Relation between the ion flux and plasma density in an rf CCP discharge

Bogdanova, Maria; Lopaev, Dmitry; Zyryanov, Sergey; Voloshin, Dmitry; Рахимова, Т. В.

doi:10.1088/1361-6595/aaa237

Cited by 10 publications

(13 citation statements)

References 55 publications

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“…This ratio characterizes the plasma density profile [67]. It was obtained in [68] by the flat probe measurements and the 2D PICMCC simulations [69] that in the absence of ionization in sheaths k-value depends on a gas pressure and is almost independent of a plasma density. For Ar plasma k-value changes with pressure from ∼0.55 for collisionless plasma to ∼0.15 at 200 mTorr [68].…”

Section: Resultsmentioning

confidence: 92%

“…It was obtained in [68] by the flat probe measurements and the 2D PICMCC simulations [69] that in the absence of ionization in sheaths k-value depends on a gas pressure and is almost independent of a plasma density. For Ar plasma k-value changes with pressure from ∼0.55 for collisionless plasma to ∼0.15 at 200 mTorr [68]. In the present work PIC MC simulation gives k∼0.2 that agrees well with the results [68] for Ar pressure of 100 mTorr.…”

Section: Resultsmentioning

confidence: 99%

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Experimental and PIC MCC study of electron cooling—re-heating and plasma density decay in low pressure rf ccp argon afterglow

Proshina

Рахимова

Kovalev

et al. 2020

Plasma Sources Sci. Technol.

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In this work, experimental and theoretical study of pulsed discharge in argon has been carried out. The experimental data on the dynamics of electron density, electron temperature, and plasma potential have been obtained by probe measurements (using hairpin and Langmuir probes) in the afterglow between two RF pulses. This dynamics is thoroughly analyzed by comparison with the results of the kinetic PIC MC simulations. The main processes that cause electron cooling have been revealed for two different time stages. The first afterglow stage is characterized by the rapid decrease of the electron temperature. During this stage, inelastic electron collisions with Ar atoms in the ground state play an important role in the electron cooling. During the second longscale stage, only diffusion along the electron energy scale via Coulomb or elastic collisions can provide the observed effect of the gradual electron cooling. The effects of elastic and Coulomb collisions on the electron cooling have been separated and analyzed by means of PIC MC simulations. The temporal evolution of the electron concentration spatial distribution and the plasma boundary sheaths size has been also analyzed on the base of 1D PIC MC simulations. A good agreement between the probe measurements and the PIC simulations data on plasma density, ambipolar potential and electron temperature is observed. To perform a more detailed study of EEDF and electron temperature dynamics, the relative intensity of Ar( 2 p 1 )→Ar( 1 s 2 ) emission at 750 nm has been measured. A very good agreement between the measured emission intensity and the calculated excitation rate of Ar( 2 p 1 ) at different time scales validates the electron temperature temporal dynamics obtained by the used PIC model.

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Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Experimental and PIC MCC study of electron cooling—re-heating and plasma density decay in low pressure rf ccp argon afterglow

Proshina

Рахимова

Kovalev

et al. 2020

Plasma Sources Sci. Technol.

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“…⁄ , if it is closer to a constant, or , if it is closer to the sine. But what is much more important for a correct estimation is to accurately measure the ion flux or the plasma density [15].…”

Section: Effect Of Sheath Thicknessmentioning

confidence: 99%

“…Conclusion is given in the last Section 5. Experiments to validate the concept of the virtual IED sensor are carried out in an asymmetric dual-frequency (df) rf CCP discharge [15,16]. It is schematically shown in figure 1 along with the diagnostics used.…”

Section: Introductionmentioning

confidence: 99%

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‘Virtual IED sensor’ for df rf CCP discharges

Bogdanova¹,

Lopaev²,

Рахимова³

et al. 2021

Plasma Sources Sci. Technol.

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Ion-assisted surface processes are the basis of modern plasma processing. Ion energy distribution (IED) control is critical for precise material modification, especially in atomic-level technologies such as atomic layer etching. Since this control should be done in "real time", it requires "real-time" feedback using fast process sensors. In the general case of an industrial plasma reactor, when direct IED measurement is not possible, the IED can be estimated using the concept of a "virtual IED sensor". In this paper, a similar "virtual IED sensor" is considered using an asymmetric dual-frequency (df) rf CCP discharge as an example. It is based on a fast calculation method of the IED at an rf-biased electrode. This approach uses the experimentally measured sheath voltage waveform and plasma density (or ion flux) as input data, and also includes Monte-Carlo simulation of ion motion in the sheath to take into account the effect of ion-neutral collisions. To validate this approach, experiments were carried out using various plasma diagnostics in several gases: argon and xenon as examples of plasma with atomic ions and nitrogen as an example of plasma with molecular ions. It is shown that in all cases it is possible to obtain an adequate IED estimation, close to the experimental one, in a reasonably short time ( tens of seconds when using a modern PC). The results obtained demonstrate the possibility of using a virtual IED sensor in real plasma processing.So, on the one hand, modern plasma processing requires the development of new plasma approaches and systems to ensure an appropriate level of control. On the other hand, this control requires the development of fast sensors.The dual-frequency (df) rf ICP and CCP discharges are widely used today in plasma surface treatment. The simultaneous use of high-frequency and low-frequency rf voltages is aimed at realizing separate control of ion flux and energy. This idea was presented in the works of Goto in the early 1990s [1,2]. Since then, these discharges have been extensively studied both experimentally and theoretically [3,4]. However, one of the main results of these studies is that the two frequencies are generally coupled and the desired functional separate control can only be achieved over a limited range of discharge parameters (frequencies, pressures, and input powers).The multi-frequency discharge excitation was also investigated [5] to reveal the role of the third frequency in controlling the IED shape [6]. In order to better control the ion energy, some new methods of rf discharge excitation have recently been developed. One of them is the excitation of a symmetric rf CCP discharge with two frequencies (the fundamental frequency and its second harmonic) with a phase shift between them. In this configuration, the dc self-bias voltage appears due to the electrical asymmetry effect (EAE) [7]. This voltage is adjusted by the phase shift value between the two frequencies and is used for additional control of ion energy. This idea was further developed in the so-call...

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Improved reliability of breakdown voltage measurement of yttrium oxide coatings by plasma spray

Song

Choi

et al. 2019

Ceramics International

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Relation between the ion flux and plasma density in an rf CCP discharge

Cited by 10 publications

References 55 publications

Experimental and PIC MCC study of electron cooling—re-heating and plasma density decay in low pressure rf ccp argon afterglow

Experimental and PIC MCC study of electron cooling—re-heating and plasma density decay in low pressure rf ccp argon afterglow

‘Virtual IED sensor’ for df rf CCP discharges

Improved reliability of breakdown voltage measurement of yttrium oxide coatings by plasma spray

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