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机械品质因数QM是高次谐波体声波谐振器(High-overtone Bulk Acoustic Resonator,HBAR)一个关键的特性参数。首次较系统地研究了QM随构成HBAR的3个组成部分(基底、压电薄膜和电极)的结构参数(厚度)和性能参数(特性阻抗与机械衰减因子)的变化规律。在谐振频率附近,将HBAR的分布参数等效电路简化为集总参数等效电路,首次用解析表达式给出它们的变化规律,分析了QM在给定频率最近谐振点的变化情况。结果表明,固定压电层厚度,QM随基底厚度的连续增加略呈振荡(非单调)上升,当基底厚度很大时趋于基底材料的机械品质因数;固定基底厚度,QM随压电层厚度的连续增加呈波浪式下降;选择低损耗的蓝宝石或YAG作为基底可以获得较大的QM值;电极的损耗必须考虑,它会降低QM值;与Au电极相比,具有较低损耗的A1电极选择适当厚度可以获得较高的QM值;此外,QM随频率的增加呈下降趋势。上述的结果为HBAR的优化设计提供了相应的理论依据。根据我们对K_(eff)~2的研究,Q_M与K_(eff)~2的变化规律往往是相悖的,因此在设计HBAR时要在这两者作适当的权衡。
The mechanical quality factor QM is a key characteristic parameter of a High-overtone Bulk Acoustic Resonator (HBAR). For the first time, the structural parameters (thickness) and the performance parameters (characteristic impedance and mechanical attenuation factor) of QM with the three components of HBAR (substrate, piezoelectric film and electrode) were systematically studied systematically. In the vicinity of the resonant frequency, the equivalent circuit of HBAR distributed parameter is simplified as the lumped parameter equivalent circuit. For the first time, the variation regularity of HBAR is given by analytic expression, and the change of QM at the nearest resonance point of given frequency is analyzed. The results show that the QM increases slightly (non-monotonically) with the continuous increase of the thickness of the piezoelectric substrate. The QM increases with the thickness of the piezoelectric substrate Of the continuous increase in a wave-like decline; the choice of low-loss sapphire or YAG as the substrate can get a larger QM value; electrode loss must be considered, it will reduce the QM value; compared with the Au electrode, with lower loss of A1 electrode Select the appropriate thickness can get higher QM value; In addition, QM decreases with increasing frequency. The above results provide the theoretical basis for the optimal design of HBAR. According to our research on K ~ (eff) ~ 2, the change rule of Q_M and K_eff ~ 2 often runs counter to each other. Therefore, it is necessary to make a proper trade-off between the two when designing HBAR.