Germanium diffusion and nanocrystal formation in silicon oxide on silicon substrate under rapid thermal annealing

Abstract

The effect of rapid thermal annealing temperature on the diffusion of silicon (Si) and germanium (Ge) and the formation of Ge nanocrystals in a silicon oxide matrix was investigated. The formation of Ge nanocrystals was attributed mainly to the reduction of Ge suboxides by Si diffused from the Si substrate. For samples annealed at 800°C, the nanocrystals were uniform in size and distributed evenly in the bulk of the oxide but became denser nearer to the silicon–silicon oxide (Si–SiO2) interface. When the sample was annealed at 900°C, two regions with different nanocrystal densities and size distributions separated by a region void of nanocrystals were observed. The region of denser nanocrystals was located near the Si–SiO2 interface. For annealing at 1000°C, nanocrystals were only observed at the Si–SiO2 interface and these have significant size variation, with the rest of the oxide being void of nanocrystals. The nanocrystals formed at 900 and 1000°C were generally found to be defective.