The HiPIMS Process

The work presented in this thesis involves experimental and theoretical studies related to a thin film deposition technique called high power impulse magnetron sputtering (HiPIMS), and more specifically the plasma properties and how they influence the coating. HiPIMS is an ionized physical vapor deposition technique based on conventional direct current magnetron sputtering (DCMS). The major difference between the two methods is that HiPIMS has the added advantage of providing substantial ionization of the sputtered material, and thus presents many new opportunities for the coating industry. Understanding the dynamics of the charged species and their effect on thin film growth in the HiPIMS process is therefore essential for producing high-quality coatings. In the first part of the thesis a new type of anomalous electron transport was found. Investigations of the transport resulted in the discovery that this phenomenon could quantitatively be described as being related and mediated by highly nonlinear waves, likely due to the modified two-stream instability, resulting in electric field oscillations in the MHz-range (the lower hybrid frequency). Measurements in the plasma confirmed these oscillations as well as trends predicted by the theory of these types of waves. Using electric probes, the degree of anomalous transport in the plasma could also be determined by measuring the current density ratio between the azimuthal current density (of which the Hall current density is one contribution) and the discharge current density, J ϕ / J D . The results were verified in another series of measurements using Rogowski probes to directly gain insight into the internal currents in the HiPIMS discharge. The results provided important insights into understanding the mechanism behind the anomalous transport. It was furthermore demonstrated that the current ratio J ϕ / J D is inversely proportional to the transverse resistivity, η ⊥ , which governs how well momentum in the direction of the current is transferred from the electrons to the ions in the plasma. By looking at the forces involved in the charged particle transport it was expected that the azimuthally rotating electrons would exert a volume force on the ions tangentially outwards from the circular race track region. The effect of having an anomalous transport would therefore be that the ions were transported across the magnetic field lines and to a larger extent deflected sideways, instead of solely moving from t