Global modeling of hiPIMS systems: Transition from homogeneous to self organized discharges

Summary form only given. High Power Impulse Magnetron Sputtering (HiPIMS) discharges are characterized by a near-target magnetized region, where the confined electrons ionize a consistent fraction of both the gas and the sputtered neutrals. HiPIMS discharges are dynamical systems, evolving through different regimes of operation: both the plasma composition and the plasma spatial organization change during the pulse [1].A fluid and a kinetic volume averaged model are applied to the simulation of the ionization region, for a low (I peak "" 5 . 10-2 Alcm2) and a high current (Ipeak "" 5 Alcm2) discharge. In the low current case, the kinetic code yields a highly non equilibrium electron energy distribution function, which explains the unrealistic quantities obtained by the fluid model. As for the high current case, even the kinetic code is not able to reproduce the discharge current-voltage (VI) characteristics: the discharge cannot be sustained because of the strong gas depletion. However, an artificially enhanced Ar diffusion term, allows for the matching of the VI curve. Experimental observations show the re-organization of the discharge in ionization zones (spokes) rotating in the E x 13 direction (e.g. [2]): based on our findings, we attribute the appearance of rotation zones to the need for an additional source of neutral particles [3]. In addition to this analysis, we investigate the plasma composition by means of the kinetic model, and we comment on the influence and evolution of doubly charged ions [4,5].