Flexible film bulk acoustic resonators and filter-like structure made directly on polymer substrates

This paper reports a novel solid-mounted flexible film bulk acoustic resonator (FBAR) directly on polymer substrate with the merits of flexibility and no need for back etching process. (0002) oriented ZnO films deposited by sputtering, and aluminum and gold as the electrodes were used to fabricate the FBARs. Results show that the devices with aluminum electrodes have a resonant frequency at 1.2 GHz with an effective electromechanical coupling coefficient of ∼ 4.7%, a filter-like architecture improved the quality factor of FBAR from 19.6 to 164.2, and the devices remained working after bending at a large angle for hundreds of times