A quantitative study of oxygen behavior during CrSi2 and TiSi2 formation

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Abstract
Oxygen behavior during the formation of CrSi2 and TiSi2 was studied using 16O(α,α)16O resonant scattering and mass dispersive recoil detection analysis. The Ti and Cr films were deposited by e‐beam evaporation in a cryopumped system. The oxygen content in the films was varied by evaporating at different pressures. The silicide films were formed by solid‐solid reaction of the metal layers with the silicon substrate, and the annealing conditions were such that both partly and fully reacted silicides were obtained. The extent of the silicide formation was monitored by backscattering spectrometry. In the case of CrSi2, oxygen was found to be uniformly distributed throughout the silicide layer after annealing. For the Ti/TiSi2 system, however, oxygen seems to have preferentially remained in the Ti layer during the silicide growth, and its final distribution was confined in a region in the silicide close to the surface. It was also observed in the latter case that silicon diffused to the surface at the initial stage of annealing. A model based on the Nernst–Einstein equation is proposed to provide a general explanation for the oxygen behavior in metal/silicon systems. In addition, it was shown that oxygen which was initially in the form of metal oxides and in solid solution had been transformed into SiO2 after the silicide formation. Oxygen loss is observed for all samples, and increases with the extent of annealing.