METHOD FOR PRODUCING HIGH-PURITY SILICON POWDER Russian patent published in 1997 - IPC

FIELD: non-ferrous metallurgy; production of semiconductor-grade silicon, environmental control. SUBSTANCE: finely divided technical-grade silicon contaminated with calcium is subjected to treatment with solution of mixture of mineral acids. Treatment is carried out in two steps. In first step, precursor silicon is treated with solution of mixture of nitric and hydrochloric acids taken in weight ratio HNO₃:HCl equal to (5-50):1. In second step, treatment is continued with hydrofluoric acid solution. EFFECT: 1) better protection for environment; 2) higher corrosion resistance of process equipment. 1 tbl