Fabrication and Characteristics of Thin Film Bulk Acoustic Resonators with Highly c-Axis Oriented AlN Films

Thin film bulk acoustic resonators are fabricated by using silicon bulk micromachining technology, which are constructed mainly from aluminium nitride (AlN) piezoelectric films. The results of x-ray diffraction, scanning electron microscopy and atomic force microscopy show that the AlN films exhibit highly c-axis orientation with good surface morphology. The resonators with the AlN films possessed a reflection coefficient -10.6dB at the resonant frequency 2.537GHz, an effective electromechanical coupling coefficient 3.75%, series quality 101.8, and parallel quality 79.7.