Transport coefficients and scattering cross-sections for plasma modelling in CF₄-Ar mixtures: a swarm analysis

Abstract

Electron transport coefficients and the excitation, attachment and ionization rates in pure CF4 and in CF4-Ar mixtures have been calculated for a set of cross-sections which was based on the work of Nakamura (1991 Gaseous Electronics and Their Applications ed R W Crompton et al (Tokyo: KTK Scientific) pp 178-200) but which was modified to include more complex dissociation and ionization kinetics required to develop an adequate plasma chemical model. The procedure for the calculation was the direct numerical procedure (DNP) solution to the Boltzmann equation which makes no approximations in the number of terms used to represent the anisotropy of the distribution function in the velocity space. However, its accuracy may be limited by the density of the grid used. In this paper, we apply the DNP technique to establish its adequacy for plasma modelling in pure CF4 and in 5% CF4-Ar mixture, as well as establishing the adequacy of the cross-section set that was used.

Slope and amplitude asymmetry effects on low frequency capacitively coupled carbon tetrafluoride plasmas

“…2(a). The cross-sections are taken from Kurihara et al, 34 except for electron attachment processes which are taken from Bonham et al 35 A complete list of the electron impact collision processes used in this model can be found in Schulze et al 25 Although a large number of ion-CF 4 reactions take place in CF 4 discharges, 27,32,36 only a limited set of reactions are included here. The energy dependent cross sections for these reactions are shown in Fig.…”

Modeling of the effect of radicals on plasmas used for etching in microelectronics

“…The basic cross sections of pure CF 4 were used from [8] with a modification made in [13,14] in order to include production of CF 3 -ions. Complete cross section set is shown in Figure 1.…”

“…Such calculations are usually based on compilations of cross sections from various sources [8]. Requirement to establish reliable transport coefficients for CF 4 plasmas is especially demanding since practical conditions include many reactive species.…”

Modelling of anomalous Doppler broadened lines, thermalization of electrons and the role of radicals in discharges at high E/N

“…It is a characteristic of the cross sections for electron scattering in CF 4 [19] that attachment has a threshold at a relatively high energy. On the other hand some of the radicals, CF 2 and F 2 in particular have a threshold at lower energies [13,20].…”