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Title: Floating probe for electron temperature and ion density measurement applicable to processing plasmas

Abstract

A floating-type probe and its driving circuit using the nonlinear characteristics of the probe sheath was developed and the electron temperature and the plasma density which is found from the ion part of the probe characteristic (ion density) were measured in inductively coupled plasmas. The floating-type probe was compared with a single Langmuir probe and it turned out that the floating-type probe agrees closely with the single probe at various rf powers and pressures. The ion density and electron temperature by the floating-type probe were measured with a film on the probe tip coated in CF{sub 4} plasma. It is found that the ion density and electron temperature by the floating-type probe were almost the same regardless of the coating on the probe tip while a single Langmuir probe does not work. Because the floating-type probe is hardly affected by the deposition on the probe tip, it is expected to be applied to plasma diagnostics for plasma processing such as deposition or etching.

Authors:
; ;  [1]
  1. Department of Electrical and Computer Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)
Publication Date:
OSTI Identifier:
20982666
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 3; Other Information: DOI: 10.1063/1.2204352; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CARBON TETRAFLUORIDE; DEPOSITION; ELECTRON TEMPERATURE; ETCHING; ION DENSITY; ION TEMPERATURE; LANGMUIR PROBE; NONLINEAR PROBLEMS; PLASMA; PLASMA DENSITY; PLASMA DIAGNOSTICS; PLASMA SHEATH; THIN FILMS

Citation Formats

Lee, Min-Hyong, Jang, Sung-Ho, and Chung, Chin-Wook. Floating probe for electron temperature and ion density measurement applicable to processing plasmas. United States: N. p., 2007. Web. doi:10.1063/1.2204352.
Lee, Min-Hyong, Jang, Sung-Ho, & Chung, Chin-Wook. Floating probe for electron temperature and ion density measurement applicable to processing plasmas. United States. doi:10.1063/1.2204352.
Lee, Min-Hyong, Jang, Sung-Ho, and Chung, Chin-Wook. Thu . "Floating probe for electron temperature and ion density measurement applicable to processing plasmas". United States. doi:10.1063/1.2204352.
@article{osti_20982666,
title = {Floating probe for electron temperature and ion density measurement applicable to processing plasmas},
author = {Lee, Min-Hyong and Jang, Sung-Ho and Chung, Chin-Wook},
abstractNote = {A floating-type probe and its driving circuit using the nonlinear characteristics of the probe sheath was developed and the electron temperature and the plasma density which is found from the ion part of the probe characteristic (ion density) were measured in inductively coupled plasmas. The floating-type probe was compared with a single Langmuir probe and it turned out that the floating-type probe agrees closely with the single probe at various rf powers and pressures. The ion density and electron temperature by the floating-type probe were measured with a film on the probe tip coated in CF{sub 4} plasma. It is found that the ion density and electron temperature by the floating-type probe were almost the same regardless of the coating on the probe tip while a single Langmuir probe does not work. Because the floating-type probe is hardly affected by the deposition on the probe tip, it is expected to be applied to plasma diagnostics for plasma processing such as deposition or etching.},
doi = {10.1063/1.2204352},
journal = {Journal of Applied Physics},
number = 3,
volume = 101,
place = {United States},
year = {Thu Feb 01 00:00:00 EST 2007},
month = {Thu Feb 01 00:00:00 EST 2007}
}
  • Spatially resolved measurements of the ion density and electron temperature in a dual-frequency capacitively coupled Ar discharge plasma are performed with a newly developed complete floating double probe. Axial and radial distributions of the ion density and electron temperature under various high-frequency (HF) power and gas pressure were studied in detail. Both the ion density and the electron temperature increased with increasing HF power. With increasing gas pressure from 1.3 to 9.3 Pa, the radial profile of ion density below the driven electrode experienced a change from ''bimodal'' to ''unimodal'' shape, with better uniformity being achieved at the optimal pressuremore » of about 5 Pa. In addition, changing the axial profile of ion density was also observed with the peak shift toward the powered electrode at higher pressures. The measured results showed satisfying consistency with that of improved two dimensional fluid simulations.« less
  • For novel plasma diagnostics, the rf floating probe was revisited. For inducing the self-bias effect, ac bias voltage (approxkilohertz) was applied through a dc blocking capacitor between a probe and a signal generator. The dc self-bias potential was changed not only with ac bias voltages but also with electron temperatures, and therefore, the electron temperature was derived from the variations in the self-bias potential with and without ac bias voltage. The harmonic component of the probe contains information about the ion flux, and using a fast Fourier transform analysis of the probe current, the ion density was derived from themore » first harmonic current of the probe. The experimental results were compared with a single Langmuir probe. The electron temperature and the ion density were in good agreement with those from the Langmuir probe. Because the amplitude of the ac bias voltage is very low (<3 V), local ionizations affected by a high bias-voltage can be neglected.« less
  • A diagnostic concept is presented which enables the simultaneous determination of plasma density, electron temperature, and collision rate in low-pressure gas discharges. The proposed method utilizes a radio-frequency driven probe of particular spherical design which is immersed in the plasma to excite a family of spatially bounded surface resonances. An analysis of the measured absorption spectrum S({omega}) of the probe provides information on the distribution of the plasma in its vicinity, from which the values of the plasma parameters can be inferred. In its simplest realization, the probe consists of two dielectrically shielded, conducting hemispheres, which are symmetrically driven bymore » an radio-frequency source, and the excited resonances can be classified as multipole fields, which allows an analytical evaluation of the measured signal. The proposed method is robust, calibration free, economical, and can be used for ideal and reactive plasmas alike.« less
  • The microwave cut-off probe for the electron density measurement in low-temperature plasmas is described in this article. It is based on the wave cutoff in an unmagnetized plasma. The measurement principle is analyzed theoretically using a model of plasma slab. Because of the high-pass characteristic of plasma, the waves above the cut-off frequency can penetrate the plasma slab, whereas the lower frequency waves are reflected from the cut-off layer. Therefore, an obvious critical point can be observed in the wave transmission spectrum. The abscissa of the critical point indicates the cut-off frequency, which is directly related to the maximum electronmore » density between transmitting/receiving antennas of the cut-off probe. The measured electron densities are in agreement with the data obtained by the Langmuir probe. Experimental results show that the microwave cut-off probe can be used to diagnose the plasmas with a wide range of parameters.« less