Process for producing a silicon nitride compound

Abstract

A process for producing a silicon nitride compound is presented. A starting solution comprising fluorosilicic acid is provided. The starting solution is derived from a silicon, etching process wherein silicon is etched with a solution comprising hydrofluoric acid and where silicon powder has been removed. The starting solution is heated to yield a vapor solution comprising silicon tetrafluoride, hydrogen fluoride, and water. The hydrogen fluoride is separated from the vapor solution wherein a pure stream of silicon tetrafluoride and water vapor remain. The silicon tetrafluoride and water vapor are hydrolyzed to yield a concentrated fluorosilicic acid solution. The fluorosilicic acid is reacted with a base to yield a fluorosilicic salt. The fluorosilicic salt is heated to yield anhydrous silicon tetrafluoride. The anhydrous silicon tetrafluoride is reacted with a metal hydride to yield a monosilane. The monosilane is reacted to form a silicon compound and a silicon nitride compound. The silicon and the silicon nitride compounds are recovered. In an alternate embodiment, the hydrogen fluoride is recovered from the reaction process and reintroduced into the porous silicon etching process.