Abstract
We reported laser-assisted maskless metal patterning on p-type silicon previously. The process uses photo-excited electrons, and therefore it is applicable only to p-type silicon, because the n-type has abundant free electrons, and selective metal deposition cannot be expected. In the present work, we studied the possibility of achieving the metal patterning on n-type silicon. Various noble metals can be deposited on silicon by immersion plating. In the immersion plating of copper, deposition is observed on a porous silicon surface, but not on a flat silicon surface. Porous silicon is formed by silicon anodization. The reaction requires holes, and n-type silicon lacks enough holes to promote the dissolution reaction. When the surface is locally illuminated by a laser, the photo-excited area can be locally anodized, and a porous silicon pattern can be formed in n-type silicon without a mask. Using the above, copper deposition dependent upon the surface state and porous silicon patterning on the surface, we succeeded in patterning copper on n-type silicon without using a mask.
