Extreme Ultraviolet Bragg mirrors with suppressed infrared reflectivity properties

Many optical applications demand high reflectivity in a particular wavelength range while simultaneously requiring suppression of radiation outside this range. Such parasitic radiation can for instance lead to image distortions in imaging applications or poor signal-noise ratios in spectroscopy. The most obvious need for radiation with high “spectral purity” can be found in extreme UV lithography (EUVL). EUVL utilizes narrow-band (13.5 nm ± 1%) radiation being extracted from a broad-band spectrum emitted by dense hot plasma sources. For this purpose we proposed and investigated various methods to integrate EUV reflecting multilayers with resonant infrared anti-reflecting structures. We discuss our pilot experiments, physics and optical properties of the realized structures in broad spectral range – from the EUV up to the infrared ranges.