PZT transduced high-overtone width-extensional resonators above 1 GHz

This paper provides the theoretical modeling, simulation, and quantitative comparison that explore the design space of PZT-only (Lead Zirconate Titanate) and PZT-on 3, 5 and 10 µm single-crystal silicon high-overtone width-extensional mode (WEM) resonators with identical lateral dimensions for incorporation into radio frequency microelectromechanical systems (RF MEMS) filters and oscillators. A novel fabrication technique was developed to fabricate the resonators with and without silicon layer using the same mask-set on the same wafer. The air-bridge metal routings were implemented to carry electrical signals while avoiding large capacitances from the bond-pads. We theoretically verified and experimentally measured the correlation of motional impedance (R X ), quality factor (Q), and resonance frequency (f) with the resonators' silicon layer thickness (t Si ) up to above 1 GHz frequency of operation. For identical lateral dimensions and PZT-layer thickness (t PZT ), the resonators with thicker silicon layer have higher f. The resonators with thicker silicon also have higher Q and lower R X up to 900 MHz frequency.