By Topic

Plasma Science, IEEE Transactions on

Issue 5 • Date Oct. 1999

Filter Results

Displaying Results 1 - 25 of 43
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Guest editorial special issue on the modeling of collisional or near-collisionless low-temperature plasmas

    Page(s): 1223 - 1224
    Save to Project icon | Request Permissions | PDF file iconPDF (81 KB)  
    Freely Available from IEEE
  • A molecular dynamics simulation of ultrathin oxide films on silicon: Growth by thermal O atoms and sputtering by 100 eV Ar+ ions

    Page(s): 1416 - 1425
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    Molecular dynamics was applied to study the growth and sputtering of ultrathin oxide films on (100) Si surfaces. A multibody potential which stabilized the Si/SiO2 interface was used for this purpose. Oxide growth by exposure to O atoms was found to follow Langmuir-type kinetics with unity initial sticking coefficient of O and saturation coverage of around four monolayers, in agreement with experimental data. Sputtering of an ultrathin oxide film on silicon by 100 eV Ar+ ions was simulated to study ion-assisted surface cleaning. Ion irradiation was found to promote restructuring of the surface into oxide islands, as observed experimentally. Island formation was accompanied with an increase in surface roughness. The evolution of the surface state with ion dose was predicted quantitatively View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Benchmark calculations for Monte Carlo simulations of electron transport

    Page(s): 1241 - 1248
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    Benchmark calculations have been performed for electron transport coefficients with an aim to produce a body of data required to verify the codes used in plasma modeling. The present code for the time resolved Monte Carlo simulation (MCS) was shown to represent properly DC transport coefficients in a purely electric field, in crossed electric and magnetic fields, and in the presence of nonconservative collisions, ionization, and attachment. In addition, we have suggested tests of the time dependent solutions. Relaxation of the initial transport coefficient may serve as an accurate test of the code as well as the input data for some fluid codes. In this paper, we show only one example, but several different sets of conditions and cross sections should be used as well. Finally, we propose application of the quasi-steady state results in RF fields. As an example we suggest calculation of the components of diffusion tensor showing anomalous longitudinal diffusion and calculations made with nonconservative collisions (ionization in this case). We also check the application of approximate formulas to determine drift velocity on the basis of total collision frequency and to determine a diffusion coefficient by using the Einstein relation. Other tests required to verify the transport data calculations are discussed as well View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Study of open cavity filled with plasma density grating

    Page(s): 1495 - 1500
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB)  

    The dielectric open cavity filled with the plasma is studied. The plasma density grating formed by the slow wave modulation influences the resonant parameters. Based on an equivalent model of the plasma density grating, a dispersion relation is derived and the resonant frequency, the diffraction Q value, and the field function are calculated. The field magnitude in the slow-wave region increases greatly as the plasma density increases, which can help to explain the enhancement of the beam-wave interaction efficiency View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ion-beam-driven instabilities in bounded dusty plasmas

    Page(s): 1449 - 1453
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    The ion-beam dynamics is simulated for a bounded dusty plasma with the immobile dust particles. Since there is no dust motion, the growth of an instability is induced dominantly from the Pierce instability, but the beam motion is also greatly influenced by the Debye-shielding thermal electrons whose densities are determined from the Boltzmann relation. The analytic calculation of a dispersion relation shows the nonexistence of a uniform equilibrium which is confirmed by simulations. A period-doubling route to chaos is observed and the various nonlinear oscillations are classified in view of a diagnostic parameter which is applied to many other beam systems View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Experimental and theoretical investigation of oxygen glow discharge structure at low pressures

    Page(s): 1279 - 1287
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    An experimental and theoretical investigation of the oxygen glow discharge structure at low pressures has been performed. Radial dependencies of the electron energy distribution function, the ambipolar plasma potential, and the negative ion concentration, as well as the axial electric field and the concentrations of atomic and singlet oxygen were measured. A new approach to the application of laser photodetachment method has been used to measure the negative ion concentration. It allows one to obtain information about fast processes after the photodetachment at low frequencies (~100-200 Hz) by using the simplest modulation technique. A self-consistent model involving the electrodynamics and kinetics of the discharge was developed. The observed variations of the negative ion densities with current density and oxygen pressure were explained in the model frame by a dependence of the detachment rate constant of the O-+O→e+O2 process on the effective ion temperature (k=1.9·10-10-√1100/Tieff). It was shown that the feature of oxygen dc discharge at low pressures is a possibility to change the basic type of negative ions from the O- to the O2-. This effect become more pronounced with decreasing current density View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On approximations involved in the theory of charged particle transport in gases in electric and magnetic fields at arbitrary angles

    Page(s): 1249 - 1253
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB)  

    Various approximations and computer codes for the calculation of charged particle transport in gases in electric and magnetic fields have found their may into mainstream applications of various types. Some of these codes/approximations avoid the mathematical complexity associated with an accurate solution of Boltzmann's equation, but because of assumptions of symmetry and/or near isotropy in velocity space they may be incorrect. Using an accurate multiterm solution of Boltzmann's equation for electric and magnetic fields oriented at arbitrary angles with respect to each other, we highlight the inadequacies of such assumptions. In addition we explore the validity of Tonks' theorem and the effective field approximation as applied to the more general case of arbitrary orientation angles View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Nonlocal transport and dissipation properties of electrons in inhomogeneous plasmas

    Page(s): 1254 - 1261
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    The spatial evolution of the electron component in a neon plasma is investigated under the action of spatially inhomogeneous electric fields. In the center of the studies are those macroscopic quantities which describe the transport and the dissipation of power and momentum of the electrons. These quantities are determined from the velocity distribution function of the electrons obtained by the solution of the spatially inhomogeneous Boltzmann equation. Both a spatially limited disturbance of the field as well as a strongly modulated periodic field typical of s striations are considered. Moreover, the results of the strict kinetic treatment are compared with the corresponding ones obtained by the so-called local field approximation which corresponds to a hydrodynamic description of the electron component assuming a local compensation of power and momentum gain by the respective loss processes. The large deviation of both results from each other confirms the strongly nonlocal character of the electron transport and dissipation coefficients under the plasma conditions considered View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Studies of a sheath structure in an RF discharge using experimental, analytical, and simulation approaches

    Page(s): 1510 - 1515
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB)  

    Electric field distributions in a helium RF discharge in a collisional regime were measured using laser-induced fluorescence. The measured distributions and sheath thicknesses obtained from the electric field distributions were compared with those obtained from an existing analytical theory and with a numerical simulation, together with the thicknesses obtained using the Child-Langmuir law for a DC discharge. The comparison yielded reasonable agreement, both in general tendency with regard to the pressure dependence and in the absolute magnitude. These results provide, for the first time, evidence of the validity of these analytical and simulation approaches View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Direct simulation Monte Carlo analysis of flows and etch rate in an inductively coupled plasma reactor

    Page(s): 1379 - 1388
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (548 KB)  

    The direct simulation Monte Carlo (DSMC) method was employed to predict the etch rate distribution on Si wafer. The etchant is assumed to be Cl. The production rate of Cl due to electron impact was obtained separately by preprocessing an inductively coupled chlorine plasma by use of the particle-in-cell/Monte Carlo method. Under the condition of constant total pressure, the etch rate increases with the mass flow rate of source gas Cl2. The density of the etch product SiCl2 rapidly decreases with increasing the flow rate. The density of the etchant hardly depends on the flow rate. The recombination 2Cl→Cl2 on the inner walls of etching apparatus has a large effect on the etch rate; recombination probability of 0.1 results in 50% reduction of the etch rate. The etch rate distribution becomes more uniform when the reaction probability at the wafer surface is reduced View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Three-dimensional spatiokinetic distributions of sputtered and scattered products of Ar+ and Cu+ impacts onto the Cu surface: molecular dynamics simulations

    Page(s): 1426 - 1432
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    Energy and angular distributions of reflections and sputtered atoms are essential inputs for feature profile evolution simulations. Molecular dynamics simulations are used to compute the three-dimensional energy and angular distributions for reflected and sputtered products when both Ar+ and Cu+ ions bombard a copper surface. We term these “spatiokinetic” distribution functions (SKDF's). We show by example that SKDF's for reflected Ar+ ions focus as the incident angle θi (normal=0°) is increased from 60-75° and broaden as the incident energy Ei is increased from 55-175 eV. We show that the SKDF's for glancing-angle reflected Cu+ ions focus when Ei is increased from 55-175 eV. We show that the SKDF's for copper atoms sputtered by 175 eV Ar+ are insensitive to θi;. We report total sputter yields for Ar+ and Cu+ ions at 55 and 175 eV for incident angles between 0° and 85°, and sticking probabilities for Cu+ ions for these energies and angles. Comparison to representative experimental results (Doughty et al., 1997) is given View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Kinetic two-dimensional modeling of inductively coupled plasmas based on a hybrid kinetic approach

    Page(s): 1297 - 1309
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    In this paper, we present a two-dimensional (2-D) kinetic model for low-pressure inductively coupled discharges. The kinetic treatment of the plasma electrons is based on a hybrid kinetic scheme in which the range of electron energies is divided into two subdomains. In the low energy range the electron distribution function is determined from the traditional nonlocal approximation. In the high energy part the complete spatially dependent Boltzmann equation is solved. The scheme provides computational efficiency and enables inclusion of electron-electron collisions which are important in low-pressure high-density plasmas. The self-consistent scheme is complemented by a 2-D fluid model for the ions and the solution of the complex wave equation for the RF electric field. Results of this model are compared to experimental results. Good agreement in terms of plasma density and potential profiles is observed. In particular, the model is capable of reproducing the transition from on-axis to off-axis peaked density profiles as observed in experiments which underlines the significant improvements compared to models purely based on the traditional nonlocal approximation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dependence of resonance condition on pressure in an RF resonance method

    Page(s): 1353 - 1357
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB)  

    The plasma density is shown as functions of pressure and magnetic flux density in an RF resonance method using the XPDP1 simulation code. The RF resonance method has the unique feature that a strong electric field in bulk controls the plasma density. Owing to the balance between the electric field decrease and the collision rate increase, the plasma density in the RF resonance method has a peak with respect to pressure. The plasma density with respect to the magnetic flux density depends on the condition of the RF resonance method, and the dependence is strong at low pressure because of the strong resonance. Sheath thickness is the most important parameter that determines the strength of the resonance induced. It is shown that the sheath thickness s is related to the plasma density n as a function of ns, obtained from a dispersion relation at constant external parameters. The magnetic flux density which induces the strong resonance is determined from sheath thickness. The plasma density in the RF resonance method can be predicted from discharge parameters using the relation between plasma density and sheath thickness View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Extension of the nonlocal approach to evaluate the electron velocity distribution

    Page(s): 1271 - 1278
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    The method of the nonlocal approach is used to describe the spatially dependent electron kinetics in an inert gas dc column plasma taking into account the space charge confinement. The historical concept of the method, the applied simplification of the electron kinetic equation, and the specifications about its validity are critically discussed. The accuracy of the results are evaluated by means of detailed comparisons with a strict solution of the relevant kinetic equation based on the two-term approximation. An extension of the method is deduced to estimate the anisotropic part of the electron velocity distribution which allows an approximate description of the electron particle and power fluxes. These estimations are used for a consistent treatment of the spatially resolved electron power balance in the column plasma View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Two-dimensional modeling of a micro-cell plasma in Xe driven by high frequency

    Page(s): 1372 - 1378
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    Two-dimensional simulation of a micro-cell plasma driven by high frequency at 13.56 MHz is described in Xe. The minimum sustaining voltage (Vs)min in an ideal infinite parallel plates at high frequency is first discussed as a function of both pd and fd (f the applied frequency, d the electrode distance, and p the gas pressure). As decreasing d,(Vs)min increases at fixed f, while (Vs)min decreases with increasing fd at fixed pd in a high frequency discharge under the condition of a spatial ion trapping. A capability for maintaining a micro-cell plasma is investigated under fd<υ(de)/π for different two-dimensional geometry of the micro cell (υ(de) is the effective drift velocity of electrons). The influence of the secondary electron from the electrode becomes important for the maintenance of a microcell plasma and emission efficiency. A powered ring electrode and ground plate system realizes the micro-cell plasma with high density at 13.56 MHz View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Efficiency enhancement of a coaxial virtual cathode oscillator

    Page(s): 1543 - 1544
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (48 KB)  

    The microwave field intensity around the virtual cathode oscillator was enhanced by using a microwave reflector in the output waveguide. The experimental results show that the microwave output power strongly depends on the position and geometry of the microwave reflector. The maximum microwave efficiency obtained was twice as large as that without field enhancement by the microwave reflector View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Viscous effects on motion and heating of electrons in inductively coupled plasma reactors

    Page(s): 1310 - 1316
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (160 KB)  

    A transport model is developed for nonlocal effects on motion and heating of electrons in inductively coupled plasma reactors. The model is based on the electron momentum equation derived from the Boltzmann equation, retaining anisotropic stress components which in fact are viscous stresses. The resulting model consists of transport equations for the magnitude of electron velocity oscillation and terms representing energy dissipation due to viscous stresses in the electron energy equation. In this model, electrical current is obtained in a nonlocal manner due to viscous effects, instead of Ohm's law or the electron momentum equation without viscous effects, while nonlocal heating of electrons is represented by the viscous dissipation. Computational results obtained by two-dimensional numerical simulations show that nonlocal determination of electrical current indeed is important, and viscous dissipation becomes an important electron heating mechanism at low pressures. It is suspected that viscous dissipation in inductively coupled plasma reactors in fact represents stochastic heating of electrons, and this possibility is exploited by discussing physical similarities between stochastic heating and energy dissipation due to the stress tensor View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Two-dimensional radio-frequency methane plasma simulation: comparison with experiments

    Page(s): 1476 - 1486
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    Plasma variables are predicted using a glow discharge physics model and compared with experimental data obtained from plasma assisted chemical vapor deposition (PACVD) reactors. The present study provides insights to charged species dynamics and their effects on deposition in a polyatomic gas (methane) discharge. Swarm data as a function of electron energy are provided as input to the model. The necessary DC bias for the discharge is also predicted such that the cycle-averaged current to the powered electrode becomes zero. The simulations are performed for the operating conditions of two different experimental reactors. The model predictions of electron density, self-generated DC bias, and power requirement compare very well with the experimental results. The model predictions of axial and radial variations of plasma density also compare well with the experimental data. The radial and axial variations of plasma variables in the reactors are also presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Temporal relaxation of plasma electrons acted upon by direct current electric and magnetic fields

    Page(s): 1262 - 1270
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    On the basis of the time-dependent electron Boltzmann equation the temporal relaxation of the electrons in the presence of electric and magnetic fields in weakly ionized, collision dominated plasmas has been studied. The relaxation process is treated by using a strict time-dependent two-term approximation of the velocity distribution function expansion in spherical harmonics. A new technique for solving the time-dependent electron kinetic equation in this two-term approximation for arbitrary angles between the electric and magnetic fields has been developed and the main aspects of the efficient solution method are presented. Using this new approach and starting from steady-state plasmas under the action of time-independent electric fields only, the impact of superimposed DC magnetic fields on the electron relaxation is analyzed with regard to the control of a neon plasma. The investigations reveal an important effect of the magnetic field on the temporal relaxation process. In particular, it has been found that the relaxation time of the electron component with respect to the establishment of steady-state can be enlarged by some orders of magnitude when increasing the magnetic field strength View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modeling of a nonequilibrium cylindrical column of a low-current arc discharge

    Page(s): 1458 - 1463
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (112 KB)  

    Numerical modeling of a wall-stabilized low-current arc discharge in the high pressure argon plasma is performed with account both of a deviation of the electron temperature from the heavy-particle temperature and of a deviation from the ionization equilibrium. Results are presented for a current range from currents of the order of 100 A down to several A, in which a regime of the discharge varies from the one typical for an arc discharge (local thermodynamic equilibrium (LTE) in the hot core, energy supplied to electrons by the electric field is mainly removed by the electron heat conduction) to the one typical for a glow discharge. (The electron temperature is substantially higher than the heavy-particle temperature and does not change much across the column, the ionization exceeds or substantially exceeds the recombination in every point of the column, energy supplied to electrons by the electric field is mainly locally transferred to heavy particles). On the axis of the discharge, the deviations from LTE become appreciable when the current decreases to several tens A. The deviation from the ionization equilibrium comes into play at higher currents than the deviation from the thermal equilibrium. Comparison with available experimental data is given View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Brownian motion of a charged particle in a magnetic field

    Page(s): 1288 - 1296
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    We develop and numerically illustrate an exact solution of the multivariate, stochastic, differential equations that govern the velocity and position of a charged particle in a plane normal to a uniform, stationary, magnetic field. The equations self-consistently incorporate the Lorentz force into an Ornstein-Uhlenbeck collision model. Properties of the solution in the infinite dissipation limit are explored and the spectral energy density function is found View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Monte Carlo model for the argon ions and fast argon atoms in a radio-frequency discharge

    Page(s): 1406 - 1415
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB)  

    A three-dimensional Monte Carlo model has been developed for the argon ions and fast argon atoms in the RF sheath of a capacitively coupled RF glow discharge in argon. Our interest in the argon ions and fast argon atoms in the RF sheath arises from the fact that the glow discharge under study is used as sputtering source for analytical chemistry. This source operates at typical working conditions of a few torr pressure and about 10 W incoming power. The argon ion and atom Monte Carlo model has been coupled to a hybrid Monte Carlo-fluid model for electrons and argon ions developed before to obtain fully self-consistent results. Typical results of this model include, among others, the densities, fluxes, collision rates, mean energies, and energy distributions of the argon ions and atoms. Moreover, we have investigated how many RF cycles have to be followed before periodic steady state is reached, and the effects of all previous RF cycles are correctly accounted for. This is found to be the case for about 20-25 RF cycles View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Gamma-electron dynamics and radio frequency capacitive sheath diagnostics

    Page(s): 1348 - 1352
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB)  

    Time-resolved measurements of gamma-electrons energy spectra in low-pressure capacitively coupled RF discharge are presented. Time dependence of the sheath voltage is calculated from experimental results and compared with theoretical predictions. Good quantitative agreement is observed for collisional sheath. In low pressure discharge sheath voltage time dependence is close to [1+cos(ωτ)], which qualitatively corresponds to the theoretical results. Asymmetry of electron energy spectra for increasing and decreasing sheath voltage is observed and explained by divergence and convergence of electron trajectories in plasma (klystron-effect) View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Particle-in-cell plus direct simulation Monte Carlo (PIC-DSMC) approach for self-consistent plasma-gas simulations

    Page(s): 1389 - 1398
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    The particle-in-cell (PIC) and direct simulation Monte Carlo (DSMC) approaches have been combined into a PIC-DSMC model for self-consistent simulations of low-temperature collisional plasmas and the background gas. This novel approach is based on the weighting collision simulation scheme allowing for disparate number densities and time scales of different species. The applicability of the developed algorithm is illustrated by simulations of one-dimensional direct current and two-dimensional magnetron sputtering discharges in argon. An appreciable effect of the energetic discharge species on the density, temperature, and flow field of the background gas shows the importance of the coupled plasma-gas simulation for such technologies as sputtering, dry etching, plasma enhanced vapor deposition, etc View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IEEE Transactions on Plasma Sciences focuses on plasma science and engineering, including: magnetofluid dynamics and thermionics; plasma dynamics; gaseous electronics and arc technology.

 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Steven J. Gitomer, Ph.D.
Senior Scientist, US Civilian Research & Development Foundation
Guest Scientist, Los Alamos National Laboratory
1428 Miracerros Loop South
Santa Fe, NM  87505  87505  USA
tps-editor@ieee.org
Phone:505-988-5751
Fax:505-988-5751 (call first)