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Proceedings Paper

Evaluation of coma aberration in projection lens by various measurements
Author(s): Takashi Saito; Hisashi Watanabe; Yoshimitsu Okuda
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Paper Abstract

In this paper, evaluation of lens coma aberration in projection lens of a stepper by various measurement methods is described. The measurement methods were based on asymmetry of the printed images caused by coma aberration. We used three measurement methods. They are conventionally used method and two new methods. The three methods are: (a) measuring the CD difference between both ends of line-and-space, (b) observing the side lobe patterns using an attenuated phase shifting mask (a-PSM), and (c) measuring the registration error using overlay patterns that have assist patterns. These measurement patterns are printed on Si wafers by a KrF stepper (NA equals 0.55) with various (sigma) . The dependence of the feature size and (sigma) on the influence of coma aberration was easily measured by these methods. As each method has merits and demerits, proper use of each method is necessary. Then the influence of coma aberration was evaluated by method (a). The influence of coma aberration had two components and they were due to primary coma aberration and de-centering coma aberration respectively. We estimated the influence of coma aberration by simulation and got good agrement with the experimental results. The measurement methods we demonstrated here are applicable for lens evaluation of steppers by the users.

Paper Details

Date Published: 29 June 1998
PDF: 12 pages
Proc. SPIE 3334, Optical Microlithography XI, (29 June 1998); doi: 10.1117/12.310759
Show Author Affiliations
Takashi Saito, Matsushita Electronics Corp. (Japan)
Hisashi Watanabe, Matsushita Electronics Corp. (Japan)
Yoshimitsu Okuda, Matsushita Electronics Corp. (Japan)

Published in SPIE Proceedings Vol. 3334:
Optical Microlithography XI
Luc Van den Hove, Editor(s)

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