Grid-Structured Cantilever Beam Fabrication Technique Based on Cavity-SOI Process for MEMS Micromirror

This work introduces a fabrication method for Cavity-SOI substrates featuring grid-structured cavities in the device layer. The effectiveness of this structure was demonstrated through its application in a MEMS micromirror, which verified the improved performance of the cantilever beam. By advancing key processes such as high-selectivity non-Bosch deep silicon etching, low-temperature silicon-oxide bonding, and low-stress chemical mechanical polishing, grid-structured cavities with high uniformity have been successfully fabricated. A quasi-static micromirror based on this Cavity-SOI substrate exhibited a significant improvement in deflection angle: under a 90 V driving voltage, the mechanical deflection angle reached 45.6 mrad, which is 241% higher than that of a micromirror fabricated using conventional SOI under the same process conditions. Although the resonant frequency decreased from 1.972 kHz to 0.913 kHz, the f∙θ increased by 58.3%. These results demonstrate that integrating grid-structured cavities into cantilevers can effectively enhance actuation efficiency and overall device performance. This study provides a viable substrate solution for the design and fabrication of high-performance MEMS devices.