Abstract
The characteristics of cold plasma, especially for a dual-frequency capacitively coupled plasma (CCP), play an important role for plasma enhanced chemical vapor deposition, which stimulates further studies using different methods. In this paper, a 2D fluid model was constructed for N2 gas plasma simulations with CFD-ACE+, a commercial multi-physical software package. First, the distributions of electric potential (Epot), electron number density (Ne), N number density (N) and electron temperature (Te) are described under the condition of high frequency (HF), 13.56 MHz, HF voltage, 300 V, and low-frequency (LF) voltage, 0 V, particularly in the sheath. Based on this, the influence of HF on Ne is further discussed under different HF voltages of 200 V, 300 V, 400 V, separately, along with the influence of LF, 0.3 MHz, and various LF voltages of 500 V, 600 V, 700 V. The results show that sheaths of about 3 mm are formed near the two electrodes, in which Epot and Te vary extensively with time and space, while in the plasma bulk Epot changes synchronously with an electric potential of about 70 V and Te varies only in a small range. N is also modulated by the radio frequency, but the relative change in N is small. Ne varies only in the sheath, while in the bulk it is steady at different time steps. So, by comparing Ne in the plasma bulk at the steady state, we can see that Ne will increase when HF voltage increases. Yet, Ne will slightly decrease with the increase of LF voltage. At the same time, the homogeneity will change in both x and y directions. So both HF and LF voltages should be carefully considered in order to obtain a high-density, homogeneous plasma.