Cu/Ni-P multilayers of 10μm thickness, consisting of pure Cu sublayers and Ni-P sublayers of which thicknesses are 50, 100, and 200nm, have been prepared on Cu substrates by electrodeposition from a single bath by using modulated (i.e. periodic pulse control) current density. Change in hardness of the multilayers with annealing temperature ranging between 473K and 873K has been examined and discussed in relation to the concomitant structural change. Cross-sectional views of the multilayers by a transmission electron microscope demonstrate that the layered structure disappears on annealing at temperatures above 673K. The hardness of the multilayers increases with an increase in annealing temperature, exhibiting the maximum value at 673K and decreases. The hardness behavior of the multilayers is discussed on the basis of dislocation inhibition at the interface in the multilayers.
Two kinds of flexible composite films, V2OX-PPTA and V2OX/Au-PPTA, were prepared by electrodeposition methods. The V2OX-PPTA film was obtained by electrooxidation of VOSO4 using the electrode with which poly (p-phenylene terephtal amide) (PPTA) film was covered as a matrix film. The V2OX/Au-PPTA film was obtained by over-electrodepositing gold on the V2OX-PPTA film. Both films exhibited bright electrochromism: from catholic to anodic polarization, dark green-green-yellow color change for the V2OX-PPTA film, and black green-dark green-red color change for the V2OX/Au-PPTA film. The electrochromic properties were examined using cyclic voltam-mograms, absorption spectra, XPS spectra, and so on; the red was estimated due to the lower valence vanadium. The film was self-supporting because the matrix film was mechanically strong and flexible.
Electroless silver plating intended to have a “neutral pH” and to be “cyanide free” was investigated using imidazole as the reducing agent and succinimide as the complexing agent. Complex baths exhibited good storage stability, and pure silver films were deposited. Deposition is achieved by plating in a composition that displys neither displacement for electroless-nickel-coated substrates nor autocatalysis. The displacement deposition of silver decreased with an increase in the phosphorus content of the electroless nickel substrate. Experiments in polarization characteristics confirmed the mixed potential theory including local potential-current relationships for silver deposition.
Electrochemical displacement of a portion of a TiN thin film, a diffusion barrier, on a Si-based wafer with copper was examined at ambient temperature, with the ultimate purpose of developing a novel copper metallization for the manufacture of ULSI-interconnects. The rate of oxidative dissolution of TiN was increased with a decrease in the pH of the solution used for displacement and was independent of Cu (II) ion concentration, suggesting that hydrogen ions act as an oxidizing agent even in the presence of Cu (II). The deposition rate of Cu was affected by both pH and fluoride ion concentration and increased with a decrease in fluoride ions. This dissolution/deposition behavior was discussed thermodynamically using a potential-pH diagram of the Cu-F-H2O system.
Electroless silver plating using the oxidation reaction of Co (II) was investigated. Co (II) complexes with ammonia of amines were found to be an effective reducing agent for deposition. Plating reaction was promoted autocatalytically without hydrogen evolution. Deposited silver films displayed excellent optical reflection properties like those of vacuum silver deposits. However, the deposition rate gradually decreased with the reaction time since Co (II)-amine complex ions are readily self oxidized in an air atmosphere and bath life diminished. Bath life can be prolonged with the prevention of Co (II) oxidation in a nitrogen atmosphere.
Isotropic chemical wet etching of n-Si (110) was investigated in KOH solution under applied voltage. It was shown that isotropic etching was achieved in 32wt% KOH at 110°C when applied voltage to the Si wafer was greater than 0.6V (vs. Pt electrode), while the Si wafer was etched anisotropically without applying voltage. This result shows that the etching property, isotropic or anisotropic, is varied by applying voltage. The etching rate of Si (110) for isotropic and the anisotropic etching were 0.1μm/min and 9μm/min, respectively at 110°C. In addition, the etching rate of the isotropic etching did not dependent on the applied voltage when using n-Si. The cause of the isotropic etching in KOH solution originated from etching through the anodic oxide layer formed on the Si surface due to XPS-analysis and the temperature dependence of the etching rate.