The profiles of O atoms which diffused, as interstitials, from SiO2 films and into Si substrates during high-temperature annealing were studied by means of infra-red absorption spectroscopy - using 18O as a tracer. It was found that the measured absorption profiles in the substrates could be explained in terms of a simple diffusion model in which the SiO2 layer acted as a reservoir of O; with no energy barrier to diffusion across the Si/SiO2 interface. The driving force for diffusion was the temperature-dependent solubility of O interstitials in Si. Evidence was found for the out-diffusion of O from the oxide layer and into the Si during extended annealing, and for retro-diffusion back into the oxide layer during down-ramping of the temperature. On the basis of etch-back profiling data on O interstitials, it was possible to revise the Arrhenius law for O diffusion in Si and to deduce an activation energy of 2.57eV and a pre-exponential factor of 0.22cm2/s. It was also suggested that there was evidence for an enhancement, of the O diffusion coefficient in Si at low temperatures, which resulted from the presence of foreign species such as H.

R.A.B.Devine, D.Mathiot, W.L.Warren, B.Aspar: Journal of Applied Physics, 1996, 79[5], 2302-8