Surface micromachined AlN thin film 2Â GHz resonator for CMOS integration

This paper describes the development of the aluminum nitride (AlN) thin film bulk acoustic resonator (FBAR) using noble MEMS techniques for CMOS integration. An air-gap was fabricated under the resonator for acoustic isolation. Germanium (Ge) was used as a sacrificial layer to make the air-gap. This technique gives high CMOS compatibility. The resonator achieved a Q factor of 780 and an effective electro-mechanical coupling constant (keff2) of 5.36% at a resonant frequency of 2 GHz.