Microstructural and electrical properties of heat treated resistive Ti/Pt thin layers

Abstract Study of DC sputtered Ti/Pt thin film layers on SiO 2 /n-Si substrate with the emphasis on post deposition heat treatment is presented. Microstructural and morphological properties of Ti/Pt thin films annealed in the range 300–700 °C in air are investigated and correlated with measured electrical properties. AES depth profile and composition of the sample annealed at 400 °C and 700 °C showed significant diffusion of Ti throughout the Pt layer toward surface, accompanied with enhanced oxygen incorporation, while keeping rather constant TiO x composition throughout the structure. AFM and SEM analyses of Ti/Pt film morphology showed that Pt grain size was almost temperature independent up to 400 °C, while above 500 °C, grain growth was enhanced. XPS analyses confirmed that most of Ti incorporated in the film was in oxide state (Ti 4 + ) after annealing at 700 °C. EBSD analyses confirmed strong (111) texture of Pt polycrystalline grains annealed above 500 °C. Resistance of meandered Ti/Pt resistors was found to decrease significantly above 500 °C and complies well with the microstructural rearrangements determined by AFM and AES analyses. It was further determined that by increasing the annealing temperature from 300 °C to 700 °C, a monotonic increase of temperature coefficient of resistance from 1400 ppm/°C to 2400 ppm/°C, respectively, was obtained. This represents a considerable improvement in sensitivity of Ti/Pt layers used as a temperature sensing devices. Resistance exhibited linear temperature dependency with nonlinearity better than 0.84%.