Doppler spectroscopic measurements of sheath ion velocities in radio-frequency plasmas
作者:
B. K. Woodcock,
J. R. Busby,
T. G. M. Freegarde,
G. Hancock,
期刊:
Journal of Applied Physics
(AIP Available online 1997)
卷期:
Volume 81,
issue 9
页码: 5945-5949
ISSN:0021-8979
年代: 1997
DOI:10.1063/1.364382
出版商: AIP
数据来源: AIP
摘要:
We have measured the distributions ofN2+ion velocity components parallel and perpendicular to the electrode in the sheath of a radio-frequency nitrogen reactive ion etching discharge, using pulsed laser-induced fluorescence. Parallel to the electrode, the ions have throughout a thermal distribution that is found to be consistent with the rotational temperature of 355 K. In the perpendicular direction, we see clearly the acceleration of the ions towards the electrode, and our results agree well with theoretical predictions although an unexpected peak of unaccelerated ions persists. We have also determined the absolute ion concentrations in the sheath, which we have calibrated by analyzing the decay in laser-induced fluorescence in the plasma bulk after discharge extinction. At 20 mTorr, the bulk concentration of1.0×1010 cm−3falls to around2×108 cm−3at 2 mm from the electrode. ©1997 American Institute of Physics.
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