用于N77频段的高优值S0兰姆波声表面波谐振器仿真与制备

Simulation and Fabrication of High Figure of Merit S0 Lamb Wave SAW Resonators for the N77 Band

摘要:

N77 频段对声表面波滤波器提出了大带宽、低损耗等要求，但使用低声速声学模态以及单层功能层衬底结构的谐振器无法同时实现高频、宽带的目标，因此提出了基于 X-37°Y 铌酸锂薄膜与 SiO₂/Ta₂O₅布喇格反射层设计，并制备了固态装配型的声表面波谐振器。首先确定谐振器的工作模态为高相速度 S₀兰姆波，通过仿真各层薄膜厚度对器件性能的影响，确定了谐振器中各层薄膜材料的厚度；然后基于该器件结构参数，针对 N77 频段制备了一组电极周期为 1. 40~1. 86 μm 的谐振器并对其性能进行测试。结果表明，实测结果与仿真基本一致，实测谐振器具有大机电耦合系数（k² ＞22%）和高品质因子（Q_max＞900）的特性，且优值因子超过 200，性能优于采用同种声学模式的其他谐振器，有望应用于 N77 等 5G 频段的滤波器。

Abstract:

N77 band demands wide bandwidth and low insertion loss in surface acoustic wave （SAW） filters. However， conventional resonators that employ low-velocity acoustic modes and single functional layer substrate structures face challenges in simultaneously achieving high frequency and wide bandwidth. To address the challenges， solidly mounted SAW resonators based on X-37° Y lithium niobate （LiNbO₃， LN） films combined with SiO₂/ Ta₂O₅ Bragg reflector layers were designed and fabricated. First， the operating mode of the resonators was chosen to be the high-phase-velocity S₀ Lamb wave. Then， the optimal thicknesses of the thin film materials used in the resonator were determined by simulating the influence of each layer’s thickness on device performance. Subsequently， based on these structural parameters， a set of resonators for N77 band with electrode periods， ranging from 1. 40 μm to 1. 86 μm， was fabricated and tested. The results indicate that the measured data closely match the simulation outcomes. The fabricated resonators show a large electromechanical coupling coefficient （k² exceeding 22%） and highquality factor （Q_max exceeding 900）. Furthermore， the figure of merit （FoM） exceeds 200， showcasing superior performance when compared to other resonators utilizing the same acoustic mode and indicating potential applications in filters for N77 and other 5G bands.