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

Sandia National Laboratories, Albuquerque, New Mexico 871 85-1 056 PT"3 1 j 3 r 3 q a,,3 We show that Fe, Coy Cu, and Au impurities in Si are strongly gettered to boron-silicideprecipitates formed by supersaturation B implantation and annealing. Effective binding fr energies relative to interstitial solution range from somewhat above 1 to more than 2 eV. The B-Si precipitates formed at temperatures 51 100°C lack long range structural order but closely resemble the icoashedral B3 Si phase in composition, local bonding, and 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.