The effect of carbon on diffusion in silicon

Abstract

This paper presents experimental studies on the interaction between C and interstitials in crystalline Si. Boron doped Si superlattices, grown by molecular beam epitaxy, were used to detect the injection of excess Si self-interstitials (I) from near-surface 5 × 1013 cm−2, 40 keV Si implants during annealing. The interstitial-enhanced diffusion of the B marker layers is fully suppressed when the C content is uniformly raised from 1018 to 2 × 1019 cm−3, demonstrating that C acts as a trap for interstitials. The incorporation of a buried layer of C leads to a local reduction of the interstitial concentration without fully obstructing the interstitial flow towards the bulk. The interstitial trapping presumably involves the formation of mobile C-I complexes which pair with substitutional C to become immobile. The effect of C on the diffusion of interstitials in marker layer experiments and metal diffusion studies is analyzed in light of the present observations.