A simulation program for the sensitivity and linearity of piezoresistive pressure sensors

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. Surface-micromachined 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 /spl mu/m and thickness from 1.5 to 2.2 /spl mu/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 100-/spl mu/m-wide 2-/spl mu/m-thick square-shape pressure sensor, calculated and experimental results show that int sensitivity of 0.24 mV/V/(Ibf/in/sup 2/) is achieved. Experimentally, non a maximum linearity error of /spl plusmn/0.1% full-scale span) is found out on a 100-/spl mu/m-wide 2.2-/spl mu/m-thick square-shape pressure sensor. Both sensitivity and linearity are characterized by the diaphragm thickness and the length of the sensing resistors.