Guan Chongrui, He Xingli
School of Electronic and Information Engineering, Soochow University, Suzhou 215006, China.
Micromachines (Basel). 2024 Nov 26;15(12):1416. doi: 10.3390/mi15121416.
High-performance acoustic resonators based on single-crystalline piezoelectric thin films have great potential in wireless communication applications. This paper presents the modeling, fabrication, and characterization of laterally excited bulk resonators (XBARs) utilizing the suspended ultra-thin (420 nm) LiTaO (LT, with 42° YX-cut) film. The finite element analysis (FEA) was performed to model the LT-based XBARs precisely and to gain further insight into the physical behaviors of the acoustic waves and the loss mechanisms. In addition, the temperature response of the devices was numerically calculated, showing relatively low temperature coefficients of frequency () of ~-38 ppm/K for the primary resonant mode. The LT-based XBARs were fabricated and characterized, which presents a multi-resonant mode over a wide frequency range (0.110 GHz). For the primary resonance around 4.1 GHz, the fabricated devices exhibited a high-quality factor (Bode-Q) ~ 600 and piezoelectric coupling () ~ 2.84%, while the higher-harmonic showed a greater value of ~ 3.49%. To lower the resonant frequency of the resonator, the thin SiO film (~20 nm) was sputtered on the suspended device, which created a frequency offset between the series and shunt resonators. Finally, a ladder-type narrow band filter employing five XBARs was developed and characterized. This work effectively demonstrates the performance and application potential of micro-acoustic resonators employing high-quality LT films.
基于单晶压电薄膜的高性能声学谐振器在无线通信应用中具有巨大潜力。本文介绍了利用悬浮超薄（约420 nm）钽酸锂（LT，42° YX切割）薄膜的横向激发体声波谐振器（XBAR）的建模、制造和特性表征。进行了有限元分析（FEA）以精确模拟基于LT的XBAR，并进一步深入了解声波的物理行为和损耗机制。此外，对器件的温度响应进行了数值计算，结果表明主谐振模式的频率温度系数（）相对较低，约为-38 ppm/K。制造并表征了基于LT的XBAR，其在宽频率范围（0.1~10 GHz）内呈现多谐振模式。对于4.1 GHz左右的主谐振，制造的器件表现出高品质因数（Bode-Q）约为600，压电耦合（）约为2.84%，而高次谐波显示出更大的值，约为3.49%。为了降低谐振器的谐振频率，在悬浮器件上溅射了薄SiO薄膜（约20 nm），这在串联和并联谐振器之间产生了频率偏移。最后，开发并表征了一种采用五个XBAR的梯形窄带滤波器。这项工作有效地展示了采用高质量LT薄膜的微声学谐振器的性能和应用潜力。
