Oxidation of titanium disilicide on polycrystalline silicon
Oxidation mechanisms of titanium disilicide on polycrystalline silicon was investigated. Poly-Si was deposited on the oxidized Si wafer by CVD method, Ti was then deposited on the poly-Si by the electron beam gun and thus TiSi2 was formed by thermal annealing in vacuum. During the wet oxidation, Rutherford backscattering spectroscopy (RBS) results show a two-step oxidation process, namely, TiSi2 first dissociates and forms TiOx and SiO2, while after the formation of TiOx reaches the saturation level, the poly-Si rapidly diffuses through the TiSi2 to form SiO2. The calculated activation energy of reaction is 2.06 eV, and that of diffusion is 1.51 eV. Sheet resistances were measured and found to be consistent with the two-step oxidation model. Radioactive31Si was used as a marker to study the kinetics of the oxidation and found that during the diffusion process of oxidation, the poly-Si atoms transported through TiSi2 by grain boundary and/or interstitial diffusion.