Incorporating the gas flow in a numerical model of rf discharges in methane

Abstract

A two-dimensional modified fluid model for a capacitively coupled rf discharge in methane, used for the deposition of diamond-like carbon layers, is presented. The gas velocity calculated with a computational fluid dynamics code is used as an input for the modified fluid model. Convection is taken into account as an additional transport mechanism as well as diffusion and migration. The calculations show that the gas flow results in a shift of the maximum of the densities of the plasma species toward the grounded electrode. It is shown that this shift has a large effect on the fluxes of the ions and radicals toward the substrate where the deposition occurs. As a result, the deposition rate will increase if the gas velocity has a component directed to the surface and it will decrease in the opposite case. However, the uniformity of the layer can become worse when the convection velocity is too high for the reactor geometry studied here.

Hollow cathode discharges with gas flow: numerical modelling for the effect on the sputtered atoms and the deposition flux

“…In [28,29] the gas flow was included in the flux equation, in models for ICP discharges in nitrogen. In our group, we have recently developed some models, which incorporate the effect of gas flow, by adding a convection term in the flux equations, for two types of discharges: a dc glow discharge in argon, used as ion source for mass spectrometry [30], and a cc rf discharge in CH 4 , used for plasma-enhanced chemical vapour deposition, to study the effect on the deposition rate and the uniformity of the deposition flux [31]. To our knowledge, there exist, however, no models in the literature that include the gas flow in simulations of hollow cathode discharges.…”

The Effect of Gas Flow Rate on Radio-Frequency Hollow Cathode Discharge Characteristics

“…Comparing the distributions of N + 2 densities when the flow rate is included and not included, the flow rate not only causes the maximum of the ions density to decrease, and the total ion density in the whole discharge space to decrease, but also causes the ions density to increase near the inlet. A Bogaerts et al have simulated capacitively coupled radio-frequency (ccrf) discharge in methane with a fluid model and have shown that calculated time-averaged CH + 5 ion density decreases with increasing flow rate [9] . The distribution of the mean density of N + ions is similar to that of N + 2 , and the density of N + is about six times less than N + 2 by our calculation, the reason for which can be found in our previous work [12] .…”

“…Lee et al [7] and Tanaka et al [8] studied the problem of gas flow rate for an ICP discharge in argon and nitrogen. Okhrimovskyy and Bogaerts et al [9] simulated a capacitively coupled radio-frequency (rf) discharge in methane using a twodimension (2D) fluid model including the flow rate in a plasma-enhanced chemical-vapor deposition reactor of H-type geometry. The results explicitly indicate that the flow rate can affect the deposition rate and the uniformity of the deposited layer.…”

Gas flow characteristics of argon inductively coupled plasma and advections of plasma species under incompressible and compressible flows

“…[19]. In addition, the density profile alters when changing the gap between the electrodes due to the competition of the above time scales, [20] or by considering a gas flow module into the fluid model or not, [21] in a capacitively coupled plasma source. Still, the gas flow, together with the feedstock gas fragmentation, multi component mass transport, gas heating, pumping speed, etc., influence the accuracy of gas pressure measurements at the chamber outlet.…”