Fabrication and modeling of high-frequency PZT composite thick film membrance resonators

High-frequency, thickness mode resonators were fabricated using a 7 /spl mu/m piezoelectric transducer (PZT) thick film that was produced using a modified composite ceramic sol-gel process. Initial studies dealt with the integration of the PZT thick film onto the substrate. Zirconium oxide (ZrO/sub 2/) was selected as a diffusion barrier layer and gave good results when used in conjunction with silicon oxide (SiO/sub 2/) as an etch stop layer. Using these conditions, devices were produced and the acoustic properties measured and modeled. The resonators showed a resonant frequency of about 200 MHz, an effective electromechanical coupling coefficient of 0.34, and a Q factor of 22. Modeling was based on a Mason-type model that gave good agreement between the experimental data and the simulations. The latter showed, for the PZT thick film, an electromechanical coupling coefficient of 0.35, a stiffness of 8.65/sup */10/sup 10/ N.m/sup -2/ and an e/sub 33/,/sub f/ Piezoelectric coefficient of 9 cm/sup -2/.