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

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.