Simulation of circular silicon pressure sensors with a center boss for very low pressure measurement

A characteristics simulation method of circular silicon-diaphragm piezoresistive pressure sensors was developed to obtain accurate sensors for very-low-pressure measurement. The anisotropic stress-strain relationship of a silicon single-crystal plate and the nonlinear characteristics of silicon piezoresistive gauges were considered. Nonlinear deflection and strain formulas of circular silicon diaphragm sensors with a center boss and sensors with a center boss and ribs were derived by taking the effects of the large deflection and the support stiffness of the diaphragms into account. Based on these considerations, the characteristics of the sensors were simulated. The simulated results show good agreement with the observed results and indicate that output voltage can be greatly increased while maintaining low nonlinearity even in the low-pressure range by narrowing the rib width and thinning the diaphragm thickness of sensors with a center boss and ribs. This is because the rib strain that produces output voltage is increased while maintaining small deflection by using this type of sensor