Cleaning technology for EUV multilayer mirror using atomic hydrogen generated with hot wire

• Published in: Thin solid films Vol. 516; no. 5; pp. 839 - 843
• Main Authors: Motai, Kumi, Oizumi, Hiroaki, Miyagaki, Shinji, Nishiyama, Iwao, Izumi, Akira, Ueno, Tomoya, Namiki, Akira
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Lausanne Elsevier B.V 15.01.2008; Elsevier Science
• Subjects: Atomic hydrogen; Cleaning; Condensed matter: structure, mechanical and thermal properties; Deoxidization; Electrons and positron radiation effects; EUV lithography; Exact sciences and technology; Hydrogen radicals density; Physical radiation effects, radiation damage; Physics; Ru-capped mirror; Structure of solids and liquids; crystallography; Transport; Atomic hydrogen; Hydrogen radicals density; Deoxidization; Ru-capped mirror; Cleaning; Transport; EUV lithography; Hydrogen neutral atoms; Catalytic reaction; Multilayer; Lithography; Surface treatments; Molybdenum; Molecular dissociation; Multilayers; Vacuum techniques; Electron irradiation; Silicon oxides; Experimental design; Oxidation; Silicon; Absorption spectra; X-ray photoelectron spectra
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2007.06.182

A method of removing contaminants from Ru-capped Mo/Si multilayer mirrors for extreme ultraviolet lithography has been developed. It employs atomic hydrogen generated by a heated catalyzer consisting of a W wire. A new experimental system was designed and constructed to examine the cleaning capability of atomic hydrogen transported through a quartz tube. The chemical state of an oxidized Ru surface was investigated by X-ray photoelectron spectroscopy before and after cleaning; and it was found that transported hydrogen radicals deoxidized the surface and reduced the amount of oxide to the level before oxidation. Although the time needed was longer, transported atomic hydrogen was found to be capable of deoxidizing an oxidized Ru surface. The dependence of the density of atomic hydrogen on W catalyzer temperature and hydrogen gas pressure was measured by a vacuum ultraviolet absorption technique; and the potential to increase the density, and thereby to reduce the treatment time, was demonstrated.