The ECWR discharge as an effective power absorber / Time-resolved diagnostics of a pulsed magnetron sputtering discharge with a Co target operated in an argon/oxygen gas mixture

Dr. Sushkov: The ECWR discharge as an effective power absorber

Although ECWR (Electron Cyclotron Wave Resonance) is related to the well-known ECR (Electron Cyclotron Resonance), the underlying physical mechanisms are quite different. ECWR phenomenon can be utilized to drive a radio-frequency discharge. The necessary magnetic field is relatively weak and the efficiency of the discharge increases drastically at the resonance condition. This type of discharge can be viewed as a weakly-magnetized ICP.

In this talk, a study of a large-volume ECWR plasma source under very low pressures (< 1 mTorr, argon) is presented. The plasma diagnostics (OES, Z-scan) and the discharge properties are discussed. The measured discharge impedance shows a pronounced resonance peak. The degree of ionization is in per mille regime. Electron temperature is about 5 eV and grows much higher as the pressure goes down. An increase in the number density of metastable atoms is caused by the temperature-dependent dynamics of their coupling to 2p-states.

Dr. Hippler: Time-resolved diagnostics of a pulsed magnetron sputtering discharge with a Co target operated in an argon/oxygen gas mixture

High power impulse magnetron sputtering (HiPIMS) discharges are of interest from a basic point of view and for deposition of functional films. HiPIMS discharges are characterized by large plasma densities and high ionization fractions. Here we report new results for the diagnostics of a HiPIMS discharge in an argon/oxygen gas mixture with a Co target utilizing energy-resolved mass spectrometry and time-resolved optical emission spectroscopy. Measured ion energy distributions are dominated by Co ions. With increasing oxygen pressure the Co ion density decreases and Co ions are more and more replaced by O ions. The measured discharge voltage for a constant discharge power displays an unusual behavior as function of oxygen gas flow. The discharge voltage increases with oxygen gas flow and, after reaching a maximum, decreases again. This is in part explained by target oxidation, the associated reduction of the sputtering yield, and a changing secondary electron yield. Time-resolved optical emission spectroscopy reveals the dominance of Ar excitation (and ionization) in the early stage which is taken over by Co excitation (and ionization) in a later stage of the discharge.

This work was supported by ESIF and MEYS (Project IOP researches mobility - CZ.02.2.69/0.0/0.0/16_027/0008215).