The low pressure Cl₂/O₂discharge and the role of ClO

Abstract

A global (volume averaged) model is applied to a low pressure (1-100 mTorr) high density chlorine discharge that is diluted with oxygen. The influence of oxygen dilution on the particle densities and the electron temperature is explored. The electronegativity is found to increase strongly with increased pressure in a chlorine-rich mixture, whereas it is nearly pressure independent in an oxygen-rich mixture. The chlorine dissociation fraction increases with increased oxygen dilution, although the increase is neither pronounced nor sharp at low oxygen content. We explore the role of the ClO molecule in the discharge and confirm that the ClO molecule is mainly created through recombination of Cl and O atoms at the chamber wall, which in turn significantly increases the loss of Cl atoms in oxygen-rich mixtures. The most important loss process for ClO is electron impact dissociation in the plasma bulk. The molecular ion ClO + is almost entirely created by charge transfer for oxygen dilution below 67%, while electron impact ionization becomes the dominant creation process for ClO + at higher dilution.

Global (volume-averaged) model of inductively coupled chlorine plasma: Influence of Cl wall recombination and external heating on continuous and pulse-modulated plasmas

“…A recently updated vibrational excitation cross-section (reaction (10)) by Gregório et al [12] is preferred over the one used in the paper [26], since it improves the agreement with experimental observations. The electronic excitation cross-section to level Cl( 2 P 1/2) (reaction (17)) is calculated by Wang et al [13] and to level Cl( 1 P 5/2) (reaction (18)) by Griffin et al [36].…”

Ion Energy and Angular Distribution in Biased Inductively Coupled Ar/O2 Discharges by Using a Hybrid Model

“… is the mean thermal velocity. for atoms and for . The recombination coefficient of is related to wall materials, and gas pressure, and affects the densities of atomic oxygen, ionic components and electrons, we use a coefficient of 0.26 .…”

Numerical Investigation of SiO2 Coating Deposition in Wafer Processing Reactors with SiCl4/O2/Ar Inductively Coupled Plasmas

“…As far as the reaction products are concerned, various Cl x O y products might exist in principle, such as ClO, Cl 2 O, ClO 2 , and Cl 2 O 2 . However, compared to ClO, other Cl x O y products have low densities and therefore only ClO is considered in our model . Finally, it is most likely that SiCl x O y species are present in the plasma .…”

“…Concerning the ion‐ion neutralizations, not all rate constants of these combinations are known, but for the typical chemistry under study, these are generally in the order of 10 −7 –10 −8 cm 3 · s −1 . Indeed, for neutralizations between Ar + and Cl − ions, Subramonium and Kushner have provided coefficients which are 10 −7 [ T /298 K ] 0.5 cm 3 · s −1 while Thorsteinsson and Gudmundsson have used a coefficient of 5.00 × 10 −8 [ T /298 K ] 0.5 cm 3 · s −1 for ion–ion neutralizations between chlorine and oxygen ions . For the other combinations of ion–ion neutralizations, no data could be found in literature, and therefore we have adopted the same values.…”