Method and apparatus for substrate heating in an axially symmetric

Abstract

In an epitaxial deposition reactor with an axially symmetric gas flow carrying the deposition materials, apparatus and method for heating the substrate and associated susceptor uniformly is described. The apparatus includes at least one chamber having a plurality of heat lamps passing therethrough, the chamber being generally disposed symmetrically with respect to an axis of the substrate. The walls of the chamber are appropriately coated to reflect the light from the heat lamps and the outermost lamps can be energized to produce a higher temperature than the centrally located lamps to compensate for regions of the reactor that provide access to the substrate and therefore promote thermal losses. The spacing of the lamps can be varied also to compensate for thermal non-uniformity of the heating cavity. In a first embodiment, a lower chamber can be a chamber similar to the first chamber with the exception that the lamps are rotated 90.degree.. In a second embodiment, the lower chamber consists only of reflecting surfaces with no sources of heat generated therein. However, in this embodiment a portion of the lower chamber has a reflectivity different from the reflectivity of the remainder portion of the chamber. The substrate can be rotated to provide a further averaging of possible thermal structure. In a third embodiment, parabolic reflectors are associated with each lamp to provide greater uniformity in the radiation impinging on the substrate-susceptor combination. Chambers having heating lamps with both parabolic reflectors and with planar reflecting surfaces are also described.