Abstract
Thermal oxides that were grown at 800°C on the sidewalls of polysilicon gates were found to exhibit two types of flaws. One type occurred predominantly where the polysilicon land lies on top of a thick, isolation oxide, and has a convex contour. The other type occurred immediately above the oxide wedge formed under the leading edge of the polysilicon gate. Two mechanisms are proposed to account for the formation of these two types of flaws. The first originates from the tensile stress developed in an oxide grown on a convex surface, while the second results from a combination of the volume expansion in the oxide wedge and grain boundary sliding in the polysilicon. Experimental evidence to support these mechanisms is presented.