Zhao Zinan, Wang Bin, Zhu Jiaqi, Qian Zhenghua, Huang Bin
IEEE Trans Ultrason Ferroelectr Freq Control. 2019 Aug;66(8):1331-1339. doi: 10.1109/TUFFC.2019.2914587. Epub 2019 May 3.
Mode coupling vibration of a multilayered ZnO thin film bulk acoustic wave resonator (FBAR) with its c-axis along the wave propagation direction operating at the fundamental thickness-shear (TSh) mode is studied in this paper. The accurate dispersion curve from 3-D piezoelectric theory indicates that the operating TSh mode could couple to the flexural mode, which influences the performance of a sensing resonator and needs to be eliminated through the so-called frequency spectrum analysis. Frequency spectra of coupling vibration in this FBAR can be obtained by substituting the displacement solutions consisting of the mode branches in the dispersion curve into several weak boundary conditions, which gives the integral boundary conditions across the plate thickness at the side edge of FBARs. The results show that the content of mode couplings to spurious modes depends on the plate length/thickness ratios. The character of desirable values of plate aspect ratios under which the operating TSh mode dominates among all modes is stated specifically, which provides fundamental guidance to the design of structural parameters of FBARs.
本文研究了一种多层ZnO薄膜体声波谐振器（FBAR）的模式耦合振动，该谐振器的c轴沿波传播方向，以基波厚度剪切（TSh）模式工作。三维压电理论给出的精确色散曲线表明，工作的TSh模式可能会与弯曲模式耦合，这会影响传感谐振器的性能，需要通过所谓的频谱分析来消除。通过将色散曲线中由模式分支组成的位移解代入几个弱边界条件，可以得到该FBAR中耦合振动的频谱，这些弱边界条件给出了FBAR侧边沿板厚度方向的积分边界条件。结果表明，与杂散模式的模式耦合含量取决于板长/厚度比。具体阐述了在所有模式中工作的TSh模式占主导地位时板长宽比的理想值特征，这为FBAR结构参数的设计提供了基本指导。
