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Proceedings Paper

Experimental investigation of the Coulomb effect in electron projection lithography (EPL)
Author(s): Jiro Yamamoto; Fumio Murai; Akemi Moniwa
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Paper Abstract

Electron projection lithography (EPL) is a promising tool for next-generation lithography. However, beam blur due to the Coulomb effect becomes significant and degrades resolution when a high beam current is used to improve throughput. Suppressing the impact of the Coulomb effect is thus necessary to make EPL a practical tool for fabricating ULSI devices. We discuss the influence of the Coulomb effect in EPL based on our experimental results obtained using a Nikon experimental EPL column. To investigate the influence of the Coulomb effect on exposure results, we prepared three kinds of mask with different opening rates to vary the beam current on a wafer over a wide rage without affecting the lens illumination. We found that the Coulomb effect decreased the dose and focus latitude, and that the optimum focus condition varied within a sub-field. Furthermore, we found that the beam blue caused by the Coulomb effect was increased by shrinkage of the rectangular pattern end. Such shrinkage is also a problem in optical lithography, and complex pattern reshaping is necessary to correct it. The shrinkage becomes greater as the beam current increased. We estimated the amount of beam blue caused by the Coulomb effect by fitting our results through an energy deposition simulation. Our overall conclusion s that pattern reshaping and low-Coulomb-effect optics will be necessary to overcome the Coulomb effect.

Paper Details

Date Published: 1 July 2002
PDF: 11 pages
Proc. SPIE 4688, Emerging Lithographic Technologies VI, (1 July 2002); doi: 10.1117/12.472270
Show Author Affiliations
Jiro Yamamoto, Hitachi, Ltd. (Japan)
Fumio Murai, Hitachi, Ltd. (Japan)
Akemi Moniwa, Hitachi, Ltd. (Japan)

Published in SPIE Proceedings Vol. 4688:
Emerging Lithographic Technologies VI
Roxann L. Engelstad, Editor(s)

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