| 摘要 |
The invention relates to a narrow-band spectral filter. The aim of the invention is to reduce the radiation exposure of optical elements used in highly ultraviolet light by using an optical filter that is simple in construction and that preselects a wavelength band of a predetermined bandwidth. To this end, an optical filter is provided that comprises at least one zirconium, niobium, or molybdenum layer interposed between two silicon layers. In order to increase the mechanical stability and the service life of the filter and in order to further restrict the spectral characteristics, another two ruthenium or rhodium layers each can follow the silicon layers. The filters of this kind are especially used in illumination systems and projection illumination systems for highly ultraviolet light that are used in semiconductor lithography.
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