Correlation between vibrational temperature of N₂ and plasma parameters in inductively coupled Ar/N₂ plasmas

Vibrational temperature (T_vib) of N₂ gas and electron energy distribution function (EEDF) were measured in Ar/N₂ mixture inductively coupled plasma (ICP). At a low gas pressure of 5 mTorr where the EEDF is bi-Maxwellian distribution, plasma density n_p and T_vib (from 7000 K to 5600 K) slightly decrease. However, remarkable decrease in n_p and T_vib is found with the dilution of N₂ gas at a high gas pressure of 50 mTorr, where the EEDF is depleted Maxwellian distribution at a fixed ICP power of 150 W. When the ICP power increases from 150 W to 300 W at the gas pressure of 50 mTorr, the depleted tail on the EEDF is replenished, while n_p is little changed with the dilution of N₂ gas. In this case, T_vib slightly decreases from 9500 K to 7600 K. These results indicate that the variation of T_vib is strongly correlated to the plasma parameters, such as the plasma density and EEDF