New approach for the formation and separation of a thin porous silicon layer

A new one-step method is developed for the formation and separation of a th in porous silicon film (PSF) by electrochemical etching of silicon in hydro fluoric (HF) acid based solution. This provides advantages over the existin g techniques, which are requiring multiple-steps for fabrication and separa tion of a thin layer horn the substrate. The in-situ change in the fluoride ion concentration results in the formation of a high porosity layer beneat h the low porosity layer under the same formation condition, which is confi rmed by detailed morphological analysis. In-situ separation of a thin porou s silicon film from the substrate is obtained by carrying out an anodizatio n for sufficiently long Lime. A two-step approach is also proposed which co nsists of an electrochemical etching followed by an electrochemical polishi ng step and provides a better control over the separation condition than th e one-step approach.