AVS 50th International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS-ThA

Paper PS-ThA9
Novel Plasma Monitoring Scheme by Surface Wave Probe

Thursday, November 6, 2003, 4:40 pm, Room 315

Session: Plasma Diagnostics: Mechanisms
Presenter: H. Sugai, Nagoya University, Japan
Authors: H. Sugai, Nagoya University, Japan
H. Kawai, Nagoya University, Japan
K. Nakamura, Chubu University, Japan
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A novel and simple technique for measuring the electron density@footnote 1@ and temperature@footnote 2@ of plasma reactors using a surface wave probe (SW probe) is presented. This probe is also called plasma absorption probe as it is based on absorption of surface waves by plasma. The SW probe enables us to measure the local absolute electron density even when the probe surface is soiled with processing plasmas. The technique relies on absorption of surface waves resonantly excited around the probe head at critical frequencies which mainly depend on the electron density. The probe consists of a small antenna connected with a coaxial cable and is enclosed in a tube of dielectric constant @epsilon@@sub d@ inserted in a plasma of electron plasma frequency @omega@@sub p@. A network analyzer feeds a rf signal to the antenna and displays the frequency dependence of the power absorption. The absorption is observed at frequencies slightly above the surface wave resonance frequency, @omega@@sub p@/ (1+ @epsilon@@sub d@),@footnote 1,2@ which allows us to determine the electron density. Use of a pair of SW probes of different sizes enables measurements of both electron temperature and electron density. The measurements were made in a wide range of electron density (10@super 8@ - 10@super 13@ cm@super -3@) and gas pressure (10 mTorr -10 Torr) with high resolutions of space (@DELTA@x~2 mm) and time (@DELTA@t~1 µs). Time-variation of a few percents of electron density is detectable. @FootnoteText@ @footnote 1@H. Kokura, K. Nakamura, I. Ghanashev and H. Sugai, Jpn. J. Appl. Phys. 38, 5262 (1999)@footnote 2@K. Nakamura, M. Ohata and H. Sugai:, J. Vac. Sci. Technol. A21, 325 (2003).