EUV reflectivity and stability of tri-component Al-based multilayers

Abstract

We report on further development of three-material multilayer coatings made with a use of aluminum for the extreme ultra-violet (EUV) applications such as solar physics, high-order harmonic generation or synchrotron radiation. It was found that an introduction of refractory metal in Al-based periodic stack helps to reduce significantly an interfacial roughness and provides for a higher theoretical reflectance in the spectral range from 17 to 40 nm. The normal incidence reflectivity as high as 55 % at 17 nm, 50 % at 21 nm and 42 % at 30 nm was achieved with the new Al/Mo/SiC and Al/Mo/B₄C multilayer mirrors, which have been optimized, fabricated and characterized with x-rays and synchrotron radiation. A good temporal and thermal stability of the tri-component Al-based multilayers has been observed over 3 years.