Process for coating substrates by means of a magnetron cathode

In a process for coating substrates by means of cathode sputtering, a magnetron cathode is used which has an annularly closed target 9. The sputter surface 9a of this target has an inner edge 9c and an outer edge 9d. The corresponding system of permanent magnets 7 has a first pole 7c which is disposed inside the inner edge and a second pole 7d disposed outside the outer edge. The characteristics of the poles geometrically resemble those of the target edges. This results in the generation of a circumferentially closed magnetic tunnel over the sputter surface. The flux lines thereof which are important to the enclosure of the plasma, are only slightly curved. In order to achieve a good material efficiency at high sputter rates and yet a high plasma density at the substrates, the spatial course of the magnetic flux lines is selectively distorted in such a way that the area of maximum target erosion, in absence of additional magnetic fields, is shifted to the vicinity of the outer edge 9d of the target 9. An averaged time value of an excitation current is applied to an additionally disposed magnetic coil 26. It serves to shift the zone of maximum target erosion approximately to the center between the two target edges. A periodic change of the average value of the excitation current shifts the zone of maximum target erosion from the center toward both sides.