IMPROVED RADIATION SHIELDING FOR A CVD REACTOR

A reaction chamber includes an enclosure having an interior coated with a metal nitride compound providing an average reflectivity to internal infra-red radiation of greater than 90%. The metal nitride compound can be titanium nitride, zirconium nitride, hafnium nitride, or a nitride of another metal, and can be between 0.1 and 10 microns thick, preferably between 4 and 5 microns thick. The layer does not tarnish, and can withstand reaction chamber temperatures up to at least 250° C., preferably up to 300° C. It is applied by a deposition process, such as PVD, CVD, thermal spray, or cathodic arc, wherein the enclosure itself is the metal nitride deposition enclosure. Uniformity of deposition can be improved by rotating the deposition source through T degrees and back through T±d, with a total of 360/d repetitions. The reactor can be a CVD reactor that deposits polysilicon onto a heated filament.