Makkonen Tapani, Pensala Tuomas, Vartiainen Juha, Knuuttila Jouni V, Kaitila Jyrki, Salomaa Martti M
Materials Physics Laboratory, Helsinki University of Technology, P.O. Box 2200 (Technical Physics), FIN-02015 HUT, Helsinki, Finland.
IEEE Trans Ultrason Ferroelectr Freq Control. 2004 Jan;51(1):42-51. doi: 10.1109/tuffc.2004.1268466.
The dispersion curves of Lamb-wave modes propagating along a multilayer structure are important for the operation of thin-film bulk acoustic wave (BAW) devices. For instance, the behavior of the side resonances that may contaminate the electrical response of a thin-film BAW resonator depends on the dispersion relation of the layer stack. Because the dispersion behavior depends on the materials parameters (and thicknesses) of the layers in the structure, measurement of the dispersion curves provides a tool for determining the materials parameters of thin films. We have determined the dispersion curves for a multilayer structure through measuring the mechanical displacement profiles over the top electrode of a thin-film BAW resonator at several frequencies using a homodyne Michelson laser interferometer. The layer thicknesses are obtained using scanning electron microscope (SEM) measurements. In the numerical computation of the dispersion curves, the piezoelectricity and full anisotropy of the materials are taken into account. The materials parameters of the piezoelectric layer are determined through fitting the measured and computed dispersion curves.
沿多层结构传播的兰姆波模式的色散曲线对于薄膜体声波（BAW）器件的运行至关重要。例如，可能会干扰薄膜BAW谐振器电响应的边带谐振行为取决于层堆叠的色散关系。由于色散行为取决于结构中层的材料参数（和厚度），因此色散曲线的测量提供了一种确定薄膜材料参数的工具。我们通过使用零差迈克尔逊激光干涉仪在几个频率下测量薄膜BAW谐振器顶部电极上的机械位移分布，确定了多层结构的色散曲线。层厚度通过扫描电子显微镜（SEM）测量获得。在色散曲线的数值计算中，考虑了材料的压电性和完全各向异性。通过拟合测量和计算的色散曲线来确定压电层的材料参数。
