## 2 Fluid Model, Plasma Chemistry, and Reactor Configuration
### Chemistry of Ar/O\({}_{2}\) Plasma and O\({}^{-}\) Chemical Kinetics  
As listed in Table 3, the gas phase chemistry of the Ar/O\({}_{2}\) plasma fluid simulation considers (1) elastic, ionization, dissociative attachment, electronic excitation, de-excitation, and detachment between the electrons and neutral species, and (2) metastable quenching,  
\begin{table}
\begin{tabular}{c c c c} \hline
**No.** & **Reaction** & **Rate Coefficient \({}^{\text{a}}\)** & **Threshold (eV)** & **Ref.** \\ \hline  & & Dissociation reactions & \\  
\text{SF}\to\text{S}+\text{SF}_{\text{2}}\) & \(2.5\times 10^{-11}\) & 0 & [28,29] \\
52 & \(\text{SF}_{\text{x}}+\text{F}_{\text{2}}\to\text{SF}_{\text{x}+1}+\text{F}\)\({}^{\text{b}}\) & \(7.0\times 10^{-15}\) & 0 & [28,29] \\
53 & \(\text{X}^{+}+\text{Y}^{-}\to\text{X}+\text{Y}^{\text{c}}\) & \(5.0\times 10^{-9}\) & 0 & [28,29] \\  & Detachment reactions & & \\
54 & \(Z+\text{Y}^{-}\to Z+\text{Y}+\text{e}^{\text{d}}\) & \(5.27\times 10^{-14}\) & 0 & [28,29] \\  & Other reactions & & \\
55 & \(\text{Ars}+\text{Ars}\to\text{e}+\text{Ar}+\text{Ar}^{+}\) & \(6.2\times 10^{-10}\) & 0 & [28,29] \\
56 & \(\text{Ars}+\text{Ar}\to\text{Ar}+\text{Ar}\) & \(3.0\times 10^{-15}\) & 0 & [28,29] \\
57 & \(\text{Ar}^{+}+\text{SF}_{\text{6}}\to\text{SF}_{\text{5}}\)\({}^{+}+\text{F}+\text{Ar}\) & \(9.0\times 10^{-10}\) & 0 & [28,29] \\
58 & \(\text{SF}_{\text{s}}{}^{+}+\text{SF}_{\text{6}}\to\text{SF}_{\text{s}}\)\({}^{+}+\text{SF}_{\text{6}}+\text{F}_{\text{2}}\) & \(6.0\times 10^{-12}\) & 0 & [28,29] \\ \hline  & & & & \\ \end{tabular} \({}^{\text{a}}\) The unit of the rate coefficient is cm\({}^{3}\) s\({}^{-1}\). For certain collisions of electron impact, such as the elastic scattering, excitation and de-excitation, and the attachment, the cross sections are used. The rate coefficients of these reactions are calculated through the cross sections and assumed Maxwellian-type of electron energy distribution function, as expressed by the following formula: \(k(r,z)=\int_{0}^{\infty}f(r,z,\epsilon)\times\left(\frac{2x}{m}\right)^{1/2} \sigma(\epsilon)d\epsilon\). Herein, \(k(r,z)\) is the rate coefficient of two-dimensional space, \(f(r,z,\epsilon)\) is the assumed electron energy distribution function, \(\epsilon\) is the translational energy of electrons, \(m\) is the electron mass, and \(\sigma(\epsilon)\) is the related cross section. \({}^{\text{b}}\) x stands for the number 1–5. \({}^{\text{c}}\) X = SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), or F\({}_{\text{2}}\); \({}^{\text{d}}\) Z = SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), SF\({}_{\text{s}}\), F\({}_{\text{s}}\), or F\({}_{\text{2}}\). \({}^{\text{e}}\)\recombination, associative detachment, and charge transfer between the heavy species. In total, the chemical set contains five charged species, i.e., electron, O\({}^{-}\), O\({}^{+}\), O\({}^{2+}\), and Ar\({}^{+}\); three metastable molecules, i.e., O\({}_{2}\)*, O\({}^{*}\), and Ar*; and three grounded molecules, i.e., O, Ar, and O\({}_{2}\). The surface reactions of reactive species are listed in Table 4. The rate coefficients and cross sections of these reactions, as well as the surface kinetics, are taken from the Refs. [31; 32; 33; 34; 35; 36; 37; 38]. Specially, the reactions for the O\({}^{-}\) generation and loss are collected in Tables 5 and 6, respectively, for the convenience of observing O\({}^{-}\) chemical kinetics (see the results and discussion parts). In the chemical kinetics of O\({}^{-}\), reaction No. 3 mainly contributes to the O\({}^{-}\) generation, and reaction No. 42 mainly contributes to the O\({}^{-}\) loss.