Optimization of SOI CMOS MEMS piezo resistive pressure sensor

In this paper, we are presenting the optimization of SOI (silicon on insulator) CMOS (complementary metal oxide semiconductor) piezo resistive pressure sensor based on the design parameters. The design parameters against which sensor has been optimized are, membrane shape, piezo resistive material and geometric shape of piezo resistors. FEA (finite element analysis) was used to simulate and optimize the pressure sensor. The simulations have been carried out in COMSOL Multiphysics modeling and simulation software. The side length (edge length) of square membrane is 400 micrometers, while thickness of square membrane is 3 micrometers. Square and circular membranes have been studied for the membrane shape optimization. The piezo resistors materials which have been studied for optimization are p-doped and n-doped monolithic silicon as well as p-doped and n-doped polysilicon. Optimization of piezo resistor layout is based on various parameters which are, offset of resistors from the membrane, resistor size and the distance between piezoresistors. Based on simulations, square membrane is considered better than the circular membrane in terms of sensitivity of MEMS (micro electromechanical systems) pressure sensor. Whereas n-doped monolithic silicon gives the optimum response among the materials studied. Piezo resistive design has been optimized to get best sensitivity.