Control of plasma uniformity in a capacitive discharge using two very high frequency power sources

Bera, Kallol; Rauf, Shahid; Ramaswamy, K.; Collins, Ken

doi:10.1063/1.3183946

Cited by 49 publications

(33 citation statements)

References 17 publications

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“…In the phase shift control method mentioned above, the frequency of the two VHF sources connected to the two electrodes is identical. In addition, Bera et al 62 indicated that multiple VHF sources at different frequencies can also control the plasma spatial profile, specifically when the plasma distributions at the individual frequencies are different. However, the underlying physics for the two cases is quite different.…”

Section: Multiple Vhf Sources Controlmentioning

confidence: 99%

Electromagnetic effects in high-frequency large-area capacitive discharges: A review

Liu¹,

Zhang²,

Bogaerts³

et al. 2015

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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In traditional capacitively coupled plasmas, the discharge can be described by an electrostatic model, in which the Poisson equation is employed to determine the electrostatic electric field. However, current plasma reactors are much larger and driven at a much higher frequency. If the excitation wavelength k in the plasma becomes comparable to the electrode radius, and the plasma skin depth d becomes comparable to the electrode spacing, the electromagnetic (EM) effects will become significant and compromise the plasma uniformity. In this regime, capacitive discharges have to be described by an EM model, i.e., the full set of Maxwell's equations should be solved to address the EM effects. This paper gives an overview of the theory, simulation and experiments that have recently been carried out to understand these effects, which cause major uniformity problems in plasma processing for microelectronics and flat panel display industries. Furthermore, some methods for improving the plasma uniformity are also described and compared.

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Section: Multiple Vhf Sources Controlmentioning

confidence: 99%

Electromagnetic effects in high-frequency large-area capacitive discharges: A review

Liu¹,

Zhang²,

Bogaerts³

et al. 2015

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

View full text Add to dashboard Cite

show abstract

“…In recent years, several theoretical studies [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] and experimental research [22][23][24][25][26][27][28][29][30] have been published on the plasma characteristics in a CCP sustained by VHF sources. Lieberman et al 6 first employed a uniform slab model to investigate the standing-wave and skin effects in VHF discharges.…”

Section: Introductionmentioning

confidence: 99%

“…Besides, considerable effort has also been made on studying the discharge mechanisms with dual frequency excitation in the VHF regime. [15][16][17][18][19][20][21] Yang and Kushner 19-21 utilized a full-wave Maxwell solver, and studied the properties of plasmas sustained in Ar and Ar/ CF 4 at different discharge conditions.…”

Section: Introductionmentioning

confidence: 99%

Comparison of electrostatic and electromagnetic simulations for very high frequency plasmas

Zhang

Zhao

et al. 2010

Physics of Plasmas

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A two-dimensional self-consistent fluid model combined with the full set of Maxwell equations is developed to investigate an argon capacitively coupled plasma, focusing on the electromagnetic effects on the discharge characteristics at various discharge conditions. The results indicate that there exist distinct differences in plasma characteristics calculated with the so-called electrostatic model (i.e., without taking into account the electromagnetic effects) and the electromagnetic model (which includes the electromagnetic effects), especially at very high frequencies. Indeed, when the excitation source is in the high frequency regime and the electromagnetic effects are taken into account, the plasma density increases significantly and meanwhile the ionization rate evolves to a very different distribution when the electromagnetic effects are dominant. Furthermore, the dependence of the plasma characteristics on the voltage and pressure is also investigated, at constant frequency. It is observed that when the voltage is low, the difference between these two models becomes more obvious than at higher voltages. As the pressure increases, the plasma density profiles obtained from the electromagnetic model smoothly shift from edge-peaked over uniform to a broad maximum in the center. In addition, the edge effect becomes less pronounced with increasing frequency and pressure, and the skin effect rather than the standing-wave effect becomes dominant when the voltage is high.

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“…11 If the discharge frequency is very high, in order to eliminate the standing wave effect, it is helpful to use a special electrode, for example, a lens-shaped electrode. 13 By applying graded conductivity electrodes, it also can improve the plasma uniformity significantly in VHF discharges. 13 By applying graded conductivity electrodes, it also can improve the plasma uniformity significantly in VHF discharges.…”

Section: Introductionmentioning

confidence: 99%

Phase-shift effect in capacitively coupled plasmas with two radio frequency or very high frequency sources

Zhao

Zhang

et al. 2010

Journal of Applied Physics

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Control of plasma uniformity in a capacitive discharge using two very high frequency power sources A two-dimensional fluid model was built to study the argon discharge in a capacitively coupled plasma reactor and the full set of Maxwell equations is included in the model to understand the electromagnetic effect in the capacitive discharge. Two electrical sources are applied to the top and bottom electrodes in our simulations and the phase-shift effect is focused on. We distinguish the difference of the phase-shift effect on the plasma uniformity in the traditional radio frequency discharge and in the very high frequency discharge where the standing wave effect dominates. It is found that in the discharges with frequency 13.56 MHz, the control of phase difference can less the influence of the electrostatic edge effect, and it gets the best radial uniformity of plasma density at the phase difference . But in the very high frequency discharges, the standing wave effect plays an important role. The standing wave effect can be counteracted at the phase difference 0, and be enhanced at the phase difference . The standing wave effect and the edge effect are balanced at some phase-shift value between 0 and , which is determined by discharge parameters.

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Control of plasma uniformity in a capacitive discharge using two very high frequency power sources

Cited by 49 publications

References 17 publications

Electromagnetic effects in high-frequency large-area capacitive discharges: A review

Electromagnetic effects in high-frequency large-area capacitive discharges: A review

Comparison of electrostatic and electromagnetic simulations for very high frequency plasmas

Phase-shift effect in capacitively coupled plasmas with two radio frequency or very high frequency sources

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