Analytical and experimental study on sensitivity of planar piezoresistive vibration sensor

We are engaged in developing a planar high-sensitivity piezoresistive vibration sensor with lower process cost and fewer package difficulties. For the pursuit of high sensitivity, the design and optimization of the sensor structure are studied together via a theoretical principle approach and finite-element method (FEM) analysis. The effects of the vibration sensor dimensions, including the solid width and length of flexure, the structure thickness, and the piezoresistor width, have been analyzed comprehensively. Design guidelines are presented for the fabrication of vibration sensors, and the sensitive position of the piezoresistor on a flexure beam is obtained for resolution optimization. To calculate the relative resistance changes in one-beam flexure, the theoretical approach and the FEM simulation are used. The results of the two methods agree well, the relative error being only 3.8%. Moreover, dynamic measurement of the structure of the prototype vibration sensor is implemented. The calculated and measured results of the relative displacement between the proof mass and substrate are in good agreement, which also demonstrated the FEM-based design to be reasonable.