Hybrid simulation of instabilities in capacitively coupled RF CF4/Ar plasmas

2022 ◽  
Author(s):  
Wan Dong ◽  
Yi Fan Zhang ◽  
ZhongLing Dai ◽  
Julian Schulze ◽  
Yuan-Hong Song ◽  
...  
Keyword(s):  
Electric Field ◽  
Electron Temperature ◽  
Electron Impact ◽  
Electron Density ◽  
Etching Rate ◽  
Reaction Rates ◽  
High Energy ◽  
Density Fluctuations ◽  
Negative Ion ◽  
Capacitively Coupled

Abstract Radio frequency capacitively coupled plasmas (RF CCPs) sustained in fluorocarbon gases or their mixtures with argon are widely used in plasma-enhanced etching. In this work, we conduct studies on instabilities in a capacitive CF4/Ar (1:9) plasma driven at 13.56 MHz at a pressure of 150 mTorr, by using a one-dimensional fluid/Monte-Carlo (MC) hybrid model. Fluctuations are observed in densities and fluxes of charged particles, electric field, as well as electron impact reaction rates, especially in the bulk. As the gap distance between the electrodes increases from 2.8 cm to 3.8 cm, the fluctuation amplitudes become smaller gradually and the instability period gets longer, as the driving power density ranges from 250 to 300 W/m2. The instabilities are on a time scale of 16-20 RF periods, much shorter than those millisecond periodic instabilities observed experimentally owing to attachment/detachment in electronegative plasmas. At smaller electrode gap, a positive feedback to the instability generation is induced by the enhanced bulk electric field in the highly electronegative mode, by which the electron temperature keeps strongly oscillating. Electrons at high energy are mostly consumed by ionization rather than attachment process, making the electron density increase and overshoot to a much higher value. And then, the discharge becomes weakly electronegative and the bulk electric field becomes weak gradually, resulting in the continuous decrease of the electron density as the electron temperature keeps at a much lower mean value. Until the electron density attains its minimum value again, the instability cycle is formed. The ionization of Ar metastables and dissociative attachment of CF4 are noticed to play minor roles compared with the Ar ionization and excitation at this stage in this mixture discharge. The variations of electron outflow from and negative ion inflow to the discharge center need to be taken into account in the electron density fluctuations, apart from the corresponding electron impact reaction rates. We also notice more than 20% change of the Ar+ ion flux to the powered electrode and about 16% difference in the etching rate due to the instabilities in the case of 2.8 cm gap distance, which is worthy of more attention for improvement of etching technology.

scholarly journals Diagnostics of low-pressure capacitively coupled RF discharge argon plasma

2019 ◽  
Vol 13 (27) ◽  
pp. 76-82
Author(s):  
Kadhim A. Aadim
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Langmuir Probe ◽  
Gas Flow ◽  
Low Pressure ◽  
Gas Pressure ◽  
Rf Discharge ◽  
Electrode Gap ◽  
Probe Characteristic ◽  
Capacitively Coupled

Low-pressure capacitively coupled RF discharge Ar plasma has been studied using Langmuir probe. The electron temperature, electron density and Debay length were calculated under different pressures and electrode gap. In this work the RF Langmuir probe is designed using 4MHz filter as compensation circuit and I-V probe characteristic have been investigated. The pressure varied from 0.07 mbar to 0.1 mbar while electrode gap varied from 2-5 cm. The plasma was generated using power supply at 4MHz frequency with power 300 W. The flowmeter is used to control Argon gas flow in the range of 600 standard cubic centimeters per minute (sccm). The electron temperature drops slowly with pressure and it's gradually decreased when expanding the electrode gap. As the gas pressure increases, the plasma density rises slightly at low gas pressure while it drops little at higher gas pressure. The electron density decreases rapidly with expand distances between electrodes.

scholarly journals Analysis of Observations near the Fourth Electron Gyrofrequency Heating Experiment in EISCAT

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 191
Author(s):  
Zeyun Li ◽  
Hanxian Fang ◽  
Hongwei Gong ◽  
Zhe Guo
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Parametric Instability ◽  
Density Fluctuations ◽  
Lower Hybrid ◽  
Langmuir Waves ◽  
Ionospheric Heating ◽  
Superthermal Electron ◽  
Temperature Electron ◽  
Electron Gyrofrequency

We present the observations of the artificial ionospheric heating experiment of EISCAT (European Incoherent Scatter Scientific Association) on 22 February 2012 in Tromsø, Norway. When the pump is operating near the fourth electron gyrofrequency, the UHF radar observation shows some strong enhancements in electron temperature, electron density, ion line, and the outshifted plasma lines. Based on some existing theories, we find the following: first, Langmuir waves scattering off lower hybrid density fluctuations and strong Langmuir turbulence (SLT) in the Zakharov model cannot completely explain the outshifted plasma lines, but the data suggest that this phenomenon is related to the cascade of the pump wave and should be researched further; second, the spatiotemporal consistency between the enhancement in electron density/electron temperature reaches up to three to four times that of the undisturbed state and HF-enhanced ion lines (HFILs) suggest that SLT excited by parametric instability plays a significant role in superthermal electron formation and electron acceleration; third, some enhancements in HFILs and HF-induced plasma lines (HFPLs) are generated by parametric decay instability (PDI) during underdense heating in the third cycle, we suggest that this is due to the existence of a second cut-off in the upper hybrid dispersion relation as derived from a kinetic description.

Characteristics of 2.45GHz Microwave Plasma by Langmuir Probe Measurements

2007 ◽  
Vol 124-126 ◽  
pp. 1621-1624 ◽  
Author(s):  
Sun Yong Choi ◽  
Wataru Minami ◽  
Lae Hyun Kim ◽  
Hee Joon Kim
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Microwave Power ◽  
Langmuir Probe ◽  
Microwave Plasma ◽  
Debye Length ◽  
Plasma Source ◽  
Mean Free Path ◽  
High Energy ◽  
Langmuir Probe Measurements

The characteristics, such as electron temperature and the electron density, of CF4/Ar discharge in 2.45GHz microwave has been investigated by using a Langmuir probe with the microwave power and position. The results showed that the electron temperature and the electron density decrease with increasing distance from the plasma source. Increasing power enhances the dissociation and ionization of gas, and increases the electron densities. The electron temperature was decreased by reducing the mean free path of electrons with increasing microwave power. The electron temperature is 7.63 ~ 2.49 eV, and the electron density is 0.85×1011 ~ 4.3×1011 cm-3. From obtained electron energy distribution function, we known that high energy electron decreased with increasing microwave power and distance from the plasma source. The generated plasma by developed our system has good quality as results of Debye length λD = 35.8 ~ 67.3 μm, and Ln(ND) = 33.4 ~ 35.2.

scholarly journals Estimation of electron-impact line widths for singly-, doubly- and triply-charged vanadium ions

1998 ◽  
pp. 109-114
Author(s):  
L.C. Popovic ◽  
M.S. Dimitrijevic
Keyword(s):  
Electron Temperature ◽  
Electron Impact ◽  
Electron Density ◽  
Semiempirical Method ◽  
Line Widths ◽  
Vanadium Ions

In this paper we present the electron-impact widths for 28 transitions of singly-, doubly-, and triply- ionized vanadium estimated by using the modified semiempirical method. The electron-impact widths have been estimated for the electron density of 1023m?3 and presented as a function of electron temperature.

scholarly journals Negative ions in the auroral mesosphere during a PCA event around sunset

1999 ◽  
Vol 17 (6) ◽  
pp. 782-793 ◽  
Author(s):  
C. F. del Pozo ◽  
E. Turunen ◽  
T. Ulich
Keyword(s):  
Electron Density ◽  
Negative Ions ◽  
Spectral Width ◽  
High Energy ◽  
Negative Ion ◽  
Ion Temperature ◽  
Ion Chemistry ◽  
Ion Chemistry And Composition ◽  
Proton Precipitation ◽  
Precipitation Events

Abstract. This is a study of the negative ion chemistry in the mesosphere above Tromsø using a number of EISCAT observations of high energy proton precipitation events during the last solar maximum, and in particular around sunset on 23 October, 1989. In these conditions it is possible to look at the relative importance of the various photodetachment and photodissociation processes controlling the concentration of negative ions. The data analysed are from several UHF GEN11 determinations of the ion-plasma ACF together with the pseudo zero-lag estimate of the `raw' electron density, at heights between 55 km and 85 km, at less than 1 km resolution. The power profiles from the UHF are combined with the 55-ion Sodankylä model to obtain consistent estimates of the electron density, the negative ion concentrations, and the average ion mass with height. The neutral concentrations and ion temperature are given by the MSIS90 model. These parameters are then used to compare the calculated widths of the ion-line with the GEN11 determinations. The ion-line spectrum gives information on the effects of negative ions below 70 km where they are dominant; the spectral width is almost a direct measure of the relative abundance of negative ions.Key words. Ionosphere (auroral ionosphere; ion chemistry and composition; particle precipitation).

The structure of the convection sustained ion sheath

1976 ◽  
Vol 54 (15) ◽  
pp. 1627-1636
Author(s):  
P. R. Smy
Keyword(s):  
Reynolds Number ◽  
Electric Field ◽  
Electron Temperature ◽  
Electron Density ◽  
Plasma Flow ◽  
Ion Mobility ◽  
Free Space ◽  
Characteristic Length ◽  
Electron Charge ◽  
Detailed Structure

The detailed structure of the convection sustained ion sheath has been examined. With Re = vfL/μikTe/e (the electric Reynolds number) and α = (ε0kTe/nee2)1/2(1/L), where vf = plasma flow velocity, μi = ion mobility, k = Boltzmann's constant, Te = electron temperature, e = electron charge, ε0 = permittivity of free space, ne = electron density, and L = characteristic length, it is found that for [Formula: see text], no 'presheath' or diminution of electron density outside the sheath is evident, whereas for [Formula: see text], a very substantial density gradient exists which is in fact similar to the quasi-neutral region which occurs in stationary plasmas. Calculations are presented which enable ion and electron densities and electric field and potential to be calculated through the presheath and sheath regions.

Electron and Ion Densities Measurement in Reactive Magnetron Zinc Sputtering Plasma

2013 ◽  
Vol 832 ◽  
pp. 344-349
Author(s):  
Nayan Nafarizal ◽  
Mohd Zainizan Sahdan ◽  
Riyaz Ahmad Mohamad Ali ◽  
Sharifah Amira ◽  
Salwa Omar ◽  
...  
Keyword(s):  
Thin Film ◽  
Electron Temperature ◽  
Electron Density ◽  
Flow Rate ◽  
Ion Bombardment ◽  
Oxygen Flow Rate ◽  
Oxygen Flow ◽  
Negative Ion ◽  
Reactive Magnetron ◽  
Working Pressure

Abstract. Investigation on the plasma properties is an essential fundamental works in order to precisely control the growth of nanoscale thin film. In the present work, we produced and study the reactive magnetron sputtering plasma in Ar+O2 ambient using a solid Zn target as sputter source. We evaluate the electron temperature, electron density and ion density using Langmuir probe measurement as a function of O2 flow rate and working pressure. We found that the electron temperature increased spontaneously with the oxygen flow rate. The electron temperature was almost doubled when O2 flow rate increased from 0 sccm to 10 sccm. The electron and ion densities increased with the oxygen flow rate between 0 sccm and 5 sccm. However, after 5 sccm of O2 flow rate which is approximately 11% of O2/(O2+Ar) flow rate ratio the electron density decreased drastically. This is due to the electron attachment and the production of negative ion species in Ar+O2 plasma environment. In addition, we found that the ion flux increase monotonically with the O2 flow rate thus will increase the ion bombardment effect on the deposited thin film and eventually damage the thin film. Our experimental results suggest that the O2 flow rate and the working pressure would have a significant influence on ion bombardment effect on deposited thin film.

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