Development of Laser-Micromachined 4H-SiC MEMS Piezoresistive Pressure Sensors for Corrosive Environments

Making full use of the availability and excellent performance of silicon carbide (SiC) substrates, SiC-based MEMS piezoresistive pressure sensors have been extensively investigated. In this article, a femtosecond laser was adopted instead of dry plasma etching technology to realize mass fabrication of 128 bulk SiC piezoresistive pressure sensor diaphragms from half a 4H-SiC wafer. These diaphragms were completed in 2 h with an average thickness error of less than 7.5% and a surface roughness of 108 nm. The 4H-SiC sensor was characterized with a nonlinear error of 0.13% FS and a repeatability error of 1.49% FS in the pressure range of 0–5 MPa at room temperature. The tolerance to temperature was measured in high and low temperature of −50 °C–300 °C with the temperature coefficient of sensitivity (TCS) of −0.11% FS°C at −50 °C and −0.16% FS°C at 300 °C. In addition, resistance measurement of the sensor in strongly alkaline corrosive solution proved the robustness with an average daily drift of only 1.61%. This integrated solution that combines femtosecond laser technology and MEMS processing provides exciting opportunities for rapid and large-scale manufacturing of bulk SiC pressure sensors.