Fabrication of ring-shaped silicon resonator using (2,1) in-plane resonance mode

A ring-shaped low-frequency resonator operating in the (2,1) in-plane vibration mode was designed and fabricated by anodic bonding of a 9-μm-thick single-crystal silicon layer to a glass substrate. Although the gap between the ring and the electrodes was relatively large (900 nm), a high quality factor of 4212 was realized at 1.609 MHz. Further, the motional resistance was 1.853 MΩ. In addition, the resonant frequency could be electrically tuned by varying the dc bias of the drive electrodes at a rate of 21.5 ppm/V. Thus, this resonator is expected to replace the conventional quartz resonators for use at low frequencies of a few MHz.