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Indexed by:Journal Papers

Date of Publication:2016-01-01

Journal:PLASMA SCIENCE & TECHNOLOGY

Included Journals:SCIE、EI、Scopus

Volume:18

Issue:1

Page Number:58-61

ISSN No.:1009-0630

Key Words:plasma diagnosis; Langmuir probe; harmonics; insulative deposition

Abstract:Conventional Langmuir probe techniques usually face the difficulty of being used in processing plasmas where dielectric compounds form, due to rapid failure by surface insulation. A solution to the problem, the so-called harmonic probe technique, had been proposed and shown effectiveness. In this study, the technique was investigated in detail by changing bias signal amplitudes V-o, and evaluated its accuracy by comparing with the conventional Langmuir probe. It was found that the measured electron temperature T-e increased with V-o, but showing a relatively stable region when V-o > T-e/e in which it was close to the true Te value. This is contrary to the general consideration that V-o should be smaller than Te/e for accurate measurement of Te. The phenomenon is interpreted by the non-negligible change of the ion current with V-o at low V-o values. On the other hand, the measured n(i) also increased with V-o due to the sheath expansion, and to improve the accuracy of n(i) it needs to linearly extrapolate the n(i)-V-o trend to V-o=0. The results were applied to a diagnosis of the plasmas for chemical vapor deposition of diamond-like carbon thin films and the relationship between plasma parameters and films deposition rates was obtained.