FABRICATION OF BULK ACOUSTIC WAVE RESONATOR BASED ON ALN THIN FILM

AlN thin film is an ideal material for preparing BAW resonator. Bulk acoustic wave (BAW) resonator based on AlN thin films is compatible with standard IC technologies. This advantage makes sense for realizing a one-chip front-end circuit. In this study, a reliably process for making an air-gap bulk acoustic wave resonator based on AlN thin film was reported. Highly c-axis oriented AlN thin film was achieved on Mo electrode by reactive radio frequency sputtering technique. An improved planarization process and extending the edge of bottom electrode were introduced to avoid AlN thin film cracking at the steps. The BAW resonator, with 100nm bottom electrode, 2500nm AlN piezoelectric layer and 300nm top electrode, has exhibits a resonant frequency of around 1.51GHz.