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 lm 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 20.3 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/ m. One can expect to achieve a certain desired surface state of TiN films for potential applications.