The contribution of vacancies to carbon out-diffusion in silicon

Diffusion of carbon is mostly assumed to be governed by carbon interstitials via the kick-out mechanism. Carbon in-diffusion experiments are associated with thermal equilibrium concentrations of point defects, whereas in the case of carbon out-diffusion a remarkable undersaturation of Si self-interstitials may develop provided the carbon concentration is several orders of magnitude over its solubility value. New carbon out-diffusion experiments demonstrate that this model qualitatively describes the observed carbon diffusion profiles. However, we demonstrate that an accurate description of the experimental profiles is only possible if the Frank-Turnbull mechanism, involving vacancies, is additionally taken into account. Detailed investigations of carbon and boron profiles in the same sample can be used to determine the splitting of the known vacancy component of the silicon self- diffusion coefficient into the vacancy diffusion coefficient and the vacancy thermal equilibrium concentration at 900 degrees C. (C) 1999 American Institute of Physics. [S0003-6951(99)02202- 0].