Solid phase reaction of Ti with Si−Ge layers prepared by Ge-implantation

Abstract

Titanium germanosilicide films from thin Ti films (∼27.5 nm) are formed by solid phase reaction of Ti/Si0.62Ge0.38 bilayer at different annealing temperatures ranging from 600°C to 800°C. The effect of crystallographic state of Si−Ge alloy film on the reaction, phase formations, and polymorphic phase transformations, stability of germanosilicides have been investigated by x-ray diffraction, atomic force microscope, and sheet resistance measurements. Both amorphous and relaxed epitaxial Si0.62Ge0.38 films are prepared by Ge-multiple implantations into Si wafers with appropriate dose and energy followed by different post-implantation RTA schemes comprising alternative implantation and annealing in on case, and single final annealing in another one. XRD results indicate that the reaction sequence in both cases is found to be Ti/Si like with the formation of C49-Ti(Si−Ge)2 as a precursor to the low resistivity C54-Ti(Si−Ge)2. The films formed on amorphous alloy layer exhibit lower polymorphic transition temperature (∼750°C), smoother surface, lower sheet resistance and less agglomeration as compared to those on c:Si−Ge films. These characteristics are due to enhanced nucleation of C54 phase as a result of greater number of nucleation sites in the reaction with amorphous films. The formation of Ti(Si−Ge)2 films is, however, accompanied by the decrease of Ge content in Ti(Si−Ge)2 films formed on both amorphous and crystalline alloy films and indicates possible segregation/diffusion effects during the germanosilicidation.