The reflectivity of multilayered EUV mirrors tuned for 11-16 nm, for which
the two-component Mo/Be and Mo/Si multilayered systems are commonly used,
is enhanced by incorporating additional elements and their compounds
mainly from period 5 of the periodic table. In addition, the reflectivity
performance of the multilayer stacks is further enhanced by a numerical
global optimization procedure by which the layer thicknesses are varied
for optimum performance in, contradistinction to the constant layer
thickness--i.e. constant partition ratio--multilayer stacks commonly
designed and, fabricated hitherto. By incorporating additional materials
with differing complex refractive indices in various regions of the stack,
or by wholly replacing one of the components (typically Mo), we have
observed peak reflectivity enhancements of up to 5% for a single reflector
compared to a standard unoptimized stack.
