Multilayer coatings for the EUVL front-end test bed

Good illumination uniformity at the mask and wafer planes, and high wafer thoroughput in the EUVL front-end test bed facility at LLNL require graded period multilayer (ML) coatings on several of the optics. The ML deposition was accomplished using a newly developed deposition technique which avoids the use of {open_quotes}uniformity masks{close_quotes} to define the spatial dependence of the ML period variation. The capabilities of the process in providing the specified ML coatings are discussed for both EUVL condenser and imaging systems.