An electrostatic micro-electromechanical systems micromirror with low-torsional stress supported by three-asymptote beam

Micro-electromechanical systems (MEMS) micromirrors are preferred actuators in the field of light beam steering. Electrostatic micromirrors have gained vital attention due to their simple and compact structure. Among performance characteristics, the large field of view (FOV) and high structural reliability are key research hotspots. This work introduced a novel design of a three-asymptote support beam to improve the structural reliability, which is defined as a function with a shape coefficient, A. Simulation results reveal that the three-asymptote beam can reduce the chamfer stress from 690 MPa to 280 MPa compared with the conventional straight beam. Additionally, the resonant frequency of the micromirror can be adjusted via the shape coefficient. The micromirror prototype was fabricated using silicon-on-insulator-based micromachining and double-sided lithography technology. The vertically asymmetric electrostatic actuator comprises movable combs in the device layer and fixed combs in the handle layer. Furthermore, the performance of the prototype was tested in both static and resonant modes. The maximum static mechanical angle is 4.3° with a direct current voltage of 60 V, and the maximum angle is 3.1° at 445 Hz with a peak-to-peak voltage of 20 V in resonant mode.