A High-Precision Four-Wire MEMS Pt Thin-Film Temperature Sensor Applied to the Medium-to-High Temperature Range

This study designed and fabricated a MEMS Pt thin-film temperature sensor suitable for the medium-to-high temperature range of 33-600 °C. A Pt film with a thickness of approximately 1 μm was deposited on an Al₂O₃ ceramic substrate via magnetron sputtering, and annealing experiments were conducted within the temperature range of 500-1000 °C. The microstructure, morphology, and crystal orientation of the thin film were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), while the resistance-temperature curve, resistance change rate, and temperature coefficient of resistance (TCR) of the sensor were tested. The results show that annealing at 800 °C for 4 hours is the optimal process: under this condition, the platinum thin film exhibits a strong (111) crystal orientation preference with uniform and dense grains. The TCR increases from 2740 ppm/°C before annealing to 3742 ppm/°C, and the resistance change rate reaches -26.14%. Within the range of 33-600 °C, the maximum temperature measurement error is less than 0.2%, the temperature drift is less than 0.08% FS, and the resistance-temperature curve shows excellent linearity. This sensor, featuring both high precision and stability, is suitable for high-precision temperature measurement scenarios in medium-to-high temperature environments, such as hot-end monitoring of aerospace engines and diagnosis of automotive exhaust systems.