skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Comprehensive analysis of chlorine-containing capacitively coupled plasmas

Abstract

Capacitively coupled discharges of strongly reactive atmospheres containing mixtures of boron trichloride (BCl{sub 3}) and chlorine (Cl{sub 2}) are investigated employing spatially resolved Langmuir probe measurements, and three probes that are spatially integrating methods: optical emission spectroscopy (OES), self-excited electron resonance spectroscopy (SEERS), and impedance characteristics of the discharge. The analysis covers the pure gases including some mixtures, discharge pressure, and rf power over nearly two orders of magnitude, and their impact on important plasma parameters of ''first order,'' such as plasma density, plasma potential, electron temperature, temperature of the plasma bulk, electron collision rate with neutrals, and actual rf power coupled into the discharge. From these, other properties (electrical conductivity, capacitance, plasma bulk resistance, sheath resistance, and its electrically defined thickness) can be derived. Since the methods are partially complementary, a mutual control of the obtained data is made possible, and we finally obtain a self-consistent model for capacitive coupling connecting data obtained with electrical and optical probes. Compared to electropositive discharges of inert atomic gases (Ar) and molecular gases (H{sub 2}), which are used as calibration standard for BCl{sub 3} and Cl{sub 2}, the electron plasma density n{sub e} is definitely lower, whereas the electron temperature T{sub e}more » is significantly higher, which would be expected by electron attachment to the electronegative molecules--at least at higher discharge pressures. Furthermore, we compared values for T{sub e} and n{sub e} obtained with OES and SEERS, respectively, and with the Langmuir-probe system. The agreement in electron plasma density and electron temperature for Ar is surprisingly good, despite the fact that the electron energy distribution would be described with two temperatures. For argon plasma, the variation of the calculated dc conductivity for nearly pure capacitive coupling either from impedance measurements or SEERS is within 30%. This is a result of uncertainties in current path rather than principal faults of the various methods. For the reactive, molecular gases, however, the results vary significantly. These data serve to determine several derived properties. Among these, are the sheath thickness, which is compared with optical and electrical data, and the conductivity of the plasma bulk. As they are derived from simultaneous, but independent measurements, they confirm the relative simple model of an electropositive discharge (argon and argon/krypton), and stress the difficulty to describe plasmas consisting of electronegative constituents (Cl{sub 2}, BCl{sub 3}, and their mixtures) which is due mainly to a pressure-dependent transition from stochastic to ohmic heating and from electropositive to electronegative behavior.« less

Authors:
 [1]
  1. Munich University of Applied Sciences, D-80335 Munich (Germany)
Publication Date:
OSTI Identifier:
20637082
Resource Type:
Journal Article
Journal Name:
Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films
Additional Journal Information:
Journal Volume: 23; Journal Issue: 3; Other Information: DOI: 10.1116/1.1894725; (c) 2005 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0734-2101
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ARGON; BORON CHLORIDES; CALIBRATION STANDARDS; CAPACITANCE; CHLORINE; ELECTRIC CONDUCTIVITY; ELECTRIC DISCHARGES; ELECTRON ATTACHMENT; ELECTRON COLLISIONS; ELECTRON SPECTROSCOPY; ELECTRON SPIN RESONANCE; ELECTRON TEMPERATURE; EMISSION SPECTROSCOPY; ENERGY SPECTRA; LANGMUIR PROBE; PLASMA DENSITY; PLASMA POTENTIAL; PRESSURE DEPENDENCE

Citation Formats

Franz, Gerhard. Comprehensive analysis of chlorine-containing capacitively coupled plasmas. United States: N. p., 2005. Web. doi:10.1116/1.1894725.
Franz, Gerhard. Comprehensive analysis of chlorine-containing capacitively coupled plasmas. United States. https://doi.org/10.1116/1.1894725
Franz, Gerhard. 2005. "Comprehensive analysis of chlorine-containing capacitively coupled plasmas". United States. https://doi.org/10.1116/1.1894725.
@article{osti_20637082,
title = {Comprehensive analysis of chlorine-containing capacitively coupled plasmas},
author = {Franz, Gerhard},
abstractNote = {Capacitively coupled discharges of strongly reactive atmospheres containing mixtures of boron trichloride (BCl{sub 3}) and chlorine (Cl{sub 2}) are investigated employing spatially resolved Langmuir probe measurements, and three probes that are spatially integrating methods: optical emission spectroscopy (OES), self-excited electron resonance spectroscopy (SEERS), and impedance characteristics of the discharge. The analysis covers the pure gases including some mixtures, discharge pressure, and rf power over nearly two orders of magnitude, and their impact on important plasma parameters of ''first order,'' such as plasma density, plasma potential, electron temperature, temperature of the plasma bulk, electron collision rate with neutrals, and actual rf power coupled into the discharge. From these, other properties (electrical conductivity, capacitance, plasma bulk resistance, sheath resistance, and its electrically defined thickness) can be derived. Since the methods are partially complementary, a mutual control of the obtained data is made possible, and we finally obtain a self-consistent model for capacitive coupling connecting data obtained with electrical and optical probes. Compared to electropositive discharges of inert atomic gases (Ar) and molecular gases (H{sub 2}), which are used as calibration standard for BCl{sub 3} and Cl{sub 2}, the electron plasma density n{sub e} is definitely lower, whereas the electron temperature T{sub e} is significantly higher, which would be expected by electron attachment to the electronegative molecules--at least at higher discharge pressures. Furthermore, we compared values for T{sub e} and n{sub e} obtained with OES and SEERS, respectively, and with the Langmuir-probe system. The agreement in electron plasma density and electron temperature for Ar is surprisingly good, despite the fact that the electron energy distribution would be described with two temperatures. For argon plasma, the variation of the calculated dc conductivity for nearly pure capacitive coupling either from impedance measurements or SEERS is within 30%. This is a result of uncertainties in current path rather than principal faults of the various methods. For the reactive, molecular gases, however, the results vary significantly. These data serve to determine several derived properties. Among these, are the sheath thickness, which is compared with optical and electrical data, and the conductivity of the plasma bulk. As they are derived from simultaneous, but independent measurements, they confirm the relative simple model of an electropositive discharge (argon and argon/krypton), and stress the difficulty to describe plasmas consisting of electronegative constituents (Cl{sub 2}, BCl{sub 3}, and their mixtures) which is due mainly to a pressure-dependent transition from stochastic to ohmic heating and from electropositive to electronegative behavior.},
doi = {10.1116/1.1894725},
url = {https://www.osti.gov/biblio/20637082}, journal = {Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films},
issn = {0734-2101},
number = 3,
volume = 23,
place = {United States},
year = {2005},
month = {5}
}