Formation mechanism of porous silicon layers obtained by anodization of monocrystalline n-type silicon in HF solutions

Abstract

A mechanism for porous silicon layer formation during n-type silicon anodization in hydrofluoric acid is proposed. The mechanism is based on the idea that silicon dissolution takes place at active impurity sites which are responsible for local electric field enhancement resulting in the breakdown of the depletion charge layer and initiation of pores. It is shown that the depletion charge layer exerts an essential influence on the process of pore channel formation. The equation for calculation of the average pore sizes and of the average distance between the pore walls in dependence on the conditions of the porous silicon layer formation is obtained. The mechanism presented explains earlier observed experimental data.