New measurements of O out-diffusion from Czochralski-type material confirmed that it occurred over an anomalously wide range at temperatures below 700C. The surface concentration decreased with increasing annealing time at 430C, while the depth to which the concentration was depleted remained almost constant. The rate of decrease of the surface concentration was related to the rate of loss of isolated O atoms from the bulk. All of the observations were explained by supposing that isolated O atoms were converted slowly, during annealing, into an O-containing fast-diffusing species which diffused over long distances before being trapped. High concentrations (6 x 1016 to l.7 x 1017/cm3) of substitutional C in the crystal increased the trapping-rate of the fast-diffusing species, but this rate tended to decrease with increasing annealing time and tended towards the value for C-free material. Estimates of the rate of formation of the fast-diffusing species were close to the expected rate of dimerization in a dilute solution at temperatures below 450C, but tended to be below the expected rate at higher temperatures. There was no clear indication of fast-diffusing species-dissociation at temperatures of up to 700C. It was concluded that the formation of the fast-diffusing species was more complicated than would be the case if it were an O2 dimer. One of the proposed alternatives was the O vacancy complex.

The Conversion of Isolated Oxygen Atoms to a Fast Diffusing Species in Czochralski Silicon at Low Temperatures S.A.McQuaid, B.K.Johnson, D.Gambaro, R.Falster, M.J.Ashwin, J.H.Tucker: Journal of Applied Physics, 1999, 86[4], 1878-87