On the chemistry mechanism for low-pressure chlorine process plasmas

A chemical reaction mechanism of chlorine plasma under low-pressure conditions that is widely used in the literature is validated against the experimental data of Y. Wang and J. K. Olthoff [J. Appl. Phys. 85, 6358 (1999)] for an inductively coupled plasma reactor. The model used in the present study is a self-consistent two-dimensional fluid plasma model coupled with Maxwell's equations. The quantities of interest in the plasma are the fluxes and energy distribution functions of Cl-2(+) and Cl+ ions. We find that the charge exchange reaction between Cl+ and Cl-2 that is typically included in chlorine plasma reaction mechanisms results in poor predictability of the model compared to experiments. Neglecting this reaction allows for a correct prediction of the dominant ion species in the low-pressure chlorine plasma and dependence of their fluxes on the gas pressure. Additionally, neglecting the charge exchange reaction allows for a rather accurate prediction of ion energy distribution functions at the grounded electrode. Overall, we conclude that the rate coefficient of the charge exchange reaction between Cl+ and Cl-2 reported in the literature significantly exceeds what may in fact explain the role of this process in a low-pressure plasma discharge.