Radiative heat transfer in hot-filament chemical vapor deposition diamond reactors

Abstract

Hot-filament chemical vapor deposition is a common method employed for diamond deposition. Due to the filament-substrate proximity, large temperature variations across the substrate is often possible. Variations in substrate temperature need to be minimized in order to deposit polycrystalline diamond films of uniform thickness over large areas. Thus heat transfer calculations which consider radiation from the filament to the substrate, radiation from the substrate to the reactor walls, and finally conduction in the silicon wafer have been developed to predict substrate temperature profiles as a function of the filament shape and geometry. The calculated values are found to be in reasonable agreement with experimentally measured substrate temperatures. It was found that hydrogen atom recombination makes a significant contribution to the absolute substrate temperature, but that the normalized temperature profiles are determined primarily by the radiation flux distribution. The effects of the other deposition parameters are also discussed. Comparison with experimental results show an apparent correlation between growth rate profiles and radiation flux profiles from the filament as predicted by the calculations.