Metal gettering by boron-silicide precipitates in boron-implanted silicon

We show that Fe, Co, Cu and Au impurities in Si are strongly gettered to boron-silicide precipitates formed by supersaturation boron implantation and annealing. Effective binding free energies relative to interstitial solution are extracted and range from about 1.2 to 2.2 eV. The B-Si precipitates formed at temperatures less than or equal to 1100 degrees C lack long range structural order but are similar to crystalline B3Si in composition and B chemical potential, Evidence indicates that the metal atoms go into solution in the B-Si phase, and this is interpreted in terms of the novel bonding and structural characteristics of B-rich icosahedral compounds.