Silicon self-diffusion and B diffusion in SiO2 were investigated as functions of the distance of diffusing Si from the Si/SiO2 interface at 1150 to 1250C by using natSiO2/28SiO2 isotope heterostructures and 30Si- and B-implanted 28SiO2 without and with a 30-nm-thick silicon nitride layer on the surface of each sample. The self-diffusivity of Si in SiO2 did not depend on the O concentration in the annealing ambient without the silicon nitride layer. The diffusion profiles of Si and B in the sample capped with the silicon nitride layer became broader as the distance from the Si/SiO2 interface decreased. This dependence on the distance from the interface was caused by SiO molecules, which were generated at the interface and diffused into SiO2. The simulated results, taking into account the role of SiO molecules, exhibited good agreement with each experimental profile of 30Si and B.

Effect of Si/SiO2 Interface on Silicon and Boron Diffusion in Thermally Grown SiO2. S.Fukatsu, K.M.Itoh, M.Uematsu, H.Kageshima, Y.Takahashi, K.Shiraishi: Japanese Journal of Applied Physics, 2004, 43[11B], 7837-42