title: Towards High Accuracy Reflectometry for Extreme-Ultraviolet Lithography.
abstract: Currently the most demanding application of extreme ultraviolet optics is connected with the development of extreme ultraviolet lithography. Not only does each of the Mo/Si multilayer extreme-ultraviolet stepper mirrors require the highest attainable reflectivity at 13 nm (nearly 70 %), but the central wavelength of the reflectivity of these mirrors must be measured with a wavelength repeatability of 0.001 nm and the peak reflectivity of the reflective masks with a repeatability of 0.12 %. We report on two upgrades of our NIST/DARPA Reflectometry Facility that have given us the ability to achieve 0.1 % repeatability and 0.3 % absolute uncertainty in our reflectivity measurements. A third upgrade, a monochromator with thermal and mechanical stability for improved wavelength repeatability, is currently in the design phase.
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD, 20899-8410 USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Tarrio
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD, 20899-8410 USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Grantham
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD, 20899-8410 USA.
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Squires
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD, 20899-8410 USA.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Vest
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD, 20899-8410 USA.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Lucatorto
keywords: extreme ultraviolet; lithography; metrology; reflectometry; synchrotron radiation