Abstract: Disclosed is a process for production of silicon tetrafluoride which can reduce the cost for the silicon tetrafluoride production and can also reduce the quantities of waste products produced in the process. Also disclosed is an apparatus for use for the process. The method comprises the steps of: (a) a high-silica fluorosilicic acid production step in which a raw material (1) containing silicon dioxide is reacted with a mixed solution containing hydrofluoric acid and hydrofluorosilicic acid to yield an aqueous high-silica fluorosilicic acid solution: (c) a silicon tetrafluoride production step in which the aqueous high-silica fluorosilicic acid solution is reacted with sulfuric acid to yield silicon tetrafluoride; and (d) a sulfuric acid production step in which a sulfuric acid fraction containing hydrogen fluoride which is a by-product in the silicon tetrafluoride production step (c) is subjected to steam stripping to yield sulfuric acid.

Abstract: High purity silicon usable for production of solar cells is easily produced with high production efficiency. In a rotary chamber (50) made of quartz, which is evacuated and filled with an hydrogen-argon atmosphere containing SiF4, a plasma area (60) is generated by supplying electric power from a coil (51) to decompose SiF4 and produce silicon as being fine powder particles. Fine particles of seed silicon (Si) in the rotating reaction chamber are picked up and transported upward by weirs (52), and then they can fall by gravity into the plasma area where silicon elements produced by decomposition of SiF4 are deposited onto surfaces of the silicon fine particles.