Behavior of Excited Oxygen Atoms in Rare gas mixture O$_{2}$ Surface Wave Excited Plasma

Excited oxygen atom (O($^{1}$D$_{2}))$ has attracted very much on the oxygen-based plasma processes, such as plasma oxidation, surface cleaning, resist ashing, etc. Since it is supposed that the O($^{1}$D$_{2})$ atom is the most reactive species in all species in the oxygen-based plasma. Therefore, it is strongly required to investigate the behaviors of O($^{1}$D$_{2})$ atom in the oxygen-based plasmas, the quantitative information of O($^{1}$D$_{2})$ atom have never been clear, because the convenient light sources for absorption spectroscopic techniques of O($^{1}$D$_{2})$ atoms have not developed. The vacuum ultraviolet laser absorption spectroscopy (VUVLAS) has a great potential to measure the atomic radicals in the process plasmas. Therefore, in this study, we have measured the absolute density of O($^{1}$D$_{2})$ atom in the rare gas mixture O$_{2}$ surface wave excited oxygen plasma (SWP) by using VUVLAS with tunable VUV laser. The absolute densities of O($^{1}$D$_{2})$ atom in the O$_{2}$/Ar and O$_{2}$/Kr SWPs were evaluated as a function of various plasma conditions. From these results, the O$_{2}$/Ar SWP has a potential to realize the high O($^{1}$D$_{2})$ atom density compared with the O$_{2}$/Kr SWP and the density in the O$_{2}$/Ar SWP was the maximum around 2$\times $10$^{12}$ cm$^{-3}$ at the high Ar flow rate ratio and low pressure.