Practical magnetron sputtering system for the deposition of optical multilayer coatings

A magnetron sputtering system is described in which, at any one time, as many as four different 15-cm x 46-cm rectangular planar magnetron targets can be mounted vertically in the deposition chamber. These can be attached to either dc or rf power supplies for direct or reactive deposition of metal, metal oxide, or nitride films. Typical target materials include Ag, Al, C, Mo, Nb, Ni, Si, W, and Zr. Good uniformity can be obtained on stationary substrates, although better results are possible with oscillating substrates. The refractive indices are given for several useful oxide materials. The materials and thicknesses of the individual layers that comprise an optical multilayer system are entered into a computer that subsequently controls the deposition parameters, the substrate motion, and the deposition time. After a relatively simple calibration process, coatings that consist of between 20 and 60 layers can be produced to within an accuracy of 1% or 2%. A wideband optical monitor is available for checking the performance of the multilayer system during its deposition. Several examples of multilayer coatings that were prepared on this equipment are given.