Diffusion of Sb, Ga, Ge, and (As) in TiSi₂

Abstract

Gallium, Sb, and Ge were implanted into thick (about 400 nm) layers of TiSi2 prepared by metal-silicon reaction. The diffusion of the implanted atoms was analyzed by means of secondary ion mass spectrometry. Gallium was introduced because a former study had shown that the usual p-type dopant B does not diffuse in TiSi2. Germanium was used in lieu of a Si tracer. Its diffusion characteristics are compared to those of P and As (as well as Si) which had been investigated previously. Germanium and Ga diffuse readily above 600°C, but Sb does not. Its diffusion appears to be limited to grain-boundary effects. Accumulations of the diffusing atoms are observed (except for Sb) at the silicide-silicon interface. These are due to kinetic effects, namely fast diffusion at grain boundaries and interfaces, rather than to real adsorption which is an equilibrium condition. Because diffusion in intermetallic compounds has been shown to be significantly affected by variations in stoichiometry, experiments were conducted with films implanted not only with foreign atoms but with Ti as well. These did not lead to significantly different observations.