Dependences of titanium silicide properties on the ratio of silicon to titanium used for electron-beam coevaporation onto heated substrates

Abstract

Variations of the properties of titanium silicides prepared under various deposition conditions were investigated. An amorphous phase was observed to form when samples were prepared by codeposition of silicon and titanium at the substrate temperature T s of 120°C. However, it was found that considerable crystallization takes place at T s = 300° C, even though island-like amorphous regions are present at the silicide-silicon substrate interface. The film properties of samples prepared at relatively high T s were observed to change with the deposition conditions in a systematic manner. It was suggested that the amorphous phase is probably the first product of the intermixing even at elevated substrate temperatures. It was also postulated that the silicide formation process may involve evaporation of the amorphous phase. Thus, the film properties were said to be determined by silicon diffusion from the substrate, and crystallization as well as evaporation of the amorphous phase. Each of these mechanisms becomes dominant depending on the initial composition used for codeposition. This conjecture was shown to be successful in explaining the observed variations of properties such as voids, silicon precipitates, interface roughness, and resistivity.