The contribution of vacancies to carbon out-diffusion in silicon

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