In- and out-diffusion of oxygen during the buried-oxide formation in oxygen-implanted silicon

Formation mechanism of buried oxide in silicon wafers during the annealing process after oxygen implantation has been investigated by using Fourier-transform infrared absorption spectroscopy and secondary ion mass spectrometry. The implanted Si wafers were annealed at a different temperature, for a different time, and in a different atmosphere. We found that the implanted oxygen density decreased by the out-diffusion after a very short time at an elevated temperature. We also found that the in-diffusion of oxygen took place after a long time at the same temperature. The in- and out-diffusion behaviors clearly depended on the annealing atmosphere. This can be explained by taking account that the equilibrium surface concentration of oxygen differs between the annealing atmospheres. (C) 2000 American Institute of Physics. [S0021-8979(00)03211-4].