Exploring the nonlinear piezoresistive effect of 4H-SiC and developing MEMS pressure sensors for extreme environments

Microelectromechanical system (MEMS) pressure sensors based on silicon are widely used and offer the benefits of miniaturization and high precision. However, they cannot easily withstand high temperatures exceeding 150 degrees C because of intrinsic material limits. Herein, we proposed and executed a systematic and full-process study of SiC-based MEMS pressure sensors that operate stably from -50 to 300 degrees C. First, to explore the nonlinear piezoresistive effect, the temperature coefficient of resistance (TCR) values of 4H-SiC piezoresistors were obtained from -50 to 500 degrees C. A conductivity variation model based on scattering theory was established to reveal the nonlinear variation mechanism. Then, a piezoresistive pressure sensor based on 4H-SiC was designed and fabricated. The sensor shows good output sensitivity (3.38 mV/V/MPa), accuracy (0.56% FS) and low temperature coefficient of sensitivity (TCS) (-0.067% FS/degrees C) in the range of -50 to 300 degrees C. In addition, the survivability of the sensor chip in extreme environments was demonstrated by its anti-corrosion capability in H2SO4 and NaOH solutions and its radiation tolerance under 5W X-rays. Accordingly, the sensor developed in this work has high potential to measure pressure in high-temperature and extreme environments such as are faced in geothermal energy extraction, deep well drilling, aeroengines and gas turbines.

Automated summary

In this study, a MEMS pressure sensor based on 4H-SiC was proposed and demonstrated to operate stably from -50 to 300 degrees C, with good output sensitivity, accuracy, and low temperature coefficient of sensitivity. The sensor also showed excellent resistance to corrosion and radiation, making it suitable for high-temperature and extreme environments.