17–22 Jun 2018
Europe/Zurich timezone
15th European Vacuum Conference

Controlling the Boron-to-Titanium Ratio in Magnetron-Sputter-Deposited TiBx Thin Films via Preferential Ionization of Sputter-Ejected Ti

18 Jun 2018, 11:55
20m
Room 2 (CICG)

Room 2

CICG

Contributed Thin Film & Surface Engineering Thin Films & Surface Engineering

Speaker

Ivan Petrov (Department of Physics (IFM), Linköping University, SE-58183 Linköping, Sweden and Frederick Seitz Materials Research Laboratory and Department Materials Science, University of Illinois, Urbana, Illinois 61801, USA)

Description

TiBx thin films grown from compound TiB2 targets by magnetron sputter deposition are typically highly over-stoichiometric, with x ranging from 2.4 to 3.5, due to differences in Ti and B preferential ejections angles and gas-phase scattering during transport between the target and the substrate. We show that the use of highly-magnetically-unbalanced magnetron sputtering of TiB2 target leads to selective ionization of sputter-ejected Ti atoms which are steered via an external magnetic field to the film, thus establishing control of the B/Ti ratio with the ability to obtain stoichiometric TiB2 films over a wide range in Ar sputtering pressures.1
We further demonstrate that stoichiometric TiB2 films can be obtained using high power impulse magnetron sputtering (HiPIMS) in Ar; the B/Ti ratio x is controllably varied from 2.08 to 1.83 by adjusting the length of HiPIMS pulses tau between 100 and 30 µs, while maintaining average power and pulse frequency constant. Energy- and time-dependent mass spectrometry analyses of ion fluxes incident at the substrate position show that the density of metal ions increases with decreasing tau, due to a dramatic increase in the peak target current density and strong gas rarefaction. With tau < 60 µs, film growth is increasingly controlled by incident ions rather than neutrals. Thus, since sputter-ejected Ti atoms have a higher probability of being ionized than B atoms due to their lower first ionization potential and larger ionization cross-section, the Ti concentration in as-deposited films increases with decreasing ton as ionized sputtered species are steered to the substrate by the plasma in order to maintain charge neutrality.


1 I. .Petrov. A. Hall, A.B Mei, N. Nedfors, I. Zhirkov, J. Rosen, A. Reed, B. Howe, G. Greczynski, J. Birch, L. Hultman, JE Greene, J Vac Sci Technol A, 35 050601 (2017)

Author

Ivan Petrov (Department of Physics (IFM), Linköping University, SE-58183 Linköping, Sweden and Frederick Seitz Materials Research Laboratory and Department Materials Science, University of Illinois, Urbana, Illinois 61801, USA)

Co-authors

Babak Bakhit (Department of Physics (IFM), Linköping University, SE-58183 Linköping, Sweden) J.E. Greene (Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-58183 Linköping, Sweden and Frederick Seitz Materials Research Laboratory and Department Materials Science, University of Illinois, Urbana, Illinois 61801, USA) Lars Hultman (Department of Physics (IFM), Linköping University, SE-58183 Linköping, Sweden ) Johanna Rosen (Department of Physics (IFM), Linköping University, SE-58183 Linköping, Sweden) Grzegorz Greczynski (Department of Physics (IFM), Linköping University, SE-58183 Linköping, Sweden)

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