Abstract
The Oxidation Behaviors of MoSi2 and WSi2 on Single Crystalline Si and Polycrystalline Si have been carried out. For 180 nm thick MoSi2 layer on (111)Si, a high density of defects was found to form in silicon in samples oxidized in wet O2. The defects were identified to be of interstitial type with 1/2<011> Burgers vectors. However, no defects were found in silicon after dry oxidation. Metal oxide mixed with SiO2 was found to form at 700 oC in samples oxidized in wet O2. The parabolic activation energies were found to be 1.4 ± 0.15 eV and 1.2 ± 0.2 eV for dry and wet oxidation, respectively.For the oxidation kinetics of WSi2 on (001)Si and poly-Si in the dry oxidation process, the linear activation energy and the parabolic activation energy of WSi2 on (001)Si were found to be 0.8 ± 0.2 eV and 1.0 ± 0.2 eV for samples dry oxidized at 800-890 oC for 10-60 min, respectively. On the other hand, the linear activation energy and parabolic activation energy of WSi2 on polycrystalline silicon for samples dry oxidized at 800-890 oC for 10-60 min were 1.0 ± 0.2 eV and 1.8 ± 0.2 eV.The linear activation energy is attributed to the diffusion of Si atoms from substrate to the reaction interface. The different parabolic activation energies of 1.0 eV and 1.8 eV for WSi2 on (001)Si and poly-Si, respectively, indicate significant difference in diffusion of O2 through grown SiO2. It is conceivable that difference in oxide quality, stress generated during oxidation and amount of fluorine atoms, introduced during the LPCVD process, present in the silicide layer and grown oxide, can influence the oxidation kinetics.For oxidation kinetics of WSi2 on (001)Si and poly-Si in the wet oxidizing ambient, the linear activation energies of WSi2 on (001)Si and WSi2 on poly-Si were found to be 1.6 ± 0.2 eV and 1.4 ± 0.2 eV for samples wet oxidized at 750-860 oC for 5-50 min, respectively. The parabolic activation energies of WSi2 on (001)Si and WSi2 on poly-Si for samples wet oxidized at 750-860 oC for 5-50 min were 1.0 ± 0.2 eV and 1.1 ± 0.2 eV, respectively. A little defects were found for samples wet oxidized at 800 oC for 20 min. The loop size was found to decrease with wet oxidation temperature. The dislocation loop was identified to be of interstitial type with 1/2<110> Burgers vector.The wet oxidation product of MoSi2 film on Si, formed by solid state reaction of metal layer of Mo with silicon substrate, was found to be related to the silicidation process of MoSi2 film. No metal oxide was found for samples prepared with two step silicidation process at 700 oC for 10 min. A model based on the stress generated by the diffusion of the fast moving atoms was used to explain the experimental results. It is suggested the lateral diffusion of silicon atoms during silicidation process can release the film stress and cause the rough interface of MoSi2 and Si. The lateral diffusion of silicon atoms decreases with temperature. Thus, the stress of MoSi2 film increases with silicidation temperature.