Temperature characteristics research of SOI pressure sensor based on asymmetric base region transistor

Based on the asymmetric base region transistor, a pressure sensor with temperature compensation circuit is proposed in this paper. The pressure sensitive structure of the proposed sensor is constructed by a C-type silicon cup and a Wheatstone bridge with four piezoresistors ($R_1$, $R_2$, $R_3$ and $R_4)$ locating on the edge of a square silicon membrane. The chip was designed and fabricated on a silicon on insulator (SOI) wafer by micro electromechanical system (MEMS) technology and bipolar transistor process. When the supply voltage is 5.0 V, the corresponding temperature coefficient of the sensitivity (TCS) for the sensor before and after temperature compensation are −1862 and −1067 ppm/°C, respectively. Through varying the ratio of the base region resistances $r_1$ and $r_2$, the TCS for the sensor with the compensation circuit is −127 ppm/°C. It is possible to use this compensation circuit to improve the temperature characteristics of the pressure sensor. (paper)