X-ray mask for optical heterodyne alignment

Masanori Suzuki; Mitsuo Fukuda; F. Omata; H. Tsuyuzaki; Takashi Ohkubo; Ikuo Okada

doi:10.1117/12.191945

3 November 1994 X-ray mask for optical heterodyne alignment

Masanori Suzuki, Mitsuo Fukuda, F. Omata, H. Tsuyuzaki, Takashi Ohkubo, Ikuo Okada

Proceedings Volume 2254, Photomask and X-Ray Mask Technology; (1994) https://doi.org/10.1117/12.191945
Event: Photomask Japan '94, 1994, Kawasaki City, Kanagawa, Japan

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.

Citation Download Citation

Masanori Suzuki, Mitsuo Fukuda, F. Omata, H. Tsuyuzaki, Takashi Ohkubo, and Ikuo Okada "X-ray mask for optical heterodyne alignment", Proc. SPIE 2254, Photomask and X-Ray Mask Technology, (3 November 1994); https://doi.org/10.1117/12.191945

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