A Simulation Studies of Piezoresistive Sensing Resistor in MEMS Square Diaphragm

A piezoresistive sensing resistor in MEMS square diaphragm has been studied using the MEMCAD 4.0 suite of tools, and in particular the piezoresistive module. It is seen that the effect of resistor size and position significantly effects the performance and behavior of the sensor. A 0.55 MPa pressure is used for the simulation on a 500um to 200um wide square shape diaphragm with 50um in thickness. Each resistor is built in arranged into a full Wheatstone Bridge configuration. To determine the optimal resistor, effective resistor length on sensor output is simulated. The best resistor length is about 20% of the diaphragm length, by increasing or decreasing the resistor length from the effective resistor length, it will greatly reduce the voltage output and the sensitivity of the sensor. The temperature effect on piezoresistive were also evaluated over a temperatures range of -19°C to 85°C. The normalized resistance change with the temperature was linear but the voltage output and the sensitivity decrease with increasing temperature.