[关键词]
[摘要]
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hSiO2 =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hAl/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。
[Key word]
[Abstract]
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.
[中图分类号]
TN65;TN713
[基金项目]
