6.3-GHz Film Bulk Acoustic Resonator Structures Based on a Gallium Nitride/Silicon Thin Membrane

This letter describes the fabrication and the morphological and microwave characterization of film bulk acoustic resonator structures, supported on very thin GaN membranes. We have demonstrated, by employing both white-light profilometry as well as X-ray diffraction, the low deflection and low stress of the GaN membranes supporting the resonator metallization. Using as test structure two FBAR structures connected in series, by a floating backside metallization, we have obtained resonance frequencies of 6.3 GHz for a 0.5-mum-thick membrane. The quality factor, at 6.3 GHz, was higher than 1100.