| AVS 65th International Symposium & Exhibition | |
| Advanced Surface Engineering Division | Tuesday Sessions |
| Session SE+PS-TuM |
| Session: | Plasma-assisted Surface Modification and Deposition Processes |
| Presenter: | Niklas Hellgren, Messiah College |
| Authors: | N. Hellgren, Messiah College J. Thörnberg, Linkӧping University, Sweden I. Zhirkov, Linkӧping University, Sweden G. Greczynski, Linköping University, Sweden J.P. Palisaitis, Linköping University, Sweden M. Sortica, Uppsala University, Sweden P.O.A. Persson, Linköping University, Sweden I. Petrov, University of Illinois at Urbana-Champaign J.E. Greene, University of Illinois at Urbana-Champaign L. Hultman, Linköping University, Sweden J. Rosen, Linköping University, Sweden |
| Correspondent: | Click to Email |
We report on titanium boride, TiBx, thin films grown by both direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS) from a compound TiB2 target, in an attempt to grow high-quality stoichiometric TiB2 films. The composition, microstructure, and texture was analyzed as a function of deposition temperature (room temperature – 900 °C) and pressure (5 – 20 mTorr). Films deposited by DCMS at low pressure, regardless of temperature, result in over-stoichiometric films (B/Ti ≈ 3), while high pressure gives close to stoichiometric films. This can be explained by differences in angular distribution of sputtered B and Ti atoms, as well as differences in gas scattering [1]. These high-pressure films, however, are under-dense and have a mixed 100/101 preferred crystal orientation.
The composition of the HiPIMS-deposited films show a more complex dependence on pressure and temperature: At low temperatures, the trend vs pressure is opposite to DCMS, with the higher pressure resulting in higher B/Ti ratio. At higher temperatures, the effect of pressure is smaller, and even reverses slightly, with higher pressure giving lower B/Ti ratio.
We attribute these trends to a combination of several factors: (1) The much higher degree of ionization in HiPIMS, and the different transport of the ionized sputtered particles in the presence of a magnetic field, (2) gas density decrease at higher temperature resulting in less scattering, and (3) more sublimation, primarily of boron, at higher substrate temperatures. The highest quality stoichiometric TiB2 films, with 001-textured nano-columnar structure, form by HiPIMS at 5 mTorr and 500-700 °C.
[1] J. Neidhardt et al., Appl. Phys. 104, 063304 (2008).