Early stage evolution kinetics of the polysilicon/single-crystal silicon interfacial oxide upon annealing

Abstract

We demonstrate by high-resolution electron microscopy studies that the breakup upon annealing of the once nearly continuous oxide in polysilicon/thin oxide/single-crystal silicon structures occurs by a process of nucleation and growth of oxide voids. A kinetic model is developed that assumes capillarity as a driving force and one-dimensional diffusion along the interface as a kinetic pathway. Detailed measurements of void radii (before coalescence) as a function of anneal time and temperature show an excellent fit of the model to experiment, confirming a linear dependence of void size with time and an Arrhenius dependence on temperature. Different activation energies are extracted for oxide void growth occurring in thick and thin oxides, suggesting two competing diffusion mechanisms are in effect. It is postulated that oxygen diffusion through both the oxide and the silicon above and underneath is taking place.