Abstract:

To further understand the discharge mechanism and the particle states incident to the pole plate during the capacitively coupled plasma discharge, the discharge of argon and methane gas mixture is simulated by PIC/MCC program, and the electron density, CH₄⁺ and CH₃⁺ group particle concentrations, electron energy probability distribution, as well as the energy angle distribution and particle species of the particles reaching the pole plate boundary are simulated and calculated under different Ar/CH₄ ratios and different pole plate gap conditions. The simulation results show that the electron density, Ar⁺, CH₂^- and H^- ion density in the discharge center decrease and then increase with the increase of the pole plate spacing at a fixed Ar/CH₄ of 9∶1, and the CH₄⁺ and CH₃⁺ ion density change in the opposite trend; the electron energy probability function (EEPF) from double Maxwell distribution to single Maxwell distribution when the pole plate spacing increases; the percentage of electrons arriving at the pole plate is larger and changes less with the pole plate spacing, the probability of Ar⁺ arriving at the pole plate first decreases and then increases, and the percentage of CH₄⁺, CH₃⁺ and CH₂⁺ ions arriving at the pole plate increases with the increase of the pole plate spacing. At fixed pole plate spacing, the electron density and Ar⁺ density in the discharge center show a decreasing trend with increasing CH₄ content, and the densities of CH₄⁺, CH₃⁺, CH₂^- and H^- ions show an increasing trend; the effect of the change in pole plate spacing on the EEPF distribution is more obvious than the effect of the change in CH₄ ratio on the EEPF distribution; with the increase in CH₄ content, the change in the percentage of electrons arriving at the pole plate is not obvious, and the percentage of Ar⁺ ions decreases significantly, while the percentage of CH₄⁺, CH₃⁺, CH₂⁺ and the rest of ions arriving at the pole-plate increase.

Key words: capacitively coupled plasma discharge, Ar/CH₄ mixed plasma, PIC/MCC simulation