Pulse magnetron sputtering in a reactive gas mixture of variable composition to manufacture multilayer and gradient optical coatings

Abstract

Optical interference coatings have been produced by pulse magnetron sputtering a silicon target in a variable mixture of the reactive gases oxygen and nitrogen. Conventional H/L multilayer stacks with sharp transition of refractive index and gradient layer systems with inhomogeneous refractive index profile have been designed and deposited on glass and plastic substrates. Design examples and results of deposited films will be presented for multi-band rugate filters, edge and dichroic filters as well as for graded index antireflection coatings. All films were grown at a single sputtering station only, without interruption of the plasma process. The avoidance of substrate movement and process interruption, together with accurate process control, guarantees a very stable and highly efficient process with high reproducibility of the coating on 8″ substrates with a film thickness uniformity of ± 1%.