Reaction chambers for cvd systems

Abstract

An improved reaction chamber for use in an epitaxial deposition process or processing a single wafer-at-a-time. The reaction chamber includes a cold-wall reactor having a substantially rectangular cross-section. The cross-sectional area of the reactant chamber is substantially reduced to increase the efficiency of the system. Wall deposits are restricted to those which can be readily gas-etched array at various stages of the deposition process by the use of a cooling chamber or plenum about at least the downstream portion of the reactor. Apparatus is provided to maintain the wall temperature within a predetermined range for insuring that only readily cleanable deposits are formed. The reduced cross-sectional area results in insufficient room to mount a susceptor. Therefore, the susceptor assembly is mounted within a well distending vertically downward from the bottom of the chamber or within a second portion of a duel height chamber having a greater cross-sectional area. A method and apparatus is provided for supplying purge gas into the system to prevent the flow of reactant gas and the undesirable deposits resulting therefrom from forming beneath the susceptor. Furthermore, the flow of reactant gas beneath the susceptor is controlled by a quartz plate for narrowing the gap between the input end of the reactor and the susceptor and for simultaneously shaping the gap to provide a desired velocity profile. Alternatively, a horizontal extension of the floor of the cavity can be provided to perform substantially the identical function. Furthermore, two types of reactant gas injectors can be used for controlling the result in velocity profile of the injected gases.