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 projection optics and has been tested with accelerated 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 ~40× longer lifetimes than Si-capped multilayers, which translates to 3 months to many years, depending on the mirror dose.
© 2003 Optical Society of America
(220.4840) Optical design and fabrication : Testing
(230.4170) Optical devices : Multilayers
(260.7200) Physical optics : Ultraviolet, extreme
(310.1860) Thin films : Deposition and fabrication
(350.1820) Other areas of optics : Damage
Sasa Bajt, Henry N. Chapman, Nhan Nguyen, Jennifer Alameda, Jeffrey C. Robinson, Michael Malinowski, Eric Gullikson, Andrew Aquila, Charles Tarrio, and Steven Grantham, "Design and Performance of Capping Layers for Extreme-Ultraviolet Multilayer Mirrors," Appl. Opt. 42, 5750-5758 (2003)