Development of a piezoresistive MEMS pressure sensor for a precision air data module

In this paper, the design and fabrication techniques of a differential pressure sensor used in precision air data module (ADM) are described, and its performance test results are presented. A differential pressure senor for an ADM detects the differential pressure between static and total pressure, which can cover differential pressure of 0~20psi range with less than 1% accuracy. In order to satisfy these requirements, the piezoresistive Wheatstone bridge on the silicon diaphragm is used as a strain gauge. The p-type piezoresistors are implanted on the diaphragm under high doping concentration level for achieving smaller temperature sensitivity, and each resistor is designed to have same shape to compensate common errors. A constant current is applied to the bridge, which makes the temperature effects on piezoresistive coefficients and resistors compensate each other. The proposed differential sensor is designed through FEM analysis in order to satisfy nonlinearity requirements for an ADM. The repeatability and nonlinearity of the sensor are less than 0.09% and 0.27%, respectively, and the pressure hysteresis is less than 0.63%, which contributes to the root sum square (RSS) accuracy of 0.69%.