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Proceedings Paper

Advanced alignment optical system for DUV scanner
Author(s): Tadashi Nagayama; Masahiko Yasuda; Yuho Kanaya; Takahiro Masada; Ayako Sugaya
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Paper Abstract

Advanced scanners need an extremely high accuracy wafer alignment system, and nowadays it is also necessary that the alignment marks occupy a smaller area in order to expand the available area for IC patterns. Therefore, narrower lines with a smaller pitch must form the alignment marks. In this paper, a higher Numerical Aperture (NA) and lower aberration alignment optical system are studied for these requirements. At first the small alignment marks are shown, and suitable NA in the optical system is then discussed. As a result, the necessity for higher NA is shown. As for low aberration, the necessary specification of wavefront aberration is discussed. Assuming it is possible to suitably select the NA and the illumination NA in the optical system, the results of simulation -- that simulate image signals and perform image processing -- are reported. These results show the optical system that has aberration causes position shift, so that the specification of wavefront aberration is estimated in order that the position shifts may be sufficiently small. To make sure that with such a strict specification the system will be possible, a trial optical system has been made. Finally the techniques of manufacturing and the results of evaluation are reported.

Paper Details

Date Published: 24 May 2004
PDF: 9 pages
Proc. SPIE 5375, Metrology, Inspection, and Process Control for Microlithography XVIII, (24 May 2004); doi: 10.1117/12.535083
Show Author Affiliations
Tadashi Nagayama, Nikon Corp. (Japan)
Masahiko Yasuda, Nikon Corp. (Japan)
Yuho Kanaya, Nikon Corp. (Japan)
Takahiro Masada, Nikon Corp. (Japan)
Ayako Sugaya, Nikon Corp. (Japan)

Published in SPIE Proceedings Vol. 5375:
Metrology, Inspection, and Process Control for Microlithography XVIII
Richard M. Silver, Editor(s)

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