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Control of the metal/gas ion ratio incident at the substrate plane during high-power impulse magnetron sputtering of transition metals in Ar
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0002-4898-5115
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
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2017 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 642, 36-40 p.Article in journal (Refereed) Published
Abstract [en]

High-power impulse magnetron sputtering (HiPIMS) of materials systems with metal/gas-atom mass ratios m(Me)/m(g) near, or less than, unity presents a challenge for precise timing of synchronous substrate-bias pulses to select metal-ion irradiation of the film and, thus, reduce stress while increasing layer density during low-temperature growth. The problem stems from high gas-ion fluxes Fg+(t) at the substrate, which overlap with metal-ion fluxes FMe+(t). We use energy-and time-dependent mass spectrometry to analyze FMe+(t) and Fg+(t) for Group IVb transition-metal targets in Ar and show that the time-and energy-integrated metal/gas ion ratio NMe+/NAr+ at the substrate can be controlled over a wide range by adjusting the HiPIMS pulse length tau(ON), while maintaining the peak target current density J(T,peak) constant. The effect is a consequence of severe gas rarefaction which scales with J(T)(t). For Ti-HiPIMS, terminating the discharge at the maximum J(T)(t), corresponding to tau(ON) = 30 mu s, there is an essentially complete loss of Ar+ ion intensity, yielding NTi+/NAr+ similar to 60. With increasing tau(ON),J(T)(t) decreases and NTi+/NAr+ gradually decays, due to Ar refill, to similar to 1 with tau(ON) = 120 s. Time-resolved ion-energy distribution functions confirm that the degree of rarefaction depends on tau(ON): for shorter pulses, tau ONHTC/SUBTAG amp;lt; FORTITLEHTC_RETAIN 60 [rs, the original sputtered-atom Sigmund-Thompson energy distributions are preserved long after the HiPIMS pulse, which is in distinct contrast to longer pulses, tau(ON) amp;gt;= 60 mu s, for which the energy distributions collapse into narrow ther-malized peaks. Thus, optimizing the HiPIMS pulse width minimizes the gas-ion flux to the substrate independent of m(Me)/m(g).

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA , 2017. Vol. 642, 36-40 p.
Keyword [en]
High power impulse magnetron sputtering; High power pulsed magnetron sputtering; Physical vapor deposition; Sputtering; Gas rarefaction; Transition metals
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:liu:diva-142963DOI: 10.1016/j.tsf.2017.09.027ISI: 000413807200007OAI: oai:DiVA.org:liu-142963DiVA: diva2:1156573
Note

Funding Agencies|Swedish Research Council VR [2014-5790]; Aforsk Foundation [16-359]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO Mat LiU) [2009 00971]; Knut and Alice Wallenberg Foundation Fellowship [KAW 2015.0043]; Carl Tryggers Stiftelse for Vetenskaplig Forskning [CTS 15:219, CTS 14:431]

Available from: 2017-11-13 Created: 2017-11-13 Last updated: 2017-12-05

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Greczynski, GrzegorzZhirkov, IgorPetrov, IvanGreene, Joseph ERosén, Johanna
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