Aluminum nitride (AlN) thin films are deposited on Corning 7059 glass at low substrate temperature by reactive RF magnetron sputtering. The structural and morphological characterizations are found to be sensitive to deposition conditions such as sputtering pressure, RF power, substrate temperature and N2 concentration. A highly oriented AlN (002) plane parallel to the substrate surface is identified by X-ray diffraction (XRD) measurement and a dense pebble-like surface texture is observed by scanning electron microscopy (SEM). The cross-sectional SEM micrograph shows that well-aligned columnar structures with preferred orientation along the c-axis exist in the AlN thin film. However, a selected-area diffraction (SAD) pattern shows that some other planes exist in the deposited film, though only a hexagonal AlN (002) plane is obtained by XRD.