Design And Performance Research Of MEMS Thermal Gas Flow Sensor Based On Thermopile

Gas flow sensors are indispensable in industrial control,medical health,automotive electronics,scientific research,and other areas.In recent years,with the rapid development of the Internet of Things,artificial intelligence technology and MEMS technology,a large number of emerging needs for gas flow sensor applications have arisen.Compared with other principles of gas flow sensors,MEMS thermal gas flow sensors based on the heat transfer principle have received close attention from researchers and technology companies due to simple structure,high measurement sensitivity,easy integration,and low cost.To this purpose,a thermal gas flow sensor based on MEMS technology is designed and prepared in this paper,and its performance is tested and analyzed,as well as its application value is initially explored.In this paper,a thermal gas flow sensor is designed and studied with a thermopile temperature measurement structure and a microheater.In which,the thermopile is made of N/P type polysilicon material double-stacked and aluminum heating resistors are used as microheaters.Firstly,by summarizing and discussing the basic working principle of thermal gas flow sensor as well as the structure and material combination of thermopiles,the main body of the designed sensor structure and material selection were initially determined.The thermal gas flow sensor is modeled using COMSOL finite element simulation software,and multiphysics field coupling simulations of electric,thermal and flow fields are performed.After determining the structure and dimensions of each part of the sensor based on the simulation results,the integration process was designed and the layout was drawn.Then,the sensor chip with two structural forms,heat loss type and heat distribution type,was processed and fabricated based on the 0.35 ?m CMOS process development platform of the Institute of Microelectronics,Chinese Academy of Sciences.The experimental platform for gas flow testing was built with the help of Wuxi IOT Innovation Center laboratory,and a series of tests on sensor performance were conducted,including: electrical characteristics of the heating resistor;temperature of the sensor chip surface center under different operating voltages of the heating resistor;correspondence between sensor output and gas flow size(0～1000 sccm);sensitivity of sensor response to gas flow under different heating powers;sensor response time and stability;and the effect of ambient temperature on sensor output.The test results show that the designed MEMS thermal gas flow sensor has excellent characteristics such as high normalized sensitivity(15.50 m V/(m/s)/m W and 4.36 m V/(m/s)/m W),small size(1.3 mm×1.3mm),fast response(142.4 ms)and stability and reliability.In addition,the potential applications of the designed MEMS thermal gas flow sensor in two scenarios,nasal breathing status monitoring and wind speed and direction detection,are presented and initially tested.In summary,this paper presents a series of studies on the performance improvement of current gas flow sensors from the perspectives of sensing principle,device structure design,device process development and intelligent application,which provides a research basis and reference value for realizing the practical application of MEMS gas flow sensors.