Study of a Novel MEMS Accelerometer with Low Noise Reduced by Actuators

Abstract

A novel MEMS (Micro Electronic Mechanical System) capacitive accelerometer is presented, which is mainly composed of supporting beam, seismic mass, grid strip capacitances, comb capacitances and electrostatic driver. The damping of grid strip capacitances with variable overlapping area is mainly affected by the slide film air damping, which is small and neglectful, and the damping between comb capacitor is squeeze film air damping. The comb sensing gap can be reduced by electrostatic actuators by which the aspect ratio can reach to 75:1 which greatly depress the limitation of DRIE (Deep reactive ion etching) process on high aspect ratio, and the initial sensing capacitance increases from 2.97 pf to 14.87 pf. The squeeze film damping is reduced from 0.046 Nm/s to 0.0015 Nm/s by designing the comb-shaped grooves on the fixed comb electrodes. The comb initial sensing gap is optimized according to formation factors of system noise, and the noise is reduced from 1.395 μg/√HZ to 0.591 μg/√HZ. The simulation results show that the accelerometer sensitivity achieves 8.40 pf/g, which is two times of the conventional devices.

Keywords:

• MEMS accelerometer
• electrostatic driver
• squeeze film damping
• noise
• comb-shaped groove

Acknowledgments

Project supported by the National Natural Science Foundation of China (No. 60506015) and Zhejiang Provincial Natural Science Foundation of China (No. Y1100590).