An apodized 3-GHz thin film piezoelectric on substrate FBAR

An apodization method is illustrated in this work to enable displacement and strain energy confinement at the central section of the composite thin Film Bulk Acoustic wave Resonator (c-FBAR) while in operation at the resonance mode. The device is excited at a higher order thickness extensional mode. The proposed resonator is designed in sinc shape to attain high degree of energy localization. Here, the thin film piezoelectric on substrate (TPoS) configuration implemented by the Aluminum Nitride (AlN) MEMS-CMOS InvenSense Inc. platform is used to realize the resonators. The c-FBAR performance parameters are extracted through de-embedding the CMOS+MEMS measured data. An equivalent electrical modeling for c-FBAR operating in the Super High Frequency (SHF) is demonstrated. We successfully report a sinc c-FBAR resonator operating at 3.264 GHz with an electromechanical coupling coefficient >2.12%, an unloaded Q >2,500, and Figure of Merit of 53.