基于X-LiNbO3/SiO2/Si低温漂、大机电耦合SH-SAW谐振器的设计

铌酸锂(LN)单晶薄膜具有较高的机电耦合系数(k² eff＞30%),其水平剪切(SH)声学模式常被应用于开发具有大机电耦合系数的薄膜声学谐振器和超宽带滤波器。但LN 的频率温度系数较大(TCF ＞ -50×10^-6/℃),这不仅会降低滤波器的可用有效带宽,同时也会限制器件的功率处理能力。采用3D周期有限元模型对基于X 切LN/SiO₂/Si结构SH 声表面波(SH-SAW)谐振器进行了优化研究。研究结果表明,当SH-SAW 传播角ψ=-10°~-20°、LN和SiO₂ 膜厚分别为hLN=0.1λ 和h_SiO2 =0.2λ(λ 为叉指换能器周期)、铝电极金属化率η=0.4、电极相对厚度h_Al/λ=5%~10%时,SH-SAW 谐振器的 k² eff 约为30%,且其TCF＜-20×10^-6/℃,有望用于开发新一代的低温漂、超宽带5G SAW 滤波器。

Design of Low Drift, Large Electromechanical Coupling SH-SAW Resonators Based on X-Cut LiNbO3/SiO2/Si

Owing to its high electromechanical coupling coefficient (k² _eff>30%), the horizontal shear (SH) acoustic

modes in lithium niobate (LN) single-crystal films are typically investigated to develop thin-film acoustic resonators

with large electromechanical coupling and ultra-wideband acoustic filters. However, its temperature coefficient

of frequency (TCF) is extremely high (>-50×10^-6/℃). A high TCF not only reduces the effective bandwidth

but also limits the power-management capability of the filters. Herein, we present an investigation into the

optimization design of a low drift, large electromechanical coupling horizontal-shear surface acoustic wave (SHSAW)

resonator based on the X-cut LN/SiO₂/Si structure using a threedimensional periodic finite-element model.

Simulation results show that when the SH-SAW propagation angle ψ is between -10° and -20°, the film thicknesses

of LN and SiO₂ are 0.1λ and 0.2λ (where λ is the period of the interdigital transducer) respectively, the metallization

rate of the aluminum electrode (η) is 0.4, the relative thickness of the electrode is between 5% and 10%, the k² _eff of the SH-SAW resonator remains at ~30%, and the TCF is less than -20×10^-6/℃. Hence, the resonator is

suitable for developing the next generation of low-temperature drift, ultra-wideband 5G SAW filters.