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Sahu BB, Nakane K, Ishikawa K, Sekine M, Tsutsumi T, Gohira T, Ohya Y, Ohno N, Hori M. Study of optical emission spectroscopy using modified Boltzmann plot in dual-frequency synchronized pulsed capacitively coupled discharges with DC bias at low-pressure in Ar/O 2/C 4F 8 plasma etching process. Phys Chem Chem Phys 2022; 24:13883-13896. [PMID: 35621157 DOI: 10.1039/d2cp00289b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We consider the corona model and local thermal equilibrium approximations of a real plasma to measure the electron temperature (Te) and density (ne), respectively, using the optical emission spectroscopy (OES) method in dual-frequency pulsed capacitively coupled plasmas (CCPs) in a reactive mixture of Ar/O2/C4F8 at a low operating pressure. The operation conditions such as DC continuous and synchronized were used for the study and plasma characterization for the intended plasma application such as high aspect ratio etching (HARE). We show that the present plasma conditions are dominated by a corona balance rather than the supremacy of multi-step excitation. This fact has enabled us to utilize the modified Boltzmann plot technique to evaluate the Te values. In the second method, we simultaneously used the Boltzmann and Saha equations to determine the ne value using the line intensity ratio and the value of Te. Time-resolved measurements of Te and ne were performed for completeness, and the insight of the pulsed discharge was investigated. Time evolution of ne and Te using the OES method revealed a similar trend in the change of plasma parameters, indicating electron impact ionization during the pulse on phase. It was seen that ne in the afterglow speedily decreased within a short time of ∼5 μs. Analysis suggests the formation of afterglow plasmas, which are composed of positive and negative ions with very low electron density. The results revealed that the DC-synchronized operation could be useful for plasma application such as HARE due to different plasma characteristics. It also suggests the production of ion-ion plasmas by the effective utilization of negative ions in the afterglow phase. The corona balance condition was validated in our experiments, and the results were compared with the existing literature.
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Affiliation(s)
- Bibhuti Bhusan Sahu
- Center for Low-temperature Plasma Sciences, Nagoya University, Nagoya 464-8601, Japan. .,Multi-Functional Plasma Laboratory, Department of Energy Science and Engineering, Indian Institute of Technology Delhi, Delhi-110016, India
| | - Kazuya Nakane
- Center for Low-temperature Plasma Sciences, Nagoya University, Nagoya 464-8601, Japan.
| | - Kenji Ishikawa
- Center for Low-temperature Plasma Sciences, Nagoya University, Nagoya 464-8601, Japan.
| | - Makoto Sekine
- Center for Low-temperature Plasma Sciences, Nagoya University, Nagoya 464-8601, Japan.
| | - Takayoshi Tsutsumi
- Center for Low-temperature Plasma Sciences, Nagoya University, Nagoya 464-8601, Japan.
| | - Taku Gohira
- Tokyo Electron Miyagi Ltd., Kurokawa, Miyagi 981-3629, Japan
| | - Yoshinobu Ohya
- Tokyo Electron Miyagi Ltd., Kurokawa, Miyagi 981-3629, Japan
| | - Noriyasu Ohno
- Center for Low-temperature Plasma Sciences, Nagoya University, Nagoya 464-8601, Japan. .,Department of Energy Engineering & Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Masaru Hori
- Center for Low-temperature Plasma Sciences, Nagoya University, Nagoya 464-8601, Japan.
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Sun GY, Sun AB, Zhang GJ. Intense boundary emission destroys normal radio-frequency plasma sheath. Phys Rev E 2020; 101:033203. [PMID: 32289891 DOI: 10.1103/physreve.101.033203] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 02/12/2020] [Indexed: 11/07/2022]
Abstract
The plasma sheath is the non-neutral space charge region that isolates bulk plasma from a boundary. Radio-frequency (RF) sheaths are formed when applying RF voltage to electrodes. Generally, applied bias is mainly consumed by a RF sheath, which shields an external field. Here we report evidence that an intense boundary emission destroys a normal RF sheath and establishes a type of RF plasma where external bias is consumed by bulk plasma instead of a sheath. Ions are naturally confined while plasma electrons are unobstructed, generating a strong RF current in the entire plasma, combined with a unique particle and energy balance. The proposed model offers the possibility for ion erosion mitigation of a plasma-facing component. It also inspires techniques for reaction rate control in plasma processing and wave mode conversion.
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Affiliation(s)
- Guang-Yu Sun
- Research Center for Advanced High Voltage and Plasma Technology, State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - An-Bang Sun
- Research Center for Advanced High Voltage and Plasma Technology, State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Guan-Jun Zhang
- Research Center for Advanced High Voltage and Plasma Technology, State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
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Jiang XZ, Li WL, Wumaier T, Yao HB. Diagnostic study of argon and oxygen mixtures in dual-frequency capacitively coupled plasmas using quadrupole mass spectrometer. Chem Phys Lett 2019. [DOI: 10.1016/j.cplett.2019.06.044] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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4
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Zhao K, Wen DQ, Liu YX, Lieberman MA, Economou DJ, Wang YN. Observation of Nonlinear Standing Waves Excited by Plasma-Series-Resonance-Enhanced Harmonics in Capacitive Discharges. PHYSICAL REVIEW LETTERS 2019; 122:185002. [PMID: 31144895 DOI: 10.1103/physrevlett.122.185002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 03/20/2019] [Indexed: 06/09/2023]
Abstract
We report the first experimental observation of nonlinear standing waves excited by plasma-series-resonance-enhanced harmonics in low pressure, very high frequency, parallel plate, capacitively coupled plasmas. Spatial structures of the harmonics of the magnetic field, measured by a magnetic probe, are in very good agreement with simulations based on a nonlinear electromagnetics model. At relatively low pressure, the nonlinear sheath motion generates high-order harmonics that can be strongly enhanced near the series resonance frequencies. Satisfying certain conditions, such nonlinear harmonics induce radial standing waves, with voltage and current maxima on axis, resulting in center-high plasma density. Excitation of higher harmonics is suppressed at higher pressures.
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Affiliation(s)
- Kai Zhao
- Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams (Ministry of Education), School of Physics, Dalian University of Technology, Dalian 116024, China
- Plasma Processing Laboratory, Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, USA
| | - De-Qi Wen
- Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams (Ministry of Education), School of Physics, Dalian University of Technology, Dalian 116024, China
| | - Yong-Xin Liu
- Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams (Ministry of Education), School of Physics, Dalian University of Technology, Dalian 116024, China
| | - Michael A Lieberman
- Department of Electrical Engineering, University of California, Berkeley, California 94720, USA
| | - Demetre J Economou
- Plasma Processing Laboratory, Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, USA
| | - You-Nian Wang
- Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams (Ministry of Education), School of Physics, Dalian University of Technology, Dalian 116024, China
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Park S, Choe W, Moon SY, Shi JJ. Electron Information in Single- and Dual-Frequency Capacitive Discharges at Atmospheric Pressure. Sci Rep 2018; 8:7516. [PMID: 29760408 PMCID: PMC5951922 DOI: 10.1038/s41598-018-25892-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 04/26/2018] [Indexed: 11/25/2022] Open
Abstract
Determining the electron properties of weakly ionized gases, particularly in a high electron-neutral collisional condition, is a nontrivial task; thus, the mechanisms underlying the electron characteristics and electron heating structure in radio-frequency (rf) collisional discharges remain unclear. Here, we report the electrical characteristics and electron information in single-frequency (4.52 MHz and 13.56 MHz) and dual-frequency (a combination of 4.52 MHz and 13.56 MHz) capacitive discharges within the abnormal α-mode regime at atmospheric pressure. A continuum radiation-based electron diagnostic method is employed to estimate the electron density (ne) and temperature (Te). Our experimental observations reveal that time-averaged ne (7.7–14 × 1011 cm−3) and Te (1.75–2.5 eV) can be independently controlled in dual-frequency discharge, whereas such control is nontrivial in single-frequency discharge, which shows a linear increase in ne and little to no change in Te with increases in the rf input power. Furthermore, the two-dimensional spatiotemporal evolution of neutral bremsstrahlung and associated electron heating structures is demonstrated. These results reveal that a symmetric structure in electron heating becomes asymmetric (via a local suppression of electron temperature) as two-frequency power is simultaneously introduced.
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Affiliation(s)
- Sanghoo Park
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Wonho Choe
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea. .,Department of Physics, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea.
| | - Se Youn Moon
- Department of Quantum System Engineering, Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju, 54896, Republic of Korea
| | - Jian Jun Shi
- College of Science, Donghua University, Shanghai, 201620, China
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Yang S, Zhang Y, Wang HY, Wang S, Jiang W. Electrical asymmetry effects in magnetized capacitively coupled plasmas in argon. ACTA ACUST UNITED AC 2017. [DOI: 10.1088/1361-6595/aa6ef1] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Bruneau B, Gans T, O'Connell D, Greb A, Johnson EV, Booth JP. Strong ionization asymmetry in a geometrically symmetric radio frequency capacitively coupled plasma induced by sawtooth voltage waveforms. PHYSICAL REVIEW LETTERS 2015; 114:125002. [PMID: 25860749 DOI: 10.1103/physrevlett.114.125002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Indexed: 06/04/2023]
Abstract
The ionization dynamics in geometrically symmetric parallel plate capacitively coupled plasmas driven by radio frequency tailored voltage waveforms is investigated using phase resolved optical emission spectroscopy (PROES) and particle-in-cell (PIC) simulations. Temporally asymmetric waveforms induce spatial asymmetries and offer control of the spatiotemporal dynamics of electron heating and associated ionization structures. Sawtooth waveforms with different rise and fall rates are employed using truncated Fourier series approximations of an ideal sawtooth. Experimental PROES results obtained in argon plasmas are compared with PIC simulations, showing excellent agreement. With waveforms comprising a fast voltage drop followed by a slower rise, the faster sheath expansion in front of the powered electrode causes strongly enhanced ionization in this region. The complementary waveform causes an analogous effect in front of the grounded electrode.
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Affiliation(s)
- Bastien Bruneau
- LPICM-CNRS, Ecole Polytechnique, route de Saclay, 91120 Palaiseau, France
| | - Timo Gans
- York Plasma Institute, Department of Physics, University of York, Heslington, YO10 5DD York, United Kingdom
| | - Deborah O'Connell
- York Plasma Institute, Department of Physics, University of York, Heslington, YO10 5DD York, United Kingdom
| | - Arthur Greb
- York Plasma Institute, Department of Physics, University of York, Heslington, YO10 5DD York, United Kingdom
| | - Erik V Johnson
- LPICM-CNRS, Ecole Polytechnique, route de Saclay, 91120 Palaiseau, France
| | - Jean-Paul Booth
- LPP-CNRS, Ecole Polytechnique, route de Saclay, 91120 Palaiseau, France
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Liu YX, Zhang QZ, Jiang W, Hou LJ, Jiang XZ, Lu WQ, Wang YN. Collisionless bounce resonance heating in dual-frequency capacitively coupled plasmas. PHYSICAL REVIEW LETTERS 2011; 107:055002. [PMID: 21867075 DOI: 10.1103/physrevlett.107.055002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2011] [Indexed: 05/31/2023]
Abstract
We present the experimental evidence of the collisionless electron bounce resonance heating (BRH) in low-pressure dual-frequency capacitively coupled plasmas. In capacitively coupled plasmas at low pressures when the discharge frequency and gap satisfy a certain resonant condition, the high energy beamlike electrons can be generated by fast sheath expansion, and heated by the two sheaths coherently, thus the BRH occurs. By using a combined measurement of a floating double probe and optical emission spectroscopy, we demonstrate the effect of BRH on plasma properties, such as plasma density and light emission, especially in dual-frequency discharges.
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Affiliation(s)
- Yong-Xin Liu
- School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian, China
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Mussenbrock T, Brinkmann RP, Lieberman MA, Lichtenberg AJ, Kawamura E. Enhancement of ohmic and stochastic heating by resonance effects in capacitive radio frequency discharges: a theoretical approach. PHYSICAL REVIEW LETTERS 2008; 101:085004. [PMID: 18764627 DOI: 10.1103/physrevlett.101.085004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2008] [Indexed: 05/26/2023]
Abstract
In low-pressure capacitive radio frequency discharges, two mechanisms of electron heating are dominant: (i) Ohmic heating due to collisions of electrons with neutrals of the background gas and (ii) stochastic heating due to momentum transfer from the oscillating boundary sheath. In this work we show by means of a nonlinear global model that the self-excitation of the plasma series resonance which arises in asymmetric capacitive discharges due to nonlinear interaction of plasma bulk and sheath significantly affects both Ohmic heating and stochastic heating. We observe that the series resonance effect increases the dissipation by factors of 2-5. We conclude that the nonlinear plasma dynamics should be taken into account in order to describe quantitatively correct electron heating in asymmetric capacitive radio frequency discharges.
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Affiliation(s)
- T Mussenbrock
- Institute for Theoretical Electrical Engineering, Center for Plasma Science and Technology, Ruhr University Bochum, D-44780 Bochum, Germany
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