Titanium diffusion and residual stress of platinum thin films on Ti∕SiO2∕Si substrate

The residual stresses of Pt thin films deposited on Ti∕SiO2∕Si substrate and annealed at different temperatures in air were quantified by x-ray-diffraction method. A grazing-incidence x-ray-diffraction technique was applied to effectively investigate the diffusion and oxidation of Ti. The surface morphology of the Pt film was examined with field-emission scanning electron microscopy. TiO2 phase was detected on the surface of the Pt thin film after the annealing process, indicating strong diffusion and oxidation of Ti through the Pt layer. The dependence of the residual stress on annealing temperature was strongly related to the diffusion and oxidation of Ti, which generally increased the compressive stress, probably due to the associated volume expansion. However, stress release happened when the stress reached a certain high level. The diffusion and oxidation of Ti also resulted in serious hillock formation on the surface of the Pt film. The effects of Pt deposition temperature on the residual stress and Ti diffusion are also discussed.