Cold wall reactor and method for chemical vapor deposition of bulk polysilicon

Abstract

A method and apparatus, and product by process, for the production of bulk polysilicon by a chemical vapor deposition process on a removable tube section. A quartz envelope and base plate form a CVD reactor enclosure, with external radiant heaters providing process heat through the wall of the reactor, and with process gas inlet and outlet ports located in the base plate. A tube section, preferably an EFG silicon tube-section, vertically emplaced on the base plate and capped to close the top is used as the reaction chamber. During the CVD process, deposition occurs on the inside surface of the chamber tube, the inner diameter of the deposit layer becoming increasingly smaller as the yield accumulates. In a two tube reactor, a smaller diameter, vertical middle tube is uniformly spaced and supported inside the chamber tube for fall flow of process gas over and under the middle tube so that deposition occurs on the three exposed tube surfaces. A co-axial core tube and heater mounted on the base plate provides yet more deposition surface area, improved thermal gradient in the reaction chamber, and greater thermal efficiency to the process. The full, double sided deposit on the middle tube and exterior deposit on the core tube are unique products of the process.