Effect of Si/SiO₂Interface on Silicon and Boron Diffusion in Thermally Grown SiO₂

Silicon self-diffusion and boron diffusion in SiO 2 were investigated as functions of the distance of diffusing silicon from the Si/SiO 2 interface at various temperatures in the range of 1150–1250°C using nat SiO 2 / 28 SiO 2 isotope heterostructures and 30 Si- and B-implanted 28 SiO 2 without and with a 30-nm-thick silicon nitride layer on the surface of each sample. The self-diffusivity of Si in SiO 2 did not depend on the oxygen 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/SiO 2 interface decreased. This dependence on the distance from the interface was caused by SiO molecules, which are generated at the interface and diffuse into SiO 2 . The simulated results, taking into account the role of SiO molecules, showed good agreement with each experimental profile of 30 Si and B.