A novel electromagnetically actuated MEMS scanning mirror integrated with rotation angle sensor

作者:Chen Li*; Wen Zhi yu; Wen Zhong quan; Qian Rong rong
来源:4th International Symposium on Photoelectronic Detection and Imaging (ISPDI) - Sensor and Micromachined Optical Device Technologies, 2011-05-24 to 2011-05-26.
DOI:10.1117/12.901043

摘要

Aiming at application of micro-spectrometer systems, a novel electromagnetically actuated MEMS scanning mirror with large size and integrated rotation angle sensor is proposed for the application of micro-spectrometer. The size of the mirror plate is 6x5mm(2), which is supported by two torsion beams. The scanning mirror is fabricated on a 500 mu m-thick single crystal silicon wafer using bulk micromachining process. Two gold coils are deposited on back side of the mirror using electroplating technology. One of them is used to generate Lorentz force to drive the mirror, and the other is used to monitor the rotation angle by measuring the induced voltage which is proportional to the angular rate. The silicon substrate is heavily doped (0.02 ohm.cm) to connect the coil central end to outside pad. A 500 nm-thick aluminum film is sputtered on the front side of the mirror plate to form a high quality mirror surface. The whole structure is released by wet etching technology, and corner compensation structure is designed to avoid convex corner undercutting. In order to achieve large deflection angle, NdFeB permanent magnets are used to provide high magnetic field. Testing results show that maximum mechanical rotation angle of the scanning mirror can achieve +/- 10 degrees at the resonant frequency of 344Hz with low driving voltage of less than 1V(eff), corresponding to a Q-factor of 137 at atmospheric pressure, and the output voltage of the angle sensor has high linearity.

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