| MEMS-based chips have the advantages of small size,high integration,low power consumption,corrosion resistance,high temperature resistance and so on,which have a broad demand in the field of national defense construction.In recent years,silicon-based pressure sensors have been widely applied to industrial production,artificial interaction and environmental monitoring due to their simple structure,low cost and high accuracy.High temperature pressure sensor is an important part of pressure sensor.It can operate stably at high temperature（≥125℃）under harsh environment with high reliability.In complex high temperature environment scenarios such as aerospace,oil exploration and engines,temperature shift,thermoelectric effect and thermal hysteresis will greatly affect the measurement accuracy of sensor.The key point of high temperature pressure sensor research is to improve the operating temperature and eliminate the temperature shift.Researchers introduced new materials and novel structures to optimize the high temperature performance of the pressure sensors.Besides the performance of high temperature,it also puts forward higher requirements for sensitivity,repeatability,linearity,hysteresis and other characteristics.Therefore,it is of great significance to comprehensively study the performance characteristics of high temperature pressure sensors with the effect of temperature.Based on the above analysis,the research on the strain resistance pressure sensor is carried.The scientific research work and results are as follows:In order to meet the requirements of pressure and high temperature of the sensor,and research the performance characteristics of the sensor at high temperature.In this thesis,FEA software is used to simulate and design the chip.Carry out research on high temperature and select suitable high temperature materials.SOI is adopted as the substrate,Mo is used as the resistance film and Al is used as the metal connection wire to form the Wheatstone bridge structure.The pressure performance and temperature performance of the sensor were simulated.Temperature performance needs to consider the resistance thermosensitive effect,thermal expansion effect and packaging thermal stress.The resistance thermosensitive effect includes the deviation of initial resistivity（（0））and TCR.The thermal expansion effect includes the contribution of pressure sensitive film and resistance.The influence of temperature and pressure on sensor temperature shift was considered.The sensor is packaged in different forms and a variety of temperature test systems were built.The pressure range of the designed sensor is 0 k Pa～120 k Pa,and can be continuously stable output at 300℃or even above.The developed sensor exhibits excellent performance characteristics at room temperature（25℃）,including a sensitivity of 0.057 m V/V/k Pa,a nonlinearity of 0.79%Full Scale（FS）,the pressure hysteresis is less than 0.029%FS,0.02%FS repeatability and 0.791%FS accuracy.This work focused on the study of high temperature performance.The thermal zero shift of-0.13%FS/℃is obtained in the 25℃to 300℃.The simulation findings illustrate that the thermal zero shift is caused by thermal mismatch and by the deviation of0 and TCR together constitutes the thermal zero shift of the sensor.The TCZ by thermal mismatch is calculated as+0.012‰FS/℃,while the TCZ obtained by the deviation of0 and TCR is-0.139%FS/℃.It can be seen that the effect of thermal mismatch on TCZ is opposite（i.e positive change）to that of the deviation ofρ0and TCR.Among both,the deviation of0 and TCR is the major contributor to thermal zero shift.The TCS is-0.031%FS/℃,indicating that the pressure response of sensor is less affected by temperature,thermal mismatch is the main factor.The thermal hysteresis of the sensor is0.308%FS.Moreover,it was found that the thermoelectric effect caused by the on-chip temperature gradient also affects the accuracy of the sensor.A temperature difference of5.4℃produces a thermoelectric potential of 37.95μV equivalent to a pressure of 670 Pa loading on the chip.Especially in the environment where the output voltage is small and the temperature difference is large,the influence of additional output voltage will be greater.The formation of thermoelectric potential can be reduced by selecting suitable connection mode and chip layout.The response characteristics of the sensor at different temperature rates were investigated.The instantaneous output signal of the sensor is closely related to the temperature rate,but the temperature rate has no influence on the static output characteristics. |
