Nitrogen Atom Densities in Rare Gas Diluted N₂ Plasmas with Capacitive and Inductive Coupling

Abstract

Nitrogen atom densities in rare-gas diluted N₂ plasmas are diagnosed by using Vacuum Ultra Violet Absorption Spectroscopy (VUVAS). The influence of rare-gas dilution for low pressure (20 mTorr) inductively coupled plasma is that N atom density shows a peak around 3 % of N₂ fraction due to the increase of the high energy electrons. The N₂ ion density, another precursor for nitridation, did not show a peak even for the high rare-gas fraction. On the other hand, capacitively coupled plasma operated at 0.5 Torr range showed no steep increase of N atom density. The optical diagnostics shows that rare-gas dilution of N₂ plasma leads to the change of reactant flux ratio between neutral atoms and ions.