ADVANTAGEOUS POSSIBILITIES, DESIGN ASPECTS AND TECHNICAL USE OF DOUBLE-RING MAGNETRON SPUTTER SOURCES

Based on the principle of the double-ring source, some problems with stationary deposition by magnetron sputtering can be solved so that several possibilities of process control are achieved. The first is the homogeneous deposition of one material on large substrates up to 300 mm in diameter. This problem can also be solved for coating distances in the range below 100 mm by superposing two concentric sputter zones with well defined diameters. Experience and results obtained during practical use of the devised magnetron solution are discussed. Another very important task is the homogeneous deposition of compounds by reactive magnetron sputtering. In this case the double-ring source with a conducting target offers the advantage of solving efficiency problems with the anode that will be covered by reaction products so that it becomes inoperative during reactive deposition. Some aspects of magnetron design are discussed with regard to these partially contradictory demands for different applications. The model for optimizing parameters such as erosion track, coating distance and power ratio of the two concentric discharges is explained. The design of a magnet system with a variable magnetic field strength is of importance for both erosion behaviour and process control. The pros and cons of systems with electromagnets and permanent magnets under different aspects of practical importance are compared.