Effect of Si/SiO ₂ interface on silicon and boron diffusion in thermally grown SiO ₂

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 ^natSiO ₂/ ²⁸SiO ₂ isotope heterostructures and ³⁰Si- and B-implanted ²⁸SiO 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 ³⁰Si and B.