Dry Etching Performance and Gas-Phase Parameters of CFO + Ar Plasma in Comparison with CF + Ar.

This research work deals with the comparative study of CFO + Ar and CF + Ar gas chemistries in respect to Si and SiO reactive-ion etching processes in a low power regime. Despite uncertain applicability of CFO as the fluorine-containing etchant gas, it is interesting because of the liquid (at room temperature) nature and weaker environmental impact (lower global warming potential). The combination of several experimental techniques (double Langmuir probe, optical emission spectroscopy, X-ray photoelectron spectroscopy) allowed one (a) to compare performances of given gas systems in respect to the reactive-ion etching of Si and SiO; and (b) to associate the features of corresponding etching kinetics with those for gas-phase plasma parameters. It was found that both gas systems exhibit (a) similar changes in ion energy flux and F atom flux with variations on input RF power and gas pressure; (b) quite close polymerization abilities; and (c) identical behaviors of Si and SiO etching rates, as determined by the neutral-flux-limited regime of ion-assisted chemical reaction. Principal features of CFO + Ar plasma are only lower absolute etching rates (mainly due to the lower density and flux of F atoms) as well as some limitations in SiO/Si etching selectivity.