A Simulation Program for the Sensitivity and Linearity of Piezoresistive Pressure Sensors

Abstract

A simulation program is developed which is capable of calculating the output responses of piezoresistive pressure sensors as a function of pressure and temperature. Analytical models based on small and large deflection theories have been applied to predict the sensitivity and linearity of pressure sensors. Surfacemicromachined diaphragms with square or circular shapes, fabricated by a low pressure chemical vapor deposition sealing process, are designed and tested to verify the program. They are made of polysilicon and have a standard width (diameter) of 100 m and thickness from 1.5 to 2.2 m. Various parameters of the piezoresistive sensing resistors, including length, orientation, and dopant concentration, have been derived and constructed on top of the diaphragms. For a 100m-wide 2m-thick square-shape pressure sensor, calculated and experimental results show that sensitivity of 0.24 mV/V/(lbf/in2) is achieved. Experimentally, a maximum linearity error of 0.1% full-scale span) is found on a 100m-wide 2.2m-thick square-shape pressure sensor. Both sensitivity and linearity are characterized by the diaphragm thickness and the length of the sensing resistors. [394]

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