Design of High Sensitivity and Linearity Microelectromechanical Systems Capacitive Tire Pressure Sensor using Stepped Membrane

This paper is focused on a novel design of stepped diaphragm for MEMS capacitive pressure sensor used in tire pressure monitoring system. The structure of sensor diaphragm plays a key role for determining the sensitivity of the sensor and the non-linearity of the output. First, the structures of two capacitive pressure sensors with clamped square flat diaphragms, with different thicknesses are investigated and their sensitivity and non-linearity are compared together. Finally, for increasing the sensitivity and linearity, a new capacitive pressure sensor with a stepped diaphragm is introduced. A numerical solution for determination of the accurate sensitivity of the sensor is presented. The results show that the sensitivity of the sensor is increased from 0.063 fF/KPa in flat diaphragm to 0.107 fF/KPa in stepped diaphragm and also the non-linearity is decreased from 2.37 to 1.857%. In this design, the sensor sensitivity and output linearity are increased simultaneously.