Design and simulation of higher-mode face shear square micromechanical resonators

Polysilicon face shear (FS) square micro-mechanical resonators based on MEMS technology operating in second-mode have been studied at frequency 70MHz. By carefully designing the electrodes and the exact support beam locations that minimize the anchor loss, these resonators actually achieved higher quality factor Q (exceeding 20,000 with straight beam support) in the second-mode than in the fundamental at the same frequency. With larger dimensions than previous fundamental mode counterparts, these second-mode face shear square resonators show many advantages over the former, such as (1) lower series motional resistance R_x; (2) higher Q; (3) very high maximum vibration amplitude (achieved 4.8nm with 1μm gap size), which is directly proportional to the output current i₀ and maximum vibration energy that a resonator can be stored. So that, the second-mode face shear square resonator is highly recommended when designing a face shear square resonator at high frequency.