The optical emission spectroscopy of nitrogen plasma driven by the 94.92 MHz/13.56 MHz dual-frequency

Abstract

The low-pressure N2 plasma were obtained by dual-frequency (DF) capacitively coupled plasma (CCP). The high frequency (HF) was 94.92 MHz and the low frequency (LF) was 13.56 MHz. The vibrational temperature Tv and rotational temperature TR were simulated with procedure for the sequence (Δν=2) of the N2 second positive band system (C3Πu−B3Πg) from 372 nm to 400 nm by comparing the measured optical emission spectroscopy (OES). The electronic excitation temperature diagnosed using the two-line intensity ratio method of NII (391.4 nm) and NIII (394.3 nm). When the discharged gas pressure was 200 mTorr, and the low frequency power was 30 W or 60 W, these results indicate that the vibrational temperature Tv has a inflection point at 60 W and rotational temperature TR have no change with the high frequency power increase. The electronic excitation temperature decrease with HF power increase when the LF power was 30 W, but increase to a constant when the LF power was 60 W. When the high frequency power was 30 W or 60 W, the vibrational temperature Tv decrease dramatically and rotational temperature TR change little with the low frequency power increase. The electronic excitation temperature both decrease with LF power increase. When high frequency power and low frequency both was 30 W, the vibrational temperature Tv first increase then decrease and rotational temperature TR change little with the gas pressure increase. The electronic excitation temperature both decrease with the gas pressure increase.