Enhanced diffusion of Sb-doped layers during Co and Ti reactions with Si

The effects of Co and Ti thin-film reactions with Si on diffusion of buried Sb-doped layers have been investigated. Sb profile analysis by secondary-ion mass spectrometry shows that greatly enhanced, nonuniform Sb diffusion occurs during reactions of various thicknesses (30–300 nm) of Co and Ti by rapid thermal annealing. A simple nonequilibrium intrinsic diffusion model is invoked to estimate time-average excess vacancy concentrations. Vacancy concentrations of about 107 times equilibrium values are shown to exist during CoSi2 formation by reaction of a 30 nm Co film at 700 °C for 5 min in Ar. Diffusion enhancements at large distances from the silicide edge are observed by bevel and etch techniques.