Gas rarefaction effects during high power pulsed magnetron sputtering of groups IVb and VIb transition metals in Ar

Grzegorz Greczynski, Igor Zhirkov, Ivan Petrov, J. E. Greene, Johanna Rosen
2017 Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films  
We use energy-and time-dependent mass spectrometry to analyze the evolution of metaland gas-ion fluxes incident at the substrate during high-power pulsed magnetron sputtering (HiPIMS) of Groups IVb and VIb transition-metal (TM) targets in Ar. For all TMs, the time-and energy-integrated metal/gas-ion ratio at the substrate plane + / + increases with increasing peak target current density JT,peak due to rarefaction. In addition, + / + exhibits a strong dependence on metal/gas-atom mass ratio ⁄
more » ... tom mass ratio ⁄ and varies from ∼1 for Ti ( ⁄ = 1.20) to ∼100 for W ( ⁄ = 4.60), with JT,peak maintained constant at 1 A/cm 2 . Time-resolved IEDFs confirm that the degree of rarefaction scales with ⁄ : for heavier TMs, the original sputteredatom Sigmund-Thompson energy distributions are preserved long after the HiPIMS pulse, which is in distinct contrast to lighter metals for which the energy distributions collapse into a narrow thermalized peak. Hence, precise timing of synchronous substrate-bias pulses, applied in order to reduce film stress while increasing densification, is critical for metal/gas combinations with ⁄ near unity, while with ⁄ ≫ 1, the width of the synchronous bias pulse is essentially controlled by the metal-ion time of flight. The good agreement between results obtained in an industrial system employing 440 cm 2 cathodes and a laboratory-scale system with a 20 cm 2 target is indicative of the fundamental nature of the phenomena. corresponding author: grzgr@ifm.liu.se; phone: +46 13 28 1213
doi:10.1116/1.4989674 fatcat:3j3j752vfjfj5pdm6np5jtb5me