The Effects of Processing Ambient on the Reaction Rate of Ti and Si Using Rapid Thermal Processing

The reaction rate of sputter deposited Ti films on c-Si as a function of process ambient was studied. Sintering temperatures ranging from 600 to 1100° C, under pure ammonia, forming gas, nitrogen and argon were used. The additional effect of a reactively sputtered TiN cap on the reaction rate was also investigated. Processed films were then analyzed using AES, RBS and four point probe resistivity mapping. It was found that for temperatures below 700° C, an ammonia ambient has the most pronounced effect on reducing the rate of formation of titanium silicide, followed by forming gas (N 2/H2 10% vol), nitrogen and argon. Additionally, the presence of the TiN cap further reduced the reaction rate while exhibiting significant diffusion of nitrogen into the silicide film. For the samples annealed in ambients containing nitrogen, a thin layer of Tix Ny was simultaneously formed on top of the silicide film. The thickness and Stoichiometry of this titanium nitride films were then correlated with the sintering temperature and ambient. The details of these findings and their impact on the formation of the self-aligned titanium silicide (salicide) will be presented.