Publication details

On ionization fraction of sputtered species



Year of publication 2019
Type Conference abstract
MU Faculty or unit

Faculty of Science

Description High Power Impulse Magnetron Sputtering (HiPIMS) is a promising physical vapor deposition technique frequently utilized for the deposition of coatings with enhanced properties. For optimization of the deposition process, the plasma diagnostics is crucial. In this study, Optical Emission Spectroscopy (OES) and Quartz Crystal Microbalance (QCM) is utilized for discharge analysis ranging from standard Direct Current Magnetron Sputtering up to the intensive HiPIMS (duty cycle less than 1%). The QCM system is equipped with a gridless biasable sensor with magnetic electron filter, which allows measuring separately the flux of atoms and flux of the ionized particles impinging the substrate. Effective Branching Fractions (EBF) method is utilized to determine the absolute ground state titanium atom and ion number densities from the self-absorption in plasma measured by OES. The systematic study is provided in three different distances from the target – in the magnetized plasma region, in a region between magnetized plasma and substrate and in the substrate level, all measured in the range of working pressures, at the constant mean power and pulse duration. For intensive HiPIMS at the lowest measured working pressure in the substrate level, the ionized density fraction of sputtered species reaches 70%. At the same conditions, ionized density fraction of sputtered species in the magnetized plasma region reaches 90%. Generally, it was observed that increasing the duty cycle, the peak current density decreases, leading to a decrease of ionized density fraction of sputtered species. Additionally, it was observed that with increasing the working pressure, in the substrate level ionized density fraction of sputtered species slightly decreases for all pulses while for intensive HiPIMS in both magnetized plasma region and transition region remains constant. The ionized metal flux fraction obtained from QCM measurements are correlated with the ionized density fraction of sputtered species in the substrate level. Both the ionized flux as well as the ionized species density evolutions with the process parameters provide valuable insight into the sputtering process in HiPIMS mode.
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