Numerical study of dual-frequency capacitively-coupled discharges in electronegative

Institute of Fluid Science, Tohoku University 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan

Corresponding author: tong@ifs.tohoku.ac.jp

Received: 14 March 2006
Accepted: 3 May 2006

Abstract

Discharge structures and properties of dual-frequency capacitively-coupled plasma (CCP) discharges in SF₆ are studied by using a one-dimensional Particle-in-Cell/Monte Carlo (PIC/MC) method. The simulations are carried out at a gas pressure of 25 for a fixed low-frequency (LF) source of 3.2 and a high-frequency (HF) source of 27–50. Results show that in dual-frequency discharges both sources nonlinearly interact even if the source frequencies are significantly different from each other (e.g., 3.2 and 50). In the presence of the LF source, the electron density in the bulk plasma reduces in comparison with the density for the case without LF source. The non-equilibrium behavior between the electron-SF₆ collisional ionization or attachment and density diffusion is found for a HF source frequency higher than 49. The electron temperature in the bulk plasma is higher than 5, which sustains the discharge by compensating the loss of electrons due to strong attachment.