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高次谐波体声波谐振器HBAR(High-overtone Bulk Acoustic Resonator)由基底、压电薄膜和上下电极组成,系统地研究了它们的结构参数(厚度)和性能参数(特性阻抗)对HBAR的重要性能参数有效机电耦合系数K_(eff)~2的影响。在谐振频率附近,通过将HBAR的分布参数等效电路简化为集总参数等效电路得到了它们之间的关系表达式,分析了K_(eff)~2在所关心频率最近谐振点的变化情况。结果表明,保持压电薄膜厚度不变,连续增加基底厚度,K_(eff)~2呈振荡(非单调)下降,当基底厚度达到一定值时K_(eff)~2与厚度成反比下降;保持基底厚度不变,连续增加压电薄膜厚度,K_(eff)~2的峰值随基底和压电层的特性阻抗之比增加快速下降,到达极小值后缓慢增加;选择低阻抗的熔融石英作为基底可以获得较大的K_(eff)~2;与Al电极相比,Au电极选择适当厚度可以获得较高的K_(eff)~2。上述揭示的一些规律为HBAR的优化设计提供了理论依据。
HBAR (High-overtone Bulk Acoustic Resonator) consists of a substrate, a piezoelectric film and upper and lower electrodes. The structural parameters (thickness) and the performance parameters (characteristic impedance) of HBAR Effect of effective electromechanical coupling coefficient K_ (eff) ~ 2 on performance parameters. In the vicinity of the resonant frequency, the expression of the relation between HBAR distributed parameter equivalent circuit and lumped parameter equivalent circuit is obtained, and the change of K_ (eff) ~ 2 at the nearest resonance point of the frequency of interest is analyzed . The results show that the K 2 eff decreases inversely with the thickness when the substrate thickness reaches a certain value, keeping the thickness of the piezoelectric film unchanged and increasing the thickness of the substrate continuously. The thickness of the piezoelectric thin film continuously increases. The peak value of K eff 2 decreases rapidly with the increase of the characteristic impedance of the substrate and the piezoelectric layer. When the thickness of the piezoelectric thin film increases, the thickness of the piezoelectric thin film increases slowly. The low- The substrate can obtain a larger K eff ~ 2. Compared with the Al electrode, the Au electrode can get a higher K eff ~ 2 by choosing proper thickness. Some of the laws revealed above provide the theoretical basis for the optimal design of HBAR.