Measured radial dependence of the peak sheath voltages present in very high frequency capacitive discharges

Barnat, Edward V.; Miller, Paul A.; Hebner, G. A.; Paterson, Alex; Panagopoulos, Theodoros; Hammond, Edward; Holland, J.

doi:10.1063/1.2735934

Cited by 17 publications

(19 citation statements)

References 20 publications

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“…These effects have been studied by using analytical EM models, 6,20 a more self-consistent transmission line approach, 19,23,25 numerical simulations, 15,17,[26][27][28] and experiments. 9,10,36,37 The three main EM effects, compromising the plasma nonuniformity, are the standing wave effect, the skin effect and the edge effect. Based on these three EM effects, especially the standing wave effect, several researchers have proposed, based on theory, modeling or experiments, effective methods to suppress the EM effects and to improve the plasma uniformity.…”

Section: Discussionmentioning

confidence: 99%

“…A more direct evidence of the standing wave effect was presented by Barnat et al 37 by measuring the radial profile of the peak voltage drop across a sheath between a 300 mm electrode and an argon plasma. The voltage drop across the sheath was derived by the integration of the electric field within the sheath, which was measured by using laserinduced fluorescence-dip spectroscopy.…”

Section: Experimental Diagnosticsmentioning

confidence: 97%

See 1 more Smart Citation

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: Discussionmentioning

confidence: 99%

Section: Experimental Diagnosticsmentioning

confidence: 97%

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

“…Recently, several experimental [28][29][30] and theoretical [30][31][32] studies have been published on the plasma characteristics in DF CCPs sustained by VHF sources. Hebner et al 28 performed measurements in a DF 300 mm-wafer plasma processing reactor, showing that the electron density was independent of the 13 MHz bias power as it increased from 0 to 1500 W when the high frequency (HF) was fixed at 60 MHz.…”

Section: Introductionmentioning

confidence: 99%

“…Hebner et al 28 performed measurements in a DF 300 mm-wafer plasma processing reactor, showing that the electron density was independent of the 13 MHz bias power as it increased from 0 to 1500 W when the high frequency (HF) was fixed at 60 MHz. Barnat et al 29 revealed that the radial distribution of the voltage drop across the sheath became nonuniform at the frequency of 60 MHz, and the nonuniformity was still present when a LF (13.56 MHz) source was applied to the electrode together with a HF (60 MHz) source. Bera et al 30 proved that, by a combination of computational modeling and diagnostic experiments, VHF mixing was an effective method for dynamically controlling the plasma uniformity.…”

Section: Introductionmentioning

confidence: 99%

Modeling and experimental investigation of the plasma uniformity in CF4/O2 capacitively coupled plasmas, operating in single frequency and dual frequency regime

Zhang

Tinck

Schepper

et al. 2015

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

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A two-dimensional hybrid Monte Carlo-fluid model, incorporating a full-wave solution of Maxwell's equations, is employed to describe the behavior of high frequency (HF) and very high frequency capacitively coupled plasmas (CCPs), operating both at single frequency (SF) and dual frequency (DF) in a CF 4 /O 2 gas mixture. First, the authors investigate the plasma composition, and the simulations reveal that besides CF 4 and O 2 , also COF 2 , CF 3 , and CO 2 are important neutral species, and CF þ 3 and F À are the most important positive and negative ions. Second, by comparing the results of the model with and without taking into account the electromagnetic effects for a SF CCP, it is clear that the electromagnetic effects are important, both at 27 and 60 MHz, because they affect the absolute values of the calculation results and also (to some extent) the spatial profiles, which accordingly affects the uniformity in plasma processing. In order to improve the plasma radial uniformity, which is important for the etch process, a low frequency (LF) source is added to the discharge. Therefore, in the major part of the paper, the plasma uniformity is investigated for both SF and DF CCPs, operating at a HF of 27 and 60 MHz and a LF of 2 MHz. For this purpose, the authors measure the etch rates as a function of position on the wafer in a wide range of LF powers, and the authors compare them with the calculated fluxes toward the wafer of the plasma species playing a role in the etch process, to explain the trends in the measured etch rate profiles. It is found that at a HF of 60 MHz, the uniformity of the etch rate is effectively improved by adding a LF power of 2 MHz and 300 W, while its absolute value increases by about 50%, thus a high etch rate with a uniform distribution is observed under this condition. V

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“…1- 10 However, when VHF is applied in a large-scale reactor having an electrode diameter greater than 30 cm, the standing-wave and skin effects become serious and limit the plasma spatial uniformity, which may affect the process characteristics. 1,2 For this reason, during the past years, VHF-CCP discharge has become the object of systematic investigations.…”

Section: Introductionmentioning

confidence: 99%

Effect on plasma and etch-rate uniformity of controlled phase shift between rf voltages applied to powered electrodes in a triode capacitively coupled plasma reactor

Sung¹,

Jeong²,

Park³

et al. 2008

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

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The influence of the phase shift between rf voltages applied to the powered electrodes on plasma parameters and etch characteristics was studied in a very high-frequency ͑VHF͒ capacitively coupled plasma ͑CCP͒ triode reactor. rf voltages at 100 MHz were simultaneously applied to the top and bottom electrodes having a controlled phase shift between them, which could be varied between 0°and 360°. Several plasma and process characteristics were measured as a function of the phase shift: ͑i͒ radial profiles of plasma-emission intensity, ͑ii͒ line-of-sight averaged plasma-emission intensity, and ͑iii͒ radial profiles of blanket SiO 2 etching rate over a 300 mm wafer. Radial profiles of plasma emission were obtained using the scanning optical probe. It has been shown that all the measured characteristics strongly depend on the phase shift: ͑i͒ plasma-emission intensity is minimal at phase shift equal to 0°and maximal at 180°for all radial positions, while the emission radial profile changes from bell-shaped distribution with considerable nonuniformity at 0°to a much more flattened distribution at 180°; ͑ii͒ line-of-sight averaged plasma-emission intensity shows a similar dependence on the phase shift with minimum and maximum at 0°and 180°, respectively; and ͑iii͒ the etch-rate radial profile at 180°shows a much better uniformity as compared to that at 0°. Some of these results can be qualitatively explained by the redistribution of plasma currents that flow between the electrodes and also from the electrodes to the grounded wall with the phase shift. We suggest that the phase-shift effect can be used to improve the plasma and etch-rate spatial uniformity in VHF-CCP triode reactors.

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Measured radial dependence of the peak sheath voltages present in very high frequency capacitive discharges

Cited by 17 publications

References 20 publications

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

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

Modeling and experimental investigation of the plasma uniformity in CF4/O2 capacitively coupled plasmas, operating in single frequency and dual frequency regime

Effect on plasma and etch-rate uniformity of controlled phase shift between rf voltages applied to powered electrodes in a triode capacitively coupled plasma reactor

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