Midway evaluation in Physics -Swetha Suresh Babu

Title: Modeling of high power impulse magnetron sputtering discharges with tungsten target

Doctoral candidate: Swetha Suresh Babu

Doctoral committee:
Jón Tómas Guðmundsson, Professor at the Faculty of Physical Sciences, University of Iceland
Snorri Þ. Ingvarsson, Professor at the Faculty of Physical Sciences, University of Iceland
Daniel Lundin, Associate Professor at Linköping University, Sweden

Abstract

The ionization region model (IRM) is applied to model a high power impulse magnetron sputtering discharge with a tungsten target. The IRM gives the temporal variation of the various species and the average electron energy, as well as internal discharge parameters such as the ionization probability and the back-attraction probability of the sputtered species. In the initial stage of the pulse argon ions dominate the discharge until the tungsten ions take over remain as the dominating ions to the end of the pulse. We demonstrate how the contribution of the W+ ions to the total discharge current at the target surface increases with increased discharge voltage for peak
discharge current densities in the range 0.33 - 0.73 A cm2 [1]. For the sputtered tungsten the ionization probability increases, while the back-attraction probability decreases with increasing discharge voltage. Furthermore, we discuss the findings in terms of the generalized recycling model and compare to experimentally determined deposition rates and find good agreement. The IRM is then validated against experimental determination of particle densities and electron temperature by comparison to the temporal evolution of the electron density and the electron temperature determined by Thomson scattering measurements and the temporal evolution of the relative neutral and ion densities determined by optical emission spectrometry.

[1] S. Suresh Babu et al. Plasma Sources Sci. Technol. 31 (2022) 065009