Staggered diamond-hole IDTs for lateral spurious mode suppression in LiNbO3 XBAR

This work presents a LiNbO 3 laterally excited bulk acoustic resonator (XBAR) with staggered diamond-hole interdigital transducers (IDTs) for suppressing higher-order A1-n spurious modes. By introducing multidirectional acoustic scattering and disrupting lateral periodicity, the proposed structure weakens the coherent buildup of lateral standing waves while preserving the target A1 mode. Comparative analysis of conventional, parallel, and staggered electrode configurations shows that the staggered layout provides a better balance between spurious suppression and main-mode preservation. Devices fabricated on 400 nm-thick Z-cut LiNbO 3 thin films operate at 4.57 GHz, exhibiting a Bode- Q max of 527 and an electromechanical coupling coefficient ( k t 2 ) of 22.2 %, corresponding to a figure of merit ( FOM = k t 2 × Q ) of 117. Compared with the conventional design, the spurious mode level is reduced from 0.588 to 0.285. The proposed structure provides a practical route toward high-frequency, low-loss LiNbO 3 acoustic resonators.