Design Of An Anti-high Overload MEMS Accelerometer With Comb Structure

Comb-type capacitive accelerometers,which are widely used in smart cars,earthquake monitoring,and geological exploration,have the advantages of high measurement accuracy,high sensitivity,and low-temperature drift.This type of accelerometer,however,will break down due to the damage of structure when going through a high overload environment,so the ordinary comb-type capacitive accelerometer cannot complete the high accuracy detection after experiencing a high overload harsh environment.Therefore,this thesis designs a MEMS comb-type capacitive accelerometer with an anti-high overload,which maintains the ability of accurate measurement in the low range of sensor,while achieving survivability in the high overload harsh environment.According to the design targets of the comb-type capacitive accelerometer:±50g range,peak of high overload resistance not less than 30000g,and pulse width of overload not less than8ms,this thesis start a study on the anti-high overload of the MEMS comb-type capacitive accelerometer.Firstly,the basic working principle and detection principle of MEMS comb-type capacitive accelerometer are analyzed theoretically.Secondly,the three sensitive structures of the proof mass,elastic support beam,and anti-high overload stop of the sensor are studied.Finally,we confirm overall structure of MEMS accelerometer and obtain parameters of the structure,and the size of the device is 5400μm×6900μm.Then,the finite element simulation software is used to analyze the model of accelerometer.Through the modal analysis,static analysis,and anti-high overload analysis,the sensitivity of the capacitive accelerometer is0.218p F/g at a range of±50g,the natural frequency is 2533.6Hz,and the maximum equivalent stress is 62.224MPa under an acceleration shock with an amplitude of 3×10~4g and a half-sine pulse width of 8ms applied to the device.The maximum equivalent stress is 62.224 MPa,which less than the maximum permissible stress of single-crystal silicon material and meets the requirement of anti-high overload of the device.Finally,the open-loop detection system model of the capacitive accelerometer was built by the Simulink simulation system,and the sensitivity of the open-loop detection system and the closed-loop detection system were obtained as37.7m V/g and 1.29V/g respectively.Combined with the bulk silicon MEMS technology,the Deep Dry Silicon on Glass（DDSOG）process is used to design the process flow of MEMS comb-type capacitive accelerometer with an anti-high overload and the key processing difficulties are discussed.Additionally,we design lithography mask.