Research On MEMS Thermal Convection Accelerometer

MEMS thermal convection accelerometer is a kind of micro-nano device that detects the exteral acceleration signal by the natural convection heat of the fluid in a closed cavity.Compared with other types of accelerometer,the most prominent feature of thermal accelerometer is that there is no physical mass,using the air bubble heated in the cavity as a sensitive mass,which greatly improves the accelerometer impact resistance and make it to play a better role in big acceleration applications.In this paper,a thermal convection acceleration sensor with high performance and simple process is designed.The platinum thermal resistance with good thermal stability and high precision is used as the sensing element,and the flexible material polyimide with good thermal insulation performance is used as a substrate to realize the planar structure design without a suspended beam.Firstly,the domestic and foreign research status of thermal convection acceleration sensors and MEMS micromachining technology are investigated and summarized,and the basic working principle of the thermal convection accelerometer is analyzed.Then,the modeling and simulation of the temperature field of the fluid in the sealed cavity under natural convection conditions is performed.The simulation results verify the linear relationship between temperature difference and acceleration,and also show that the sensitivity of the accelerometer is highest in the range of 30-70 ?m between the sensing resistor and the heating resistor.Based on this,accelerometers with different structures are designed for experimental.After the photolithography,evaporation,stripping,sputtering,electroplating,deposition,etching and other silicon surface micromachining process steps,the production of an accelerometer chip is completed,and the obtained chip is subjected to a wafer level electrical performance test.The sheet resistance of platinum is 0.746 ?,and the platinum thermal resistance values of all parts are in accordance with the design values.On this basis,the interface circuit of the thermal convection accelerometer is designed,and the chip is diced,bonded and laboratory packaged.Finally,the accelerometer is test.By comparing the performance of accelerometers with different structures,the correctness of the theoretical and simulation results has been verified.