In this study, the crystalline structure, surface roughness and nanomechanical properties of AlN thin films are investigated by using X-ray diffraction (XRD), atomic force microscopy (AFM) and nanoindentation techniques. The AlN thin films were deposited on Si(1 0 0) substrates with various sputtering powers by means of the radio frequency (RF) magnetron sputtering system. XRD results show that the crystalline structures and orientations of the AlN thin films have the strong (1 0 3) orientations. Both of the average grain size and surface roughness of AlN(1 0 3) thin films exhibit an increasing trend with the sputtering power. In addition, the hardness and Young's modulus of AlN(1 0 3) thin films increased as the sputtering power increased from 150 to 350 W, with the larger results being obtained at 350 W.