High $Q$ Single Crystal Silicon Micromechanical Resonators With Hybrid Etching Process

This letter presents a hybrid silicon etching-based technique for single crystal silicon micromechanical resonators fabrication. The proposed method differs from previous works by combining a front-side wet anisotropic pre-etching and a front-side DRIE dry anisotropic post-etching in micromachining micromechanical resonators. The wet etching is used to pre-etch a cavity for structure release in the substrate, while the post- dry etching is employed to fabricate and release the resonator structures simultaneously. A 4.126-MHz square plate Lamé-mode resonator has been successfully fabricated using this approach. An impressive quality factor (Q) as high as 5.34×10⁶ is experimentally measured at a pressure of 0.06 mbar, corresponding to a frequency Q product of 2.2×10¹³.