Particle-in-Cell/Monte Carlo simulation of CF4 discharge in capacitively coupled plasma reactor
We present the structures of the CF4 radio-frequency discharge between parallel electrodes using the Particle-in-Cell/ Monte Carlo method. The simulation takes into account four types of charged species, CF3 , CF − 3 , F − ions, and electrons. The cross-sections of electron-CF4 collision processes are based on the paper of Kurihara et al. [1]. Positive–negative ion recombination which plays an important role in the charged particle balance is also considered in the model using method proposed by Nanbu and Denpoh [2]. The structure of the CF4 discharge is typically electronegative discharge and is characterized by the presence of negative ions (F− and CF3 ), which are the dominant negative charged species (see Fig. 1(a)). The electron density profile and electric field at phase in a rf period are shown in Fig. 1. The local maxima of the electron density is significant feature of electronegative discharges, which cannot be observed in electropositive discharges. Moreover, we can observe the double-layer structure (i.e. the local maxima or minima of the electric field) and the field reversal near the bulk-sheath interface. Historically, the double layer phenomena were first described experimentally and theoretically in rf glow SiH4 discharge by T. Makabe et al. [3]. In conclusion, the abundance of negative ions is one of the main features in the discharges and this profoundly influences the sheath dynamics such as electric field reversal, double layer structure and local maxima of electron density.
Monte Carlo Collision Simulation of Positive-Negative Ion Recombination for a Given Rate Constant
Here is proposed the Monte Carlo collision simulation method for the positive-negative ion recombination whose rate constant is given as a function of temperature. The method makes it possible to simulate a nonequilibrium state of ions in electric discharges.
Kinetic Theory of Charged Particle Swarms in Neutral Gases
The kinetic theory of charged test particles in a neutral gas, in the presence of static and uniform electric and magnetic fields, is reviewed. The effects of inelastic processes and reactions are included. The general space-time development of the swarms is considered and the relation between the nonhydrodynamic anQ hydrodynamic developments is pointed out. The transport coefficients are identified as statistical averages over the configuration-space and phase-space distributions. The evaluation of these averages by computer simulations is briefly discussed.