The influence of ZnO and electrode thickness on the performance of thin film bulk acoustic wave resonators

Thin film bulk acoustic resonator (FEAR) structures have been fabricated by RF magnetron sputtering of piezoelectric ZnO layers onto silicon. Deposition at a range of different temperatures has been performed and the films were assessed using XRD, SEM and electrical characterization. A range of ZnO film thicknesses were deposited and a good correlation was obtained between the theoretical and measured resonant frequencies. The effect of top and bottom electrode thickness on the performance of the device is also reported, with specific reference to resonant frequency and Q-value. Wafer scale fabrication of devices has been carried out and excellent yields obtained on 76 mm wafers. Devices exhibiting resonant frequencies in excess of 2 GHz are reported and the prospects for manufacturing passband filters based on FBAR resonators are discussed