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

Titanium germanosilicide films from thin Ti films (similar to 27.5 nm) are formed by solid phase reaction of Ti/Si0.62Ge0.38 bilayer at different anne aling temperatures ranging from 600 degreesC to 800 degreesC. The effect of crystallographic state of Si-Ge alloy film on the reaction, phase formatio ns, and polymorphic phase transformations, stability of germanosilicides ha ve been investigated by x-ray diffraction, atomic force microscope, and she et resistance measurements. Both amorphous and relaxed epitaxial Si0.62Ge0. 38 films are prepared by Ge-multiple implantations into Si wafers with appr opriate dose and energy followed by different postimplantation RTA schemes comprising alternative implantation and annealing in one case, and single f inal annealing in another one. XRD results indicate that the reaction seque nce 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 f ormed on amorphous alloy layer exhibit lower polymorphic transition tempera ture (similar to 750 degreesC), smoother surface, lower sheet resistance an d less agglomeration as compared to those on c:Si-Ge films. These character istics are due to enhanced nucleation of C54 phase as a result of greater n umber of nucleation sites in the reaction with amorphous films. The formati on of Ti(Si-Ge)(2) films is, however, accompanied by the decrease of Ge con tent in Ti(Si-Ge)(2) films formed on both amorphous and crystalline alloy f ilms and indicates possible segregation/diffusion effects during the german osilicidation.