Spurious Mode Suppression in LiNbO3 A1 Resonators and Filters Beyond 6 GHz With Through-Holes

This paper presents the first experimental demonstration of a novel approach to suppressing spurious modes in high-frequency LiNbO3 A1 Lamb wave resonators through the integration of lithography-defined through-hole arrays. Our fabrication-friendly method effectively mitigates spurious modes without compromising resonator performance or requiring additional fabrication steps, while maintaining scalability. Fabricated on a 296-nm Z-cut LiNbO3 thin film, resonators with well-designed through-holes achieve a resonance frequency exceeding 6 GHz and an electromechanical coupling coefficient of 25%. Spurious modes are significantly suppressed, while the resonators’ total suspension area is reduced by over 50%, enhancing both mechanical and thermal stability. When extended to a $\pi $ -type filter with a center frequency of approximately 7.0 GHz and a fractional bandwidth of ~14%, the filter with through-holes demonstrates cleaner passband and improved band edge characteristics. The through-hole design functions as both acoustic scatterers and release channels, offering a unified solution for performance optimization, stability, design flexibility, and manufacturability, thereby establishing Lamb wave resonators with through-holes as a scalable solution for next-generation, multiscale RF systems. [2025-0060]