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Applied Optics

Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

  • Vol. 40, Iss. 1 — Jan. 1, 2001
  • pp: 129–135

Multilayer-Coating-Induced Aberrations in Extreme-Ultraviolet Lithography Optics

Chen Liang, Michael R. Descour, Jose M. Sasian, and Scott A. Lerner  »View Author Affiliations


Applied Optics, Vol. 40, Issue 1, pp. 129-135 (2001)
http://dx.doi.org/10.1364/AO.40.000129


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Abstract

A multilayer coating alters the amplitude and phase of a reflected wave front. The amplitude effects are multiplicative and well understood. We present a mathematical formalism that can be used to describe the phase effects of coating in a general case. On the basis of this formalism we have developed an analytical method of estimating the wave-front aberrations introduced by the multilayer coating. For the case of field-independent aberrations, we studied both uniform and graded multilayer coatings. For the case of field-dependent aberrations, we studied only the effects of a uniform multilayer coating. Our analysis is based on a coated plane mirror tilted with respect to an incident converging beam. Altogether we have found, up to the second order, the following aberrations: a field-dependent piston, a field-squared-dependent piston, defocus, field-independent tilt, field-independent astigmatism, and anamorphic magnification. To obtain numerical results we apply our analysis to the specific case of a plane mirror tilted 8.2 deg with respect to an incident converging beam with a numerical aperture of 0.1. We find that the magnitudes of the field-independent aberration coefficients for the graded coating are approximately ten times smaller than those for the uniform coating. We show that a coating can introduce anamorphic magnification.

© 2001 Optical Society of America

OCIS Codes
(110.3960) Imaging systems : Microlithography
(220.3740) Optical design and fabrication : Lithography
(230.4170) Optical devices : Multilayers
(310.1620) Thin films : Interference coatings
(310.6860) Thin films : Thin films, optical properties

Citation
Chen Liang, Michael R. Descour, Jose M. Sasian, and Scott A. Lerner, "Multilayer-Coating-Induced Aberrations in Extreme-Ultraviolet Lithography Optics," Appl. Opt. 40, 129-135 (2001)
http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-40-1-129


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References

  1. D. J. Reiley and R. A. Chipman, “Coating-induced wave-front aberrations: on-axis astigmatism and chromatic aberration in all-reflecting systems,” Appl. Opt. 33, 2002–2012 (1994).
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  10. MATHEMATICA is a product of Wolfram Research, Inc., Champaign, Ill. (1999).

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