Effect of lens aberration on hole pattern fabrication using halftone phase-shifting masks

Akihiro Otaka; Yoshio Kawai; Yutaka Sakakibara

doi:10.1117/12.277262

28 July 1997 Effect of lens aberration on hole pattern fabrication using halftone phase-shifting masks

Akihiro Otaka, Yoshio Kawai, Yutaka Sakakibara

Proceedings Volume 3096, Photomask and X-Ray Mask Technology IV; (1997) https://doi.org/10.1117/12.277262
Event: Photomask Japan '97, 1997, Kawasaki City, Japan

Abstract

In hole pattern fabrication using halftone phase-shifting masks (HT-PSM), we found that the spherical aberration has a large influence on the usable depth of focus for the full field (uDOF). Spherical aberration shifts the best-focus position, and the shift is 9 times larger for the HT-PSM than that for a conventional Cr mask. When the variation of the spherical aberration in the exposure field is more than 0.1 lambda, the uDOF of a 0.6-lambda/NA hole pattern using the HT- PSM becomes smaller than that using the conventional Cr mask. To eliminate the influence of the spherical aberration, we investigated the effect of shifting the phase of the HT-PSM from 180 degrees. Based on the results, we developed a new HT- PSM in which a phase distribution varies in accordance with the spherical aberration at each position of the field. We tested the new mask and showed that the new mask improves uDOF and that it is effective in the fabrication of fine hole patterns.

Citation Download Citation

Akihiro Otaka, Yoshio Kawai, and Yutaka Sakakibara "Effect of lens aberration on hole pattern fabrication using halftone phase-shifting masks", Proc. SPIE 3096, Photomask and X-Ray Mask Technology IV, (28 July 1997); https://doi.org/10.1117/12.277262

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