A comparative study on continuous and pulsed RF argon capacitive glow discharges at low pressure by fluid modeling

Abstract

Based on the plasma fluid theory and using the drift-diffusion approximation, a mathematical model for continuous and pulsed radial frequency (RF) argon capacitive glow discharges at low pressure is established. The model is solved by a finite difference method and the numerical results are reported. Based on the systematic analysis of the results, plasma characteristics of the continuous and pulsed RF discharges are comparatively investigated. It is shown that, under the same condition for the peak value of the driving potential, the cycle-averaged electron density, the current density, and other essential physical quantities in the continuous RF discharge are higher than those from the pulsed RF discharge. On the other hand, similar plasma characteristics are obtained with two types of discharges, by assuming the same deposited power. Consequently, higher driving potential is needed in pulsed discharges in order to maintain the same effective plasma current. Furthermore, it is shown that, in the bulk plasma region, the peak value of the bipolar electric field from the continuous RF discharge is greater than that from the pulsed RF discharge. In the sheath region, the ionization rate has the shape of double-peaking and the explanation is given. Because the plasma input power depends on the driving potential and the plasma current phase, the phase differences between the driving potential and the plasma current are compared between the continuous and the pulsed RF discharges. It is found that this phase difference is smaller in the pulsed RF discharge compared to that of the continuous RF discharge. This means that the input energy coupling in the pulsed RF discharge is less efficient than the continuous counterpart. This comparative study, carried out also under other conditions, thus can provide instructive ideas in applications using the continuous and pulsed RF capacitive glow discharges.

Effects of HF frequency on plasma characteristics in dual-frequency helium discharge at atmospheric pressure by fluid modeling

“…The electron heating rate P c plays an important role in discharge process. Figure 7 shows the spatial profiles of cycle-averaged electron heating rate P c for different HF frequencies, the electron heating rates resemble some other simulation at low pressure [28,29]. With the increase of HF frequency, the electron heating rate P c significantly increases in the sheaths.…”

Effects of gas pressure on plasma characteristics in dual frequency argon capacitive glow discharges at low pressure by a self-consistent fluid model

“…[24] Recently, Liu et al used the model again to compare the continuous and pulse RF glow discharge. [30] In this work, we use the model with similar parameter values to theirs. We study the effect of the pressures (changing from 0.3 Torr to 1.5 Torr) on the plasma characteristics in dual frequency argon capacitive glow discharge.…”

“…As is well known, the main reactions in argon discharge include the grounded state excitation, the grounded state ionization, the step-wise ionization, the superelastic collisions, the quenching to resonance, the metastable pooling, the twobody quenching, and the three-body quenching. [23,30] These reactions are listed in Table 1.…”

“…In this model, the densities of ions and electrons between the electrodes satisfy the following continuity equations. [23,24,30]…”

Acoustic standing wave modulation of capacitively coupled plasmas

“…Multiple benefits have been demonstrated with pulsed plasmas driven by time-modulated bias applied to the working electrodes and/or substrates [2]. Some favorable effects include enhanced plasma uniformity [3,4], controlled ion energy [5], tunable chemical composition [6], improved density and smoothness of deposited films [7], and increased deposition rate [8]. However, the variations in the spatiotemporal distributions of the plasmas under pulsed modulations are in fact very limited due to the 'collective behavior' of plasmas that resist the external influences [9].…”