Application of Finite Element Analysis to Predict the Performance of Piezo-Resistive Pressure Sensor

Piezo-resistive pressure sensors have been used to measure pressure in automotive, industrial and medical instruments applications. As the market demand requires measurements of extremely low pressure and the need to reduce the design cycle time, it is very important to reduce the design iterations and to use simulation techniques to help predict the device performance. A methodology is shown to combine finite element analysis, piezo-resistive theory and electrical circuit simulation to predict the performance of pressure sensors. The finite element analysis is used to compute the stresses under the application of pressure loading. The piezo-resistive theory is used to compute the output voltage or change in resistance from the computed stresses in the sensor die at the transducer location. The analysis is used to predict device performance parameters such as span, sensitivity, linearity error and the difference in response between front side and back side pressure application. The analytical results are compared with the experimental results to show close correlation. The analysis methodology presented here also discusses the limitations and possible solution in predicting non-linearity of the pressure sensor die. The use of finite element method is integrated with piezorestive theory and the methodology is extended from just an analysis tool to a predictive or simulation tool for the device performance.