Supersaturation of self-interstitials and undersaturation of vacancies during phosphorus diffusion in silicon

Abstract

A series of experiments were performed to settle the long-standing controversy on whether there is a vacancy excess or deficit during the diffusion of phosphorus in silicon. Phosphorus and antimony buried layers sandwiched between p-type substrates and p-type epitaxial layers were used to monitor the departure from equilibrium of point defects. It was found that diffusion of the antimony buried layer is retarded during high concentration phosphorus diffusion while diffusion of the phosphorus buried layer is enhanced. This finding is consistent with the hypothesis that there is simultaneously a vacancy undersaturation and a self-interstitial supersaturation. Possible causes of the interstitial supersaturation are investigated. It is concluded that the process whereby a phosphorus interstitialcy converts to substitutional form by emitting a self-interstitial is a likely source.