Abstract
A three-dimensional (3-D) mathematical model describes the transport phenomena and the resulting rate of deposition in horizontal chemical vapor deposition (CVD) reactors. The model employs a finite difference scheme to solve the governing partial differential equations to predict the velocity field, temperature distribution, and concentration profiles of various gas species. The rate of silicon deposition by the reaction of SiCl4 and H2 is predicted. The model shows that the buoyancy-driven flow in such reactors has a marked effect on the uniformity of deposition. In these calculations, the concepts of local equilibrium at the substrate and thermal diffusion of SiCl2 away from the substrate were considered in evaluating the rate of silicon deposition. Incorporation of these factors has significantly improved the predictive capability of the model. The rates of silicon deposition were calculated for two different thermal boundary conditions which had a pronounced effect on the uniformity of deposition. Substrate tilt contributes to the production of a more uniform silicon deposition. The model was used as a computer-aided design tool for process optimization; a simple addition of two fins to the top wall (without any substrate tilt) of the reactor can significantly reduce the secondary roll cell formation and should lead to more uniform deposition.
Published Version
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