Abstract
Nano-crystalline TiN thin films were successfully deposited on (100) silicon substrate utilizing a high power impulse magnetron sputtering (HIPIMS) system. The purpose of this research was to investigate the effects of ion bombardment on the texture, mechanical properties, and the deposition rate of TiN thin films, where the extent of ion bombardment was controlled by varying nitrogen flow rates (N-series) and substrate bias (B-series). Unlike the texture reported in previous literatures, X-ray diffraction (XRD) revealed that most of the specimens possess (220) preferred orientation due to ion channeling effect. The (220) texture coefficient was closely related to the extent of ion bombardment, which may increase due to increasing nitrogen flow rate or decrease as the substrate bias switched from negative to positive. The film thickness was measured from cross-sectional SEM images where the deposition rate was obtained. Owing to ion re-sputtering, the deposition rate of N-series specimens decreased linearly with increasing ion bombardment. For the B-series specimens, the decrease of deposition rate is attributed to the fact that fewer metal ions were attracted to the substrate as the substrate bias switched from negative to positive. In addition, the results showed that the ion bombardment in HIPIMS significantly influenced the residual stress and electric resistivity of the TiN films. As the extent of ion bombardment decreased, the electric resistivity decreased in both series films and similarly the compressive residual stress of B series specimens decreased when the substrate bias switched from negative to positive. The small variation of hardness of the TiN films, ranging from 21.7 to 25.9 GPa, was correlated to the grain boundary-mediated deformation mechanisms and the packing density of the films.