Formation and structure of mesoporous silicon

This paper provides the results of studying the formation kinetics and the structure of mesoporous silicon layers obtained by electrochemical anodization in an electrolyte based on 12% aqueous hydrofluoric acid. The electrolyte consisted only of deionized water and hydrofluoric acid and contained no organic additives in order to prevent contamination of porous silicon with carbon during the anodization. All the experiments were carried out on whole silicon wafers 100 mm in diameter, rather than samples of a small size, which are often used to save silicon. As the initial substrates we used monocrystalline silicon wafers of brand KES-0.01, which were cut from the ingots produced by the Czochralski method. Dependences of the thickness of porous silicon layers, its growth rate, and the volume porosity on the anodic current density and the anodization time are determined. Scanning electron microscopy was used to study the structure of porous silicon layers and to define the size and density of the pore channels. The regimes of obtaining homogeneous porous silicon layers for their subsequent use as buffer layers in epitaxy are found.