Topology and Trench Design for Energy Trapping and Quality Factor Enhancement in Film Bulk Acoustic Resonators (FBARs)

This paper presents a co-design strategy for enhancing thin-film bulk acoustic resonator (FBAR) performance through synergistic electrode topology and trench engineering. The proposed irregular pentagonal electrodes with optimized trench structures demonstrate superior anchor loss suppression in 2.6 GHz FBARs, achieving a peak quality factor of 1517. Pulsed laser interferometry measurements reveal phenomenon of spurious modes and energy confinement with enhanced active-region displacements compared to conventional designs. COMSOL simulations further elucidate the underlying physics, showing modal coupling effect and potential TE-to-TS modal conversion mechanism. These combined experimental and simulated results validate the design’s effectiveness for 5G front-end modules requiring high quality factor and spectral purity.