Abstract
A Monte Carlo model has been developed for investigating the electron behavior in a dual-magnetron sputter deposition system. To describe the three-dimensional (3D) geometry, different reference frames, i.e. a local and a global coordinate system, were used. In this study, the influence of both closed and mirror magnetic field configurations on the plasma properties is investigated. In the case of a closed magnetic field configuration, the calculated electron trajectories show that if an electron is emitted in (or near) the center of the cathode, where the influence of the magnetic field is low, it is able to travel from one magnetron to the other. On the other hand, when an electron is created at the race track area, it is more or less trapped in the strong magnetic field and cannot easily escape to the second magnetron region. In the case of a mirror magnetic field configuration, irrespective of where the electron is emitted from the cathode, it cannot travel from one magnetron to the other because the magnetic field lines guide the electron to the substrate. Moreover, the electron density and electron impact ionization rate have been calculated and studied in detail for both configurations.
GENERAL SCIENTIFIC SUMMARY Introduction and background. Magnetron sputter deposition plays a central role in the fabrication of high performance thin films. In this work, we have studied a dual magnetron configuration, which is used, for example, to deposit complex oxides. Their increasing popularity makes it necessary to thoroughly investigate this configuration. To our knowledge, no modeling has yet been performed on plasma behavior in dual magnetrons.
Main results. To simulate the behavior of the electrons in both closed (magnetic field lines travel from one target to the other) and mirror (magnetic field lines travel from the targets to the substrate) magnetic field configurations, a Monte Carlo model was developed. Calculated electron trajectories illustrate that most of the electrons are re-adsorbed at the target, or are trapped in the strong magnetic field close to the target. In a closed configuration, some electrons travel from one target to the other, and in the mirror configuration, some electrons travel to the substrate. As a result, the electron density (see the figure) and ionization rate profiles have maxima close to the targets. Moreover, in the closed configuration, the profiles overlap in between the two magnetron regions, whereas in the mirror configuration, these profiles are aligned towards the substrate.
Wider implications. This model will be extended to account for all species to investigate the sputter deposition process in dual magnetron discharges.
Figure. Calculated fast electron density profiles for both closed (a) and mirror (b) magnetic field configurations.