A nonisothermal film model for mass-transfer-limited selective epitaxial growth of silicon on patterned surfaces

Abstract

A two-dimensional film model for mass-transfer-controlled selective epitaxial growth (SEG) of Si on bare and regularly patterned wafers was developed, and the effects of bulk gas composition, pressure, substrate temperature, thermal diffusion, and oxide coverage were analyzed. SEG rates decrease with a lower concentration of the source gas and with the addition of HCl, which eventually leads to etching. The effects of pressure and substrate temperature on mass-transfer-limited SEG rates are determined by the way in which the equilibrium composition at the deposition surface depends on these variables. Thermal diffusion contributes to larger net fluxes away from the deposition surface. The effect of thermal diffusion is to inhibit SEG rates at lower bulk HCl concentrations and to extend the growth region to higher bulk HCl concentrations. Higher oxide coverages produce higher deposition rates with reduced mass transfer limitations. These model predictions are qualitatively consistent with reported observations.