High performance La/B4C multilayer mirrors with barrier layers for the next generation lithography

Results on optimization and manufacturing of La/B4C multilayers are reported. Such mirrors are promising optical elements for the development of the next generation of nano-lithography at an operation wavelength of 6.7 nm. A near-normal incidence reflectivity of up to 58.6% has been measured at the BESSY-II soft x-ray reflectometer beamline. This is the highest reflectivity measured so far at this wavelength. The potential to further increase the reflectivity of the multilayers is discussed.