Transport Coefficients For Electrons in Mixtures CF₄/Ar/O₂and CF, CF₂or CF₃Radicals

Abstract

Transport coefficients for electrons in mixtures of CF 4 with Ar and O 2 for ratios of the electric field to the gas number density E/N from 1 Td to 1000 Td (1Td = 10 −21 V m 2 ) are presented. The analysis of non-conservative collisions revealed a range of the reduced electric field E/N where electron attachment introduced by radicals significantly changes electron kinetics obtained for mixtures without dissociation of CF 4 gas. The results obtained by using a simple, Two Term solutions for Boltzmann's equation are verified by Monte Carlo simulations. It was found that three body attachments for oxygen is not significant for pressures that are standard in plasma etching equipment i.e. below 1 Torr. Furthermore, the attachment to CF, CF 2 and CF 3 at low mean energies is significant, several orders of magnitude. At the same time the mean energy and energy distribution functions for the given E/N are the same as in unperturbed gas mixture. The large changes of the attachment rate are sufficient to change the nature of plasmas and turn them into ion-ion plasmas with very few electrons for realistic abundances.

Boltzmann equation studies on electron swarm parameters for oxygen plasma by using electron collision cross – sections

“…Electron swarm parameters in oxygen were also calculated in binary gas mixtures O 2 -Ar (Jeon and Nakamura, 1998), SF 6 -O 2 (Hernandez-Avila and Urquijo, 2006;Linsheng et al, 2014), Cl 2 -O 2 (Tuan,2014), O 2 -CO (Price and Moruzzi, 1973), N 2 -O 2 (Dujko et al, 2011;Pancheshnyi, 2013;Guerra et al, 2019), TMS-O 2 (Hien, et al, 2012), TEOS-O 2 (Yoshida et al, 1996;Tuan and Jeon, 2012), CO 2 -O 2 (Yousfi et al, 2009) and TRIES-O 2 gas mixtures (Tuoi et al, 2018). The ternary mixtures of CF 4 /Ar/O 2 were analyzed by (Nikitovic et al, 2010;Nikitovic et al, 2011) Furthermore, ternary mixtures of C 5 F 10 O/CO 2 /O 2 was used in gasinsulated high-voltage switchgear (GIS) (Bousoltane et al, 2018) and C 4 F 7 N or C 5 F 10 O mixtures with CO 2 and O 2 were used as insulating and switching media in the case of high and medium voltage (Eguz et al, 2019).…”