Anodic dissolution of silicon monocrystals in anhydrous organic solutions of chlorides

Abstract

The electrochemical investigations of p- and n-silicon monocrystals were performed in anhydrous organic solutions of LiClO 4, LiCl and HCl to examine the possibility of etching and passivation of silicon semiconductors. The results obtained by means of linear sweep voltammetry (LSV), potentiostatic and galvanostatic transient technique, as well as XPS surface analysis allow us to give an explanation of the mechanism of silicon dissolution in these media. Silicon dissolves in anhydrous organic solvents (methanol, N, N-dimethyloformamide, formamide) which contain chloride ions according to the consecutive two-step mechanism. The Si(II) ad intermediate inhibits the anodic dissolution at low overpotentials. The presence of this intermediate was confirmed by means of XPS measurements on potentiostatically etched surface. The increase in chloride concentration in organic solvents stimulates desorption of the intermediate and therefore increases the rate of surface etching. The best results in anodic etching of silicon monocrystals have been obtained in anhydrous HCl solutions. Microscopic observations of surface morphology of Si monocrystals after etching show anisotropy of anodic dissolution.