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Title: Dynamics of magnetized plasma sheaths around a trench

Abstract

Considering a magnetized plasma sheath, the temporal evolution of the ion properties (the incident ion flux, the ion impact angle, and the incident ion dose) around a rectangular trench is studied numerically. Our results show that the ion flux along the bottom surface greatly reduces in the presence of magnetic field and its uniformity improves, but the magnetic field does not considerably affect the ion flux along the sidewall. In addition, the thickness of the plasma sheath increases by increasing the magnetic field while its conformality to the target surface reduces faster. Moreover, it is shown that any increase in the magnitude (inclination angle) of the magnetic field causes a decrease (an increase) in the angle of incidence of ions on the bottom and sidewall surfaces. Furthermore, in the presence of magnetic field, the ions strike nearly normal to the surface of the bottom while they become less oblique along the sidewall surface. In addition, contrary to the corners of the trench, it is found that the magnetic field greatly affects the incident ion dose at the center of the trench surfaces. Also, it is shown that the incident ion dose along the sidewall is the highest near the centermore » of the sidewall in both magnetized and magnetic-free cases. However, uniformity of the incident ion dose along the sidewall is better than that along the bottom in both magnetized and unmagnetized plasma sheath.« less

Authors:
 [1]
  1. Physics Department, K. N. Toosi University of Technology, 15418-49611 Tehran (Iran, Islamic Republic of)
Publication Date:
OSTI Identifier:
22599951
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 23; Journal Issue: 8; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; DOSES; INCIDENCE ANGLE; INCLINATION; IONS; MAGNETIC FIELDS; NUMERICAL ANALYSIS; PLASMA SHEATH; SURFACES; THICKNESS

Citation Formats

Hatami, M. M., E-mail: m-hatami@kntu.ac.ir. Dynamics of magnetized plasma sheaths around a trench. United States: N. p., 2016. Web. doi:10.1063/1.4960327.
Hatami, M. M., E-mail: m-hatami@kntu.ac.ir. Dynamics of magnetized plasma sheaths around a trench. United States. doi:10.1063/1.4960327.
Hatami, M. M., E-mail: m-hatami@kntu.ac.ir. 2016. "Dynamics of magnetized plasma sheaths around a trench". United States. doi:10.1063/1.4960327.
@article{osti_22599951,
title = {Dynamics of magnetized plasma sheaths around a trench},
author = {Hatami, M. M., E-mail: m-hatami@kntu.ac.ir},
abstractNote = {Considering a magnetized plasma sheath, the temporal evolution of the ion properties (the incident ion flux, the ion impact angle, and the incident ion dose) around a rectangular trench is studied numerically. Our results show that the ion flux along the bottom surface greatly reduces in the presence of magnetic field and its uniformity improves, but the magnetic field does not considerably affect the ion flux along the sidewall. In addition, the thickness of the plasma sheath increases by increasing the magnetic field while its conformality to the target surface reduces faster. Moreover, it is shown that any increase in the magnitude (inclination angle) of the magnetic field causes a decrease (an increase) in the angle of incidence of ions on the bottom and sidewall surfaces. Furthermore, in the presence of magnetic field, the ions strike nearly normal to the surface of the bottom while they become less oblique along the sidewall surface. In addition, contrary to the corners of the trench, it is found that the magnetic field greatly affects the incident ion dose at the center of the trench surfaces. Also, it is shown that the incident ion dose along the sidewall is the highest near the center of the sidewall in both magnetized and magnetic-free cases. However, uniformity of the incident ion dose along the sidewall is better than that along the bottom in both magnetized and unmagnetized plasma sheath.},
doi = {10.1063/1.4960327},
journal = {Physics of Plasmas},
number = 8,
volume = 23,
place = {United States},
year = 2016,
month = 8
}
  • A set of equations for magnetized plasma sheaths in rf capacitance discharges is developed within the adiabatic electron, fluid ion framework. It differs from previous approaches in that (a) ion demagnetization, i.e., the detachment of the ion flow from the magnetic lines caused by electrostatic gradients, is introduced self-consistently, (b) the ion injection velocity from the presheath is reevaluated to ensure the ion-electron flux balance, and (c) two symmetrically opposed coupled sheaths are driven by a sinusoidal driving voltage instead of a sinusoidal current. It is found that the sheath potential and thickness increase considerably with increasing magnetic inclination {theta}more » relative to the electric field compared to the unmagnetized results; the latter are recovered at the parallel magnetic field limit. Also, the ion injection velocity along the magnetic lines is subsonic and depends on the magnetic inclination. Finally, a sinusoidal ac voltage drives an anharmonic sheath current, while a sinusoidal current drives anharmonic voltage. {copyright} {ital 1999} {ital The American Physical Society}« less
  • The behavior of rf plasma sheaths has been the subject of much scientific study and also is technologically important for plasma etching and deposition in the manufacture of integrated circuits. This paper presents a semianalytic model of rf sheaths and describes an experiment that tested the model. An approximation to the first integral of the Poisson equation allows solving for the response of plasma sheaths to an imposed rf bias voltage. This approximation enables the plasma sheaths to be included within an electrical model of the plasma and external rf circuit components, and affords a prediction of the ion energymore » distributions impacting the electrodes, which are in contact with the plasma. The model is a significant advance beyond previous sheath models because it has no restriction on the ratio of the rf period to the ion transit time across the sheath. The model is applicable to those high-density, low-pressure plasmas in which the Debye length is a small fraction of the ion mean-free path, which itself is a small fraction of the plasma dimension. The experimental test of the model was conducted by comparing the predicted and measured rf potential, current, and power at the sheath adjacent to a capacitively coupled, rf-biased electrode in a plasma reactor with argon discharges sustained by an inductively coupled plasma source. The comparisons included both linear and nonlinear components of the rf electrical parameters. Results of the experiment were in substantial agreement with model predictions. {copyright} {ital 1997 American Institute of Physics.}« less
  • Spatially localized unstable waves are observed around a dipole magnet in a low-density plasma. The observed wave frequency (approx. =150--200 kHz) with a high fluctuation level (approx. =20%) is much higher than an ion-cyclotron frequency. Correlation measurements confirm azimuthal propagation of the unstable wave on the axis of the dipole magnet. The calculation using a fluid model is found to account qualitatively for the results, and predicts that the waves are excited by two stream instabilities ascribed to an electron drift caused by the density and the potential gradients perpendicular to the magnetic field.
  • The electrodynamics of a circular waveguide with a dielectric rod surrounded by a magnetized plasma layer is considered. A general dispersion relation for azimuthally asymmetric perturbations is derived, and its solutions describing slow waves-specifically, electromagnetic and plasma modes, as well as (and primarily) hybrid waves that combine the properties of both mode types-are investigated numerically. For the fundamental waveguide mode of the system-the HE{sub 11} mode-the parameters of the plasma layer are determined at which the mode cannot be subject to Cherenkov interaction with a relativistic electron beam at a given frequency. For both waveguide and plasma modes, the radialmore » profiles of the longitudinal components of the electric field and Poynting vector, the fractions of RF power carried within the dielectric and plasma regions and vacuum gap, and the coupling impedance are calculated as functions of the parameters of the plasma layer. The evolution of the field structure during the formation of asymmetric hybrid waves is traced. The results of calculating the dispersion and coupling impedance are analyzed as applied to an antenna-amplifier-a relativistic traveling-wave tube operating on the HE{sub 11} mode of the dielectric rod: specifically, the implementability of the concept in the presence of a plasma at the rod surface is estimated, and the possible role of azimuthally asymmetric and symmetric plasma modes is examined.« less
  • Investigations on near-surface diffusion during the formation of self-assembled Ge islands on Si(001) are presented. We measure the detailed shape of trenches around islands that are formed due to short range, strain enhanced diffusion. It is found that these trenches have anisotropic shape which we explain in terms of the intrinsic anisotropy of the elastic properties for the Si crystal. At high growth temperatures, long-range depletion of the substrate and trench formation between neighboring islands due to strong in-diffusion of Si into the nominally pure Ge islands is observed. A simple diffusion model which predicts trench depths as a functionmore » of island distance fits well to our experimentally observed data. Calculated diffusion lengths from this model are comparable to the average island distance on the surface. {copyright} 2001 American Institute of Physics.« less