Imaging performance of scanning exposure systems

Ryuichi Ebinuma; Kazunori Iwamoto; Hiroaki Takeishi; Hiroshi Itoh; Mitsuru Inoue; Kazuhiro Takahashi; Masakatsu Ohta

doi:10.1117/12.310772

29 June 1998 Imaging performance of scanning exposure systems

Ryuichi Ebinuma, Kazunori Iwamoto, Hiroaki Takeishi, Hiroshi Itoh, Mitsuru Inoue, Kazuhiro Takahashi, Masakatsu Ohta

Proceedings Volume 3334, Optical Microlithography XI; (1998) https://doi.org/10.1117/12.310772
Event: 23rd Annual International Symposium on Microlithography, 1998, Santa Clara, CA, United States

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.

Citation Download Citation

Ryuichi Ebinuma, Kazunori Iwamoto, Hiroaki Takeishi, Hiroshi Itoh, Mitsuru Inoue, Kazuhiro Takahashi, and Masakatsu Ohta "Imaging performance of scanning exposure systems", Proc. SPIE 3334, Optical Microlithography XI, (29 June 1998); https://doi.org/10.1117/12.310772

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KEYWORDS

Tin

Semiconducting wafers

Distortion

Imaging systems

Ions

Modulation transfer functions

Reticles

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