Study on Ion Flux From Magnetically Confined Low-Pressure Arc Discharge With a Thermionic Cathode to Substrate for High-Throughput Film Deposition Processes

The flux and energy of incident ions to a substrate are crucial parameters in plasma-assisted thin-film deposition processes. They determine film properties, such as hardness in carbon and boron-nitride (BN) films, by changing the atomic bonding networks. This study investigates the decision mechanisms of the ion flux from magnetically confined low-pressure arc discharge with a thermionic cathode to a substrate in a reactive plasma-assisted coating (RePAC) system, which is a plasma-assisted physical vapor deposition (PVD) system designed for high-throughput BN film deposition. The experimental results showed that the ion flux in a high-discharge-current regime is not linear to the discharge current and depends on the discharge conditions, such as the gas pressure, mixture, and electrode voltages. We concluded from the results that the ionization rate and electric field near the cathode decide the maximum ion flux, and the difference in current between that flowing from the anode and to the cathode can be a control parameter in the high-current regime. The analysis presented in this study is expected to contribute to designing and controlling film-deposition systems using low-pressure arc discharge with a thermionic cathode.