Plasma Parameters and Etching Characteristics of SiO(x)N(y) Films in CF(4) + O(2) + X (X = C(4)F(8) or CF(2)Br(2)) Gas Mixtures

In this work, we carried out the study of CF(4) + O(2) + X (X = C(4)F(8) or CF(2)Br(2)) gas chemistries in respect to the SiO(x)N(y) reactive-ion etching process in a low power regime. The interest in the liquid CF(2)Br(2) 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(4)/X mixing ratio, input power and gas pressure on gas-phase plasma characteristics as well as to analyze the SiO(x)N(y) 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(x)N(y) etching rates, as determined by the neutral-flux-limited process regime; and (3) non-constant SiO(x)N(y) + F reaction probabilities due to changes in the polymer deposition/removal balance. The features of CF(4) + CF(2)Br(2) + O(2) plasma are lower polymerization ability (due to the lower flux of CF(x) radicals) and a bit more vertical etching profile (due to the lower neutral/charged ratio).