It was noted that redistribution phenomena (pile-ups, push-back) of As during thermal oxidation depended upon the oxidation rate, the diffusivities of As in Si and SiO2, and the segregation rates of As impurities at the interface between the oxide and the Si. The diffusivity of As in the oxide was known to be negligible as compared with its diffusivity in Si and with the oxidation rate of Si. The As diffusivity in Si also depended upon the As concentration. Pile-ups at Si/SiO2 interfaces, as a result of a concentration dependence of As, had not been reported. In the case of Si samples which had been implanted with 1015 or 3 x 1015/cm2 of 100keV As ions, a pile-up of As was observed, using Rutherford back-scattering spectroscopy, during thermal oxidation at 1050C. In the case of samples which had been implanted to fluences of more than 3 x 1016/cm2, push-back phenomena were observed. These observations could be explained only in terms of an As diffusivity which depended upon the As concentration in the Si.

S.S.Choi, M.J.Park, W.K.Chu: Thin Solid Films, 1995, 258[1-2], 336-40