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计算了四层复合结构的薄膜体声波谐振器(FBAR)的输入阻抗谱,各层采用的材料分别是Al/Al N/Al/Si ,其尺寸为0.8μm/1.9μm/0 .8μm/100μm,得出其有效机电耦合系数ke2ff随谐振模式的分布情况,从而得到最大k2eff的独特谐振模式在1～2GHz为第40阶谐振模式。从理论上探讨了各层的尺寸及材料属性对该独特谐振模式及其频移的影响,以及串联谐振品质因数FOM等滤波器设计的主要性能参数在该模式下的分布情况。实验结果表明,工作在独特谐振模式下的FBAR的性能依赖于各层材料尺寸,当压电层厚度从0.2μm变到4 .3μm时,特殊谐振模式频率从1.2 GHz增加到4.8 GHz ;当基底厚度变厚时,有效机电耦合系数从3.2%变到0.8%,串联品质因数从2000变到700 ;而电极变厚后,有效机电耦合系数趋于一个稳定值。这些数据在实际设计过程中对滤波器的微调具有参考意义。
The input impedance spectrum of a four-layer composite FBAR was calculated. The materials used in each layer were Al / Al N / Al / Si and the size was 0.8μm / 1.9μm / 0.8μm / 100μm , The effective electromechanical coupling coefficient ke2ff is obtained with the distribution of resonant modes, so that the unique resonant mode with maximum k2eff is the 40th resonant mode at 1 ~ 2GHz. The influence of the size and material properties of each layer on the unique resonant mode and its frequency shift, and the distribution of the main performance parameters of the filter design such as the series resonant quality factor FOM in this mode are theoretically discussed. The experimental results show that the performance of FBAR operating in a unique resonant mode depends on the material size of each layer. When the piezoelectric layer thickness changes from 0.2μm to 4.3μm, the resonant frequency increases from 1.2 GHz to 4.8 GHz. When the thickness is thicker, the effective electromechanical coupling coefficient changes from 3.2% to 0.8%, the series quality factor changes from 2000 to 700. When the electrode becomes thicker, the effective electromechanical coupling coefficient tends to a stable value. The data in the actual design process for the fine-tuning of the filter reference.