Effect of substrate roughness on Mo/Si multilayer optics for EUVL produced by UHV-e-beam evaporation and ion polishing

Kleineberg U, Westerwalbesloh T, Hachmann W, et al. Effect of substrate roughness on Mo/Si multilayer optics for EUVL produced by UHV-e-beam evaporation and ion polishing. In: Thin Solid Films. THIN SOLID FILMS. Vol 433. ELSEVIER SCIENCE SA; 2003: 230-236.Our current status of Mo/Si multilayer extreme ultraviolet coatings fabricated by UHV e-beam evaporation and ion polishing is presented. Standard Mo/Si multilayer coating deposited onto 4 inch Si-wafer substrates showing peak reflectivities of 67.4% with a lateral homogeneity in coating reflectance of approximately 0.3% and a variation in peak wavelength of approximately 0.05 nm. over the full aperture have been achieved. At-wavelength reflectivities achieved for comparable multilayer coatings deposited onto Zerodur substrates with an enhanced microroughness (sigma = 0.55 nm) is shown to drop severely by almost 10%. A partial smoothing could be achieved by applying thin a-C buffer layers to these substrates, which in turn enhance the atwavelength reflectivity of the Mo/Si multilayer by 0.7%. (C) 2003 Elsevier Science B.V. All rights reserved