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Title: Geometrical Aspects of a Hollow-cathode Magnetron (HCM)

Abstract

A hollow-cathode magnetron (HCM), built by surrounding a planar sputtering-magnetron cathode with a hollow-cathode structure (HCS), is operable at substantially lower pressures than its planar-magnetron counterpart. We have studied the dependence of magnetron operational parameters on the inner diameter D and length L of a cylindrical HCS. Only when L is greater than L sub zero, a critical length, is the HCM operable in the new low-pressure regime. The critical length varies with HCS inner diameter D. Explanations of the lower operational pressure regime, critical length, and plasma shape are proposed and compared with a one-dimension diffusion model for energetic or primary electron transport. At pressures above 1 mTorr, an electron-impact ionization model with Bohm diffusion at a temperature equivalent to one-half the primary electron energy and with an ambipolar constraint can explain the ion-electron pair creation required to sustain the discharge. The critical length L sub zero is determined by the magnetization length of the primary electrons.

Authors:
;
Publication Date:
Research Org.:
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1771
Report Number(s):
PPPL-3321
ON: DE00001771
DOE Contract Number:
AC02-76CH03073
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; Energy; MAGNETRONS; PLASMA; PRESSURE DEPENDENCE

Citation Formats

Cohen, Samuel, A., and Wang, Zhehui. Geometrical Aspects of a Hollow-cathode Magnetron (HCM). United States: N. p., 1998. Web. doi:10.2172/1771.
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Cohen, Samuel, A., & Wang, Zhehui. Geometrical Aspects of a Hollow-cathode Magnetron (HCM). United States. doi:10.2172/1771.
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Cohen, Samuel, A., and Wang, Zhehui. Sun . "Geometrical Aspects of a Hollow-cathode Magnetron (HCM)". United States. doi:10.2172/1771. https://www.osti.gov/servlets/purl/1771.
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@article{osti_1771,
title = {Geometrical Aspects of a Hollow-cathode Magnetron (HCM)},
author = {Cohen, Samuel, A. and Wang, Zhehui},
abstractNote = {A hollow-cathode magnetron (HCM), built by surrounding a planar sputtering-magnetron cathode with a hollow-cathode structure (HCS), is operable at substantially lower pressures than its planar-magnetron counterpart. We have studied the dependence of magnetron operational parameters on the inner diameter D and length L of a cylindrical HCS. Only when L is greater than L sub zero, a critical length, is the HCM operable in the new low-pressure regime. The critical length varies with HCS inner diameter D. Explanations of the lower operational pressure regime, critical length, and plasma shape are proposed and compared with a one-dimension diffusion model for energetic or primary electron transport. At pressures above 1 mTorr, an electron-impact ionization model with Bohm diffusion at a temperature equivalent to one-half the primary electron energy and with an ambipolar constraint can explain the ion-electron pair creation required to sustain the discharge. The critical length L sub zero is determined by the magnetization length of the primary electrons.},
doi = {10.2172/1771},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Nov 01 00:00:00 EST 1998},
month = {Sun Nov 01 00:00:00 EST 1998}
}
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Technical Report:
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DOI:  10.2172/1771
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  • ; - Physics of Plasmas
    A hollow-cathode planar magnetron (HCPM), built by surrounding a planar sputtering-magnetron cathode with a hollow-cathode structure (HCS) [Z. Wang and S. A. Cohen, J. Vac. Sci. Technol. A {bold 17}, 77 (1999)], is operable at substantially lower pressures than its planar-magnetron counterpart. HCPM operational parameters depend on the inner diameter {ital D} and length {ital L} of its cylindrical HCS. Only when {ital L} is greater than L{sub 0}, a critical length, is the HCPM operable in the new low-pressure regime. The critical length varies with HCS inner diameter {ital D}. Explanations of the lower operational pressure regime, critical length,more » and plasma shape are proposed and compared with a one-dimension diffusion model for energetic electron transport. At pressures above 1 mTorr, Bohm diffusion (temperature{congruent}primary electron energy), with an ambipolar constraint, can explain the ion{endash}electron pair creation required to sustain the discharge. At the lowest pressure, {approximately}0.3 mTorr, collision-limited diffusion creates fewer ion{endash}electron pairs than required for steady state and therefore cannot explain the experimental data. The critical length L{sub 0} is consistent with the magnetization length of the primary electrons. {copyright} {ital 1999 American Institute of Physics.}« less

  • ;
    A new type of plasma sputtering device, named the hollow cathode magnetron (HCM), has been developed by surrounding a planar magnetron cathode with a hollow cathode structure (HCS). Operating characteristics of HCMs, current-voltage ( I-V ) curves for fixed discharge pressure and voltage-pressure ( V-p ) curves for fixed cathode current, are measured. Such characteristics are compared with their planar magnetron counterparts. New operation regimes, such as substantially lower pressures (0.3 mTorr), were discovered for HCMs. Cathode erosion profiles show marked improvement over planar magnetron in terms of material utilization. The use of HCMs for thin film deposition are discussed.

  • ; ; ; ...
    Energy distributions of N atoms in a hollow-cathode planar sputtering magnetron were obtained by use of optical emission spectroscopy. A characteristic line, N I 8216.3 Å, well-separated from molecular nitrogen emission bands, was identified. Jansson's nonlinear spectral deconvolution method, refined by minimization of {chi} w ² , was used to obtain the optimal deconvolved spectra. These showed nitrogen atom energies from 1 eV to beyond 500 eV. Based on comparisons with VFTRIM results, we propose that the energetic N atoms are generated from N 2 + ions after these ions are accelerated through the sheath and dissociatively reflect from themore » cathode.« less

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