Study of Oxidation of TiSi2 Thin Film by XPS

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Abstract
Titanium was deposited on a single-silicon wafer and made to form TiS2 by thermal annealing in vacuum. Samples were then oxidized at temperatures from 100 to 1000°C for 60 min in air. When the oxidized TiS2 was studied by X-ray photoelectron spectroscopy (XPS) in conjunction with argon-ion sputtering, SiO2 was found to be dominant in the oxide products at various oxidation temperatures. Full-width at half maximum (FWHM) and Si/Ti atomic ratio analyses led to the conclusion that various Ti oxides exist in oxidized TiSi2, but that the intermediate Ti-silicides (TiSi and Ti5Si3) do not. The growth of a Ti-free layer of SiO2 at 1000°C was also observed. SEM micrographs showed that no surface morphologies varied before or after oxidation in air at temperatures from 100 to 800°C. Above 1000°C, however, the TiSi2 film was thermally grooved at its grain boundaries, and the grain sizes were increased. Analytic electron-microscope photographs showed that the crystalline grains consisted of TiSi2, but that the grain boundaries lay within the Ti-free zone.