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Proceedings Paper

Overlay error of fine patterns by lens aberration using modified illumination
Author(s): Takashi Saito; Hisashi Watanabe; Yoshimitsu Okuda
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Paper Abstract

Overlay errors of fine patterns using modified illumination are experimentally measured and analyzed. Overlaid `vernier' patterns which fine lines and holes are overlaid on standard line patterns are used to measure the overlay errors. The experimental results using a KrF excimer laser stepper with various illumination conditions show that the overlay errors depend on the illumination coherence factor (sigma) and the pattern feature. These overlay errors consist of magnification and offset and these errors depend on the pattern feature. The offset error between line pattern and hole pattern are considerably large for device fabrication. The magnification component originates from coma aberration of the projection lens. We will confirm and estimate the effect of coma aberration on the overlay error by optical simulation. The origin of the offset error is considered to be coma aberration due to lens element decentering. This `decentering' coma aberration causes the offset error and the effect of `decentering' coma aberration has the feature dependence.

Paper Details

Date Published: 7 July 1997
PDF: 11 pages
Proc. SPIE 3051, Optical Microlithography X, (7 July 1997); doi: 10.1117/12.275988
Show Author Affiliations
Takashi Saito, Matsushita Electronics Corp. (Japan)
Hisashi Watanabe, Matsushita Electronics Corp. (Japan)
Yoshimitsu Okuda, Matsushita Electronics Corp. (Japan)


Published in SPIE Proceedings Vol. 3051:
Optical Microlithography X
Gene E. Fuller, Editor(s)

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