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 stu dy of ZnO and PbZr0.3Ti0.7O3 thin-film bulk acoustic resonators and filters . Measurements of the high-frequency responses of ZnO resonators having dif ferent area are used to develop an acoustic model that accurately represent s resonator impedance data. The models are also used to interpret S-paramet er measurements on thin-film PbZr0.3Ti0.7O3-based resonators and a value fo r the effective coupling coefficient deduced, ZnO and PbZr0.3Ti0.7O3 ladder filters were designed based on measured impedance data from single resonat ors. Ladder filters based on PbZr0.3Ti0.7O3 have been fabricated for the fi rst time. It is shown that the high coupling coefficient in PbZr0.3Ti0.7O3 leads to bandwidths in the range 100 similar to 120 MHz at a center frequen cy of 1.6 GHz, larger than the bandwidths of ZnO-based filters.