| 摘要 |
Selected areas of the surface of a base metal or semi-conductor, e.g. a tantalum or an aluminium foil capacitor, are anodized by depositing a layer of masking metal or semiconductor, e.g. aluminium or titanium respectively, on selected portions of the surface, anodizing both the surface of the base metal or semi-conductor where exposed and of the masking metal or semi-conductor to form films of base oxide and masking oxide repectively, and selectively removing the masking metal or semi-conductor and its oxide film from the surface of the base metal or semi-conductor, e.g. by etching in dilute NaOH solution (for Al etching) or 50% H2SO4 (for Ti etching), to expose unanodized areas on the base metal or semi-conductor surface. Other combinations of base and masking metal or semi-conductor are: Bi for masking Nb using HNO3 etchant solution, Al for W using KOH solution and Al for Zr using NH4OH solution, and Bi for masking Al using HNO3 etchant solution; other suitable materials may be Mo, Zr, Hf, Sb, Be, Mg, Si, Ge, Sn and U. The masking material may be applied by spraying, vapour deposition or evaporation decomposition of organo-metallic compounds, e.g. a metal carbonyl, and removed by chemical or electrolytic etching. The anodizing bath may be a solution of boric acid and sodium tetraborate, or a solution of sodium sulphate, or sulphuric, phosphoric or citric acid. Besides capacitors, the method may be applied to masking tunnel emission diodes and insulated gates for 3-terminal devices for thin film transistors. |
