Uniformity of deposited film thickness on a uneven surface by direct simulation Monte Carlo

Abstract

In CVD reactions, the reactant molecules are activated by energy sources to yield film-forming precursors above a substrate. These active precursors collide on the surface and deposit the desired film. The method of direct simulation Monte Carlo is applied to emulate one or two precursors, which undergo intermolecular collisions in the gas phase like hard spheres, and reflect or deposit on the surface according to their sticking probabilities. The coverage uniformity in a trench is improved if the sticking probability of precursor is small, the aspect ratio of rectangular trench is small, or the opening angle of wide-mouth trench is large. The minimum film thickness always occurs at the bottom corner of trench. The thickness uniformity is more influenced by the species with the larger sticking coefficient in a system of two film-forming species at the same concentration. The uniformity will be enhanced if the species with the lower sticking coefficient has a higher number density. Finally, the film growth of silicon carbide in a trench is closely simulated by the method developed.