Anode effects in magnetron sputtering

Experimental examination of anode phenomena in a magnetron plasma is performed and qualitative analysis of the phenomena observed is given. Anode size effects and potential distribution in the magnetron discharge plasma are investigated. The observed effects are discussed in the context of the well-established theory for magnetized glow discharges. When a power supply is floating and only connected to chamber ground through a sufficiently large resistor, the chamber wall is taken out of the anode circuit. In the experiments, varying the resistance between 200 to 20 000 Ohm kept the anodes designated "activated" and did not substantially change the anode size effects investigated. When the random electron impingement current, integrated over the anode area, becomes smaller than the external current imposed by the power supply, the anode assumes a positive potential with respect to the plasma. For a small anode, the positive potential reaches values high enough for an anode plasma to appear. Localized anode plasmas act as ion sources. The ions drift to the magnetron along the electric field lines and change the erosion rate of elongated targets locally. Positive control over the deposition rate distribution can be obtained, for example, by applying additional voltage between multiple small anodes. (C) 1998 Elsevier Science S.A.