Suppression of Spurious Lateral Modes and Undesired Coupling Modes in Frame-Like FBARs by 2-D Theory.

Abstract

Thin-film bulk acoustic wave resonators (FBARs) are of significant interest for wireless applications due to their good performance. To achieve excellent characteristics, the frame-like FBARs were previously invented by researchers in this field to suppress the resonances of spurious lateral modes (or spurious modes). Another aspect that has an impact on the working performance of FBAR is the undesired coupling modes, which were rarely studied due to the lack of proper theoretical tools. In this article, we thoroughly investigate the coupling modes and spurious modes in frame-like FBARs by 2-D theory, which was already derived in our previous work. The widely used state-vector approach is applied here and both free and forced vibration problems are analyzed. Frequency spectra and mode shapes obtained from free vibration analysis show the coupling vibration characteristics in this structure. Moreover, the admittance resonance obtained from the forced vibration analysis shows the efficiency of the designed structure on the suppression of both undesired coupling and spurious modes. Results in this article provide a thorough understanding of the vibration in frame-like FBAR, and the method presented can work as an effective tool in engineering design process.