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Proceedings Paper

Advances in multilayer reflective coatings for extreme ultraviolet lithography
Author(s): James A. Folta; Sasa Bajt; Troy W. Barbee Jr.; R. Fred Grabner; Paul B. Mirkarimi; Tai D. Nguyen; Mark A. Schmidt; Eberhard Adolf Spiller; Christopher C. Walton; Marco Wedowski; Claude Montcalm
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Paper Abstract

Multilayer mirror coatings which reflect extreme UV (EUV) radiation are a key enabling technology for EUV lithography but must meet stringent requirements in terms of film quality, stability, and thickness control across multi optical elements up to 300 nm in diameter. Deposition technology has been dramatically improved to meet those specifications for thickness control and repeatability over large curved optical substrates. Coating uniformity was improved to +/- 0.055 percent peak-to-valley (P-V) on 140- mm flats and +/- 0.1 percent P-V across 160 mm curved substrates. the run-to-run reproducibility of the reflectance peak wavelength was improved to 0.13 percent on flats to enable fabrication of wavelength-matched sets of optics. Multilayers with reflectances of 67.5 percent at 13.42 nm and 70.2 percent at 11.34 nm are typically achieved for Mo/Si and Mo/Be multilayers, respectively. Also, we have recently achieved a reflectance of 70.1 percent at 13.5 nm for a Mo/Si multilayer deposited with a modified process. The reflectance and stress of these multilayers appear to be stable relative to the requirements for application to EUV lithography. These improvements in EUV multilayer mirror technology enable us to meet the stringent specifications for coating the large optical substrates for our next- generation EUV lithography system. The primary remaining issues are improving the run-to-run wavelength repeatability on curved optics to realize the maximum optical throughput, and verifying long-term stability of the multilayers within the environment of a production EUV lithographic system.

Paper Details

Date Published: 25 June 1999
PDF: 8 pages
Proc. SPIE 3676, Emerging Lithographic Technologies III, (25 June 1999); doi: 10.1117/12.351156
Show Author Affiliations
James A. Folta, Lawrence Livermore National Lab. (United States)
Sasa Bajt, Lawrence Livermore National Lab. (United States)
Troy W. Barbee Jr., Lawrence Livermore National Lab. (United States)
R. Fred Grabner, Lawrence Livermore National Lab. (United States)
Paul B. Mirkarimi, Lawrence Livermore National Lab. (United States)
Tai D. Nguyen, Lawrence Livermore National Lab. (United States)
Mark A. Schmidt, Lawrence Livermore National Lab. (United States)
Eberhard Adolf Spiller, Lawrence Livermore National Lab. (United States)
Christopher C. Walton, Lawrence Livermore National Lab. (United States)
Marco Wedowski, Lawrence Livermore National Lab. (United States)
Claude Montcalm, Lawrence Livermore National Lab. (United States)

Published in SPIE Proceedings Vol. 3676:
Emerging Lithographic Technologies III
Yuli Vladimirsky, Editor(s)

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