Multilayer Extreme UV Optics, or how science can benefit from its application

Ultrathin layered structures are known to act well as Bragg reflectors for light down to sub-nanometer wavelengths. However, the application of such structures in multi-element optics for photolithography at the wavelength of 13.5 nm has imposed tremendous challenges to the underlying thin film physics. Required is full physical and chemical stability, 10 W/cm2 radiation damage resistance, atomically sharp refractive index profiles, and dimension-controlled thicknesses down to the sub-nanometer range. Pursuing such properties has been the goal of several FOM and STW research programmes, executed in collaboration with, and facilitated by the participating end users of the optics. This valorisation has enabled an improved understanding of the basic physics with results immediately being used in this and other applications.