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Optical Engineering

Fabrication of a complex-shaped mirror for an extreme ultraviolet lithography illumination system
Author(s): Hideo Takino; Teruki Kobayashi; Norio Shibata; Masaaki Kuki; Akinori Itoh; Hideki Komatsuda
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Paper Abstract

We propose and discuss several fabrication processes for a complex-shaped mirror, which is a fly-eye mirror, used in an extreme ultraviolet lithography (EUVL) illumination system. The mirror has a complex reflective surface consisting of many concave mirror elements that are sections of a sphere; the top of each element is arc shaped. In the present study, we focus on one process in which all elements are fabricated individually and then arranged side-by-side to form the mirror. Thus, as the first step in this process, we fabricate the arc-shaped elements made of invar with electroless nickel plating. The resultant reflective surfaces have a peak-to-valley (PV) surface accuracy of 0.31 μm. The surfaces have the rms roughnesses of about 0.23 and 0.35 nm in areas of 110×140 μm and 1×1 μm, respectively. The slope accuracies of the surfaces relative to the bottom surfaces are –166 and 43 arc-sec in the y and x directions, respectively. Thus, the mirror elements for the fly-eye mirror can be fabricated very accurately with smooth surfaces, although the mirror elements have a special shape compared to that of general optics.

Paper Details

Date Published: 1 September 2003
PDF: 7 pages
Opt. Eng. 42(9) doi: 10.1117/1.1591797
Published in: Optical Engineering Volume 42, Issue 9
Show Author Affiliations
Hideo Takino, Nikon Corp. (Japan)
Teruki Kobayashi, Nikon Corp. (Japan)
Norio Shibata, Nikon Corp. (Japan)
Masaaki Kuki, Nikon Corp. (Japan)
Akinori Itoh, Nikon Corp. (Japan)
Hideki Komatsuda, Nikon Corp. (Japan)

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