Reactive ion etching of silicon carbide in SF6 gas: Detection of CF, CF2, and SiF2 etch products

We have detected by laser-induced fluorescence the radicals SiF2, CF, and C F2 produced during the reactive ion etching of SiC substrates in a pure SF6 plasma. Spatially and temporally resolved measurements were used to distin guish between gas phase and etched surface radical production. Whereas CF a nd CF2 are produced directly at the etched surface, the SiF2 radicals are p roduced in the gas phase (probably by electron-impact dissociation of SiF4) . We attribute this difference to the formation of a carbon-rich layer on t he SiC substrate surface, the removal of which produces CFx (x=1,2,3) radic als. The CF2 radical represents up to 20% of the total carbon etch products under our conditions. (C) 2001 American Institute of Physics.