Issue |
Eur. Phys. J. Appl. Phys.
Volume 56, Number 2, November 2011
Topical Issue: 18th International Colloquium on Plasma Processes (CIP 2011)
|
|
---|---|---|
Article Number | 24007 | |
Number of page(s) | 5 | |
DOI | https://doi.org/10.1051/epjap/2011110159 | |
Published online | 28 October 2011 |
https://doi.org/10.1051/epjap/2011110159
Transition from edge-localized to center-localized power deposition in helicon discharges
University of Padova, CISAS “G. Colombo”, via Venezia 15, 35131 Padova, Italy
a e-mail: davide.curreli@unipd.it
Received:
15
April
2011
Revised:
28
June
2011
Accepted:
24
July
2011
Published online:
28
October
2011
In radiofrequency (RF) helicon discharges the electromagnetic power is transferred from the RF field irradiated by the antenna to the plasma medium by means of plasma-wave coupling of the electromagnetic wave with the electrons. For the common industrial frequencies of tens of MHz, and for typical pressures of few Pascals, the power deposition occurs mostly at the edge of the discharge. In these conditions, ionization and electron heating occur in a layer close to the chamber walls, where a consistent fraction of the plasma is rapidly lost by diffusion toward the surface. The remaining fraction of plasma diffuses inward toward the center of the discharge, setting up a uniform and almost flat density profile, used in applications. A one-dimensional model considering both the plasma-wave coupling of the electrons with the RF wave and the macroscopic transport of ions and neutrals along the radial dimension of a cylindrical processing chamber has been derived and used to evaluate the profiles at equilibrium. The model has been validated through Langmuir probe measurements in helicon processing chambers. The numerical model has then been used to study the power-coupling behavior of the discharge when the pressure of the neutral gas is decreased. When the Knudsen number of the neutral gas approaches unity and in conditions of slightly magnetized discharge, the power deposition shifts from being edge-localized to center-localized, thus reducing the particle fluxes toward the walls and increasing the efficiency of the coupling.
© EDP Sciences, 2011
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.