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

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... tzmann'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.