Method for filling small holes or covering small recesses in the surface of substrates

A method of filling a recess of not more than about 1 .mu.m in depth and width in a surface of a substrate, which comprises contacting the recess in the surface of the substrate by a solution of a mixture of potassium silver cyanide and potassium cyanide so that said solution wets inner surfaces of said recess to have a silver layer deposited, the method including applying a light energy to the surface of the substrate such that light energy is applied to the surface of the substrate including the recess while said silver layer is being deposited, thereby causing the solution to penetrate deeply to a bottom of the recess so as to permit a filling of the recess, the method further including depositing a Ni--B alloy on at least the silver filling layer by performing electroless plating using a solution of a mixture of NiSO.sub.4 -6H.sub.2 O, a complexing agent and a reducing agent.

• wherein:
• the step of applying a light energy includes providing a light source and directing light from said light source through a condenser lens and onto said substrate;
• a voltage is applied at a maximum of 20 volts to the surface of the substrate as the silver layer is deposited thereon;
• the voltage is applied as a pulsed waveform;
• and
• a copper layer is provided in said recess of said substrate prior to contacting said recess with the solution of a mixture of potassium silver cyanide and potassium cyanide such that said solution wets said copper layer.