The effect of titanium current on structure and hardness of aluminium titanium nitride deposited by reactive unbalanced magnetron co-sputtering

Nanocrystalline aluminium titanium nitride (AlTi₃N) thin films were deposited on Si (100) wafer and grid substrates without external heating and biasing at room temperature by reactive unbalanced magnetron co-sputtering technique using pure individual titanium and aluminium targets. The effects of titanium current (I_Ti) on the structure and hardness of these films have been studied. The films were sputtered with Ar and N₂ gases flow rate of 8 and 4 sccm, respectively. The sputtering current of the aluminium current (I_Al) was kept at 600 mA and the sputtering current of titanium (I_Ti) was varied from 600 to 800 mA. The films were deposited for different deposition times ranging from 15 to 60 min. The deposited films were then characterized and analyzed by X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and nanoindentation measurement. The results indicated that the modification of the crystal structure, surface morphology and microstructure were dependent on the deposition parameters. The XRD patterns show polycrystalline structure with preferred orientations in (112), (004) and (153) planes which agree with the standard structure of aluminium titanium nitride (AlTi₃N) films. In addition, the structure of AlTi₃N was also confirmed by TEM. These results show that the films are composed of high Al content. The root mean square surface roughness and the average thicknesses were strongly influenced by I_ti and deposition times. Cross section analysis by SEM showed dense and compact columnar morphology. The typical hardness of the films was approximately 26.24-30.37 GPa.