Piezoelectrically transduced low-impedance microelectromechanical resonators

This letter presents the design, fabrication, and testing results of a piezoelectrically transduced UHF micromechanical resonator. The resonator is designed to vibrate in the (2, i) in-plane mode, and thin-film zinc oxide is used for piezoelectric transduction. A four-mask process is developed to fabricate the resonator on silicon on insulator wafer, and the maximum processing temperature is kept below 250°C. Prototypes with various diameters are fabricated, with a measured resonant frequencies span from 44.97 MHz to 1.14 GHz. Quality factors around 200 are obtained on different devices. Motional impedance in the range of several hundred ohms is demonstrated.