Combinational approach of electrochemical etching and metal-assisted chemical etching for p-type silicon wire formation

Ordered porous silicon and silicon wire arrays are conventionally fabricated by electrochemical etching in an electrolyte incorporating hydrofluoric acid through formation of a periodical etch pit with an inversed pyramid shape created by KOH etching depending on the crystal orientation of silicon. We propose a new process to form an etch pit using metal-assisted chemical etching, which is not dependent on the crystal orientation of the silicon substrate. The proposed process involves a simpler electrochemical etching process and lower manufacturing cost. Furthermore, it is exploited to produce p-type silicon wire arrays with aspect ratio of more than 5.