Finite Element Simulations Of Piezoresistive Pressure Sensors Under The Influence Of Elastic Thermal And Electric Fields

Due to the development of technologies such as internet of things,artificial intelligence,integrated circuit,smart phones and so on,piezoresistive pressure sensors based on MEMS technology has become widely used.The design of pressure sensors with better performances and higher reliabilities has aroused the attention of many researchers.Therefore,it is very important to study the factors that affect the performance of piezoresistive pressure sensors.In this thesis,a three-dimensional finite element model of a piezoresistive pressure sensor is developed using Free Fem++(a finite element software),and the output behaviors of the pressure sensor under the influence of multi-physics fields are studied.The goal is to help the design of piezoresistive pressure sensor and to improve its performance.The conclusions from this work are listed below:(1)Under the influence of elastic,thermal and electric fields,the output voltage of the piezoresistive pressure sensor decreases with both the increase in the thickness of the elastic membrane of the sensor and the increase in the resistance width of the sensor.At the same time,when the doping resistance of the pressure sensor is arranged at the edge of the elastic membrane,the pressure sensor yields a larger output voltage.(2)As the input voltage increases,piezoresistive pressure sensors become less and less sensitive to variations in the externally applied pressure.Thus,it results in a lower accuracy of the pressure measurement when the pressure sensor is subjected to large input voltages.(3)The electric field has a great influence on the temperature field of the piezoresistive pressure sensor.The maximum temperature in the pressure sensor increases rapidly with the increase of the input voltage.In addition,when the externally applied pressure is the same,the output voltage of the pressure sensor also increases rapidly as the input voltage increases.(4)When designing a piezoresistive pressure sensor,the thickness of the elastic membrane of the pressure sensor should be reduced as much as possible,the width of the doping resistance should be reduced,and four doping r esistances should be arranged as close as possible to the edge of the elastic membrane.Thus,a larger output voltage can be obtained and the accuracy of the measurement can be improved for the pressure sensor.Moreover,in order to make the pressure sensor more sensitive to variations in the externally applied pressure,an appropriate input voltage should be used instead of using an excessively large input voltage to achieve a large output voltage.