Outdiffusion and Subsequent Desorption of Volatile SiO Molecules during Annealing of Thick SiO2 Films in Vacuum

The depth profile of so-called suboxides in the surface region for 1000-A-thick SiO 2 films annealed in vacuum at 800°C was measured by angle-resolved X-ray photoelectron spectroscopy. It was found that the amount of suboxide distributed under the surface increases rapidly and almost saturates with annealing time, while the change in the amount of suboxide present on the surface is very small and increases gradually with annealing time. This indicates that very fast outdiffusion of SiO molecules through thick SiO 2 films takes place at as low as 800 o C, leading to desorption from the SiO 2 surface