Electroless Ni-B Research Articles

Maskless Fabrication for Micropad Interconnection using Electroless NiB Deposition and Application to "Chemical" Flip-Chip Bonding

Deposition behavior of localized electroless NiB deposition for pad-to-pad connection was investigated. Localized deposition occurred mainly on the area between facing pads, and anisotropic deposition toward each facing pad was obtained. Thus, this connection, "preferential bridge connection", is no need of photolithographic technique. These results indicated that this process is one of the maskless fabrication processes. Moreover, chemical flip-chip bonding containing preferential bridge interconnection was demonstrated. The chip-to-substrate interconnection with 30 micrometer pitch was successfully achieved.

Bridge Connection for Facing Pads Arrays with Pad-position Shifts Using Controlled Extraneous Deposition of Electroless NiB

Bridge Connection for Facing Pads Arrays with Pad-position Shifts Using Controlled Extraneous Deposition of Electroless NiB

Interconnection of Multi-Pad Electrodes by "Controlled Anisotropic Extraneous (CAEx) Deposition" of Electroless NiB Film

Interconnection of multi-pad array was developed by using the electroless CAEx deposition of NiB for application to the new flip-chip bonding technology. Behavior of CAEx deposition of Electroless NiB films was depended on pad width and distance between facing pads, and pad with nearer distance and wider pad size was achieved. Practical feasibility of this technique was demonstrated by forming interconnection between pads separated by 5 micrometer and measuring 5 micrometer in both height and width. This method was applied successfully to interconnecting the pads forming an array with a pitch of 20 micrometer.

Chemical flip-chip bonding method for fabricating 10-.MU.m-pad-pitch interconnect

A flip-chip bonding method has been developed for fabricating ultrafine-pitch pad-to-pad interconnects. The method utilizes the preferential growth of Ni-B bridge layers on resin walls in a microscale cavity structure fabricated in the underfill resin between copper pads facing each other under some conditions of electroless Ni-B plating. In this method, the interconnect can be fabricated without loading and/or heating. By controlling the growth of the bridge layer on the resin walls in the microscale cavity under optimized plating conditions, the feasibility of ultrafine-pitch flip-chip bonding with a 10-µm pad pitch is experimentally demonstrated at a temperature of 60°C.

Electrooxidation of Ethanol at Ni-B Amorphous Alloy Electrode and Measurements of Kinetic Parameters

Electrocatalytic oxidation of ethanol at the nano Ni-B amorphous alloy powder microelectrode and the electroless Ni-B amorphous alloy microdisk electrode in alkaline media was studied by using cyclic voltammetry. It was found that the nano Ni-B amorphous alloy microelectrode had higher electrocatalytic activity for the oxidation of ethanol than the electroless Ni-B amorphous alloy microdisk electrode. The kinetic parameters were determined with the steady polarization curves. The rates of electrocatalytic oxidation of ethanol at the nano Ni-B amorphous alloy microelectrode in alkaline media were much higher than those at the highly preferred orientation (220) nickel electrode. The proton diffusion coefficient of Ni(OH)2 at the nano Ni-B amorphous alloy powder microelectrode determined by cyclic voltammetry was increased by about 2 orders of magnitude, in comparison with the reported values at Ni nanowire electrode and the spherical Ni(OH)2 microencapsulated by cobalt.

Interconnection of Multi-Pad Electrodes by "Controlled Anisotropic Extraneous (CAEx) Deposition" of Electroless NiB Film

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Characterization Of The film Of Ni-B Electroless on Steel S7, Through Optical Microscopy and Scanning Electron Microscopy.

Microstructural characterization is a fundamental tool for the study of plating, since the macroscopic behavior of films can be correlated with microstructure of films. In this work we show the results of characterization of an electroless Ni-B film deposited on a steel S7; it was found that boron content was lower as immersion time on Ni-B bath increases and hardness was also lower as thickness of film increased. At interface, equiaxed growth of grains is probably induced by the high amount of nucleation sites on substrate surface. After thermal treatment, the highest hardness was near the Ni-B film-substrate interface. The thermal treatment at 400 {degree sign}C reduced the amount of equiaxed grains and induces the formation of Ni3B phase.

Interconnection of Micropad Electrodes by Controlled “Extraneous” Deposition of Electroless NiB Film

A method of interconnecting micropad electrodes was developed by using the electroless of NiB for application to the flip-chip bonding technology. The phenomenon of bridge formation by the so-called deposition was utilized as a technique to perform selective of NiB on noncatalytic surfaces. The process of extraneous electroless was controlled by optimizing conditions so that the deposit grew anisotropically along the surface between the facing pads. Practical feasibility of this technique was demonstrated by forming an interconnection between pads separated by 5 μm and measuring 5 μm in both height and width. This method was applied successfully to interconnecting the pads forming an array with a pitch of 20 μm.

An overall aspect of electroless Ni-P depositions—A review article

Literature on electroless Ni-P deposition, in recent decades, has dwelled primarily on surface engineering and corrosion-resistant applications. By contrast, we have many research articles devoted to the engineering aspects of the electroless Ni-P depositions and their technology. The present article deals with the development of electroless Ni-P bath, advantages and mechanisms of deposition, and applications of the Ni-P deposits. We also present a comparison of the properties of electroless Ni-P and Ni-B as well as the recent developments in nickel-phosphorous research. We attempt to review these in a detailed manner. We also briefly discuss the future developments of electroless Ni-P.

Electroless Ni-B plating for electrical contact applications

Electroless Ni-B plating has been tried on steel substrate in an effort to employ low-cost starting materials for electrical contacts or connectors. By selected conditions of heat treatment in a high vacuum environment the plating can acquire Cr-equivalent hardness without the effluents of the hard chromium plating process. The surfaces were characterized under scanning electron microscope and by XRD. The fabricated materials were tested under corrosion conditions by polarization measurements. Semispherical nickel plated steel joints were tested in a computer controlled contact make-break apparatus, under simultaneous application of a mechanical and a low-voltage electrical load for 20,000 cycles. After heat treatment the plating acquires a crystalline structure with very good adhesion to the substrate material. Corrosion decreases and increased hardness is obtained. The surface is also characterized by good electrical properties during aging accelerated tests.

All-wet fabrication process for ULSI interconnect technologies

“All-wet process” for fabrication of Cu wiring on a silicon chip was proposed as a novel ultra-large scale integration (ULSI) interconnect technology for integrated circuits (ICs) applications. Electroless-NiB film was deposited on SiO 2/Si substrate modified by self-assembled-monolayer (SAM) activated with PdCl 2. The NiB film formed by this method has highly uniform, with good adhesion to the substrate and with good diffusion barrier characteristics against Cu diffusion. Cu was electrodeposited directly on the electroless NiB film that acted as a seed layer. This was done without any conventional conductive or adhesive layer that is conventionally formed by physical vapor deposition (PDV). The thermal stability of electroless NiB layer as a barrier preventing copper from diffusing into the SiO 2/Si substrate was evaluated by secondary ion mass spectroscopy (SIMS) and sheet resistance measurement at several annealing temperatures. It was confirmed that the electroless NiB film blocked Cu diffusion and kept the layer integrity under annealing temperatures of up to 400 °C for 30 min. The same process of electroless NiB was used for the capping layer that was also formed by “wet process”, as the electroless NiB film deposited selectively onto a surface of Cu wiring was also applicable to a capping layer. We conclude that the proposed process is very promising for sub-100 nm technologies as it offers a variety of desirable properties: it has good step coverage while showing good barrier and seed layer properties.

高アスペクト比トレンチ内における無電解めっき反応の解析

Electroless plating has been extensively applied to electronic devices, since it provides superior throwing power and uniform film formation for complicated geometries. In this study, the formation of a conductive layer in the deep-recessed trenches by using electroless Ni-B plating was investigated. The selection of the complexing agent is important to obtain high uniformity of Ni films in the deep-recessed trenches. Superior uniformity of Ni films in the deep-recessed trenches was obtained by using DL-malic acid as a complexing agent. On the other hand, Ni films from a bath containing glycine were not uniformly deposited, and no deposition was observed at the bottom of the deep-recessed trenches. The influence of the complexing agent on the initial plating reaction was investigated by electrochemical analysis. The deposition reaction obtained from the glycine bath is based on diffusion control. Therefore, nickel ions are mainly reduced at the aperture area of the trenches, and little or no reaction occurred at the bottom area of the trenches in the glycine bath. That is because almost all the Ni ions are consumed at the surface and aperture area. On the other hand, the Ni deposition is not dominated by diffusion control in the DL-malic acid bath. Accordingly, uniform deposition in the trenches can be achieved since the nickel ions reached the bottom of the trenches. In conclusion, it is important to plate uniformly in deep-recessed trenches so that the deposition reaction will not be dominated by the diffusion control state.

Microstructure evolution of electroless Ni-B film during its depositing process

An electroless Ni-B film was deposited in natural state of the plating bath. The structure and composition distribution in depth of the film were explored by X-ray diffraction (XRD) and Auger electron spectroscopy (AES) after the deposition. It was found that the film experienced morphologic transformations during the deposition. The morphology of the film varied in-step with its structure and was presumably relevant with the changes of depositing rate. The mechanism that leads to the morphologic transformations has been discussed.

Influence of the Complexing Agents on the Thickness Uniformity of Electroless Nickel Plating in Deep-Recessed Trenches

Electroless plating has been extensively applied to electronic devices because it provides superior throwing power and uniform film formation for complicated geometries. In this study, the formation of the conductive layer in the deep-recessed trenches using electroless Ni-B plating was investigated. Uniformity of plating films was greatly influenced by the selection of the complexing agent. Superior uniformity of Ni films in deep-recessed trenches was obtained by the electroless plating bath containing DL-malic acid. On the other hand, Ni films from a bath containing glycine were not uniformly deposited and no deposition was obtained at the bottom of deep-recessed trenches. Dependence on a selected complexing agent to the initial plating reaction was investigated by the electrochemical analysis. It is confirmed that the induction time before initiation of deposition was influenced by the complexing agent, and adsorbed Pd catalyst in the trenches was dissolved during the induction time and Ni films are not uniformly deposited by the dissolution of adsorbed Pd in the trenches if the plating bath shows the long induction time. © 2004 The Electrochemical Society. All rights reserved.

Effect of Heat Treatment of the Diffusion Barrier for Bus Electrode of Plasma Display by Electroless Ni-B Deposition

Thin Ni-B films, 1 <TEX>${\mu}m$</TEX> thick, were electrolessly deposited on Cu bus electrode fabricated by electro deposition. The purpose of these films is to encapsulate Cu electrodes for preventing Cu oxidation and to serve as a diffusion barrier against copper contamination of dielectric layer in AC-plasma display panel. The layers were heat treated at <TEX>$580^{\circ}C$</TEX>(baking temperature of dielectric layer) with and without pre-annealing at <TEX>$300^{\circ}C$</TEX>(<TEX>$Ni_{3}B$</TEX> formation temperature) for 30 minutes. In the layer with pre-annealing, amount of Cu diffusion was lower about 5 times than that in the layer without pre-annealing. The difference of Cu concentration could be attributed to Cu diffusion before <TEX>$Ni_{3}B$</TEX> formation at grain boundaries. However, the diffusion behavior of the layer with pre-annealing was similar to that of the layer without pre-annealing after <TEX>$Ni_{3}B$</TEX> formation. With increasing annealing time, Cu concentration of both layers increased due to grain growth.

Formation and characterization of borohydride reduced electroless nickel deposits

The present work aims to study the formation of electroless Ni-B deposits and evaluation of their characteristic properties. An alkaline bath having nickel chloride as the source of nickel and borohydride as the reducing agent was used to prepare the electroless Ni-B deposits. The influence of variation in bath constituents as well as operating conditions on the plating rate, and, the nickel and boron content, of the resultant Ni-B deposits were studied. Selected deposits were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), evolved gas analysis (EGA), vibrating sample magnetometer (VSM) and transmission electron microscope (TEM), respectively, for assessing the phase content, phase transformation behaviour, liberation of hydrogen during crystallization, saturation magnetic moment and micro-structural features. The corrosion resistance of Ni-B deposits, in 3.5% sodium chloride solution, both in as-plated and heat-treated (450 °C/1 h) conditions, was also evaluated by potentiostatic polarization and electrochemical impedance studies. XRD patterns reveal that Ni-B deposits of the present study are amorphous in as-plated condition and undergo phase transformation to crystalline nickel and nickel borides upon heat-treatment. DSC traces exhibit two exothermic peaks at 306 and 427 °C, corresponding to the phase transformation of amorphous Ni-B to crystalline nickel and Ni 3B phases and the transformation of a higher phase compound to Ni 3B and Ni 2B, respectively. TEM microstructures and EGA strongly support the occurrence of phase transitions at 306 and 427 °C. Electroless Ni-B deposits demonstrate a moderate corrosion resistance in 3.5% sodium chloride solution. The extent of corrosion resistance offered by electroless Ni-B deposits is relatively less compared to electroless Ni-9 wt.% P deposit.

Fabrication of the Diffusion Barrier for Bus Electrode of Plasma Display by Electroless Ni-B Plating

【In this study, we have investigated the availability of the electroless Ni-B plating for a diffusion barrier of the bus electrode. The Ni-B layer of 1 $\beta$ : thick was electroless deposited on the electroplated Cu bus electrode for AC plasma display. The layer was to encapsulate Cu bus electrode to prevent from its oxidation and to serve as a diffusion barrier against Cu contamination of the transparent dielectric layer in AC plasma display. The microstructure of the as-plated barrier layer was made of an amorphous phase and the structure was converted to crystalline at about 30 $0^{\circ}C$ . The concentration of boron was about 5∼6 wt.% in the electroless Ni-B deposit regardless of DMAB concentration. The electroless Ni-B deposit was coated on the surface of the electroplated Cu bus electrode uniformly. And the electroless Ni-B plating was found to be an appropriate process to form the diffusion barrier.】

Substrate (Ni)-Catalyzed Electroless Gold Deposition from a Noncyanide Bath Containing Thiosulfate and Sulfite : I. Reaction Mechanism

Electroless gold deposition is known to take place on Ni-based substrates even when the conventional reducing agent is excluded from the autocatalytic bath containing thiosulfate and sulfite as ligands for gold ions. It is shown in this paper that the reaction of gold deposition from this bath on electroless Ni-B substrate is not autocatalytic but, instead, proceeds primarily by the mechanism of substrate catalysis with galvanic displacement playing a secondary role. It was established that sulfite serves as the reducing agent for the substrate-catalyzed gold deposition reaction. © 2002 The Electrochemical Society. All rights reserved.

ＤＭＡＢを還元剤とした無電解ＮｉＢめっきの浴安定性とめっき膜のはんだ濡れ性評価

ＤＭＡＢを還元剤とした無電解ＮｉＢめっきの浴安定性とめっき膜のはんだ濡れ性評価

Formation and Analysis of High Resistivity Electroless NiReB Films Deposited from a Sodium Citrate Bath

An electroless NiB plating bath including ammonium perrhenate was used to investigate the effect of Re and B on the resistivity and the structure of NiReB film. The Re content in the film increased rapidly while the B content decreased with increasing ammonium perrhenate concentration of the electrolyte. The films exhibit an increasing specific resistance (ρ) and decreasing temperature coefficient of resistance (TCR) as the Re content increased. For films with less than 14 wt % Re content, the value of TCR is stable until a 300°C heat-treatment; its stability is maintained until 500°C for the higher Re content films. According to X-ray diffraction measurement, the as-deposited films were amorphous for the low Re content films, while a fine devitrified structure of hexagonal close-packed ReNi was observed for films with a high Re content. After heat-treating the low Re content film at 500°C crystallized the forming face-centered cubic NiRe and phases. On the other hand, the crystalline structure of the high Re content films was not altered by annealing to 500°C. © 2001 The Electrochemical Society. All rights reserved.