Integrated Design Of Capacitive Accelerometer Based On Wafer-level Packaging

MEMS accelerometers are used in medical,electronic consumption,auto-driving and aerospace applications because of their small size,low power consumption and high sensitivity.The accelerometer is composed of sensor and its interface readout circuit,so it is very important to study the sensor structure and the design of interface readout circuit.In this paper,a capacitive sensor and its closed-loop feedback interface readout circuit are proposed.The structure design,process design and circuit design of the accelerometer are carried out.Through the analysis of various elastic beam structures and the demand of this subject,the sensor structure is confirmed,and the electrostatic force,damping,noise and other factors of the accelerometer are analyzed and calculated.The ANSYS software is used to simulate the statics and dynamics of the sensor sensitive structure.The resonant frequency of the capacitive acceleration sensor proposed in this paper is32.239 kHz;Then MATLAB SIMULINK software is used to model and simulate the interface readout circuit,and the measuring range of the accelerometer proposed in this paper is ± 20 g;In the simulation process,the performance parameters of symmetric comb structure and asymmetric comb structure,wafer level package and device level package are compared and analyzed.The voltage sensitivity of symmetric comb structure with wafer level package is 328 mV/g,the nonlinear error is 0.15 % and stability time is 2 ms,The voltage sensitivity of symmetric comb structure with device level package is 264 mV/g,the nonlinear error is 0.3 % and stability time is 4 ms.Finally,the schematic diagram and layout of the accelerometer are designed and drawn,and the welding board is made,and the board and the car and the commercial acceleration sensor constitute the test system.By testing the performance of the accelerometer,the voltage sensitivity is 310 mV/g,and the voltage sensitivity error of the simulation output is 7.9 %.