A secondary-ion mass spectroscopic study was made of BF2+-implanted material. Anomalous B diffusion was observed in the excess Si region of amorphized layers at below 300C. This was explained in terms of a diffusion model in which B was assumed to diffuse via an intermediate species, Bi, which consisted of interstitial Si plus substitutional B. It was also found that F played an important role in enhancing B diffusion; even at annealing temperatures as low as 300C. However, the enhanced B diffusion was reported to occur only at annealing temperatures above 600C. The F was suggested to hinder interstitial Si from growing into large clusters which would require high-temperature annealing in order to dissociate them into freely migrating species. An exponential F diffusion profile could be explained in terms of a model for complexes of interstitial Si with F. Such a complex consumed interstitial Si which resulted from small Si clusters which could dissociate at low annealing temperatures. The results suggested that B diffusion at high annealing temperatures could be suppressed by co-implantation of F.

Fluorine Implantation Effect on Boron Diffusion in Si. Y.J.Park, J.J.Kim: Journal of Applied Physics, 1999, 85[2], 803-6