Plasma discharge characteristics for balanced magnetron sputtering cathode

The sputtering technique is valuable for film deposition processes such as semiconductor manufacturing and surface modification and functionalization. Most commonly used magnetron sputtering cathodes (MCs) are categorized as unbalanced MCs whose magnetic field lines (B-lines) diverge to the substrate surface from the target material surface for obtaining an efficient plasma irradiation to the substrate surface. In contrast, MCs with a non-divergent B-field are called balanced MCs which has an advantage for plasma confinement. In this study, B-field lines of unbalanced MC have been modified to be an almost completely balanced MC that loops B-field lines near the target and produces magnetic-mirror confinement on crossing area of B-field lines on target surface, namely the magnetic mirror-type magnetron cathode (M3C)[1]. The M3C is low power and low gas pressure operations available because permanent magnets inside the cathode form a B-field with the magnetic-mirror ratio of ~25 near the target surface. In this presentation, we will present the experimental results for the Langmuir probe measurement and the plasma discharge performances in a low RF or DC power of ~30 W and a gas pressure operation of ~0.1 Pa.

[1] T. Motomura and T. Tabaru, AIP Adv. 7, 125225 (2017).