Analytical model of MEMS-based piezoresistive pressure sensor using Si3N4 diaphragm

Abstract

In this paper, Piezoresistive Pressure Sensor (PPS) with four Polysilicon piezoresistors on Si3N4 diaphragm with improved sensitivity is successfully designed by using MEMS technology. Sensing is accomplished via deposited polysilicon resistors like metal resistors. The analytical model of PPS is optimized for the geometry and different aspect ratios of the diaphragm. The system output sensitivity of the PPS is evaluated here by interpreting the proper selection of the geometry of a thin Si3N4 diaphragm. The maximum deflection, maximum induced stress and highest sensitivity for this sensor are obtained for the diaphragm when aspect ratio is minimum. It is found that sensitivity of the sensor is influenced more powerfully by diaphragm thickness. The applied pressure range is considered from 5 kPa to 40 kPa related to the equivalent minimum and maximum measurable blood pressure of human body.