Characteristics of AlN thin films deposited by electron cyclotron resonance dual-ion-beam sputtering and their application to GHz-band surface acoustic wave devices

A(001) plane of hexagonal aluminum nitride (AlN) has been deposited on R-plane sapphire ((11-bar·2)Al2O3) with inclination of about 26deg against the substrate by electron cyclotron resonance (ECR) dual-ion-beam sputtering. A shear horizon (SH) wave as well as a modified Rayleigh wave could be excited on this AlN film. The phase velocities of the SH wave (VSH) and Rayleigh wave (VR) were 6000-6730 m/s and 5600-5950 m/s, respectively. VR has no effect on the propagation direction. However, VSH has considerable influence on the propagation direction, and becomes maximum at the propagation direction of 45 degrees against [12·0]AlN. The insertion loss and temperature coefficient of delay time (TCD) of the 1.21-GHz-band two-port-type resonator using SH waves were 7.5 dB and 35.4 ppm/degC, respectively. These values are acceptable for practical use. (author)