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Proceedings Paper

Imaging performance of scanning exposure systems
Author(s): Ryuichi Ebinuma; Kazunori Iwamoto; Hiroaki Takeishi; Hiroshi Itoh; Mitsuru Inoue; Kazuhiro Takahashi; Masakatsu Ohta
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Paper Abstract

Relative position between the projected image on the wafer and the wafer itself changes during exposure. Factors of change are, for example, stage control error, difference of scanning direction between wafer stage and reticle stage (skew) and distortion of projection optics. We can define a kind of probability density function (PDF) concerning these changes of relative position. Fourier transform of this PDF is the transfer function of image transformation by relative motion. In this paper, we call this transfer function MoTF. The modulation of MoTF becomes a barometer of image contrast and the phase of MoTF gives position deviation (distortion). By analytical study of MoTF, standard deviation and expected value of said PDF are found to be the key parameters. Derived approximate equation in this paper agree with a computer simulation result of image contrast deterioration by vibration. With these studies, we can establish adequate specifications of scanning stage control demanded by imaging performance. Canon has developed a new stage structure for scanning exposures. By this structure the wafer stage is separated from main body on which projection optics and measurement systems are mounted so that reaction forces of stage acceleration can not be transferred directly to the maim body. With this structure we achieved excellent stage performance which has achieved imaging performance below 0.18 micrometer with high speed scanning.

Paper Details

Date Published: 29 June 1998
PDF: 11 pages
Proc. SPIE 3334, Optical Microlithography XI, (29 June 1998); doi: 10.1117/12.310772
Show Author Affiliations
Ryuichi Ebinuma, Canon Inc. (Japan)
Kazunori Iwamoto, Canon Inc. (Japan)
Hiroaki Takeishi, Canon Inc. (Japan)
Hiroshi Itoh, Canon Inc. (Japan)
Mitsuru Inoue, Canon Inc. (Japan)
Kazuhiro Takahashi, Canon Inc. (Japan)
Masakatsu Ohta, Canon Inc. (Japan)

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

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