Resonant sheath heating in weakly magnetized capacitively coupled plasmas due to electron-cyclotron motion

Zhang, Quan‐Zhi; Sun, Jing-Yu; Lu, Wen‐Zhong; Schulze, Julian; Guo, Yongan; Wang, You‐Nian

doi:10.1103/physreve.104.045209

Cited by 31 publications

(28 citation statements)

References 47 publications

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“…Recently, a new operational regime is identified in low-pressure very high frequency (VHF) CCP discharge in the presence of a weak uniform external magnetic field. It is shown that high plasma density and thereby high ion flux can be achieved even at a very weak external magnetic field (~ 10 G) where ion energy can also be optimized simultaneously [34][35][36][37][38]. It is also reported in the literature that using magnetic field asymmetry in single-frequency CCP can independently control the ion flux and ion energy [39][40].…”

Section: Introductionmentioning

confidence: 96%

High frequency sheath modulation and higher harmonic generation in a low pressure very high frequency capacitively coupled plasma excited by sawtooth waveform

Sharma

Sirse

Turner

2020

Plasma Sources Sci. Technol.

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A particle-in-cell simulation study is performed to investigate the discharge asymmetry, higher harmonic generations and electron heating mechanism in a low pressure capacitively coupled plasma excited by a saw-tooth like current waveform for different driving frequencies; 13.56 MHz, 27.12 MHz, and 54.24 MHz. Two current densities, 50 A m−2 and 100 A m−2 are chosen for a constant gas pressure of 5 mTorr in argon plasma. At a lower driving frequency, high frequency modulations on the instantaneous sheath electric field near to the grounded electrode are observed. These high frequency oscillations create multiple ionization beam like structures near to the sheath edge that drives the plasma density in the discharge and responsible for discharge/ionization asymmetry at lower driving frequency. Conversely, the electrode voltage shows higher harmonics generation at higher driving frequencies and corresponding electric field transients are observed into the bulk plasma. At lower driving frequency, the electron heating is maximum near to the sheath edge followed by electron cooling within plasma bulk, however, alternate heating and cooling i.e. burst like structures are obtained at higher driving frequencies. These results suggest that electron heating in these discharges will not be described accurately by simple analytical models.

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Section: Introductionmentioning

confidence: 96%

High frequency sheath modulation and higher harmonic generation in a low pressure very high frequency capacitively coupled plasma excited by sawtooth waveform

Sharma

Sirse

Turner

2020

Plasma Sources Sci. Technol.

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“…[23] Very recently, Zhang et al revealed another similar resonance heating effect in a weakly magnetized CCP at low pressure. [24] If half of the electron cyclotron period coincides with the RF period, electrons will coherently collide with the expanding sheath and gain substantial energy via each interaction, which significantly enhances the plasma density. The dynamics can be revealed in Fig.…”

Section: Electron Heatingmentioning

confidence: 99%

Fundamental study towards a better understanding of low pressure radio-frequency plasmas for industrial applications

Liu¹,

Zhang²,

Zhao³

et al. 2022

Chinese Phys. B

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Two classic radio-frequency (RF) plasmas, i.e., the capacitively and the inductively coupled plasma (CCP and ICP), are widely employed in material processing, e.g., etching and thin film deposition, etc. Since RF plasmas are usually operated in particular circumstances, e.g., low pressures (mTorr ~ Torr), high-frequency electric field (13.56 MHz ~200 MHz), reactive feedstock gases, diverse reactor configurations, etc., a variety of physical phenomena, e.g., electron resonance heating, discharge mode transitions, striated structures, standing wave effects, etc., arise. These physical effects could significantly influence plasma-based material processing. Therefore, understanding the fundamental processes of RF plasma is not only of fundamental interest, but also of practical significance for the improvement of the performance of the plasma sources. In this article, we review the major progresses that have been achieved in the fundamental study on the RF plasmas, and the topics include 1) electron heating mechanism, 2) plasma operation mode, 3) pulse modulated plasma, and 4) electromagnetic effects. These topics cover the typical issues in RF plasma field, ranging from fundamental to application.

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“…Another electron heating mechanism related to the magnetic field and based on the resonance between the sheath motion and the Larmor rotation leading to the condition ω = 2 ω ce was investigated in [25] and named there "electron sheath resonance". Recently, it has been revisited in a number of papers [26,27,28], where it acquired a new name "electron bounce-cyclotron resonance heating". This effect, however, requires rather weak magnetic fields (e.g., for the driving frequency of 13.56 MHz studied in the present work the resonance condition leads to B = 0.24 mT).…”

Section: Introductionmentioning

confidence: 99%

Electron dynamics in planar radio frequency magnetron plasmas: II. Heating and energization mechanisms studied via a 2d3v particle-in-cell/Monte Carlo code

Eremin¹,

Berger²,

Engel³

et al. 2022

Preprint

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The present work investigates electron transport and heating mechanisms using an (r, z) particle-in-cell (PIC) simulation of a typical rf-driven axisymmetric magnetron discharge with a conducting target. Due to a strong geometric asymmetry and a blocking capacitor, the discharge features a large negative self-bias conducive to sputtering applications. Employing decomposition of the electron transport parallel and perpendicular to the magnetic field lines, it is shown that for the considered magnetic field topology the electron current flows through different channels in the (r, z) plane: a "transverse" one, which involves current flow through the electrons' magnetic confinement region (EMCR) above the racetrack, and two "longitudinal" ones, where electrons' guiding centers move along the magnetic field lines. Electrons gain energy from the electric field along these channels following various mechanisms, which are rather distinct from those sustaining dc-powered magnetrons. The longitudinal power absorption involves mirror-effect heating (MEH), nonlinear electron resonance heating (NERH), magnetized bounce heating (MBH), and the heating by the ambipolar field at the sheath-presheath interface. The MEH and MBH represent two new mechanisms missing from the previous literature. The MEH is caused by a reversed electric field needed to overcome the mirror force generated in a nonuniform magnetic field to ensure sufficient flux of electrons to the powered electrode, and the MBH is related to a possibility for an electron to undergo multiple reflections from the expanding sheath in the longitudinal channels connected by the arc-like magnetic field. The electron heating in the transverse channel is caused mostly by the essentially collisionless Hall heating in the EMCR above the racetrack, generating a strong E × B azimuthal drift velocity. The latter mechanism results in an efficient electron energization, i.e., energy transfer from the electric field to electrons in the inelastic range. Since the main electron population energized by this mechanism remains

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Resonant sheath heating in weakly magnetized capacitively coupled plasmas due to electron-cyclotron motion

Cited by 31 publications

References 47 publications

High frequency sheath modulation and higher harmonic generation in a low pressure very high frequency capacitively coupled plasma excited by sawtooth waveform

High frequency sheath modulation and higher harmonic generation in a low pressure very high frequency capacitively coupled plasma excited by sawtooth waveform

Fundamental study towards a better understanding of low pressure radio-frequency plasmas for industrial applications

Electron dynamics in planar radio frequency magnetron plasmas: II. Heating and energization mechanisms studied via a 2d3v particle-in-cell/Monte Carlo code

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