Development of high temperature resistant of 500 °C employing silicon carbide (3C-SiC) based MEMS pressure sensor

This works reports a packaged MEMS capacitive pressure sensor (CPS) employing single crystal 3C-SiC thin film as a diaphragm. The details of the design and fabrication steps involved bulk micromachining process. The 3C-SiC-on-Si wafer is back-etched the bulk Si to leave 3C-SC thin film by applied ProTEK PSB coating as a newly photosensitive layer. The ProTEK PSB is exposed into desired pattern of MEMS capacitive pressure sensor and the exposed pattern is developed by developer (ethylene lactate). The photosensitive can be stripped off with strong combination acid such as 2-(1-methoxy)propyl acetate, ethyl acetoacetate and photoacid generator which is attack the exposed ProTEK PSB while unexposed ProTEK PSB areas remain contact the alignment on the wafer surfaces. The prototypes of a MEMS capacitive pressure is packaged for high temperature up to 500 °C and characterized under static pressure of 5.0 MPa in a stainless steel chamber with direct capacitance measurement using LCR meter. The diaphragm of 3C-SiC thin film has the thicknesses of 1.0 µm and the size of 2.0 × 2.0 mm. At room temperature (27 °C), the sensitivity of the sensor is 0.00962 pF/MPa in the range of (1.0–5.0 MPa), with nonlinearity of 0.49 %. At 300 °C, the sensitivity is 0.0127 pF/MPa, and nonlinearity of 0.46 %. The sensitivity increased by 0.0031 pF/MPa, corresponding temperature coefficient of sensitivity is 0.058 %/ °C. At 500 °C, the maximum temperature coefficient of output change is 0.073 %/ °C being red at 5.0 MPa. The main impact of this work is the ability of the sensor to operate up to 500 °C, compare to the previous work using similar 3C-SiC diaphragm that can operates only 400 °C. The main impact of this work is the ability our CPS to operate up to 500 °C and pressure of 5 MPa to surpass the performance of previous work at lower temperature and pressure. In addition, this CPS has reliable stainless steel (SS) o-ring packaging with a direct assembly approach to reduce manufacturing cost and easy installation and maintenance environment.