High-temperature piezoresistive pressure sensor based on implantation of oxygen into silicon wafer

Silicon on insulator (SOI) substrates can be prepared using ion implantation of oxygen. For piezoresistive detection, the top layer (0.2 μm thickness) of silicon is used as the active material due to its excellent monocrystalline properties. The piezoresistive effect of the top silicon layer of the SOI wafer is analyzed using a cantilever structure. Results show that under certain doping concentration conditions, the longitudinal piezoresistive coefficients of 〈1 1 0〉 crystal direction silicon decrease with temperature, while transverse piezoresistive coefficients are less affected by temperature. At 300 °C, Si 〈1 1 0〉 crystal direction has larger longitudinal and transverse piezoresistive coefficients, which make it suitable for high temperature piezoresistive pressure sensor production. The pressure sensor chip structure is simulated and analyzed using the finite element method. The pressure gauge chips are manufactured using MEMS techniques. The manufactured sensors are measured with an applied pressure from 0 to 6.0 MPa at 300 °C. The test results show that the sensitivity is approximately 30 mV/(mA MPa), the non-linearity is less than 1.5‰FS, and the repeatability is less than 0.3‰FS. This research shows that the SOI piezoresistive pressure sensor could reliably work at high temperatures up to 300 °C.