Role of magnetic field and bias configuration on HiPIMS deposition of W films

In this work, the deposition of tungsten (W) films by High Power Impulse Magnetron Sputtering (HiPIMS) has been investigated. By adopting a combined modeling and experimental approach, the role of magnetic field strength and bias configuration on growth of W films has been studied since they are relevant parameters for the energetic and ionized HiPIMS environment. Modeling results showed that increasing the magnetic strength from 40 to 60 mT led to larger W ion fraction in the plasma and, contemporary, to higher ion back-attraction to the target. This, in turn, resulted in a similar W ion fraction in the flux towards the substrate for the two magnetic field strengths considered during the on-time of the voltage pulse. On the contrary, the W ion fraction became significantly different in the afterglow and the same happened to the ion flux composition. Exploiting the studied discharges, W films have been grown applying at substrate negative pulsed bias voltages, both synchronized and delayed to the voltage pulse onset. Films morphology, microstructure, residual stress, composition and density have been examined. In light of plasma differences retrieved from the numerical investigation, film growth and properties are discussed.