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Title: Ion energies in high power impulse magnetron sputtering with and without localized ionization zones

Abstract

High speed imaging of high power impulse magnetron sputtering discharges has revealed that ionization is localized in moving ionization zones but localization disappears at high currents for high yield targets. This offers an opportunity to study the effect ionization zones have on ion energies. We measure that ions have generally higher energies when ionization zones are present, supporting the concept that these zones are associated with moving potential humps. We propose that the disappearance of ionization zones is caused by an increased supply of atoms from the target which cools electrons and reduces depletion of atoms to be ionized.

Authors:
 [1];  [2];  [3];  [4];  [3];  [2];  [3]
  1. School of Materials Science and Engineering, State Key Lab for Materials Processing and Die and Mold Technology, Huazhong University of Science and Technology, Wuhan 430074 (China)
  2. (United States)
  3. Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States)
  4. (Japan)
Publication Date:
OSTI Identifier:
22398796
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 12; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ATOMS; AVAILABILITY; ELECTROMAGNETIC PULSES; ELECTRONS; IONIZATION; IONS; MAGNETRONS; POTENTIALS; SPUTTERING; VELOCITY; YIELDS; ZONES

Citation Formats

Yang, Yuchen, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, Tanaka, Koichi, Central Research Institute, Mitsubishi Materials Corporation, 1002-14 Mukohyama, Naka-shi, Ibaraki 311-0102, Liu, Jason, Department of Physics, University of California Berkeley, Berkeley, California 94720, and Anders, André. Ion energies in high power impulse magnetron sputtering with and without localized ionization zones. United States: N. p., 2015. Web. doi:10.1063/1.4916233.
Yang, Yuchen, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, Tanaka, Koichi, Central Research Institute, Mitsubishi Materials Corporation, 1002-14 Mukohyama, Naka-shi, Ibaraki 311-0102, Liu, Jason, Department of Physics, University of California Berkeley, Berkeley, California 94720, & Anders, André. Ion energies in high power impulse magnetron sputtering with and without localized ionization zones. United States. doi:10.1063/1.4916233.
Yang, Yuchen, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, Tanaka, Koichi, Central Research Institute, Mitsubishi Materials Corporation, 1002-14 Mukohyama, Naka-shi, Ibaraki 311-0102, Liu, Jason, Department of Physics, University of California Berkeley, Berkeley, California 94720, and Anders, André. Mon . "Ion energies in high power impulse magnetron sputtering with and without localized ionization zones". United States. doi:10.1063/1.4916233.
@article{osti_22398796,
title = {Ion energies in high power impulse magnetron sputtering with and without localized ionization zones},
author = {Yang, Yuchen and Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 and Tanaka, Koichi and Central Research Institute, Mitsubishi Materials Corporation, 1002-14 Mukohyama, Naka-shi, Ibaraki 311-0102 and Liu, Jason and Department of Physics, University of California Berkeley, Berkeley, California 94720 and Anders, André},
abstractNote = {High speed imaging of high power impulse magnetron sputtering discharges has revealed that ionization is localized in moving ionization zones but localization disappears at high currents for high yield targets. This offers an opportunity to study the effect ionization zones have on ion energies. We measure that ions have generally higher energies when ionization zones are present, supporting the concept that these zones are associated with moving potential humps. We propose that the disappearance of ionization zones is caused by an increased supply of atoms from the target which cools electrons and reduces depletion of atoms to be ionized.},
doi = {10.1063/1.4916233},
journal = {Applied Physics Letters},
number = 12,
volume = 106,
place = {United States},
year = {Mon Mar 23 00:00:00 EDT 2015},
month = {Mon Mar 23 00:00:00 EDT 2015}
}
  • Cited by 7
  • Ion energy distribution functions measured for high power impulse magnetron sputtering show features, such as a broad peak at several 10 eV with an extended tail, as well as asymmetry with respect to E×B, where E and B are the local electric and magnetic field vectors, respectively. Here it is proposed that those features are due to the formation of a potential hump of several 10 V in each of the traveling ionization zones. Potential hump formation is associated with a negative-positive-negative space charge that naturally forms in ionization zones driven by energetic drifting electrons.
  • High power impulse magnetron sputtering (HIPIMS) is a novel deposition technology successfully implemented on full scale industrial machines. HIPIMS utilizes short pulses of high power delivered to the target in order to generate high amount of metal ions. The life-span of ions between the pulses and their energy distribution could strongly influence the properties and characteristics of the deposited coating. In modern industrial coating machines the sample rotates on a substrate holder and changes its position and distance with regard to the magnetron. Time resolved measurements of the ion energy distribution function (IEDF) at different distances from the magnetron havemore » been performed to investigate the temporal evolution of ions at various distances from target. The measurements were performed using two pressures, 1 and 3 Pa to investigate the influence of working gas pressure on IEDF. Plasma sampling energy-resolved mass spectroscopy was used to measure the IEDF of Ti{sup 1+}, Ti{sup 2+}, Ar{sup 1+}, and Ar{sup 2+} ions in HIPIMS plasma discharge with titanium (Ti) target in Ar atmosphere. The measurements were done over a full pulse period and the distance between the magnetron and the orifice of the mass spectrometer was changed from 25 to 215 mm.« less
  • The plasma over the magnetron’s erosion “racetrack” is not azimuthally uniform but concentrated in distinct dense plasma zones which move in the {vector E}×{vector B} direction with about 10% of the electrons’ {vector E}×{vector B}/B{sup 2} drift velocity. The plasma zones are investigated with a gated camera working in concert with a streak camera for Al, Nb, Cu, and W targets in Ar or Kr background gas. It is found that each plasma zone has a high density edge which is the origin of a plasma-generating electron jet leaving the target zone. Each region of strong azimuthal density gradient generatesmore » an azimuthal electric field which promotes the escape of magnetized electrons and the formation of electron jets and plasma flares. The phenomena are proposed to be caused by an ionization instability where each dense plasma zone exhibits a high stopping power for drifting high energy electrons, thereby enhancing itself.« less