Thin-film bulk acoustic resonators and filters using ZnO and lead-zirconium-titanate thin films

TLDR

The study designs, models, and fabricates ZnO and PbZr₀.₃Ti₀.₇O₃ thin‑film bulk acoustic resonators and filters. High‑frequency impedance measurements of ZnO resonators of varying area were used to build an acoustic model that also interprets S‑parameter data of PbZr₀.₃Ti₀.₇O₃ resonators and informs ladder‑filter design. PbZr₀.₃Ti₀.₇O₃ ladder filters were fabricated for the first time, achieving 100–120 MHz bandwidths at 1.6 GHz—wider than ZnO‑based filters due to the material’s high coupling coefficient.

Abstract

This paper presents the findings of a design, modeling, and fabrication study of ZnO and PbZr/sub 0.3/Ti/sub 0.7/O/sub 3/ 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 S-parameter measurements on thin-film PbZr/sub 0.3/Ti/sub 0.7/O/sub 3/-based resonators and a value for the effective coupling coefficient deduced. ZnO and PbZr/sub 0.3/Ti/sub 0.7/O/sub 3/ ladder filters were designed based on measured impedance data from single resonators. Ladder filters based on PbZr/sub 0.3/Ti/sub 0.7/O/sub 3/ have been fabricated for the first time. It is shown that the high coupling coefficient in PbZr/sub 0.3/Ti/sub 0.7/O/sub 3/ leads to bandwidths in the range 100/spl sim/120 MHz at a center frequency of 1.6 GHz, larger than the bandwidths of ZnO-based filters.