Fabrication and testing of beam supported AlN FBARs

Thickness-activated piezoelectric resonators, also called film bulk acoustic resonators (FBAR), are fabricated using aluminum nitride films sputtered directly on <100> silicon. The geometry of the single port device is a suspended circular membrane of AlN sandwiched between metal electrodes and connected to the substrate with AlN beams. Known silicon microfabrication techniques are used to make the FBAR. A resonator with eight 100 μm long beams exhibits an effective electromechanical coupling factor of 4.6% and a quality factor of 200 at the first harmonic series frequency of 1.342 GHz.