Protective Free-Standing Films for Projection Lithography Installations in the Extreme UV Range

Variants of the structures of free-standing films with a high transmittance coefficient at a wavelength of 13.5 nm, which were developed for use in the projection of extreme ultraviolet (EUV) lithography as protective and filtering elements, are considered. Our attention is focused on the most problematic—in terms of manufacturing and the requirements on their characteristics—ultrathin free-standing films (pellicles), which are installed in front of the mask (photomask) in modern EUV scanners and serve to protect the surface of the mask from contamination. The main approaches used to manufacture ultrathin free-standing large-aperture films are compared. A brief review of the research on the development of high transmittance pellicles at a wavelength of 11.2 nm, which may become an operating wavelength for future EUV lithography, is given.