Effects of argon thermal annealing on surface structure, microstructural and silicide formation of Silicon-Titanium-Cobalt thin film

Abstract

Co-Ti system was prepared on Si (1 0 0) substrates using an electron beam evaporator equipped with thickness monitor. Co (10 nm) thin film was deposited on top of pre-deposited Ti (10 nm) film at 0.6 Å/sec deposition rate. First three samples were then argon and vacuum annealed at temperatures between 350 °C and 550 °C for three hours. Scanning electron microscopy images depicted formation of small structure attributing to rough surface as an indication of film transformation especially at 550 °C. Surface roughness increased with temperature from 350 °C to 550 °C due to the formation of nanostructures for argon annealed samples. In-situ real-time RBS revealed intermixing of layers at the interface and exchange of atoms between Co, Si and Ti layers that started below 450 °C forming silicide with stoichiometry CoSi, CoSi2 and CoSi3. Diffusion of Ti atoms through the Co layer towards the surface, allowing Co to diffuse inward to react with Si to form silicide was also observed. X-ray diffraction pattern also revealed the presence of the CoSi2 phase in addition to TiCo2 phase in the argon annealed sample at 550 °C. No indication of the silicide formation in the vacuum annealed samples. The results pointed toward a successful utilization of this approach to prepare CoSi2 at temperatures lower than the one reported in the literature, which is above 600 °C.