Properties of c-C4F8 inductively coupled plasmas. II. Plasma chemistry and reaction mechanism for modeling of Ar/c-C4F8/O2 discharges

Abstract

Gas mixtures containing Ar, cC 4 F 8 , O 2 , and CO are often used for the plasma etching of silicon dioxide. Gas phase reaction mechanisms are required for first principles modeling of these systems to both provide insights to the plasma chemistry and to help optimize the process. In this article, results from computational and experimental investigations of the plasma chemistry of inductively coupled plasmas ͑ICPs͒ sustained in Ar, O 2 , Ar/c-C 4 F 8 and O 2 /c-C 4 F 8 gas mixtures with and without magnetic confinement are discussed. These results were used to develop a reaction mechanism for low-pressure and low-temperature plasmas sustained in mixtures initially consisting of any combination of Ar/c-C 4 F 8 /O 2 /CO. Predictions for ion saturation current and ion mass fractions were compared to experiments for validation. The consequences of charge exchange of fluorocarbon species with Ar ϩ and CO ϩ on the ratio of light to heavy fluorocarbon ion densities in Ar/c-C 4 F 8 /O 2 /CO plasmas are discussed. We found that the electron density and ion saturation current significantly increase with the addition of Ar to cC 4 F 8 but weakly depend on the addition of O 2. The ratio of light to heavy fluorocarbon ion densities increases with power, especially for ICPs with magnetic confinement.

Effect of plasma dissociation on fluorocarbon layers formed under C4F8/Ar pulsed plasma for SiO2etching

“…The C 2 F 4 was generated from C 4 F 8 by electron impact. [33][34][35] The C 3 F 6 was mainly created by the removal of CF 2 species from C 4 F 8 . 8,[33][34][35] From these results, we found that the dissociation creating CF 2 species relatively increased at 2.0 Pa, then the CF 2 flux decreased when the pressure increased to 8.0 Pa owing to the low dissociation of C 4 F 8 .…”

Experimental Study of Capacitive RF c-C4F8 Discharge with Synchrotron Vacuum Ultraviolet Photoionization Mass Spectrometry

“…[19]. Vasenkov et al [20] explored chemistry mechanism of the inductively coupled plasma of c-C 4 F 8 /Ar and c-C 4 F 8 /O 2 computationally and experimentally.…”

Challenges of Tailoring Surface Chemistry and Plasma/Surface Interactions to Advance Atomic Layer Etching

“…For conventional discharges, electron-impact driven species generation favors those species with the lowest threshold and so not only will radical formation be high, it may be difficult to control relative radical densities. 35 However, alternative approaches to plasma generation, such as electron beam generated plasmas, could offer additional paths for maintaining precursor molecule chemistry, where in depth characterization of the dissociation and radical generation pathways have the potential to produce significantly different chemistry as compared to more standard discharge plasma sources used today. 36 If the dissociation pathways of the precursor molecule are understood well, reverse engineering of etch mechanisms based on deposition chemistry 37 seems feasible even under plasma conditions.…”