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Proceedings Paper

Iso-focal characteristics of line patterns in dark field imaging
Author(s): Shuji Nakao; Shinji Tarutani; Ayumi Minamide; Akira Tokui; Kouichirou Tsujita; Ichiriou Arimoto
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Paper Abstract

Iso-focal characteristics of line patterns in dark field imaging are investigated by optical image calculations and basic experiments for application to gate pattern in current logic devices. In dark field imaging, isolated line image, that is bright line image, shows iso-focal characteristics at exposure level higher than that in usual printing condition. The effective image contrast is enough high to resolve the line pattern by the application of high contrast resist. By the investigation of imaging characteristics throughout pattern pitch, good focus latitude of DOF > approximately 0.50 micrometers is obtained for almost all pitches down to approximately 300 nm in KrF wavelength utilizing modified illumination and attenuating phase shift mask. It is also revealed that mask error enhancement factor (MEF) is less than 2.0 and exposure latitude, which is defined by ((Delta) CD/CD)/((Delta) Exp.Dose/Exp. Dose), is smaller than approximately 1.0 throughout the pattern pitch. Although these very superior characteristics are obtained by this imaging, minimum image CD of isolated line with iso-focal characteristics is no smaller than approximately 180 nm for KrF wavelength even with extremely high NA. Also, range of line width for high DOF is not so large of approximately100 nm for isolated line. However, by application of appropriate CD trimming, such as partial ashing, this method can be applied for gate pattern formation of logic devices in 100 nm node. Accordingly, we believe that this work will provide a cost effective method of gate pattern formation down to 100 nm node in use of KrF wavelength.

Paper Details

Date Published: 30 July 2002
PDF: 9 pages
Proc. SPIE 4691, Optical Microlithography XV, (30 July 2002); doi: 10.1117/12.474548
Show Author Affiliations
Shuji Nakao, Mitsubishi Electric Corp. (Japan)
Shinji Tarutani, Mitsubishi Electric Corp. (Japan)
Ayumi Minamide, Mitsubishi Electric Corp. (Japan)
Akira Tokui, Mitsubishi Electric Corp. (Japan)
Kouichirou Tsujita, Mitsubishi Electric Corp. (Japan)
Ichiriou Arimoto, Mitsubishi Electric Corp. (Japan)

Published in SPIE Proceedings Vol. 4691:
Optical Microlithography XV
Anthony Yen, Editor(s)

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