Thickness shear mode vibrations in silicon bar resonators
This paper demonstrates a dielectrically transduced high quality factor (Q) quarter-wave thickness shear silicon resonator. Dielectric transduction provides a κ2 reduction in motional impedance relative to air-gap electrostatic transduction. The resonator is fabricated on the 1.8 µm thick device layer of a heavily doped SOI wafer with 68 nm thick silicon nitride thin-film on top. The quarter-wave thickness shear mode of the silicon bar resonator has a resonant frequency of 713 MHz, a motional impedance Rx of 10.5 kΩ and Q of 1,517 in air. After partial release, the bar resonates at 723 MHz, exhibiting a motional impedance Rx of 2.4 kΩ and Q of 4,400 in air. Additionally, by varying a tuning voltage between the resonator and silicon substrate from 50 V to 150 V across a 2.5 micron gap, approximately 5 MHz of frequency tuning is observed.
IEEE Ultrasonics Symposium, 2005
Hengky Chandrahalim, Dana Weinstein, Lih Feng Cheow, and Sunil A. Bhave, "Thickness shear mode vibrations in silicon bar resonators," IEEE International Ultrasonics Symposium, 2005, pp. 898-901.