Investigation of the nucleation of oxygen precipitates in Czochralski silicon at an early stage

Abstract

The nucleation of oxygen precipitates in Czochralski silicon is examined in an early stage by measuring vacancy profiles with platinum diffusion. Using an analytical expression, which was deduced from the equations of the Frank–Turnbull diffusion mechanism, the vacancy profiles are calculated from measured platinum diffusion profiles. The vacancy concentration of differently treated Czochralski (CZ) material is compared to the vacancy concentration of float zone (FZ) silicon. In CZ silicon a decrease of the vacancy concentration with increasing nucleation time and platinum diffusion time is found. This decrease cannot be explained by a supersaturation of silicon self-interstitials caused by nucleation and by recombination of self-interstitials and vacancies alone. A direct consumption of vacancies during nucleation also is present. The annihilation rate of the vacancies during nucleation can be estimated to be smaller than 5×108 cm−3 s−1 at 770 °C.