Design of a High-Temperature SOI Piezoresistive Pressure Sensor via Direct Electrical-Output Simulation with an Empirical Piezoresistive Coefficient Model

SOI (silicon-on-insulator) piezoresistive pressure sensors are well suited for high-temperature applications because the buried oxide layer suppresses the p-n junction leakage current above 150 °C. Accurate simulation of the output voltage is essential for design. However, conventional approaches obtain the electrical output indirectly, first calculating the diaphragm stress with structural finite-element analysis and then converting it analytically into resistance or voltage changes. Although the output can be calculated directly by finite-element simulation incorporating the piezoresistive effect, the constant piezoresistive coefficients commonly used cannot reflect their dependence on temperature and doping concentration, limiting simulation accuracy. In this work, a coupled piezoresistive finite-element model with an empirical formula was developed to directly simulate the output voltage, in which the temperature- and doping-dependent coefficient π44 (T, N) is incorporated into the simulation. Using this method, a 0–20 MPa flat-diaphragm SOI pressure sensor was designed and simulated over 25–300 °C. The fabricated sensor delivers full-scale outputs of 104.91 and 73.39 mV with sensitivities of 1.0491 and 0.7339 mV/V/MPa at 25 °C and 300 °C, respectively; the simulated outputs deviate from the measurements by 7.26% and 10.28%, with an average deviation of 5.76%, improving the verifiability between design and experiment.