Aluminum nitride (AIN) thin films were prepared using reactive cathodic vacuum are deposition in conjunction with a macrodroplet shield plate. Various bias conditions, such as no bias (floating), 0-V bias (same potential as anode), DC bias of -10 to -30 V, and RF power of 25-200 W, were applied to the substrate table. For floating bias, a-axis-oriented film was obtained. For O-V bias, the films prepared on molybdenum substrate showed no preferential orientation, although the film prepared on silicon and borosilicate glass showed a-axis-orientation. For RF bias, the orientation changed from the a-to the c-axis as the RF power increased. The hardest (27 GPa) film was obtained for O-V bias, and the hardness of the other films ranged from 19 to 24 Cpa. The refractive index of the film prepared on quartz substrate was approximately 2.0 over the visual and infrared regions for ail films. The extinction coefficient was less than 0.01 over the visual and infrared regions, with the exception of the film prepared under the O-V bias condition, which showed a higher value.