Slope and amplitude asymmetry effects on low frequency capacitively coupled carbon tetrafluoride plasmas

TY - JOUR

T1 - Slope and amplitude asymmetry effects on low frequency capacitively coupled carbon tetrafluoride plasmas

AU - Bruneau, Bastien

AU - Korolov, I

AU - Lafleur, T

AU - Gans, Timo

AU - O'Connell, Deborah

AU - Greb, Arthur

AU - Derzsi, A

AU - Donko, Z

AU - Brandt, S

AU - Schüngel, E

AU - Schulze, J

AU - E, Johnson

AU - Booth, J-P

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PY - 2016/4/26

Y1 - 2016/4/26

N2 - We report investigations of capacitively coupled carbon tetrafluoride (CF4) plasmas excited with tailored voltage waveforms containing up to five harmonics of a base frequency of 5.5 MHz. The impact of both the slope asymmetry, and the amplitude asymmetry, of these waveforms on the discharge is examined by combining experiments with particle-in-cell simulations. For all conditions studied herein, the discharge is shown to operate in the drift-ambipolar mode, where a comparatively large electric field in the plasma bulk (outside the sheaths) is the main mechanism for electron power absorption leading to ionization. We show that both types of waveform asymmetries strongly influence the ion energy at the electrodes, with the particularity of having the highest ion flux on the electrode where the lowest ion energy is observed. Even at the comparatively high pressure (600 mTorr) and low fundamental frequency of 5.5 MHz used here, tailoring the voltage waveforms is shown to efficiently create an asymmetry of both the ion energy and the ion flux in geometrically symmetric reactors.

AB - We report investigations of capacitively coupled carbon tetrafluoride (CF4) plasmas excited with tailored voltage waveforms containing up to five harmonics of a base frequency of 5.5 MHz. The impact of both the slope asymmetry, and the amplitude asymmetry, of these waveforms on the discharge is examined by combining experiments with particle-in-cell simulations. For all conditions studied herein, the discharge is shown to operate in the drift-ambipolar mode, where a comparatively large electric field in the plasma bulk (outside the sheaths) is the main mechanism for electron power absorption leading to ionization. We show that both types of waveform asymmetries strongly influence the ion energy at the electrodes, with the particularity of having the highest ion flux on the electrode where the lowest ion energy is observed. Even at the comparatively high pressure (600 mTorr) and low fundamental frequency of 5.5 MHz used here, tailoring the voltage waveforms is shown to efficiently create an asymmetry of both the ion energy and the ion flux in geometrically symmetric reactors.

U2 - 10.1063/1.4947453

DO - 10.1063/1.4947453

M3 - Article

SN - 0021-8979

VL - 119

SP - 163301-1 - 163301-10

JO - Journal of Applied Physics

JF - Journal of Applied Physics

M1 - 163301

ER -