GHz-Band Surface Acoustic Wave Devices Using Aluminum Nitride Thin Films Deposited by Electron Cyclotron Resonance Dual Ion-Beam Sputtering

Abstract

AlN thin films have been deposited on basal plane ((001)Al 2 O 3 ) and R-plane ((11̄2)Al 2 O 3 ) sapphire by an ECR dual ion-beam sputtering method. The (001) plane of AlN was epitaxially grown on (001)Al 2 O 3 . On the other hand, it was found that the (001) plane of AlN was deposited on (11̄2)Al 2 O 3 with an inclination of about 26 degrees against the substrate, and a surface wave having high coupling and high velocity (6684 m/s) was excited on this substrate. Resonator-type 1.67 GHz band SAW filters have been fabricated using AlN thin film deposited on (11̄2)Al 2 O 3 . The insertion loss, suppression and TCD were 7.9 dB, more than 20 dB and 35 ppm/°C, respectively. These are the best values yet in a GHz band SAW filter based on AlN thin film, and are good enough to allow practical use.