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Self Bias of an R.F. Driven Probe in an R.F. Plasma

Published online by Cambridge University Press:  22 February 2011

N M P Benjamin ,
N St J Braithwaite  and
J E Allen
N M P Benjamin
Affiliation:
Department of Engineering Science, Oxford University, OX1 3PJ, U.K.
N St J Braithwaite
Affiliation:
Now at The Open University, Walton Hall, Milton Keynes, MK7 6AA, U.K.
J E Allen
Affiliation:
Department of Engineering Science, Oxford University, OX1 3PJ, U.K.
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Abstract

An effect of sinusoidal r.f. voltages between a plasma and a floating Langmuir probe (or other electrode) is to produce a d.c. self bias voltage. This effect has previously been studied with r.f. applied to probes in d.c. plasmas, and the results have often been referred to in connection with d.c. probes in r.f. plasmas, although the situation is slightly different. In the current work a ‘d.c.’ probe in an r.f. plasma is examined. However, the r.f. potential difference between probe and plasma is first compensated for by superimposing a synchronous signal of appropriate amplitude and phase on to the d.c. circuit. Thus the probe can perform essentially d.c. type measurements on the r.f. plasma. The deliberate reintroduction of a measure of r.f. between probe and plasma is accomplished by overdriving the compensation signal thereby generating a controlled amount of self bias.

The observed variation of probe bias with r.f. overdrive is in good agreement with analytic theory based upon modified Bessel functions as used for d.c. generated plasmas. This work is of general interest in probe diagnostics of r.f. generated plasmas, and understanding the self bias of isolated electrodes.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 117: Symposium C – Process Diagnostics: Materials, Combustion, Fusion , 1988 , 275
Copyright
Copyright © Materials Research Society 1988

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