ZINC OXIDE-ON-SILICON SURFACE ACOUSTIC WAVE RESONATORS
Abstract
Surface acoustic wave (SAW) resonators have been fabricated on silicon substrates by using a sputtered piezoelectric ZnO overlay. Several distributed reflection schemes have been investigated including aluminum and gold grating reflectors, as well as grooves modulating the ZnO layer thickness. The performance of two-port resonators using these reflection schemes is considered. Unique design considerations result from fabricating resonators on the dispersive layered medium. The stability of ZnO-on-Si SAW resonators with regard to ageing and temperature variation is investigated. It has been found that the layered medium may be temperature compensated to a degree comparable to ST-quartz when the SiO(,2) thickness is chosen properly. The ZnO-on-Si resonator has been used as a diagnostic tool to assess the effect of a laser anneal on layered medium propagation loss. Resonator Q-values are increased slightly by a laser anneal at the appropriate laser power density. The layered ZnO-on-Si medium may be designed to support a higher-order (Sezawa) mode in addition to the lowest order (Rayleigh) mode. Resonators have been constructed which utilize both propagating modes by coherently scattering between modes at the resonant frequency. This mode scattering is found to be very efficient. Analysis shows that enhanced out-of-band signal rejection may be obtained with the mode conversion resonator.
Degree
Ph.D.
Subject Area
Electrical engineering
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