Optical Coating Laboratory, Inc.

Bradley James Pond

Scott Eugene Solberg

Richard Ian Seddon

William T Beauchamp

Scott E Solberg

It has been discovered that control of the intra-layer stress in layers of high refractive index materials, such as zirconia and titania, permits low net stress multilayer thin film stacks comprising alternating layers of the high refractive index material and silica, a low refractive index material, to be sputter-deposited on glass substrates. In particular, a simple, cost-effective and readily reproducible post-deposition annealing process is used, i.e., an annealing process that can be effected within a broad temperature range and for a brief and substantially open-ended time period, to change the post-deposition microstructure of the high refractive index film layers and create a selected intra-layer tensile stress. The intra-layer tensile stress created during such an annealing process is largely dependent on the post-deposition microstructure of the high refractive index thin film layers. It has been further discovered that the deposition conditions and, in particular, ion bombardment energy, can be controlled to provide a selected and reproducible post-deposition microstructure that is partially amorphous and partially crystalline and which transforms during annealing to a very dense crystalline microstructure. This transformation results in film shrinkage and, because the film is constrained by the glass substrate, the film shrinkage produces a selected amount of tensile stress that compensates for the compressive stress of the silica thin film layers.

Methods and apparatus for preparing low net stress multilayer thin film

Low net stress multilayer thin film coatings

The present invention is directed to a sputtering method for preparing optical coatings having low light scattering characteristics by controlling the angle of incidence of the material being sputtered without significantly reducing the coating efficiency of the sputtering process. The angle of incidence is controlled by reducing the collision scattering of the material being sputtered and by intercepting the sputtered material that would without interception arrive at the surface to be coated at high angles of incidence. The collision scattering is reduced by utilizing a sputtering gas that has a mass less than the mass of the material being sputtered.

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Sonoma, CA, United States of America

Bradley James Pond