Sol-gel derived bulk acoustic wave devices for cellular communication application

This paper reports recent advances obtained with bulk acoustic wave resonators fabricated using sol-gel thin film transducers. Acoustic resonances in the uhf/lower microwave region have been observed with unloaded Q values of the order of 800-1000. The resonator characteristics were found to be improved with poling. The relative permittivity of the films were observed to decrease with frequency, an effect we believe is due to relaxation associated with domain switching. On-wafer input impedance measurements were carried out using Cascade Microtech high frequency probes in conjunction with an HP8510C Network analyzer. The effects of parasitics at high frequencies were minimized using an on-wafer calibration scheme which was verified using impedance standards supplied by the probe manufacturer and also with verification elements realized on the sol-gel films themselves.