Fluid simulation of the electromagnetic effects and the phase shift effect in Ar/CF4 capacitively coupled plasmas

Summary form only given. A two-dimensional self-consistent fluid model combined with the full set of Maxwell equations is established to investigate the electromagnetic effects and the phase shift effect on the plasma characteristics in an Ar/CF₄ capacitively coupled plasma at various discharge conditions. The results indicate that the plasma density evolves to a different distribution when the electromagnetic effects are included in the model comparing with the results calculated with the so called electrostatic model (without taking into account the electromagnetic effects), especially at very high frequencies. Therefore, the electromagnetic effects should be taken into account for obtaining realistic results in the simulations when the frequency is in the VHF regime. Moreover, when the frequency is higher than 60 MHz, the standing-wave effect and skin effect become important, and accordingly limit the plasma spatial uniformity [Lieberman, M.A., et al., 2002]. Therefore, the phase-shift control has been presented as an effective method to increase the plasma uniformity considerably in the dual-frequency plasmas [Bera, K., et al., 2007]. The results indicate that when the phase difference increases from 0 to π, the plasma density profiles shift smoothly from edge-peaked over uniform to centre-peaked. But a better uniformity is obtained at different phase shift values when the discharge frequency or the CF₄ fraction in Ar/CF₄ mixtures is different.