Showing papers on "Electroplating published in 2002"

Electroless deposition apparatus

Abstract: An apparatus and a method of depositing a catalytic layer comprising at least one metal selected from the group consisting of noble metals, semi-noble metals, alloys thereof, and combinations thereof in sub-micron features formed on a substrate. Examples of noble metals include palladium and platinum. Examples of semi-noble metals include cobalt, nickel, and tungsten. The catalytic layer may be deposited by electroless deposition, electroplating, or chemical vapor deposition. In one embodiment, the catalytic layer may be deposited in the feature to act as a barrier layer to a subsequently deposited conductive material. In another embodiment, the catalytic layer may be deposited over a barrier layer. In yet another embodiment, the catalytic layer may be deposited over a seed layer deposited over the barrier layer to act as a “patch” of any discontinuities in the seed layer. Once the catalytic layer has been deposited, a conductive material, such as copper, may be deposited over the catalytic layer. In one embodiment, the conductive material is deposited over the catalytic layer by electroless deposition. In another embodiment, the conductive material is deposited over the catalytic layer by electroless deposition followed by electroplating or followed by chemical vapor deposition. In still another embodiment, the conductive material is deposited over the catalytic layer by electroplating or by chemical vapor deposition.

Fabrication of semiconductor interconnect structures

Abstract: A system and a method of forming copper interconnect structures in a surface of a wafer is provided. The method includes a step of performing a planar electroplating process in an electrochemical mechanical deposition station for filling copper material into a plurality of cavities formed in the surface of the wafer. The electroplating continues until a planar layer of copper with a predetermined thickness is formed on the surface of the wafer. In a following chemical mechanical polishing step the planar layer is removed until the copper remains in the cavities, insulated from one another by exposed regions of the dielectric layer.

Barrier cap for under bump metal

Abstract: A semiconductor wafer having solder bumps thereon for use in flip-chip bonded integrated circuits comprises a semiconductor substrate formed with metal bond pads at selected locations thereon, a metal electroplating buss layer or layers over the bond pads, a layer of solder-wettable under bump metal on the buss layer, a layer of barrier metal which overlies and encapsulates the solder-wettable metal, and a solder bump formed on the barrier metal.

Effects of boric acid on hydrogen evolution and internal stress in films deposited from a nickel sulfamate bath

Abstract: The effects of boric acid additions on the pH close to the electrode surface, on the hydrogen evolution reaction and on the internal stress in the plated films were studied for the high speed electroplating of nickel from a nickel sulfamate bath at a current density close to the nickel ion limiting current density. The study was carried out at 50 °C and pH 4.0 using a 1.55 M nickel sulfamate plating bath containing boric acid at concentrations ranging from 0 to 0.81 mol L−1. The variation of the internal strain in the plated nickel films was determined in situ using a resistance wire-type strain gauge fitted to the reverse side of the copper electrode substrate. The solution pH at a distance of 0.1 mm from the depositing nickel film was measured in situ using a miniature pH sensor assembly consisting of a thin wire-type antimony electrode and a Ag/AgCl/sat. KCl electrode housed in a thin Luggin capillary. The addition of boric acid was shown to effectively suppress the hydrogen evolution reaction at nickel electrodeposition rates (18.0 A dm−2) close to the limiting current density (~20 A dm−2). Consequently, the solution pH adjacent to the plating metal surface was maintained at a value close to that in the bulk solution and the development of high internal stresses in the deposited nickel films was avoided.

Process for electroplating metallic and metall matrix composite foils, coatings and microcomponents

Abstract: The invention relates to a process for forming coatings or free-standing deposits of nano-crystalline metals, metal alloys or metal matrix composites. The process employs drum plating or selective plating processes involving pulse electrode-position and a non-stationary anode or cathode. Novel nano-crystalline metal matrix composites and micro components are disclosed as well. Also described is a process for forming micro-components with grain sizes below 1,000nm.

Rapid electroplating of insulators.

Abstract: Electrochemical techniques for depositing metal films and coatings have a long history. Such techniques essentially fall into two categories, with different advantages and disadvantages. The first, and oldest, makes use of spontaneous redox reactions to deposit a metal from solution, and can be used on both insulating and metallic substrates. But the deposition conditions of these processes are difficult to control in situ, in part because of the variety of salts and additives present in the solution. The second approach-electroplating-uses an electric current to reduce metal ions in solution, and offers control over the quantity (and, to some extent, grain size) of deposited metal. But application of this technique has hitherto been restricted to conducting substrates. Here we describe an electroplating technique that permits coating of insulating substrates with metals having controlled grain size, thickness and growth speed. The basis of our approach is the progressive outward growth of the metal from an electrode in contact with the substrate, with the cell geometry chosen so that the electron current providing the reduction passes through the growing deposit. Such an approach would normally form dendritic or powdery deposits, but we identify a range of conditions in which uniform films rapidly form.

Adhesion enhanced semiconductor die for mold compound packaging

Abstract: A semiconductor die includes a metal layer deposited thereon for enhancing adhesion between the die and a mold compound package. The metal layer is substantially oxide free. The die is coated with a layer or layers of copper (Cu) and/or palladium (Pd) by electroplating or electroless coating techniques. The metal layer provides a uniform wetting surface for better adhesion of the die with the mold compound during encapsulation. The increased adhesion reduces the delamination potential of the die from the package.

Atomic layer deposition of tungsten barrier layers using tungsten carbonyls and boranes for copper metallization

Abstract: A method of tungsten layer deposition for copper metallization in semiconductor devices includes reacting a tungsten carbonyl compound and a borane compound using a cyclical deposition technique. In one embodiment, the tungsten barrier layer is formed on a patterned dielectric layer by alternately adsorbing the tungsten carbonyl compound and the borane compound onto a semiconductor substrate. The tungsten layers have substantially uniform dimensions and excellent adhesion to copper such as copper seed layers or direct electroplating of copper onto the tungsten layer.

Electroplating of Nanostructured Nickel in Emulsion of Supercritical Carbon Dioxide in Electrolyte Solution

Abstract: We report electroplating in emulsion of supercritical carbon dioxide and electrolyte solution for the first time. Compared to conventional electroplating, this technology has advantages in covering, leveling and throwing effects on plating. Moreover the particle sizes of plated nickel are sub-100 nm.

Process for forming barrier/seed structures for integrated circuits

Abstract: A process and structure are provided that allows electroplating to fill sub-micron, high aspect ratio features using a non-conformal conductive layer between the dielectric layer and the platability layer. The conductive layer is a relatively thick layer overlying the planar surface of the wafer and the bottom of the features to be filled. Little or no material of the conductive layer is formed on the feature sidewalls. The thick conductive layer on the field provides adequate conductivity for uniform electroplating, while the absence of significant conductive material on the sidewalls decreases the aspect ratio of the feature and makes void-free filling easier to accomplish with electroplating. Further, the absence of significant material on the sidewalls allows a thicker barrier layer to be formed for higher reliability.

Inhibiting the formation of (Au1−xNix)Sn4 and reducing the consumption of Ni metallization in solder joints

Abstract: The effects of adding a small amount of Cu into eutectic PbSn solder on the interfacial reaction between the solder and the Au/Ni/Cu metallization were studied. Solder balls of two different compositions, 37Pb-63Sn (wt.%) and 36.8Pb-62.7Sn-0.5Cu, were used. The Au layer (1 ± 0.2 µm) and Ni layer (7 ± 1 µm) in the Au/Ni/Cu metallization were deposited by electroplating. After reflow, the solder joints were aged at 160°C for times ranging from 0 h to 2,000 h. For solder joints without Cu added (37Pb-63Sn), a thick layer of (Au1−xNix)Sn4 was deposited over the Ni3Sn4 layer after the aging. This thick layer of (Au1−xNix)Sn4 can severely weaken the solder joints. However, the addition of 0.5wt.%Cu (36.8Pb-62.7Sn-0.5Cu) completely inhibited the deposition of the (Au1−xNix)Sn4 layer. Only a layer of (Cu1-p-qAupNiq)6Sn5 formed at the interface of the Cu-doped solder joints. Moreover, it was discovered that the formation of (Cu1-p-qAupNiq)6Sn5 significantly reduced the consumption rate of the Ni layer. This reduction in Ni consumption suggests that a thinner Ni layer can be used in Cu-doped solder joints. Rationalizations for these effects are presented in this paper.

Tin Alloy-Graphite Composite Anode for Lithium-Ion Batteries

Abstract: A composite anode material was prepared that contains nanosize (< 100 nm) particles of tin alloy Sn 65 Sb 18 Cu 17 and Sn 62 Sb 21 Cu 17 . The alloys were electroplated at high current densities (above i L ) from aqueous solutions, directly onto the copper current collector, and were coated by a polyvinylidene fluoride-graphite matrix at a ratio of alloy:graphite matrix 70:30 and 80:20 w/w, respectively. The processes involved in electrode production by this method are inexpensive, simple, and fast. Over 40 (100% depth of discharge) cycles were demonstrated, in half-cell, and over 30 were demonstrated with a LiCoO 2 battery containing 1 M LiPF 6 ethylene carbonate-diethyl carbonate electrolyte. The faradaic efficiency (Q De-ins /Q Ins ) is less than 100%. Lithium is fully deinserted from the host matrix only when the anode is cycled at low current densities. The kinetics of lithium insertion to and deinsertion from the composite anode material, slow gradually as the cycle number increases. X-ray diffraction patterns of the anode material show that the alloy becomes amorphous during cycling, while the graphite does not. X-ray photoelectron-spectroscopy measurements reveal that the solid electrolyte interphase consists of mainly LiF, small amounts of Li 2 O, and possibly, polymeric substances. The electrochemical behavior of the alloy changes with cycle number, while that of the graphite does not. The fall of the deinsertion capacity of the graphite from the first cycle to the 34th by more than 50% proves that the active material in the anode suffers from particle-to-particle break off.

Key top for pushbutton switch and method of producing the same

Abstract: According to a method of producing a key top for a pushbutton switch of the present invention, a base layer made of an insulating resin that can be plated with metal, an electroless plating layer to be formed on the surface of the base layer, and a polymer coating layer, if required, are stacked on the surface of a key top body. Alternatively, an electroplating layer formed by electroplating is further formed on the electroless plating layer. Therefore, a plating layer can be directly and easily formed on the insulating resin, whereby a key top for a pushbutton switch having a sensation of metal and being rich in design is obtained.

Method and apparatus for uniform electroplating of thin metal seeded wafers using multiple segmented virtual anode sources

Abstract: The present invention pertains to methods and apparatus for electroplating a substantially uniform layer of a metal onto a work piece having a seed layer thereon. The total current of a plating cell is distributed among a plurality of anodes in the plating cell in order to tailor the current distribution in the plating electrolyte to compensate for resistance and voltage variation across a work piece due to the seed layer. Focusing elements are used to create “virtual anodes” in proximity to the plating surface of the work piece to further control the current distribution in the electrolyte during plating.

Dynamically variable field shaping element

Abstract: In an electrochemical reactor used for electrochemical treatment of a substrate, for example, for electroplating or electropolishing the substrate, one or more of the surface area of a field-shaping shield, the shield's distance between the anode and cathode, and the shield's angular orientation is varied during electrochemical treatment to screen the applied field and to compensate for potential drop along the radius of a wafer. The shield establishes an inverse potential drop in the electrolytic fluid to overcome the resistance of a thin film of conductive metal on the wafer.

The Effect of Plating Current Densities on Self-Annealing Behaviors of Electroplated Copper Films

Abstract: In this study, the effect of plating current densities on self-annealing behaviors of electroplated Cu films was found to be relevant to the polarization resistance of electroplating systems. Porous films with defects occurred at low plating current density or at low polarization resistance. In contrast, dense films with small grains occurred at higher plating current density or at higher polarization resistance. However, when more current was further supplied, Cu aggregation occurred and deposited films became spongy or dendritic. We suggest that both the defects within porous films and the underlying energy of fine-grained deposits accelerated self-annealing. These two characteristics competed with each other to determine the resistivity drop by self-annealing. On the other hand, the (111) texture evolutions of deposited Cu films with an increase of plating current densities were consistent with the evolutions of resistivity and surface morphology. © 2002 The Electrochemical Society. All rights reserved.

Aluminium composite coatings containing micrometre and nanometre-sized particles electroplated from a non-aqueous electrolyte

Abstract: The electrolytic codeposition of micro- and nano-sized particles with aluminum from a nonaqueous electrolyte is investigated. SiC, SiO2, Al2O3, TiB2 and hexagonal BN particles were codeposited with aluminium from an AlCl3/dimethylsulfone (DMSO2) electrolyte. The effect of particle concentration and current density on the codeposition rate of SiO2 with aluminium was investigated. The codeposition of the various particles with Al from AlCl3:DMSO2 solutions is very high. The amount of codeposited particles is Langmuir dependent on the particle concentration in the electrolyte. In contrast, the effect of the current density on the amount of codeposited SiO2 is small.

Copper electroplating method and apparatus

Abstract: An electroplating apparatus prevents anode-mediated degradation of electrolyte additives by creating a mechanism for maintaining separate anolyte and catholyte and preventing mixing thereof within a plating chamber. The separation is accomplished by interposing a porous chemical transport barrier between the anode and cathode. The transport barrier limits the chemical transport (via diffusion and/or convection) of all species but allows migration of ionic species (and hence passage of current) during application of sufficiently large electric fields within electrolyte.

Electroless deposition method over sub-micron apertures

Abstract: An apparatus and a method of depositing a catalytic layer comprising at least one metal selected from the group consisting of noble metals, semi-noble metals, alloys thereof, and combinations thereof in sub-micron features formed on a substrate. Examples of noble metals include palladium and platinum. Examples of semi-noble metals include cobalt, nickel, and tungsten. The catalytic layer may be deposited by electroless deposition, electroplating, or chemical vapor deposition. In one embodiment, the catalytic layer may be deposited in the feature to act as a barrier layer to a subsequently deposited conductive material. In another embodiment, the catalytic layer may be deposited over a barrier layer. In yet another embodiment, the catalytic layer may be deposited over a seed layer deposited over the barrier layer to act as a “patch” of any discontinuities in the seed layer. Once the catalytic layer has been deposited, a conductive material, such as copper, may be deposited over the catalytic layer. In one embodiment, the conductive material is deposited over the catalytic layer by electroless deposition. In another embodiment, the conductive material is deposited over the catalytic layer by electroless deposition followed by electroplating or followed by chemical vapor deposition. In still another embodiment, the conductive material is deposited over the catalytic layer by electroplating or by chemical vapor deposition.

Sacrificial plastic mold with electroplatable base

Abstract: A sacrificial plastic mold having an electroplatable backing is provided. One embodiment consists of the infusion of a softened or molten thermoplastic through a porous metal substrate (sheet, screen, mesh or foam) and into the features of a micro-scale molding tool contacting the porous metal substrate. Upon demolding, the porous metal substrate will be embedded within the thermoplastic and will project a plastic structure with features determined by the mold tool. This plastic structure, in turn, provides a sacrificial plastic mold mechanically bonded to the porous metal substrate which provides a conducting support suitable for electroplating either contiguous or non-contiguous metal replicates. After electroplating and lapping, the sacrificial plastic can be dissolved to leave the desired metal structure bonded to the porous metal substrate. Optionally, the electroplated structures may be debonded from the porous substrate by selective dissolution of the porous substrate or a coating thereon.

Phosphorized copper anode for electroplating

Abstract: A phosphorized copper anode used for electroplating, including: 20-800 ppm of phosphorus; between 0.1 and less than 2 ppm of oxygen, and the balance being high purity copper having a purity of 99.9999% by mass or higher, wherein the average grain size of the copper anode after recrystallization is in the range between about 10 and 50 μm.

Chip package and method for manufacturing the same

Abstract: In a chip package, when a Ni/Au layer is formed by electroless plating, there is no problem with density increasing of interconnections and the like, since leads for plating and tie bars are not formed. However, the adhesive strength of solder balls to ball pads is low, so that the adhesion tends to be unstable. In the present invention, no leads for plating are formed, while the adhesive strength of solder balls to ball pads is improved by electroplating the ball pads with a Ni/Au layer. In addition, an increase in the density of interconnections and an improvement of the electrical properties is also obtained. The Ni/Au layer is formed by electroplating on the base metal layer surface which is not covered with a DFR (Dry Film Resist) by applying an electric current to the base metal layer.

Enhanced Transport by Acoustic Streaming in Deep Trench-Like Cavities

Abstract: .Fabrication of microelectronic and LIGA microdevices often requires transport of chemical species into or out of liquid-filled microcavities. Two common examples are the chemical development of patterned photoresists to produce recessed features and the filling of such features by electrodeposition. During chemical development, fragments of the resist must be transported from the bottom of narrow features into the development bath. Similarly, filling of a patterned resist by electrodeposition requires transport of metal ions from the electroplating bath into the features. This plating process is commonly used to form microelectronic interconnects having submicrometer linewidths. Although the depths of these features may be several times greater than their widths, they rarely exceed a depth of 1 mm. Over these short length scales, diffusion provides very effective transport of chemical species. Transport rates are, however, smaller by orders of magnitude in the LIGA process used to produce detailed metal parts having depth dimensions of a millimeter or more. The acronym LIGA is derived from the German words for lithography, electroforming, and molding. 1 In LIGA, a high-energy X-ray source is used to expose a thick photoresist, typically polymethylmethacrylate ~PMMA!, through a patterned absorber mask. The exposed material is then removed by chemical dissolution in a development bath. This development process yields a nonconducting mold having a conducting substrate beneath deep cavities that are subsequently filled by electrodeposition. The resulting metal parts may be the final product or may be used as injection or embossing molds for mass production. Development and deposition rates in recessed features depend on both species transport and surface reaction kinetics. Transport is rarely an issue in conventional electroplating on flat surfaces where surface ion concentrations can be maintained by pumping bath fluids or by moving the substrate relative to the bath. However, in plating or development of patterned photoresists, even a very strong external flow is not effective in providing increased transport into recessed features having aspect ratios greater than one or two. 2-4 This is because the convective cell that circulates the fluid in the top of each feature penetrates only about one feature width. Additional counter-rotating convective cells are formed deeper within high aspect ratio features, but the circulation speeds decrease by nearly two

Degradation of power contacts in industrial atmosphere: silver corrosion and whiskers

Abstract: Degradation of power contacts in a corrosive atmosphere leads to significant increase of the contact resistance and consequently to a rise in temperature, and eventually to failure. In electrical apparatus, both base metal copper and silver plating heavily corrode in environments containing sulfuric gases. In addition, expansive growth of silver filaments (whiskers) has often been found on primary current conductors of circuit breakers. This paper describes extensive whisker growth found in switchgear at a paper recycling mill. The major environmental factor to initiate the growth is a relatively low concentration of hydrogen sulfide (H/sub 2/S). As soon as a thick enough layer of silver sulfide has been formed, metal filaments start to grow virtually everywhere but most intensely in locations usually having elevated temperature while electrical units are energized. Though this hazardous phenomenon has been seen from the 1920s and caused a number of violent failures, it was practically neither studied nor understood. In just two months since the previous cleaning, we found the filaments up to several inches (6-8 cm) long and up to 0.04 in (1 mm) thick. Using SEM/EDS analysis, we have determined chemical composition and morphology of the whiskers. Most of the whiskers are made of silver with 1-3% of copper. The surface of the whiskers long exposed to atmosphere is contaminated with silver sulfide. After thoroughly investigating the factors that initiate and accelerate whisker growth, we have determined effective means of eliminating this extremely hazardous phenomenon.

Swelling of PMMA-structures in aqueous solutions and room temperature Ni-electroforming

Abstract: LIGA-structures are known to have a lateral dimensional precision of 1 μm and below. These specifications strongly depend on the process parameters. Fabrication of 400 μm tall nickel LIGA-structures by electroplating of X-ray patterned (DXRL) resist structures revealed much higher distortions. These are caused on the one hand by thermal expansion of the structured resist since the electroforming is usually performed at 52 °C, but on the other hand to a higher degree by swelling of the resist in the aqueous electroplating bath. Reducing the electrolyte temperature not only eliminates the thermal expansion but also particularly reduces the swelling. At room temperature the latter is reduced by a factor of 3 in comparison to the usual 52 °C-bath leading to an overall reduction of the deformation of up to 80%. In this paper the experimental data are presented and the results are explained. Furthermore first microstructures electroplated at room temperature with optimized precision are shown.

Electrodeposition of Nickel/Montmorillonite Layered Silicate Nanocomposite Thin Films

Abstract: In this study, the electrochemical deposition of nickel/montmorillonite nanocomposite films was investigated on stainless steel and copper substrates. Deposition variables that were investigated included electrochemical cell orientation, degree of agitation during deposition, and montmorillonite concentration in the electroplating solution. The resulting films were characterized with scanning electron microscopy, X-ray diffraction, and X-ray fluorescence techniques. By a novel electrochemical cell construction, an orderly deposition of nickel/montmorillonite nanocomposite films was ultimately achieved. Scanning electron microscopy images characterized these films with an ordered surface topography of horizontal montmorillonite platelets held in a nickel media. Profile scanning electron microscopy images further showed a heavily striated stack of aligned montmorillonite layered silicate platelets throughout the profile of the nickel/montmorillonite nanocomposite film. Also, X-ray fluorescence verified the ...