Thin-Film Bulk Acoustic Resonators and Filters Using ZnO and Lead–Zirconium–Titanate Thin Films

This paper presents the findings of a design, modeling, and fabrication study of ZnO and PbZr0 3Ti0 7O3 thin-film bulk acoustic resonators and filters. Measurements of the high-frequency responses of ZnO resonators having different area are used to develop an acoustic model that accurately represents resonator impedance data. The models are also used to interpret -parameter measurements on thin-film PbZr0 3Ti0 7O3-based resonators and a value for the effective coupling coefficient deduced. ZnO and PbZr0 3Ti0 7O3 ladder filters were designed based on measured impedance data from single resonators. Ladder filters based on PbZr0 3Ti0 7O3 have been fabricated for the first time. It is shown that the high coupling coefficient in PbZr0 3Ti0 7O3 leads to bandwidths in the range 100 120 MHz at a center frequency of 1.6 GHz, larger than the bandwidths of ZnO-based filters.