Mechanical Robust Biaxial MEMS Mirror Achieving >100° Optical Scanning Angle for LiDAR Application

Microelectromechanical system (MEMS) mirrors often face issues such as silicon material fracture during large-angle scanning. For MEMS devices with larger mirror sizes, due to the influence of air damping, the voltage amplitude is usually insufficient to drive the micromirror for large-angle scanning. This article designs a biaxial Lissajous scanning piezoelectric AlScN-driven MEMS micromirror driven by circular arc actuators, featuring large mirror with a diameter of 5 mm. To achieve large-angle scanning, optimizations are made in the following three aspects: 1) in order to reduce the risk of silicon material fracture during large-angle scanning, stress dispersion structures are adopted in the structural design and an improved non-Bosch process is utilized in the manufacturing process to achieve smooth sidewall morphology; 2) for achieving large-angle scanning of the large-size mirror at a lower voltage amplitude, vacuum packaging is employed in the packaging to reduce air damping; and 3) to find the resonant frequency under nonlinear effects, we utilize a frequency-sweeping driving method to actuate the MEMS mirror. After optimization, the mirror achieves total optical scanning angles (TOSAs) of 102.8° and 104.8° on its two axes. Furthermore, the mirror has passed 900 g shock tests and 20 g vibration tests, demonstrating its good shock and vibration resistance while achieving large scanning angles.