Alpha–gamma transition in RF capacitive discharge in low-pressure oxygen

Lisovskiy, Valeriy; Yegorenkov, Vladimir

doi:10.1016/j.vacuum.2003.11.003

Cited by 33 publications

(39 citation statements)

References 33 publications

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“…In addition, the phase between the applied rf voltage (equation 1) and the rf component of the discharge current appearing later in this manuscript (figures 8 and 10), is approximately out of phase by 90 • . By comparing this phase with literature data [85], this also indicates that the discharge burns in the α-mode. …”

Section: Control Of the Density Profilessupporting

confidence: 52%

Control of plasma properties in capacitively coupled oxygen discharges via the electrical asymmetry effect

Schüngel¹,

Zhang²,

Iwashita³

et al. 2011

J. Phys. D: Appl. Phys.

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To cite this version:E Schüngel, Q-Z Zhang, S Iwashita, J Schulze, L-J Hou, et al.. Control of plasma properties in capacitively coupled oxygen discharges via the electrical asymmetry effect. Journal of Physics D: Applied Physics, IOP Publishing, 2011, 44 (28) Abstract. By using a combined experimental, numerical and analytical approach, we investigate the control of plasma properties via the Electrical Asymmetry Effect (EAE) in a capacitively coupled oxygen discharge. In particular, we present the first experimental investigation of the EAE in electronegative discharges. A dual-frequency voltage source of 13.56 MHz and 27.12 MHz is applied to the powered electrode and the discharge symmetry is controlled by adjusting the phase angle θ between the two harmonics. It is found that the bulk position and density profiles of positive ions, negative ions, and electrons have a clear dependence on θ, while the peak densities and the electronegativity stay rather constant, largely due to the fact that the time averaged power absorption by electrons is almost independent of θ. This indicates that the ion flux towards the powered electrode remains almost constant. Meanwhile, the dc self-bias and, consequently, the sheath widths and potential profile can be effectively tuned by varying θ. This enables a flexible control of the ion bombarding energy at the electrode. Therefore, our work proves the effectiveness of the EAE to realize separate control of ion flux and ion energy in electronegative discharges. At low pressure, the strength of resonance oscillations, which are found in the current of asymmetric discharges, can be controlled with θ.

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Section: Control Of the Density Profilessupporting

confidence: 52%

Control of plasma properties in capacitively coupled oxygen discharges via the electrical asymmetry effect

Schüngel¹,

Zhang²,

Iwashita³

et al. 2011

J. Phys. D: Appl. Phys.

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“…As is known [4,9,[25][26][27][28][29][30][31][32][33][34][35], a rf capacitive discharge may burn in two different modes: a weak-current (a-) and strong-current (gmode). In the a-mode the electrons acquire their energy for ionizing gas atoms in the rf field in the quasi-neutral plasma, the electron emission from the surface of the electrodes not playing a substantial role in the discharge sustainment.…”

Section: Discussionmentioning

confidence: 99%

“…In so doing we use the values of the electron temperature determined from the probe CVCs (employing the linear section of the graph of the electron current to the probe constructed to the semi-logarithmic scale). [4,9,[25][26][27][28][29][30][31][32][33][34][35] of the rf discharge (the curve for U rf ¼ 50 V, p ¼ 0.1 Torr and the curves for U rf ¼ 100 and 165 V, p ¼ 1 Torr) counting from the discharge axis, the electron temperature first remains constant or increases weakly. However on approaching the wall of the discharge tube the electron temperature T e increases abruptly, its maximum value exceeding T e near the discharge axis almost more than twice.…”

Section: Langmuir Probe Measurements Descriptionmentioning

confidence: 99%

Radial structure of low pressure rf capacitive discharges

Lisovskiy

Kharchenko

Yegorenkov

2010

Vacuum

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a b s t r a c tThis paper studies the glow intensity distribution of the discharge plasma against the tube radius and reports the radial profiles of electron temperature and plasma concentration in the rf capacitive discharge registered with a Langmuir probe. An abrupt increase of electron temperature and glow intensity near the tube wall in the weak-current a-mode of the rf capacitive discharge is revealed, the radial distribution of plasma concentration and ion flow to the electrodes possessing a maximum near the radial sheath boundary. In the g-mode of the rf capacitive discharge the electron temperature decrease in the total plasma volume leads to an electric field weakening and the peak of the glow intensity near the tube wall vanishes. The radial sheath thickness in the a-mode of the rf capacitive discharge obtained with 2D simulation experiences pulsations during the rf field period, the changing radial electric field heating electrons and increasing the plasma concentration near the boundary of the radial sheath.

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“…As is known [13][14][15][16][17][18][19][20][21][22] an rf capacitive discharge may exist in a weak-current (α-) and a strong-current (γ -) modes. The authors of papers [13][14][15][16][17][18][19] made an assumption that in a weakcurrent α-mode the electrons acquired their energy required for ionizing gas molecules oscillating in an rf electric field within the plasma volume.…”

Section: Introductionmentioning

confidence: 99%

Modes of rf capacitive discharge in low-pressure sulfur hexafluoride

Lisovskiy¹,

Booth²,

Jolly³

et al. 2007

J. Phys. D: Appl. Phys.

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This paper presents the results of an experimental study of rf capacitive discharge in low-pressure SF 6 . The rf discharge in SF 6 is shown to exist not only in weak-current (α-) and strong-current (γ -) modes but also in a dissociative δ-mode. This δ-mode is characterized by a high degree of SF 6 dissociation, high plasma density, electron temperature and active discharge current, and it is intermediate between α-and γ -modes. The δ-mode appears due to a sharp increase in the dissociation rate of SF 6 molecules via electron impact starting after a certain threshold value of rf voltage. At the same time the threshold ionization energy of SF x (x = 1-5) radicals formed is below the ionization potential of SF 6 molecules. The double layer existing in the anode phase of the near-electrode sheath is shown to play an important role in sustaining the α-mode as well as the δ-mode but it is not a cause of the rf discharge transition from α-to δ-mode.

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Alpha–gamma transition in RF capacitive discharge in low-pressure oxygen

Cited by 33 publications

References 33 publications

Control of plasma properties in capacitively coupled oxygen discharges via the electrical asymmetry effect

Control of plasma properties in capacitively coupled oxygen discharges via the electrical asymmetry effect

Radial structure of low pressure rf capacitive discharges

Modes of rf capacitive discharge in low-pressure sulfur hexafluoride

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