Study on the suppression of parasitic resonance of film bulk acoustic wave resonators

To suppress the parasitic resonance of a film bulk acoustic resonator (FBAR) and meet the high-frequency requirements of 5G communication, an FBAR model was established based on COMSOL Multiphysics simulation software. The effects of the piezoelectric materials, electrode lateral size, electrode shape (rectangle, circle, trapezoid, and regular pentagon), and apodization angle (30 degrees, 36 degrees, 40 degrees, and 45 degrees) on parasitic resonance were studied, and the suppression effect of the step-load structure on lateral acoustic wave leakage was discussed. The simulation results show that the best suppression effect on parasitic resonance is achieved when the piezoelectric material is AlN, the electrode shape is a non-regular pentagon, and the apodization angle is 40 degrees; when the resonant area is 3600 mu m2, its non-circularity is 6.45 %, which is equivalent to the rectangular electrode when the resonant area is 10000 mu m2. The designed electrode step-load structure improved the quality factor at the parallel resonance point. When the electrode lateral size is 60 mu m, the quality factor of the second-order electrode load structure is 1378, which is 10.07 % higher than the quality factor of the electrode-free load structure.