Discharge Characteristics of Novel Dual-Pulse HiPIMS and Deposition of CrN Films with High Deposition Rate

High power impulse magnetron sputtering (HiPIMS) is of great significance for improving the quality of sputtered films because of its high ionization degree of sputtered particles and high ion fluxes. Therefore, it has been widely studied by researchers. However, the conventional HiPIMS shows a significantly low deposition rate, which greatly limits the industrial applications of HiPIMS. In this work, a novel high power impulse magnetron sputtering is proposed to enhance the low deposition rate encountered in conventional HiPIMS. The novel technology is based on dual pulses discharge mode, in which a pulsed high voltage with short duration is utilized to high-current discharge and produce initial high density plasma and a subsequent work-pulse of low voltage with long duration is employed to sustain the high-current discharge. Consequently the re-adsorption effect by magnetron target may be weakened. The influence of ignition pulse voltage discharge characteristics of Cr target and microstructure of CrN films were investigated. The discharge characteristics of Cr target and the structure characteristics of CrN coatings were characterized by digital oscilloscope, spectrometer, focused ion beam / electron beam dual-beam microscope and X-ray diffraction. The results show that the discharge of Cr target is ignited rapidly and the discharge current is substantially large with the ignition voltage applied to the target. In contrast, the pulse current gradually rises for the conventional HiPIMS meaning a weak discharge. Compared with the conventional HiPIMS, the dual-pulse HiPIMS produce a higher substrate current integral value and more amount of Ar+ and Cr-0 with the same input power. With ignition pulse voltage of 590 V, the deposition rate at unit power for CrN coating is 2.52 mu m/(h.kW) for dual-pulse HiPIMS, which is nearly three times higher than that of conventional HiPIMS. With the increase of the ignition pulse voltage, the CrN films prepared by dual-pulse HiPIMS possess denser structure with smaller grain size.