ABSTRACTDopant elements, B and Ga, P, As and Sb, and Ge as well, have been implanted into thick (350–400 nm) layers of TiSi2 prepared by Ti-Si reaction. Both B and Sb appear to be immobile, this behavior is thought to result from very small solid solubilities, rather than from very small diffusion coefficients. The other elements display about the same behavior, with detectable grain boundary diffusion at temperatures as low as 600°C, and lattice diffusion becoming considerable at 750°C, so that with the cooperation of both phenomena almost complete homogenisation of these relatively thick layers occurs in 30 minutes at 800°C. Germanium is used in lieu of a Si radioactive tracer because it can be analyzed by Secondary Ion Mass Spectroscopy. Its behavior is thought to imply that there is little equilibrium adsorption of the dopant elements at the Si/TiSi2 interface. The comparable values of the diffusion coefficients for the mobile elements confirm the anticipation that the dopants move as substitutional atoms on the Si sublattice. Results obtained with some samples implanted with both dopant and Ti indicate that in these silicon-saturated suicide layers the diffusion process is not significantly affected by small changes in stoichiometry.
Asymptotic dissipativity of the diffusion process in the asymptotic small diffusion scheme
