Residual Stress and Surface Energy of Sputtered TiN Films

Morphology, structure, residual stress, and surface energy of magnetron-sputtered titanium nitride (TiN) thin films, deposited at 300 °C with a thickness in the 0.5-1.7 μm range, were characterized. Film microstructure, the origin of residual stress, and its effect on the surface energy were analyzed. The grain size increased with the film thickness. X-ray diffraction showed (200) to (111) preferred orientation transitions with the increasing film thickness. The stress in the TiN films changed from compressive −0.3 GPa to tensile with the film thickness reaching 0.3 GPa. Larger grain size, initial porosity, and sub-grains generation are the reasons for significant changes in the residual stress. Surface energy was investigated by contact angle of water and glycerol droplets, which both show a significant change with the different stress state and crystal preferred orientation. The TiN films form a contact angle larger than 100° with water as a test liquid, demonstrating their hydrophobicity. While the residual stress changes from compressive to tensile, the contact angle reaches 118°, and the corresponding surface energy changes from 38.8 to 24.2 mJ/m2. One can expect to achieve a certain desired surface state of TiN films for potential applications.