Fabrication of TiN coatings using superimposed HiPIMS and MF technique: Effect of target poisoning ratios and MF/HiPIMS pulse on-time ratio

Abstract

The commercial application of high power impulse magnetron sputtering (HiPIMS) is hindered by its low deposition rate in thin film and coating industries. This study proposes an effective method to enhance the deposition rate of TiN films by superimposing middle-frequency (MF) pulses during the off-time of HiPIMS pulsing. The impact of Ti target poisoning ratios (ranging from 30 % to 70 %) controlled by the plasma emission monitoring (PEM) feedback control system and MF/HiPIMS pulse on-time ratios (ranging from 1.5 to 24) on the structural, morphological, and mechanical properties of thin films was investigated. Increasing the target poisoning ratio and the ratio of MF/HiPIMS on-time pulses up to 6 resulted in increased peak current and peak power density of HiPIMS for the superimposed TiN films. Compared to TiN films grown solely using HiPIMS, all the superimposed TiN films exhibited improved deposition rates ranging from 3.89 to 6.36 nm/kW·min. Analysis of crystallographic and chemical composition confirmed the formation of single-phase stoichiometric TiN films with a smooth columnar microstructure. The TiN film grown at a 60 % target poisoning ratio and an MF/HiPIMS pulse on-time ratio of 1.5 displayed the highest hardness of 34.4 GPa and elastic modulus of 485 GPa, surpassing the values obtained for pure HiPIMS-grown, MF-grown, and DC-grown films. Moreover, TiN film deposited at target poisoning ratios of 50 % and a 6 times MF/HiPIMS pulse on-time ratio exhibited a high hardness of 30.3 GPa and a high deposition rate of 5.94 nm/min/kW, which was 2.15 times higher than that of pure HiPIMS. Additionally, the formation of stoichiometric TiN films led to relatively lower electrical resistivity. Overall, the superimposition of HiPIMS and MF pulses presents a promising approach to overcome the limitations of HiPIMS and enhance the deposition rate of TiN films. The findings of this study highlight the potential of TiN films grown by the superimposed HiPIMS-MF and PEM feedback control technique for various industrial applications.