Oxygen diffusion and aggregation in silicon

The ''normal'' diffusion coefficient D-oxy = 0.13 exp (-2.53 eV/kT) cm(2) s(-1) of bond-centred interstitial oxygen atoms (O-i) in Si has been determined for 350 less than or equal to T less than or equal to 1300 degrees C. Aggregation of O-i atoms in Czochralski Si to form SiO2 precipitates is rate-limited by D-oxy for T greater than or equal to 650 degrees C. For T less than or equal to 500 degrees C, O-2 dimers would be formed predominantly but the formation of large O-n clusters, traditionally identified with thermal donor defects cannot be explained unless dimers diffuse much more rapidly than O-i atoms and there is dissociation of clusters, allowing dimers to be released and then to be re-captured by larger clusters. There is no evidence for enhanced values of D-oxy unless hydrogen is deliberately introduced into the Si. The paper is in the form of a short review.