Effect of the composition of electrolyte on separation of porous silicon film by electrochemical etching

Formation and separation of thin porous silicon films from the original substrate in combination with the transfer of such films onto a cheap foreign substrate for the photovoltaic application provides a straightforward way to cost reduction. Separation of the porous silicon film from the reusable p+ silicon substrate is achieved by electrochemical etching of silicon under specific HF concentration and current densities. The effect of HF concentration on film separation is studied. It is found that film separation is possible only for HF concentration of 22% and lower. Addition of DI water in the solution results in the formation of a thick porous silicon layer without separation from the substrate during 10 minutes. A theoretical explanation has been given to describe the phenomena of porous silicon film separation.