Effects of interelectrode gap on high frequency and very high frequency capacitively coupled plasmas

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

doi:10.1116/1.3151821

Cited by 49 publications

(26 citation statements)

References 15 publications

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“…[14][15][16][17][18][19] Many numerical simulations of plasma density profiles in facsimiles of commercial-scale VHF-CCP tools have been reported. [20][21][22][23][24][25] In addition to the aforementioned simulations by Lee and coworkers, other numerical simulations include coupled solutions of the plasma fluid and the time domain electromagnetic fields. The models used have the necessary physics components for predicting the generation of higher harmonics, but no report of their existence was made.…”

Section: Introductionmentioning

confidence: 99%

Relationship between center-peaked plasma density profiles and harmonic electromagnetic waves in very high frequency capacitively coupled plasma reactors

Sawada¹,

Ventzek²,

Lane³

et al. 2014

Jpn. J. Appl. Phys.

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An understanding of the factors that control radial plasma uniformity in very high frequency (VHF) capacitively coupled plasma (CCP) sources is important for many plasma processes in semiconductor device manufacturing. Here, we report experimental measurements and high-resolution self-consistent numerical simulations that illustrate the plasma density profile and the higher harmonic wave content in two types of VHF-CCP testbench reactors. A distinct sharp center peak superimposed on a broad center peak in argon plasma was observed for driving frequencies of 60 and 106 MHz. Experimental measurements and numerical simulations of the electric field power spectrum reveal the presence of UHF waves when the electron density is over 5 ' 10 16 (#/m 3). The presence of UHF waves closely correlates with the occurrence of a distinct and sharp-center-peaked electron density. The numerical simulations show that specific frequency bands in the UHF spectrum are amplified in the plasma and lead to the evolution of the sharp-center-peaked electron density.

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Section: Introductionmentioning

confidence: 99%

Relationship between center-peaked plasma density profiles and harmonic electromagnetic waves in very high frequency capacitively coupled plasma reactors

Sawada¹,

Ventzek²,

Lane³

et al. 2014

Jpn. J. Appl. Phys.

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“…In addition to the methods mentioned above, also many other methods were proposed by means of computer simulations and experiments. For example, Bera et al 63 demonstrated that the interelectrode gap can be used to control the uniformity in a VHF CCP discharge. At large interelectrode gaps, the EM standing-wave effect is strong, and the plasma density peaks at the chamber center.…”

Section: Other Methods To Control the Plasma Uniformitymentioning

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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“…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%

“…Lee et al 11 focused on the coupling of the electromagnetic effects with the electrostatic edge effect in a two-dimensional axisymmetric model, and they observed the so-called stop band at higher frequencies and higher pressures. Rauf et al 12,13 developed a fluid model to simulate an argon plasma, discovering that the plasma density peaked at the chamber center under the condition where the electromagnetic effects were predominant. Furthermore, they also observed that the plasma became more uniform for a small interelectrode gap at 180 MHz.…”

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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Effects of interelectrode gap on high frequency and very high frequency capacitively coupled plasmas

Cited by 49 publications

References 15 publications

Relationship between center-peaked plasma density profiles and harmonic electromagnetic waves in very high frequency capacitively coupled plasma reactors

Relationship between center-peaked plasma density profiles and harmonic electromagnetic waves in very high frequency capacitively coupled plasma reactors

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

Comparison of electrostatic and electromagnetic simulations for very high frequency plasmas

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