Low pressure chemical vapor deposition apparatus including a process gas

Abstract

A low-pressure CVD apparatus is presented including one or more gas heating subsystems which heat process gases prior to their introduction into a reaction chamber of the low-pressure CVD apparatus. As a result, thermal expansions and contractions of the walls of the reaction chamber are reduced, along with the tendency of small particles of deposits on the inner walls of the reaction chamber to flake off. Fewer loose particulates created within the reaction chamber results in a reduction in the number of particulates adhering to surfaces of processed silicon wafers. Each gas heating subsystem includes a heating element thermally coupled to a gas feed line and to a process gas flowing within the gas feed line. Each gas heating subsystem also preferably includes a thermal feedback temperature control mechanism including a temperature sensor and a temperature control unit. The temperature sensor senses the temperature of the heated flow of process gas and produces a corresponding temperature signal. The temperature control unit is coupled to receive the temperature signal from the temperature sensor and controls the temperature of the heating element in response to the temperature signal. The temperature of the process gas entering the reaction chamber may thus be controllably increased.