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Publication Citation: Design and Performance of Capping Layers for Extreme-Ulatraviolet Multilayer Mirrors

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Author(s): S Bajt; H N. Chapman; Nhan Nguyen; J Alameda; J C. Robinson; M Malinowski; E Gullikson; Andrew Aquila; Charles S. Tarrio; Steven E. Grantham;
Title: Design and Performance of Capping Layers for Extreme-Ulatraviolet Multilayer Mirrors
Published: October 01, 2003
Abstract: Multilayer lifetime has emerged as one of the major issues for the commercialization of extreme-ultraviolet lithography (EUVL). We describe the performance of an oxidation-resistant capping layer of Ru atop multilayers that results in a reflectivity above 69 % at 13.2 nm, which is suitable for EUVL projections optics and has been tested with acclerated electron-beam and extreme-ultraviolet (EUV) light in a water-vapor environment. Based on accelerated exposure results, we calculated multilayer lifetimes for all reflective mirrors in a typical commercial EUVL tool and concluded that Ru-capped multilayers have {approximately equal to} 40 x longer lifetimes thatn Si-capped multilayers, which translates to 3 months to many years, depending on the mirror dose.
Citation: Applied Optics
Volume: 42
Issue: No. 28
Keywords: capping layers;EUV;extreme ultraviolet lithography;mirrors;multilayer mirrors;optics;oxidation resistance;reflectivity;ruthenium
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