The influence of inappropriate processes on the growth of silicon epitaxial layers

The influences of inappropriate growth processes on epitaxial layers are reviewed and summarized. They cause formation of defects in the grown layer even if the substrate, the various gaseous and other materials and the growth system are of high quality. The influence of a too-high overall deposition rate causes the appearance of "pyramids" on the surface of the grown layer. The mechanism of "pyramid" formation is based on the fact that the growth rate is dependent upon the crystallographic orientation. Small irregular zones on the substrate surface each have several crystallographic orientations, and as a result, "pyramids" can grow there under certain conditions. The influence of too-low growth temperatures causes the appearance of "ledges" and "terraces", i.e., uneven, rough and sometimes irregular surfaces of the grown layer. The mechanism of formation of such a surface is associated with mobility, migration length and nucleation rates, which are decreased when the temperature is lowered. In addition, a rough surface can be formed as a result of a growth process which takes place in the gaseous phase above and not at the surface. The heterogeneous and homogeneous reaction processes are summarized, and the possibility of explaining through them the appearance of "pyramids" and rough surfaces is reviewed. Experimental results are presented.