The Influence of the Magnetic Field on the Deposition Rate and Ionized Flux Fraction in the HiPIMS Discharge

The effect of the magnetic field strength $|{\bf B}|$ and geometry (degree of balancing) on the deposition rate and ionized flux fraction $F_{\rm flux}$ in dc magnetron sputtering (dcMS) and high power impulse magnetron sputtering (HiPIMS) when depositing titanium are explored [1]. The magnetic field only influences the dcMS deposition rate slightly. The deposition rate during HiPIMS operated with fixed voltage increases from 30\% to 90\% of the dcMS deposition rate as $|{\bf B}|$ is decreased but $F_{\rm flux}$ decreases. In contrast, when operating the HiPIMS discharge in fixed peak current mode both the deposition rate and $F_{\rm flux}$ increase with decreasing $|{\bf B}|$. The measured quantities, the deposition rate and ionized flux fraction, are then related to the ionization probability $\alpha_{\ŗm t}$ and the back attraction probability of the sputtered species $\beta_{\rm t}$. We show that the fraction of the ions of the sputtered material that escape back attraction increases by 30\% when $|{\bf B}|$ is reduced during operation in fixed peak current mode while the ionization probability of the sputtered species increases with increased discharge current when operating in fixed voltage mode. [1] Hajihoseini et al. {\em Plasma} {\bf 2} (2019) 201