MEMS Pressure Sensor for High-Temperature Applications

MEMS pressure sensors have been widely used in automobiles, airplanes, submarines, and biomedical devices.For some special applications such as aerospace and underground oil exploration, pressure sensors which can endure extremely high temperature are required.In this paper, the design and simulation of a novel silicon-carbide based MEMS pressure sensor for high-temperature applications is proposed.The proposed MEMS pressure sensor is based on Si-SiC-Si compound structure.A SiC round plate supported by four flexible folded beams is sealed inside a vacuum cavity between the top silicon diaphragm and bottom silicon substrate.The gold electrodes deposited on SiC plate constitute top and bottom capacitances with top Si diaphragm and bottom Si substrate.When no external pressure is applied, the SiC round plate stays in the middle of the gap, and top capacitance equals to bottom capacitance.When an external pressure is applied, the top Si diaphragm deforms, and a DC driving voltage is applied between SiC plate and substrate to pull the SiC plate down to the middle position of the gap.In this way, the top capacitance is kept equal to the bottom capacitance.By measuring the required driving voltage, the applied external pressure is derived.This is the working principle of the SiC MEMS pressure sensor.The device model is analyzed in details, and a set of optimized design parameters of the device is derived.ANSYS FEM simulation is used to verify the vibration modes of the SiC plate.The proposed novel MEMS pressure sensor can be used for pressure sensing in high-temperature applications.