Abstract
The purpose of this study were to find the optimum conditions for the deposition of VN thin film using Taguchi DOE method, and the attained parameters were further refined by conducting single-variable experiments, where the effect of the most sensitive processing parameter on the structure and properties of VN thin films was investigated. VN thin films were deposited on Si (100) substrates by unbalanced magnetron sputtering (UBMS) with different deposition parameters. Four major processing parameters of an UBMS system, including substrate bias, nitrogen flow rate, substrate temperature and substrate rotational speed, were selected for optimizing the deposition process. Hardness and electrical resistivity of thin films were chosen as the indexes of the property optimization. After deposition, the analysis of mean (ANOM) and analysis of variance (ANOVA) were carried out to assess the sensitive parameters and predict the optimum conditions. Based on the statistical analysis, the most sensitive parameter for hardness of the deposition process was substrate bias and those for electrical resistivity were substrate bias and nitrogen flow rate. In addition, the results showed that electrical resistivity was a better property than hardness for Taguchi experiment. From the Taguchi DOE method, the optimum conditions for the minimum electrical resistivity of VN thin film are: substrate bias = -90 V, nitrogen flow rate = 3 sccm, substrate temperature = 300°C, and substrate rotational speed = 20 rpm. Further optimization of the deposition process was conducted by a single-variable experiment with refining nitrogen flow rate based on the optimum conditions from Taguchi method for the minimum electrical resistivity. The optimum conditions of VN thin film became: substrate bias = -90 V, nitrogen flow rate = 2.5 sccm, substrate temperature = 300°C, and substrate rotational speed = 20 rpm. Using the optimum deposition conditions, VN films on Si (100) substrates with high hardness and low electrical resistivity were successfully produced. Furthermore, the effect of the nitrogen flow rate on the structure and properties of VN thin films was also investigated. The results of single-variable experiment indicated that the texture transition of the VN thin films may be mainly affected by kinetics, and crystallinity plays an important role in the hardness, residual stress, and electrical resistivity of the VN thin films.