Sensitivity and Non-linearity Study and Performance Enhancement in Bossed Diaphragm Piezoresistive Pressure Sensor

This paper describes a comparative study of sensitivity and non-linearity of conventional and bossed diaphragm piezoresistive pressure sensor along with a performance enhanced design. The proposed structures take into consideration corner compensation to avoid distortion of the mesa structure during fabrication of bossed diaphragm structure using wet bulk micromachining. Optimum piezoresistors locations are calculated with the help of simulations carried out using finite element method (FEM) based tool COMSOL(C) Multiphysics. Since the sensitivity and non-linearity of conventional and bossed diaphragm structures showed a linear trend, empirical formulae are proposed using linear fit for quick and approximate calculation of sensitivity and non-linearity for a particular sensor structure. It is observed that high stress regions are also present near the boss - diaphragm interface and hence a design with piezoresistors placed at these regions is also proposed. This design is found to be enhancing the performance of piezoresistive pressure sensor compared to the conventional piezoresistor placement.