Method of plating for filling via holes

A method of plating for filling via holes, in which each of via holes formed in an insulation layer covering a substrate so as to expose, at its bottom, part of a conductor layer located on the substrate, is plated with copper to fill the via holes with plated copper, the method comprising the steps of:

• forming a copper film on the top surface of the insulation layer covering the substrate, and the side walls and bottoms of the respective via holes,
• forming a strike plating of copper on the surface of the copper film,
• immersing the substrate having the copper film and copper strike plating formed thereon in an aqueous solution containing a plating promoter to thereby deposit the plating promoter on the surface of the copper strike plating,
• removing the plating promoter from the surface of the copper strike plating located on the ton surface of the insulation layer and leaving the plating promoter on the side walls and bottoms of the respective via holes, and
• electroplating the substrate having the copper film and copper strike plating with copper to thereby fill the via holes with the plated copper and simultaneously form a continuous copper film which eventually covers the via holes filled with the plated copper as well as the copper strike plating previously formed on the top surface of the insulation layer.