| abstract |
A method of forming a copper film on a ceramic substrate comprises the steps of forming an undercoat containing copper on the ceramic substrate, heat-treating the undercoated substrate in an oxidation atmosphere to obtain a copper oxide layer in a surface of the undercoat, reducing the copper oxide layer to a metallic copper layer within a bath of a reducing solution, and forming an additional copper layer on the metallic copper layer to obtain the copper film. As the reducing solution, a solution of a boron hydride salt, dimethylamine borane, or the like, can be utilized. In particular, when the reducing solution is of dimethylamine borane, the reducing step can be performed at a temperature between 30 DEG C and 50 DEG C. A second undercoat of bismuth may be formed on the copper undercoat, and the method may be used in forming copper circuit patterns on the ceramic substrate. |