Dissociation channels of c-C$_{4}$F$_{8}$ to CF$_{2}$ radical in reactive plasma

c-C$_{4}$F$_{8}$ has been widely used in the area of dielectric etching in microelectronics fabrication processes. This trend brought about many experimental studies, in which CF$_{2}$ radical was a main component in c-C$_{4}$F$_{8}$ plasmas. This is the basis of the model of c-C$_{4}$F$_{8}$ dissociation to CF$_{2}$ through C$_{2}$F$_{4}$. Font et al. [1] considered comparatively the dissociation cross sections ($\sigma )$ of c-C$_{4}$F$_{8}$ obtained by many researchers and finally adopted the$\sigma $and rate coefficient estimated by Radtke et al. [2]. However, the main dissociation channels are yet unclear. Theoretical studies were reported for C$_{2}$F$_{4}$ excited states and electron interactions by Winstead and Mckoy [3], and Yoshida et al. [4]. The energy of the dissociation channel to CF$_{2}$ showed good agreement with the electron attachment value obtained by Goyette et al. [5]. However, they did not mention the excitation dissociation of neutral C$_{2}$F$_{4}$. Therefore, studies for dissociation reactions of c-C$_{4}$F$_{8}$ and C$_{2}$F$_{4}$ are limited and yet ambiguous. We calculated the dissociation channels of c-C$_{4}$F$_{8}$ and C$_{2}$F$_{4}$ using \textit{Gaussian 03} program, in order to clarify the main dissociation channels. [1] G. I. Font et al., J. Appl. Phys., 91 (2002) 3530. [2] M. T. Radtke et al., J. Vac. Sci. Technol., A21 (2003) 1038. [3] C. Winstead and V. Mckoy, J. Chem. Phys., 116 (2002) 1380. [4] K. Yoshida et al., J. Appl. Phys., 91 (2002) 2637. [5] A. N. Goyette et al., J. Chem. Phys., 114 (2001) 9832.