Chromium aluminium nitride (CrAlN) thin films were deposited on Si by using reactive DC unbalanced magnetron sputtering technique from alloy target and then annealed in air at different temperatures, in the range of 500 - 900 ^OC, for 1 hr. The effect of annealing temperature on the structure and morphology of
the as-deposited films were investigated. The structure, chemical composition, and morphology of the thin films were characterized using XRD, EDS, and FE-SEM, respectively. The results show that the as-deposited films were solid solutions of (Cr,Al)N with (111), (200), and (220) planes. The as-deposited film has chromium (Cr), aluminium (Al), and nitrogen (N) as the main composition in different ratios, with some oxygen (O). The lattice constant was in the range of 4.055 – 4.139 Å. The average crystal size was in the range of 14.8 – 20.3 nm. The microstructure and cross-section analysis result from the FE-SEM technique was revealed that the as-deposited CrAlN thin film shows the compact columnar structure. The microstructure of the CrAlN thin film was unchanged by heat from the annealing process at temperatures in the range of 500 - 900 ^OC. However, in this work, when the annealing temperature was increased up to 900 ^OC, a slight increase in oxygen content in the films, and the crystal structure (from XRD technique) or layer of the oxides (from FE-SEM technique) were not observed showed that alloyed aluminium in the film can improve the oxidation resistance up to 900 ^OC.