Characterization of various shaped 5 GHz TFBARs based on 3D full-wave modeling

In this paper, 3D finite element methods are used for the analysis of thin film bulk acoustic wave resonator (TFBAR) at 5 GHz. The TFBAR is placed on thin membrane after removal of substrate material for the suppression of loading effects and three different geometries (rectangular, polygonal and circular) are implemented and modeled. The size of fabricated TFBAR is from 100 × 100 μm² to 200×200 μm² and full-wave modeled results are compared with the measurement. It is found that the modeled and measured results agree within 1% in terms of series and parallel resonant frequencies. Furthermore, the different shapes of TFBAR revealed slightly different bandwidth characteristics, which are defined on frequency spacing between the series and parallel resonant frequencies. The goal of this work is to study the variation of the size of resonator on how affects the performance of TFBAR. As the size of resonator increase, the electrical impedance of TFBAR decreases at the resonant frequencies and out of resonant frequencies. These phenomena contribute to improve the effects of the attenuations of TFBAR filter in stop-band to some degree.