The Capacitance and Temperature Effects of the SiC- and Si-Based MEMS Pressure Sensor

Abstract

This project designs the pressure sensor for monitoring the extreme conditions inside the gas turbine engine. The capacitive-based instead of piezoresistive-based pressure sensor is employed to avoid temperature drift. The deflecting (top) plate and the fixed (bottom) plate generate the capacitance, which is proportional to the applied input pressure and temperature. Two thin film materials of four different sizes are employed for the top plate, namely cubic silicon carbide (3C-SiC) and silicon (Si). Their performances in term of the sensitivity and linearity of the capacitance vs pressure are simulated at the temperature of 27 ì 500ì 700àand 1000î The results show that both materials display linear characteristics for temperature up to 500ì although SiC-based sensor shows higher sensitivity. However, when the temperatures are increased to 700àand 1000ì the Si-based pressure sensor starts to malfunction at 50 MPa. However, the SiC-based pressure sensor continues to demonstrate high sensitivity and linearity at such high temperature and pressure. This paper validates the need of employing silicon carbide instead of silicon for sensing of extreme environments.