现代科技的发展对高频声表面波(SAW)器件的需求不断增加, 对其工作频率也提出了更高的要求。为了提高SAW器件的频率, 该文构建了一种IDTs电极分层布局的器件模型, 即IDTs/AlN/IDTs/R-sapphire结构, 并采用有限元法分析其声学性能, 包括导纳、相速度、机电耦合系数等。结果表明, IDTs/AlN/IDTs/R-sapphire结构可激发出瑞利波, 且当AlN压电薄膜厚度hAlN=0.4λ(λ为器件周期), 水平中心距Pb=4 μm时, 其工作频率为692 MHz, 传统的IDTs/AlN/R-sapphire结构器件提高了近1倍(356 MHz), 而此时机电耦合系数K2为0.3%, 比传统结构高。另外, 通过优化IDTs电极的结构参数可进一步改善、调制瑞利波器件的性能。当IDTs的上层铜电极和下层铝电极厚度之比Δh=1.2, Pb=4 μm, hAlN/λ=0.5时, 瑞利波器件的谐振频率为657.9 MHz, K2=1.27％; 当Pb=6 μm时, 瑞利波的工作频率为461 MHz, 机电耦合系数达到最大(K2max=1.34％), 较传统IDTs单层布局结构瑞利波器件分别提升了30%和300％。结果表明, IDTs电极分层布局结构不仅可有效地提高SAW器件的工作频率和机电耦合系数, 也可以降低高频SAW器件的制备难度。

The development of modern technology has increased the demands for high-frequency surface acoustic wave (SAW) devices, and has placed higher requirements on their operating frequencies. In order to increase the frequency of SAW devices, a device model with layered layout of IDTs electrodes is established, that is, IDTs/AlN/IDTs/R-sapphire structure. The finite element method is used to analyze its acoustic performance, including the admittance, phase velocity, electro-mechanical coupling coefficient, etc.. The results show that the Rayleigh waves can be excited in the IDTs/AlN/IDTs/R-sapphire structure, and when hAlN=0.4λ, the horizontal center distance Pb=4 μm, the operating frequency of the device is 692 MHz, which is nearly one time higher than that of the traditional device with IDTs/AlN/R-sapphire structure (356 MHz), and the electro-mechanic coupling coefficient K2 is 0.3%, which is also improved compared with the traditional structure. In addition, the performances of Rayleigh wave device can be further improved and modulated by optimizing the electrode structure parameters of IDTs. When the thickness ratio (Δh) of upper copper electrode to lower aluminum electrode of IDTs is 1.2, and Pb=4 μm, hAlN/λ=0.5, the resonant frequency of 657.9 MHz and K2 of 1.27% are obtained for the Rayleigh wave device; and when Pb=6 μm, the operating frequency of the Rayleigh wave and the maximum electromechanical coupling coefficient K2max are 461 MHz and 1.34%, respectively, which are 30% and 300% higher than that of the traditional Rayleigh wave device with single layered layout structure of IDTs electrode, respectively. From the above-mentioned results, it can be seen that the layered layout structure of IDTs can not only effectively improve the operating frequency and electromechanical coupling coefficient of SAW devices, but also reduce the fabrication difficulty of high frequency SAW devices.