1 September 2003 Fabrication of a complex-shaped mirror for an extreme ultraviolet lithography illumination system
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Optical Engineering, 42(9), (2003). doi:10.1117/1.1591797
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.
Hideo Takino, Teruki Kobayashi, Norio Shibata, Masaaki Kuki, Akinori Itoh, Hideki Komatsuda, "Fabrication of a complex-shaped mirror for an extreme ultraviolet lithography illumination system," Optical Engineering 42(9), (1 September 2003). http://dx.doi.org/10.1117/1.1591797
JOURNAL ARTICLE
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KEYWORDS
Mirrors

Surface finishing

Reflectivity

Optical components

Extreme ultraviolet lithography

Polishing

Lithographic illumination

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