Abstract
Recent demands for cheaper and more compact devices require electronic devices to have more added in printed circuit boards. To meet these demands, smooth copper foils that enable finer copper wiring has need to be fabricated. For achieving such wiring, the effect that the initial deposition of copper on a titanium cathode has on the smoothness of the resultant foil and the effect of physical polishing and chemical etching of the cathode surface on the initial deposition of copper were investigated. The morphology of the titanium surface was modified by chemical etching using dilute sulfuric acid and by physical polishing with emery paper. We confirmed that the initial deposition of copper considerably affects the smoothness of the copper foil and that smooth foil can be obtained by the etching and polishing processes. In cathode samples where physical and chemical treatments were performed on the surface, the amount of deposition on the cathode was found to be high. We also confirmed the possibility of fabricating fine copper foil with minimal surface roughness. Irregularities with a depth of approximately 0.1 µm and line defects were observed on the surface of the treated titanium cathode, and the atomic ratio of metallic titanium on the surface by a factor of increased 3 to 4 as compared to those without treatment. The surface of titanium is covered by oxides and can be exposed by chemical etching and physical polishing. It is thought that the exposed areas of metallic titanium, which has a low electrical resistivity, act as nucleation points for the initial copper deposits and are useful for obtaining smooth copper foil through uniform copper deposition.
