薄膜体声波谐振器电极效应研究

Research on Electrode Effects of Thin Film Bulk Acoustic Resonator

运用传输线路法推导了薄膜体声波谐振器(Thin Film Bulk Acoustic Resonator,FBAR)的输入阻抗公式.利用输入阻抗公式,研究了不同材料FBAR构成中电极材料和厚度对FBAR有效机电耦合系数的影响,FBAR最大有效机电耦合系数优化理论.由结论可知,FBAR的有效机电耦合系数随电极的厚度和密度变化明显,在低密度电极材料时,电极厚度增大明显降低了FBAR的有效机电耦合系数;同时,在电极厚度较厚时,电极密度越大越有利于获取高的有效机电耦合系数.所得结论,可应用于FBAR设计与优化中.

The transmission line method is used to deduce the input impedance equation of thin film bulk acoustic resonator（FBAR） in this paper. The different combinations of FBAR are studied on by the equation, and the material and the thickness of electrode effects on FBAR are obtained, which includes the maximum effective electromeehanical coupling factor theory. The results show that the effective electromechanical coupling factor verifies with the electrode and the density of the electrodes, and the electromechanical coupling factor descends with the thickness of electrodes, which is obvious if the density of electrode is small. On the other hand, the effective electromeehanical coupling factor ascends with the density of electrodes, which is obvious if the thickness is large. These results can be applied in the design and the optimization of FBARs.