Development of All-SiC Absolute Pressure Sensor Based on Sealed Cavity Structure

Silicon carbide has promising potential in high temperature pressure sensors due to its excellent material properties. This paper presents a piezoresistive n-type 4H-SiC absolute pressure sensor based on an all-SiC sealed cavity structure, which provides a new approach for the development of SiC pressure sensors. Firstly, the structural design of the pressure sensor with the measurement range of 10 MPa was conducted through the finite element method. After that, a SiC diaphragm with controllable thickness and high surface quality was achieved through grinding and chemical mechanical polishing process, which indicated that the root mean square surface roughness was 0.168 nm and the relative standard deviation of diaphragm thickness was 0.24%. A patterned SiC substrate with shallow grooves obtained by shallow etching process was directly bonded onto the SiC diaphragm to form the sealed cavity structure. Finally, the performance test of the fabricated sensor at 30 °C indicated that the sensitivity was 1.56 mV/V/MPa, the nonlinearity was 0.034% FS, and the accuracy was 0.29% FS. The temperature coefficient of sensitivity exhibited a negative value of −0.134% FS/°C at 250 °C. Moreover, the maximum temporal drift of zero pressure output at 250 °C was only 0.12 mV in 14 hours after several high temperature aging tests. The above research demonstrates the application potential of the proposed SiC sealed cavity structure in all-SiC pressure sensors, which provides a technical foundation for the development of high temperature pressure sensors.