Deactivation of Phosphorus by Carbon in Recrystallized Silicon

Abstract

Carbon has been used to suppress the diffusion of phosphorus in silicon transistors. The thermal stability of phosphorus should be considered when carbon is doped in n-type source and drain regions. In this study, carbon and phosphorus were implanted together in preamorphized silicon to investigate the effect of carbon on phosphorus activation. Phosphorus deactivation was caused by carbon at temperatures above 600°C following the solid-phase epitaxial regrowth of the amorphous layer, which was completed at 550°C. The deactivation saturated after long-term annealing at 750 or 850°C. The active phosphorus dose that was lost by the interaction between carbon and phosphorus was partially recovered at 925°C. The phosphorus deactivation that was caused by carbon was proportional to the dose of carbon. However, a larger proportion of the phosphorus was deactivated by carbon when the dose of implanted phosphorus was larger, suggesting that the deactivation was governed by a phosphorus diffusion mechanism, which was enhanced at high concentrations through charged vacancies in carbon-doped silicon.