Electron energy distribution function measurement in a CO$_{\mathrm{2}}$/Ar inductively coupled plasma

Electron energy distribution functions (EEDFs) in CO$_{\mathrm{2}}$/Ar mixed plasma were measured at various fractions of the argon. Electron density increases with ratio of the argon. Electron temperature has maximum values in a pure CO$_{\mathrm{2}}$ plasma. On the other hand, the electron temperature increases with the argon ratio in CO$_{\mathrm{2}}$/Ar plasma. EEDF becomes from Maxwellian to non-Maxwellian by increasing pressure and decreasing the Ar ratio because Maxwellization of EEDF is determined by the electron-electron collision frequency and electron energy relaxation frequency. Unusual phenomenon occurs at intermediate pressure, 50 mTorr. It is the EEDF of the pure CO$_{\mathrm{2}}$ plasma is closer to the Maxwellian than those of the CO$_{\mathrm{2}}$/Ar plasma with a small proportion of Ar. This result seems to be effect of superelastic collisions determined by vibration-vibration (V-V) exchange and vibration-translation (V-T) relaxation.