Research On Silicon-based MEMS Pressure Sensor

With the rapid development of MEMS,MEMS capacitive pressure sensors have become one of the most important research branch in the field of sensors in recent years,due to their high sensitivity,low power consumption and good thermal stability.It has been one of the research focuses in MEMS capacitive pressure sensors to further improve the trade-off characteristic between sensitivity and linearity.Aiming at the sensitivity and linearity of touch mode MEMS capacitive pressure sensor,the emphasis is put on the studies of the innovation of device structures,the analyses of the working principle and actual influence.Many research results and laws with practical value are achieved.The main research works and achievements are in the following.A MEMS touch mode capacitive pressure sensor with uneven insulation layer(UTMCPS)is proposed.The ideal uneven insulation layer thickness curve t(x)is obtained by theoretical derivation.The influence of structural parameters of ideal uneven insulation layer on sensitivity,linearity and linear range is studied in detail by ANSYS.The internal physical mechanism of the device is revealed.The results show that compared with the traditional touch mode capacitive pressure sensor(TMCPS),UTMCPS has higher linearity and wider linear range,and the sensitivity is not reduced.Simultaneous interpreting the trade-off between linearity and sensitivity of pressure sensors.In order to reduce the manufacturing difficulty of UTMCPS,two simplified and approximate structures of uneven insulation layer,slope insulation layer structure and step insulation layer structure are proposed and studied.Compared with the traditional TMCPS,the linearity of the two simplified approximate structures is still improved,the linear range is extended,and the sensitivity is not reduced.In the step insulation layer structure,by increasing the number of steps to approach the thickness distribution of the ideal uneven insulation layer,the linearity of the step structure sensor can be continuously improved.This provides an effective design way for the process realization of the uneven insulation layer.In view of the influence of practical factors on the pressure sensor,the stress and strain caused by residual stress and temperature on the sensor structure are studied in detail with the aid of numerical simulation.The influence of residual stress and temperature on the pressure-capacitance curve,sensitivity and linearity performance of UTMCPS are analyzed.The research results and laws with practical value are obtained.Based on the numerical simulation,the influence of flexible substrate bending on capacitive pressure sensor in flexible integrated application is studied.Two improvement methods,substrate groove structure and groove flexible substrate,are proposed.The improvement of the characteristics of capacitive pressure sensor is studied by simulation,which effectively solves the problem that the bending of flexible substrate leads to the displacement of capacitive pressure curve of pressure sensor.