The formation mechanism of buried oxides in wafers, during annealing following O implantation, was investigated by using Fourier-transform infra-red absorption spectroscopy and secondary ion mass spectrometry. It was found that the implanted O density decreased, due to out-diffusion, after a very short time at a high temperature. It was also found that the in-diffusion of O took place after a long time at the same temperature. The in-diffusion and out-diffusion behaviours clearly depended upon the annealing atmosphere. This could be explained by taking account of the fact that the equilibrium O surface concentration differed from one annealing atmosphere to the other.

In- and Out-Diffusion of Oxygen during Buried-Oxide Formation in Oxygen-Implanted Silicon H.Ono, A.Ogura: Journal of Applied Physics, 2000, 87[11], 7782-7