A global model for SF₆plasmas coupling reaction kinetics in the gas phase and on the surface of the reactor walls

Abstract

Gas phase and reactor wall-surface kinetics are coupled in a global model for SF6 plasmas. A complete set of gas phase and surface reactions is formulated. The rate coefficients of the electron impact reactions are based on pertinent cross section data from the literature, which are integrated over a Druyvesteyn electron energy distribution function. The rate coefficients of the surface reactions are adjustable parameters and are calculated by fitting the model to experimental data from an inductively coupled plasma reactor, i.e. F atom density and pressure change after the ignition of the discharge. The model predicts that SF6, F, F2 and SF4 are the dominant neutral species while and F− are the dominant ions. The fit sheds light on the interaction between the gas phase and the reactor walls. A loss mechanism for SFx radicals by deposition of a fluoro-sulfur film on the reactor walls is needed to predict the experimental data. It is found that there is a net production of SF5, F2 and SF6, and a net consumption of F, SF3 and SF4 on the reactor walls. Surface reactions as well as reactions between neutral species in the gas phase are found to be important sources and sinks of the neutral species.

Controlled deposition of sulphur-containing semiconductor and dielectric nano-structured films on metals in SF6 ion-ion plasma

“…24 Another possible explanation for the observed phenomena could be based on chemical asymmetry of positive and negative ions: many radicals of SF 6 are formed in ICP discharge due to intense dissociation, and these radicals have different ionization and electron attachment rates. 13,25 Hence, the positive ion and negative ion fluxes might be composed of different species, for example from SF x þ (x ¼ 3,5) as positive ions and F À , SF 6 À as negative, 13 and their impact on the film growth and electrical behavior might therefore not be the same. In addition, one should always keep in mind that negative ion extraction from real ion-ion plasma is accompanied by a certain electron flow, so electron flux-stimulated deposition or polymerization may play an important role here.…”

“…8 The problems of film deposition and surface reactions in SF 6 -containing plasmas are periodically discussed in the literature. [9][10][11][12][13] One of the expected problems is therefore chamber corrosion and deposition of insulating film on the thruster walls, diagnostics and finally on the extraction system surface, causing an important problem namely lost of the beam acceleration. Unfortunately, deposition processes in pure ion-ion plasmas formed using SF 6 are still not well investigated and understood at the moment.…”

Numerical Investigation of Ion and Radical Density Dependence on Electron Density and Temperature in Etching Gas Discharges

“…Electron collision reactions [6] Neutral-neutral reactions [24] C2F6 discharge Electron collision reactions [19] C4F8 discharge Electron collision reactions [25] Neutral-neutral reactions [25] Ion-ion reactions [25] SF6 discharge Electron collision reactions [26] Neutral-neutral reactions [26] Ion-neutral reactions [26] Ion-ion reactions [26] a…”

Correlation Characteristics Comparison of SF6 Decomposition versus Gas Pressure under Negative DC Partial Discharge Initiated by Two Typical Defects

“…In time, these insulation defects may escalate into insulation failure during operation, thus posing a risk to the safe and reliable operation of the equipment and the entire power grid [4]. Extensive studies [5,6] have reported that the SF 6 molecules crack to form low fluoride (SF x , x = 1, ..., 5) under partial discharge (PD) [5,6]. After long-term operation, different levels of trace moisture, oxygen, and other impurities may be present inside of GIS.…”