Mechanisms of radical production in radiofrequency discharges of CF3Cl, CF3Br, and certain other plasma etchants: Spectrum of a transient species

Abstract

Radiofrequency discharges in CF₃Cl, CF₃Br, and C₂F₆ emit a broad continuum centered at ∼614 nm. The variation of emission intensity with residence time, oxygen additions, power and pressure are evidence that this continuum originates from a common excited species produced by electron impact dissociation of the halocarbon feed gases. The hypothesis that this species is an excited state of the CF₃ radical, which undergoes a transition to a repulsive state to yield CF₂+F, is consistent with the spectral evidence and explains the presence of CF₂ and unsaturated fluorocarbons in these discharges.