The use of hollow cathode structured magnetron targets

Abstract

Abstract This paper details an investigation into how the current–voltage characteristics of a magnetron source can be modified by machining a circular groove into the target. In separate experiments, a groove (3 mm deep and 3 mm wide) was placed both in the position of the sputter trench and also above the outer ring of magnets on a 7.6 cm circular Cu target. The aim is to induce a hollow cathode effect by trapping magnetized electrons between the structure walls, and hence improve the discharge efficiency (i.e. to obtain high discharge currents at lower running voltages). The discharge current–voltage characteristics were compared to similar flat targets, in the pressure range 0.5–4 mTorr. It is found that higher discharge currents (greater than a factor of 3) and lower breakdown voltages (35–70 V lower) can be achieved with the new target design. An investigation into the effect of changing the position of the groove (and hence the magnetic field orientation relative to the groove walls) shows that the most effective position for the structure is directly below the magnetic trap.