| Summary: | In this work, we carried out the study of CF<sub>4</sub> + O<sub>2</sub> + X (X = C<sub>4</sub>F<sub>8</sub> or CF<sub>2</sub>Br<sub>2</sub>) gas chemistries in respect to the SiO<sub>x</sub>N<sub>y</sub> reactive-ion etching process in a low power regime. The interest in the liquid CF<sub>2</sub>Br<sub>2</sub> as an additive component is motivated by its generally unknown plasma etching performance. The combination of various diagnostic tools (double Langmuir probe, quadrupole mass-spectrometry, X-ray photoelectron spectroscopy) allowed us to compare the effects of CF<sub>4</sub>/X mixing ratio, input power and gas pressure on gas-phase plasma characteristics as well as to analyze the SiO<sub>x</sub>N<sub>y</sub> etching kinetics in terms of process-condition-dependent effective reaction probability. It was found that the given gas systems are characterized by: (1) similar changes in plasma parameters (electron temperature, ion current density) and fluxes of active species with variations in processing conditions; (2) identical behaviors of SiO<sub>x</sub>N<sub>y</sub> etching rates, as determined by the neutral-flux-limited process regime; and (3) non-constant SiO<sub>x</sub>N<sub>y</sub> + F reaction probabilities due to changes in the polymer deposition/removal balance. The features of CF<sub>4</sub> + CF<sub>2</sub>Br<sub>2</sub> + O<sub>2</sub> plasma are lower polymerization ability (due to the lower flux of CF<sub>x</sub> radicals) and a bit more vertical etching profile (due to the lower neutral/charged ratio).
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