Advanced

Analytical model for ion angular distribution functions at rf biased surfaces with collisionless plasma sheaths

Raja, LL and Linne, Mark LU (2002) In Applied Physics Reviews 92(12). p.7032-7040
Abstract
The article presents an analytical model for evaluation of ion angular distribution functions (IADFs) at a radio frequency (rf)-biased surface in a high-density plasma reactor. The model couples a unified rf sheath model to an assumed ion velocity distribution function-based formulation for determining the IADF under any general rf-bias condition. Under direct-current (dc) bias conditions the IADF profile shape shows a strong dependence on the bias voltage and the ion temperature is relatively independent of the plasma electron temperature, ion density, and the ion mass. The model establishes the importance of rf-bias frequency in determining the IADF. For conditions where the sheath current wave form is sinusoidal, low bias frequencies... (More)
The article presents an analytical model for evaluation of ion angular distribution functions (IADFs) at a radio frequency (rf)-biased surface in a high-density plasma reactor. The model couples a unified rf sheath model to an assumed ion velocity distribution function-based formulation for determining the IADF under any general rf-bias condition. Under direct-current (dc) bias conditions the IADF profile shape shows a strong dependence on the bias voltage and the ion temperature is relatively independent of the plasma electron temperature, ion density, and the ion mass. The model establishes the importance of rf-bias frequency in determining the IADF. For conditions where the sheath current wave form is sinusoidal, low bias frequencies result in a large-angle tail contribution to the IADF which can potentially lead to poor anisotropic plasma etching behavior. The large-angle tail is absent at higher bias frequencies. An increase in bias power leads to a general narrowing of the IADF, but the large-angle tail for the IADF at low frequencies persists despite increasing bias powers. Therefore, plasma etch anisotropy can be improved by increasing bias powers only if the bias frequency is sufficiently high. Tangential ion drift velocities introduce azimuthal angle dependence on the IADF and a shift in the peak IADF to off-normal polar angles. While the location of the peak IADF in the azimuthal direction is dictated purely by the direction of the drift velocity, the shift in peak IADF in the polar angle depends on both the drift velocity as well as the bias frequency. (C) 2002 American Institute of Physics. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
radio-frequency discharges high-density plasmas energy-distributions bombardment argon simulation chlorine reactors dynamics
in
Applied Physics Reviews
volume
92
issue
12
pages
7032 - 7040
publisher
American Institute of Physics
external identifiers
  • wos:000179495100010
  • scopus:0037115568
ISSN
0021-8979
DOI
10.1063/1.1524020
language
English
LU publication?
yes
id
8fe0a2d2-02cf-4f6d-a2fd-50ec841694c3 (old id 322384)
date added to LUP
2007-11-09 14:07:09
date last changed
2017-12-10 03:52:30
@article{8fe0a2d2-02cf-4f6d-a2fd-50ec841694c3,
  abstract     = {The article presents an analytical model for evaluation of ion angular distribution functions (IADFs) at a radio frequency (rf)-biased surface in a high-density plasma reactor. The model couples a unified rf sheath model to an assumed ion velocity distribution function-based formulation for determining the IADF under any general rf-bias condition. Under direct-current (dc) bias conditions the IADF profile shape shows a strong dependence on the bias voltage and the ion temperature is relatively independent of the plasma electron temperature, ion density, and the ion mass. The model establishes the importance of rf-bias frequency in determining the IADF. For conditions where the sheath current wave form is sinusoidal, low bias frequencies result in a large-angle tail contribution to the IADF which can potentially lead to poor anisotropic plasma etching behavior. The large-angle tail is absent at higher bias frequencies. An increase in bias power leads to a general narrowing of the IADF, but the large-angle tail for the IADF at low frequencies persists despite increasing bias powers. Therefore, plasma etch anisotropy can be improved by increasing bias powers only if the bias frequency is sufficiently high. Tangential ion drift velocities introduce azimuthal angle dependence on the IADF and a shift in the peak IADF to off-normal polar angles. While the location of the peak IADF in the azimuthal direction is dictated purely by the direction of the drift velocity, the shift in peak IADF in the polar angle depends on both the drift velocity as well as the bias frequency. (C) 2002 American Institute of Physics.},
  author       = {Raja, LL and Linne, Mark},
  issn         = {0021-8979},
  keyword      = {radio-frequency discharges
high-density plasmas
energy-distributions
bombardment
argon
simulation
chlorine
reactors
dynamics},
  language     = {eng},
  number       = {12},
  pages        = {7032--7040},
  publisher    = {American Institute of Physics},
  series       = {Applied Physics Reviews},
  title        = {Analytical model for ion angular distribution functions at rf biased surfaces with collisionless plasma sheaths},
  url          = {http://dx.doi.org/10.1063/1.1524020},
  volume       = {92},
  year         = {2002},
}