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Proceedings Paper

X-ray mask for optical heterodyne alignment
Author(s): Masanori Suzuki; Mitsuo Fukuda; F. Omata; H. Tsuyuzaki; Takashi Ohkubo; Ikuo Okada
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Paper Abstract

An optical heterodyne alignment system used in an SR stepper, the SS-1, is capable of high resolution, but its practical accuracy is affected by multiple reflections between the mask and the wafer. These multiple reflections cause a significant phase modulation when there is an inclination error in the heterodyne optics. In order to attain high alignment accuracy, an opaque film coating and an anti-reflection coating have been applied to an X-ray mask. The multiple reflections between the mask alignment mark and the wafer surface can be reduced by coating chrome films on X-ray mask alignment mark area. The mask distortion of less than 30 nm (3 (sigma) ), caused by forming 500-angstroms thick chrome films on a chip is obtained in the measurement. As a result, an alignment accuracy of 23 nm (3 (sigma) ) is achieved by a double-exposure experiment with the X-ray mask.

Paper Details

Date Published: 3 November 1994
PDF: 8 pages
Proc. SPIE 2254, Photomask and X-Ray Mask Technology, (3 November 1994); doi: 10.1117/12.191945
Show Author Affiliations
Masanori Suzuki, NTT LSI Labs. (Japan)
Mitsuo Fukuda, NTT LSI Labs. (Japan)
F. Omata, NTT LSI Labs. (Japan)
H. Tsuyuzaki, NTT LSI Labs. (Japan)
Takashi Ohkubo, NTT LSI Labs. (Japan)
Ikuo Okada, NTT LSI Labs. (Japan)

Published in SPIE Proceedings Vol. 2254:
Photomask and X-Ray Mask Technology
Hideo Yoshihara, Editor(s)

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