The improvement of high power impulse magnetron sputtering performance by an external unbalanced magnetic field

High power impulse magnetron sputtering (HIPIMS) is an emerging technique that improves the ionization rate of magnetron-sputtered materials. However, HIPIMS often demands further improvement in the ionization rate in some applications. In this study, we applied an unbalanced magnetic field to enhance the HIPIMS discharge, using a conventional magnetron and a coaxial electro-solenoid coil. Vanadium target discharge currents and substrate ion currents were recorded using a digitizing oscilloscope at different coil currents. The elemental composition and temporal and spatial distributions of argon and vanadium atoms and ions in the high vacuum plasma were measured by optical emission spectroscopy. The results showed that the substrate ion current increased gradually with the coil current over the range 0-6 A, and that a high-density plasma beam was formed between the substrate and target. We explained this effect as the confinement of energetic electrons by the external magnetic field. Total ion production was also increased. Finally, we observed that the line intensities of Ar0, Ar1+, V0, and V1+ increased gradually to varying degrees under the external magnetic field.