Improved fluid simulations of radio-frequency plasmas using energy dependent ion mobilities

Greb, Arthur; Niemi, Kari; O’Connell, Deborah; Ennis, Gerard J.; MacGearailt, Niall; Gans, Timo

doi:10.1063/1.4804280

Cited by 16 publications

(26 citation statements)

References 34 publications

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“…In this work, a self-consistent one-dimensional (1D) fluid model, incorporating a semi-kinetic treatment of electrons and energy dependent ion mobilities is used [65]. The domain is a 1D slice of a typical geometrically symmetric CCP reactor with a discharge gap of 25mm, similar to various commercial and research systems [22,34,66].…”

Section: Numerical Simulationmentioning

confidence: 99%

“…The domain is a 1D slice of a typical geometrically symmetric CCP reactor with a discharge gap of 25mm, similar to various commercial and research systems [22,34,66]. The simulation approach and governing equations are described in detail in [65]. Briefly, the simulation solves the mass and momentum (via the drift-diffusion approximation) conservation equations for electrons and ions.…”

Section: Numerical Simulationmentioning

confidence: 99%

“…Increases in ion temperature as a result of strong electric fields, such as in the plasma sheath, are approximated using a semi-empirical formula describing ion heating in an electric field. Furthermore, the dependence of the ion mobility on the reduced electric field is accounted for by interpolation of experimentally measured ion mobilities in the low field limit and extrapolation of these values to the high field limit assuming a rigid sphere model [65].…”

Section: Numerical Simulationmentioning

confidence: 99%

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Controlling plasma properties under differing degrees of electronegativity using odd harmonic dual frequency excitation

Gibson

Gans

2017

Plasma Sources Sci. Technol.

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The charged particle dynamics in low-pressure oxygen plasmas excited by odd harmonic dual frequency waveforms (low frequency of 13.56 MHz and high frequency of 40.68 MHz) are investigated using a one-dimensional numerical simulation in regimes of both low and high electronegativity. In the low electronegativity regime, the time and space averaged electron and negative ion densities are approximately equal and plasma sustainment is dominated by ionisation at the sheath expansion for all combinations of low and high frequency and the phase shift between them. In the high electronegativity regime, the negative ion density is a factor of 15-20 greater than the low electronegativity cases. In these cases, plasma sustainment is dominated by ionisation inside the bulk plasma and at the collapsing sheath edge when the contribution of the high frequency to the overall voltage waveform is low. As the high frequency component contribution to the waveform increases, sheath expansion ionisation begins to dominate. It is found that the control of the average voltage drop across the plasma sheath and the average ion flux to the powered electrode are similar in both regimes of electronegativity, despite the differing electron dynamics using the considered dual frequency approach. This offers potential for similar control of ion dynamics under a range of process conditions, independent of the electronegativity. This is in contrast to ion control offered by electrically asymmetric waveforms where the relationship between the ion flux and ion bombardment energy is dependent upon the electronegativity.

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Section: Numerical Simulationmentioning

confidence: 99%

Section: Numerical Simulationmentioning

confidence: 99%

Section: Numerical Simulationmentioning

confidence: 99%

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Controlling plasma properties under differing degrees of electronegativity using odd harmonic dual frequency excitation

Gibson

Gans

2017

Plasma Sources Sci. Technol.

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“…Utilizing these cross-sections, the Monte-Carlo code described in the previous section yielded mobilities for the He + ions in a He gas under atmospheric pressure, which we approximated by the analytical fits listed in the Table II. A better fit can be made to match expected the high field asymptotics, µ ∝ E −0.5 (see the discussion in [18]), more accurately, yet we have found that the simple formula given in Table II gives a good agreement for E < 5 × 10 6 V/m, which is the range of the electric field values observed in the simulations. Similarly, the analytical fit for the momentum exchange frequency in the elastic scattering between He + ions and He atoms is listed in Table III.…”

Section: Validation Of the Hybrid Codementioning

confidence: 57%

A new hybrid scheme for simulations of highly collisional RF-driven plasmas

Eremin

Hemke

Mussenbrock

2015

Plasma Sources Sci. Technol.

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This work describes a new 1D hybrid approach for modeling atmospheric pressure discharges featuring complex chemistry. In this approach electrons are described fully kinetically using ParticleIn-Cell/Monte-Carlo (PIC/MCC) scheme, whereas the heavy species are modeled within a fluid description. Validity of the popular drift-diffusion approximation is verified against a "full" fluid model accounting for the ion inertia and a fully kinetic PIC/MCC code for ions as well as electrons.The fluid models require knowledge of the momentum exchange frequency and dependence of the ion mobilities on the electric field when the ions are in equilibrium with the latter. To this end an auxiliary Monte-Carlo scheme is constructed. It is demonstrated that the drift-diffusion approximation can overestimate ion transport in simulations of RF-driven discharges with heavy ion species operated in the γ mode at the atmospheric pressure or in all discharge simulations for lower pressures. This can lead to exaggerated plasma densities and incorrect profiles provided by the drift-diffusion models. Therefore, the hybrid code version featuring the full ion fluid model should be favored against the more popular drfit-diffusion model, noting that the suggested numerical scheme for the former model implies only a small additional computational cost.

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“…A detailed description of the set of equations and associated conditions as utilized in this work can be found in Ref. 16 and the references therein.…”

Section: All Article Content Except Where Otherwise Noted Is Licensmentioning

confidence: 99%

Electron heating and mode transition in dual frequency atmospheric pressure argon dielectric barrier discharge

et al. 2017

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Plasma ionization, excitation, mode transitions and associated electron heating mechanisms in atmospheric pressure dielectric barrier discharges (DBD) driven by dual radio frequency sources are investigated in this paper. The electrons are found to be heated mainly by the high frequency component in the plasma bulk when discharged in α mode. On the contrary, the low frequency component is primarily responsible for heating in the sheath which is caused by intense motion in the sheath. It was also found that variation of the lower frequency component ratio could effectively modulate the electron energy distribution as determined from time averaged EEDF. The results above have demonstrated that the independent control of plasma parameters via non-linear synergistic effect between the dual frequency sources can be achieved through reasonable selection of processing parameters.

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Improved fluid simulations of radio-frequency plasmas using energy dependent ion mobilities

Cited by 16 publications

References 34 publications

Controlling plasma properties under differing degrees of electronegativity using odd harmonic dual frequency excitation

Controlling plasma properties under differing degrees of electronegativity using odd harmonic dual frequency excitation

A new hybrid scheme for simulations of highly collisional RF-driven plasmas

Electron heating and mode transition in dual frequency atmospheric pressure argon dielectric barrier discharge

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