Patent ID: 7541015

Claim:
A process for producing a silicon nitride compound, the process comprising the steps of: a) providing a starting solution derived from a silicon etching process wherein silicon is etched with a solution comprising hydrofluoric acid and wherein silicon powder has been removed, the starting solution comprising fluorosilicic acid; b) heating the starting solution to yield a vapor solution comprising silicon tetrafluoride, hydrogen fluoride and water; c) separating the hydrogen fluoride from the vapor solution wherein a pure stream of silicon tetrafluoride and water vapor remain; d) hydrolyzing the silicon tetrafluoride and water vapor to yield a concentrated fluorosilicic acid solution; e) reacting the fluorosilicic acid with a base to yield a fluorosilicic salt; f) heating the fluorosilicic salt to yield anhydrous silicon tetrafluoride; g) reacting the anhydrous silicon tetrafluoride with a metal hydride to yield a monosilane; h) reacting the monosilane to form a silicon nitride compound; and i) recovering the silicon nitride compound.