Impurity gettering by misfit dislocations in Si (2% Ge) epitaxy: nickel

Abstract

The microstructure associated with nickel gettering by an epitaxial misfit dislocation network generated in Si(2% Ge) chemical vapor deposition films has been determined using transmission electron microscopy. The configuration of misfit dislocations is a well-characterized network of b=a/2〈011〉 60° dislocations that all lie in the (001) interfacial plane. Nickel was deliberately introduced by deposition onto the front surface of the wafer followed by diffusion at temperatures from 600 to 1000 °C. Nickel segregated on or in the immediate vicinity of the misfit dislocations to form individual or agglomerates of fine precipitates. The strong temperature dependence of Ni solubility in Si and the nucleation enhancement by the localized strain effects in the vicinity of dislocations are considered to be the dominant factors controlling gettering by the misfit dislocations. An annealing temperature of 600 °C is suggested which appears to uniformly decorate the misfit dislocations with Ni for possible buried microwire applications.