Fabrication and characterization of EUV multilayer mirrors optimized for small spectral reflection bandwidth

Our aim was to produce EUV multilayer mirrors with a small spectral bandwid th DeltaE less than or equal to 3 eV at 70 eV peak energy using UHV electro n beam evaporation by varying the thickness ratio (Gamma = d(Abs)/d(Sp) + d (Abs)) between the absorber layer and the bilayer. The deposition process w as controlled by in situ soft X-ray reflectometry, and ion-beam polishing a s well as substrate-heating methods were applied to reduce the interface ro ughness. The reflection properties of the Mo-Si multilayer mirrors prepared were characterized by hard and soft X-ray reflectometry and details of the multilayer structure were revealed from cross-sectional transmission elect ron microscopy.