Li$^{+}$ attachment mass spectrometric investigation of high-mass neutral species in the downstream region of Ar/CF$_{4}$, Ar/CF$_{4}$/O$_{2}$ and Ar/CF$_{4}$/H$_{2}$ plasmas

Recently gaseous high-mass species have received significant attentions as important contributors to the nucleation of films and particulates in fluorocarbon plasmas. We have unambiguously identified the gaseous high-mass neutral species in the downstream region of the Ar/CF$_{4}$ plasma [1], using the Li$^{+}$ attachment ionization technique that is a fragment-free ionization method. In this report, we show the results of mass analysis of high-mass neutral species in the Ar/CF$_{4}$/O$_{2}$ and Ar/CF$_{4}$/H$_{2}$ plasmas as well as Ar/CF$_{4}$. In the Ar/CF$_{4}$ plasma, we observed C$_{n}$F$_{2n+2}$ (n = 2-7) and C$_{n}$F$_{2n}$ (n = 4-8) as neutral species. Adding O$_{2}$ to the Ar/CF$_{4}$ plasma resulted in the intensity decrease of C$_{n}$F$_{2n+2}$ and C$_{n}$F$_{2n}$, especially of those with relatively small n values. C$_{n}$F$_{2n}$O (n = 1-7) were newly observed in the Ar/CF$_{4}$/O$_{2}$ plasma. In contrast, adding H$_{2}$ to the Ar/CF$_{4}$ plasma resulted in the production of various new compounds, such as C$_{n}$F$_{2n-2}$ (n=3-8), C$_{n}$F$_{2n-4}$ (n=3-9), C$_{n}$F$_{2n+1}{\rm H}$ (n=1-7), C$_{n}$F$_{2n-1}{\rm H}$ (n=2-8), C$_{n}$F$_{2n-3}{\rm H}$ (n=4-9) and C$_{n}$F$_{2n-5}{\rm H}$ (n=5-9). These species are produced through the abstraction of F from various C$_{n}$F$_{m}$ species by the H radical and the addition of H to them. [1] K. Furuya, S. Yukita, H. Okumura, A. Harata, Chem. Lett. \textbf{34}, 224 (2005).