Effect of bias on the structure and properties of TiZrN thin films deposited by unbalanced magnetron sputtering

Abstract

The objective is to investigate the substrate bias effect on the structure and properties of the TiZrN thin films. The TiZrN thin films were deposited by direct current unbalanced magnetron sputtering system with dual guns (Ti and Zr) targets onto Si (100) substrates at different substrate bias ranging from −35V to −150V. Experimental results indicated that all the specimens have strong (111) texture in X-ray Diffraction patterns. In this study, we discovered a transition bias of −35V, above which a significant improvement of properties was found, including high hardness, excellent brilliance, low resistivity and fine surface morphology. Within the bias range of −40 to −120V, the hardness of TiZrN films is around 35.5GPa, the resistivity is about 33.5μΩ-cm, and the brilliance is larger than 80. The roughness is between 0.5nm and 0.6nm. The TiZrN films maintain excellent properties through a large range of applying bias, indicating that the process window is considerably wide. However, structure damage and thin film delamination were found when substrate bias reached −150V. The Rutherford backscatterng spectrometry result and scanning electron microscope image further support the structure damage at −150V. For protective coatings, low residual stress is required to avoid delamination. By adjusting substrate bias, residual stress can be controlled to lower value. In this study, the residual stress of TiZrN films gradually decreases with decreasing the substrate bias ranging from −65V to −35V. The TiZrN thin films with high hardness, lower residual stress could be obtained simultaneously at low substrate bias of −40V and −45V, the hardness and residual stress are 33.4–34.5GPa and −2.7 to −3.7GPa, respectively.