Experiments and modelling of high power impulse magnetron sputtering discharges with metallic target

High power impulse magnetron sputtering (HiPIMS) discharges with a number of metal targets are studied experimentally and by applying the ionization region model (IRM). The metal targets studied include, tungsten [1], chromium, zirconium [2], titanium [3], and copper [4]. Experimentally, the ionized flux fraction is determined to be in the range 10 - 80 %, and it is found to increase with increased discharge current density, and decreased working gas pressure. However, the deposition rate generally decreases with increased peak discharge current density. An overview will be given on the experimental results for various target materials and dependence on varying operating parameters such as peak discharge current density and pulse length. The IRM allows for studying the temporal evolution of the discharge current composition, the electron power absorption mechanisms, the ionization and back-attraction probabilities of the sputtered species, the dominant recycling mechanism, and the working gas rarefaction. We discuss how the discharge current composition varies between different target materials, and how the recycled species, and the processes leading to working gas rarefaction, depend on the target sputter yield [4]. In particular we will discuss how the back-attraction probability of the sputtered species depends on the sputter yield of the target material.