Bipolar HiPIMS: The role of capacitive coupling in achieving ion bombardment during growth of dielectric thin films

Dynamics of bipolar HiPIMS discharges by plasma potential probe measurements

“…A clear effect of the energy-enhanced ion bombardment was observed only in the case of a grounded substrate for U + ∈ [0, 400] V, while for a floating substrate no evidence of energetic ion bombardment was seen. Similar observations were reported by Viloan et al [29] and Du et al [30]. In [30], however, the effect of the energy-enhanced ion bombardment was observed during growth of a 1 μm thick (Al, Cr) 2 O 3 insulating film on a conducting and grounded substrate, while no effect was observed for deposition on a 0.5 mm thick insulating sapphire substrate.…”

“…In [30], however, the effect of the energy-enhanced ion bombardment was observed during growth of a 1 μm thick (Al, Cr) 2 O 3 insulating film on a conducting and grounded substrate, while no effect was observed for deposition on a 0.5 mm thick insulating sapphire substrate. In all the three works [28][29][30], the floating potential at the substrate position U fl during the positive pulse reached the value close to the applied positive voltage, i.e. U fl ≈ U + .…”

Effect of Pulsing Configuration and Magnetic Balance Degree on Mechanical Properties of CrN Coatings Deposited by Bipolar-HiPIMS onto Floating Substrate

“…This is consistent with the results reported by Pajdarova et al [40] who show similar behaviour of Vp-Vf at the beginning of the reverse pulse using an unbalanced type II magnetic field configuration. The estimated ion-accelerating voltage (Vp-Vf) during the positive reversed pulse presented in Figure 10 is also consistent with the data reported recently by Du et al [24], who simulated the efficiency of the ion bombardment process during bipolar-HiPIMS deposition on metallic substrates covered by a dielectric film with different thicknesses…”

“…The estimated ion-accelerating voltage (V p -V f ) during the positive reversed pulse presented in Figure 10 is also consistent with the data reported recently by Du et al [24], who simulated the efficiency of the ion bombardment process during bipolar-HiPIMS deposition on metallic substrates covered by a dielectric film with different thicknesses (capacitances). They showed that for a dielectric film with high capacitance to ground (small thickness), the substrate floating potential remains close to the ground potential during the entire positive HiPIMS pulse and the ion acceleration efficiency is very high, while if the dielectric film has low capacitance (large thickness), the floating potential of the substrate quickly attains the plasma potential and the ion acceleration efficiency is very low.…”

“…One of our most recent works shows that bipolar-HiPIMS enables an energy-enhanced deposition process of high-quality (high hardness, low coefficient of friction, good wear resistance, good adhesion to the substrate, very low surface roughness, and defect free) hydrogen-free DLC thin films on electrically insulated substrates, without using any substrate bias voltage, adhesion interfacial layer or substrate pre-treatment [23]. However, other studies have shown that, apart from reduced arc-generation probability and enhanced discharge stability, there were no net benefits in the case of bipolar-HiPIMS deposition of non-conductive materials [24] or deposition onto nonconductive or floating substrates [25]. The apparently contradictory results, in terms of the effect of positive target voltage on the film's properties, reported in the literature, could be due to some different deposition conditions and/or deposition systems used (e.g., different pulsing and/or magnetic field configurations).…”