title: High performance EUV multilayer structures insensitive to capping layer optical parameters.
abstract: We have designed and tested a-periodic multilayer structures containing protective capping layers in order to obtain improved stability with respect to any possible changes of the capping layer optical properties (due to oxidation and contamination, for example)-while simultaneously maximizing the EUV reflection efficiency for specific applications, and in particular for EUV lithography. Such coatings may be particularly useful in EUV lithographic apparatus, because they provide both high integrated photon flux and higher stability to the harsh operating environment, which can affect seriously the performance of the multilayer-coated projector system optics. In this work, an evolutive algorithm has been developed in order to design these a-periodic structures, which have been proven to have also the property of stable performance with respect to random layer thickness errors that might occur during coating deposition. Prototypes have been fabricated, and tested with EUV and X-ray reflectometry, and secondary electron spectroscopy. The experimental results clearly show improved performance of our new a-periodic coatings design compared with standard periodic multilayer structures.
authors.affiliation: Information Engineering Department, University of Padova, Padova 35131, Italy.
authors.forename: Maria Guglielmina
authors.initials: MG
authors.lastname: Pelizzo
authors.forename: Michele
authors.initials: M
authors.lastname: Suman
authors.forename: Gianni
authors.initials: G
authors.lastname: Monaco
authors.forename: Piergiorgio
authors.initials: P
authors.lastname: Nicolosi
authors.forename: David L
authors.initials: DL
authors.lastname: Windt
mesh_terms: D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008027:Light; D008567:Membranes, Artificial; D008962:Models, Theoretical; D055095:Optics and Photonics / Q000295:instrumentation*; D012542:Scattering, Radiation
chemical_list: D008567:Membranes, Artificial