Suppression of Buoyancy in a Prototypical CVD Reactor by Geometry Modification

Buoyancy plays a detrimental role in chemical vapor deposition reactors employed for thin film deposition. Buoyancy driven fluid flow causes complex flow patterns which alter the transport of the precursor gases to the substrate, and leads to nonuniform deposition patterns. Consequently, many CVD reactors operate under low pressure to mitigate these flow patterns. However, the growth rates at such pressures are relatively low. Operating a CVD reactor under vacuum conditions is also inconvenient because of the associated hardware that is required. In the present work, we have numerically explored the performance of a new type of stagnation flow CVD reactor at pressures close to atmospheric pressure. The new geometry resembles that of a pancake reactor, but the gases are supplied through a long vertical inlet. The annular wall above the substrate is maintained at a low temperature to avoid deposition on this surface. The substrate is also rotated to improve the hydrodynamic patterns and provide azimuthal symmetry. We report results of a number of high-resolution calculations in this reactor to demonstrate its merits for operation at sub-atmospheric and atmospheric pressures. It is shown that the growth rate is significantly large, in addition to a high degree of film uniformity.