Multilayer Mirror Technology

Abstract

Recent advances in multilayer (ML) fabrication and characterization have brought this technology to the verge of satisfying the severe requirements posed by soft x-ray projection lithography (SXPL). To enable a viable production SXPL system, the ML coatings must simultaneously demonstrate (1) high normal incidence reflectivity in the range of 65-70% at λ=130Å, (2) ML period errors of less than 0.5% over the optical surface to maintain diffraction- limited imaging and (3) long term stability under realistic operating conditions. In addition, it is possible that certain optical designs will require laterally graded coatings with similar tolerances for the ML period errors. This set of stringent requirements can only be achieved via a thorough understanding and control of the ML deposition process, ML structure and properties.