The Design And Manufacture Of The Tri-axis Capacitive Accelerometer Based On The Single Mass

Capacitive accelerometer has been widely used in military and civilian fields, just like national defense, aerospace, automotive, communications and so on. The capacitive accelerometer has become a mainstream for the market and research. Depending on the application fields, the integration of tri-axis capacitive accelerometer is an important direction of development. This paper aims to design and manufacture a tri-axis capacitive accelerometer based on the single mass. Research is focused on structure design, simulation and optimization, process to achieve the goals of dimension reduction, sensitivity improving, cross-axis sensitivity decreasing and Brown noise reduction. This thesis starts from the design of tri-axis capacitive accelerometer based on the single mass, and the details are as follows:Depending on the research of detecting methods and structures, the structure model of accelerometer is proposed, and its principle and coupling analysis are carried out. Depending on the theoretical model of the elastic beam, the stiffness formulas on working modals are achieved using mechanical and energy method. The principle and model of detecting combs is established. And the parameters of accelerometer are calculated.Depending on the finite element simulation software, the accuracy of stiffness formulas of elastic beam on working modals is verified using displacement and resonant frequency methods. The working modals, sensitivity and stress of device are simulated and analyzed. And the impact of thermo-mechanical stress of plastic packaging assembly process and external loads on device is estimated.The layouts drawing of lead layer, anchor layer, structure layer and pad layer are introduced. The EPI-poly process is utilized to realize the 18um thickness and complete the device fabrication. The influence of process on the device performance is analyzed.A test platform for capacitive tri-axis accelerometer is established to test and analyze accelerometer’s performances. The differences between test and theoretical values are utilized to verify the correctness of the theory, and confirm the performances of the capacitive accelerometer can meet the design requirements.