Process for the production of silicon of high purity

Abstract

A process is provided for the low cost, high volume production of polycrystalline high purity silicon by a vapor phase reduction of a halosilane, with hydrogen, the resulting polycrystalline silicon being particularly suited for use in the production of single crystal silicon for the manufacture of semiconductor devices, solar cells, and the like. The process of the invention involves the reaction of metallurgical grade silicon (of a purity of about 98%) with a halogen or hydrogen halide to form a halosilane intermediate; the purification of the halosilane and of hydrogen; the separate pre-heating of the purified halosilane and of the purified hydrogen to a temperature range above the chemical reaction temperature of the halosilane and the hydrogen; injection of the halosilane and the hydrogen into a continuous flow reduction tubular reactor wherein the feed materials are instantaneously mixed in a manner which causes chemical reaction to be initiated followed by nucleation and growth of solid high purity silicon particles as the reaction mass flows through the tubular reactor; introduction of the solid-gas reaction mass stream into a cyclone type separator wherein the high purity silicon particles are collected and separated from the gas stream and ejected from the bottom of pg,2 the separator; emitting the gas stream from the top of the separator and conducting the gas stream to a condenser-scrubber system wherein unreacted hydrogen is separated and then recycled to the hydrogen pre-heater for re-use, unreacted silicon halosilane is separated and recycled to the intermediate pre-heater for re-use, and reaction product hydrogen halide is separated and recycled to the silicon halosilane generator for re-use.