Experimental study on the ignition process of a pulsed capacitively coupled RF discharge: Effects of gas pressure and voltage amplitude

Wang, Xiang-Yu; Zhao, Kai; Liu, Yong-Xin; Wang, You‐Nian

doi:10.1063/5.0087182

Cited by 7 publications

(4 citation statements)

References 66 publications

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“…Particularly, the maximum of the OEI upon the overshoot becomes higher than that of P rf , provided that the scales of two vertical axes are adjusted such that the OEI and P rf curves are overlapped at p = 30 pa. This is because, as Wang et al explained in [54], the electron energy during the ignition phase is mainly dissipated via excitation collision since the pressure is relatively high and electrons are more likely to reach the threshold energies of excitation (13.5 eV). As time advances, in all the pressures investigated here, P rf increases after the ignition phase with a larger growth rate than the OEI, and the reason is given as follows.…”

Section: Pressure Effectmentioning

confidence: 99%

Experimental investigation of the radially-dependent ignition process in a pulsed capacitively coupled RF discharge: Effects of pressure, voltage and afterglow duration

Zhao

Jiang³

et al. 2023

Phys. Scr.

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The effects of the gas pressure, the voltage amplitude and the afterglow duration on the ignition process over 300 mm-diameter in a pulse-modulated capacitively coupled radio-frequency argon discharge are experimentally investigated. A home-made optical probe is used to measure the optical emission intensity (OEI) as a function of time since the beginning of each pulse at various radial positions. A voltage and a current probe are used to measure the voltage and current waveforms at the power feeding point and then the time-dependent power deposition is also obtained. It was found that the radial profile of the OEI exhibits complex evolution when changing these external conditions. At lower pressures, the ignition occurs earlier, and the radial-integral OEI and the power deposition overshoot slightly during the ignition. By increasing the pressure, these two quantities overshoot more significantly, and the OEI gradually evolves from an edge-peaked radial profile towards a center-high radial profile for a given time when the OEI increases rapidly during the ignition. When increasing the voltage amplitude, the ignition tends to occur earlier, featuring a more significant overshoot of the OEI and power deposition at a higher voltage. Compared to that at high voltage, the OEI exhibits a significant center-high radial profile at low voltage amplitude during the ignition. By increasing the afterglow duration, T off, the ignition is delayed and the overshoot becomes more significant, due to a lower initial electron density when each pulse is turned on. During the phase of the fastest increasing OEI, the OEI exhibits different radial distributions, i.e., it appears a center high profile at short T off, an edge-peaked profile at intermediate T off, and a center-high profile at relatively long T off.

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Section: Pressure Effectmentioning

confidence: 99%

Experimental investigation of the radially-dependent ignition process in a pulsed capacitively coupled RF discharge: Effects of pressure, voltage and afterglow duration

Zhao

Jiang³

et al. 2023

Phys. Scr.

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“…Figure 3(f) displays the corresponding computed values of P H and P L and the total electron impact excitation rate, K ex , as well as the computed electron and ion density, n e and n i , at the discharge center. Similar to previous works [27,28,43], the plasma ignition process is analyzed by dividing this period into three phases (see figure 3). The blue, yellow, and pink parts indicate the pre-ignition (0 ⩽ t/T L ⩽ t 1 ), ignition (t 1 ⩽ t/T L ⩽ t 2 ), and post-ignition phases (t/T L ⩾ t 2 ), respectively.…”

Section: Base Case (Vmentioning

confidence: 99%

An experimental and computational study on the ignition process of a pulse modulated dual-RF capacitively coupled plasma operated at various low-frequency voltage amplitudes

Shi,

Wang,

Liu

et al. 2024

Plasma Sources Sci. Technol.

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The ignition process of a pulse modulated capacitively coupled argon discharge driven simultaneously by two different radio frequency voltages (12.5 MHz (high frequency, HF) and 2.5 MHz (low frequwncy, LF)) is investigated by multifold experimental diagnostics and particle in cell / Monte Carlo collision (PIC/MCC) simulations. In particular, (i) the effects of the low frequency voltage amplitude measured at the end of the pulse-on period, V L,end, on the spatiotemporal distribution of the electron impact excitation rate determined by phase resolved optical emission spectroscopy, and (ii) the electrical parameters acquired by analyzing the measured waveforms of the plasma current and voltage, are studied. Computed spatiotemporal distributions of the electron impact excitation rate and electrical parameters show a good qualitative agreement with the experimental results. Generally, the HF and LF electrical parameters (amplitudes and relative phase of the voltage and the current) change with time in a similar manner during the ignition process for each V L,end. However, various scenarios of the breakdown mechanism are found as a function of V L,end. At low values of V L,end, the “RF-avalanche” mode dominates the electron multiplication process. By increasing V L,end, the ionization caused by the volume electrons is suppressed and the electron loss at the electrodes is enhanced, leading to a delayed ignition. At higher values of V L,end, the avalanche ionization is significantly enhanced by ion-induced secondary electron emission at the electrodes.

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“…Pure argon gas of a fixed flow rate of 6 sccm is introduced into the chamber, and the gas pressure is kept at 450 mTorr, of which the value is intentionally kept the same as that in our previous work [25,26]. The reason is that 450 mTorr is an intermediate pressure within the 'drift-diffusion' branch of the breakdown curve, and within the corresponding pressure range electron multiplication is primarily dominated by volume processes during plasma ignition [29].…”

Section: Experimental Setup and Diagnosticsmentioning

confidence: 99%

Effects of ‘step-like’ amplitude-modulation on a pulsed capacitively coupled RF discharge: an experimental investigation

Wang²,

Liu³

et al. 2022

Plasma Sources Sci. Technol.

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We present measurements of the time evolution of plasma and electrical parameters in a pulsed capacitively coupled argon discharge operated at a radio frequency of 12.5 MHz, whose amplitude is “step-up” and “step-down” modulated. The “step-up (-down)” amplitude-modulated waveform consists of three segments, i.e., a low (high)-voltage, a high (low)-voltage, and a zero-voltage stage. Here, we focus on the effect of the ratio (ξ=VL/VH ≤ 1) of the low-(VL) to high-voltage (VH) amplitude (measured at the end of the respective segment) on the time evolution of discharge parameters. We monitor the behavior of the discharge by measuring (i) the optical emission intensity (OEI) of a selected Ar-I spectral line, (ii) the electron density at the center of the plasma (using a hairpin probe) as well as (iii) the electrical characteristics of the discharge (by voltage and current probes). It is found that at relatively large ξ (i.e., at low disparity between the two voltage amplitudes), for both the “step-up” and “step-down” cases, these parameters evolve relatively smoothly with time upon changing the voltage amplitude, and the ignition process strongly depends on the duration of the zero-voltage period. At low ξ (i.e., at high disparity between the voltage amplitudes), an abnormal evolution of the parameters can be observed during the low-voltage period for both cases. Specifically, the voltage amplitude and the modulus of the system impedance increase to a higher value, while the relative phase, φvi, between the voltage and the current approaches 90°, resulting in a reduction of the power deposition and the OEI. The ξ-dependent evolution of electron density during the low-voltage period was found to significantly affect the subsequent ignition process and electron power absorption mode at the beginning of the high-voltage period.

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Experimental study on the ignition process of a pulsed capacitively coupled RF discharge: Effects of gas pressure and voltage amplitude

Cited by 7 publications

References 66 publications

Experimental investigation of the radially-dependent ignition process in a pulsed capacitively coupled RF discharge: Effects of pressure, voltage and afterglow duration

Experimental investigation of the radially-dependent ignition process in a pulsed capacitively coupled RF discharge: Effects of pressure, voltage and afterglow duration

An experimental and computational study on the ignition process of a pulse modulated dual-RF capacitively coupled plasma operated at various low-frequency voltage amplitudes

Effects of ‘step-like’ amplitude-modulation on a pulsed capacitively coupled RF discharge: an experimental investigation

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