Tantalum silicide, when deposited directly onto monocrystalline Si substrates and annealed at 950C, led to the enhanced diffusion of B in buried layers. This indicated a substantial vacancy component in B diffusion; at least up to 950C. The fact that the enhanced diffusion occurred in buried layers excluded a snow-plough mechanism. The Si/Ta ratio in the sputter-deposited silicide was slightly less than 2. It was suggested that further silicidation generated vacancies by removing Si atoms from the Si substrate. Enhanced diffusion was not detected when there was a 150nm intermediate layer of polycrystalline Si film between the silicide and the monocrystalline Si substrate. This indicated that polycrystalline Si was an effective sink for excess vacancies; perhaps more than for excess interstitials.

S.M.Hu: Applied Physics Letters, 1987, 51[5], 308-10