankiw, and P. Duby, Electrochim. Acta, 37, 2469

(1992),217. R. Vidal and A. C. West, J. Electrochem. Soc., 142, 2686, 2689 (1995). 218. M. Matlosz, S. Magaino, and D. Landolt, J. Electrochem. Soc., 141, 410 (1994). 219. O. Piotrowski, C. Madore, and D. Landolt, J. Electrochem. Soc., 145, 2362

(1998). 220. J. F. Wilson, Practice and Theory of Electrochemical Machining, Wiley

InterScience, New York (1971). 221. D. Landolt, in Passivity of Metals, R. P. Frankenthal and J. Kruger, Editors,

p. 484, The Electrochemical Society Corrosion Monograph Series, Princeton, NJ (1978).

222. E. Rosset and D. Landolt, Precis. Eng., 11, 79 (1989). 223. G. J. Kwan, H. Y. Sun, and H. J. Sohn, J. Electrochem. Soc., 142, 3017 (1995). 224. M. Datta, Electrochem. Soc. Interface, 4(2), 32 (1995). 225. R. V. Shenoy, M. Datta, and L. T. Romankiw, J. Electrochem. Soc., 143, 2305

(1996). 226. M. Datta and D. Harris, Electrochim. Acta, 42, 3007 (1997). 227. C. Madore, O. Piotrowski, and D. Landolt, J. Electrochem. Soc., 146, 2526

(1999). 228. P. F. Chauvy, P. Hoffmann, and D. Landolt, Electrochem. Solid-State Lett., 4, C31

(2001). 229. M. Shima, L. G. Salamanca-Riba, R. D. McMichael, and T. R. Moffat,

J. Electrochem. Soc., 148, C518 (2001).

) unless CC License in place (see abstract). ecsdl.org/site/terms_useCS terms of use (see


Documents

Electrodeposition Science and Technology in the Last Quarter of the Twentieth Century