Abstract

A visible-light microscope has been modified to obtain deep UV (190–350-nm) images using reflected illumination. Potential advantages of deep UV microscopy include better resolution, depth of focus, and contrast for certain materials and fewer artifacts when viewing multilayered structures. These advantages are especially useful when viewing organic or semiconducting materials that are transparent or colored when viewed with visible light but are completely opaque when viewed using deep UV wavelengths. The hardware and optics of this microscope are described, and several uses are proposed for integrated circuit manufacture.

© 1990 Optical Society of America

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References

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  1. J. M. Moran, D. Maydan, “High Resolution, Steep Profile, Resist Patterns,” Bell Syst. Tech. J. 58, 1027–1036 (1979).
  2. P. A. Heimann, J. M. Moran, R. J. Schutz, “Interferometric Methods and Apparatus for Device Fabrication,” U.S. Patent4,680,084 (July1987).
  3. These formulas are widely quoted but rarely referenced or derived. The resolution formula (Eq. 1a) is derived in F. A. Jenkins, H. E. White, Fundamental of Optics (McGraw-Hill, New York, 1976), p. 332ff. The depth of field formula [Eq. (1b)] is described in L. F. Thompson, C. G. Willson, M. J. S. Bowden, Eds. Introduction to Microlithography (Academic, New York, 1983), p. 44.
  4. F. A. Jenkins, H. E. White, Ref. 3, Chap. 3.
  5. See, for example, I. H. Malitson, “Interspecimen Comparison of the Refractive Index of Fused Silica,” J. Opt. Soc. Am. 55, 1205–1209 (1965), as cited in numerous reference handbooks.
    [CrossRef]
  6. Shipley Co., Inc., Newton, MA.
  7. Olin Hunt Specialty Products, Inc., West Paterson, NJ.
  8. For example, the Nanospec, from Nanometrics, Inc., Sunnyvale, CA.
  9. For example, the Leitz MPV CD, for E. Leitz Co., Rockleigh, NJ.
  10. For example, type R-166, from Hamamatsu Corp., Middlesex, NJ.
  11. D. L. White, unpublished.

1979 (1)

J. M. Moran, D. Maydan, “High Resolution, Steep Profile, Resist Patterns,” Bell Syst. Tech. J. 58, 1027–1036 (1979).

1965 (1)

Heimann, P. A.

P. A. Heimann, J. M. Moran, R. J. Schutz, “Interferometric Methods and Apparatus for Device Fabrication,” U.S. Patent4,680,084 (July1987).

Jenkins, F. A.

These formulas are widely quoted but rarely referenced or derived. The resolution formula (Eq. 1a) is derived in F. A. Jenkins, H. E. White, Fundamental of Optics (McGraw-Hill, New York, 1976), p. 332ff. The depth of field formula [Eq. (1b)] is described in L. F. Thompson, C. G. Willson, M. J. S. Bowden, Eds. Introduction to Microlithography (Academic, New York, 1983), p. 44.

F. A. Jenkins, H. E. White, Ref. 3, Chap. 3.

Malitson, I. H.

Maydan, D.

J. M. Moran, D. Maydan, “High Resolution, Steep Profile, Resist Patterns,” Bell Syst. Tech. J. 58, 1027–1036 (1979).

Moran, J. M.

J. M. Moran, D. Maydan, “High Resolution, Steep Profile, Resist Patterns,” Bell Syst. Tech. J. 58, 1027–1036 (1979).

P. A. Heimann, J. M. Moran, R. J. Schutz, “Interferometric Methods and Apparatus for Device Fabrication,” U.S. Patent4,680,084 (July1987).

Schutz, R. J.

P. A. Heimann, J. M. Moran, R. J. Schutz, “Interferometric Methods and Apparatus for Device Fabrication,” U.S. Patent4,680,084 (July1987).

White, D. L.

D. L. White, unpublished.

White, H. E.

F. A. Jenkins, H. E. White, Ref. 3, Chap. 3.

These formulas are widely quoted but rarely referenced or derived. The resolution formula (Eq. 1a) is derived in F. A. Jenkins, H. E. White, Fundamental of Optics (McGraw-Hill, New York, 1976), p. 332ff. The depth of field formula [Eq. (1b)] is described in L. F. Thompson, C. G. Willson, M. J. S. Bowden, Eds. Introduction to Microlithography (Academic, New York, 1983), p. 44.

Bell Syst. Tech. J. (1)

J. M. Moran, D. Maydan, “High Resolution, Steep Profile, Resist Patterns,” Bell Syst. Tech. J. 58, 1027–1036 (1979).

J. Opt. Soc. Am. (1)

Other (9)

Shipley Co., Inc., Newton, MA.

Olin Hunt Specialty Products, Inc., West Paterson, NJ.

For example, the Nanospec, from Nanometrics, Inc., Sunnyvale, CA.

For example, the Leitz MPV CD, for E. Leitz Co., Rockleigh, NJ.

For example, type R-166, from Hamamatsu Corp., Middlesex, NJ.

D. L. White, unpublished.

P. A. Heimann, J. M. Moran, R. J. Schutz, “Interferometric Methods and Apparatus for Device Fabrication,” U.S. Patent4,680,084 (July1987).

These formulas are widely quoted but rarely referenced or derived. The resolution formula (Eq. 1a) is derived in F. A. Jenkins, H. E. White, Fundamental of Optics (McGraw-Hill, New York, 1976), p. 332ff. The depth of field formula [Eq. (1b)] is described in L. F. Thompson, C. G. Willson, M. J. S. Bowden, Eds. Introduction to Microlithography (Academic, New York, 1983), p. 44.

F. A. Jenkins, H. E. White, Ref. 3, Chap. 3.

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Figures (8)

Fig. 1
Fig. 1

Spectrum of high pressure mercury lamp.

Fig. 2
Fig. 2

Illuminator optical path.

Fig. 3
Fig. 3

Comparison of (a) glass and (b) mirror objectives with visible light and Polaroid film.

Fig. 4
Fig. 4

Comparison of (a) glass and (b) mirror objectives with visible light and TV camera.

Fig. 5
Fig. 5

Comparison of (a) visible and (b) deep UV images: Resolution test pattern in trilevel resist.

Fig. 6
Fig. 6

Comparison of (a) visible and (b) deep UV images: Patterned trilevel resist on top of patterned thermal oxide.

Fig. 7
Fig. 7

Effect of (a) ideal vs (b) nonideal illumination.

Fig. 8
Fig. 8

Deep UV images of a resolution test pattern (a) before and (b) after the trilevel pattern transfer etch.

Tables (1)

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Table I Focal Lengths of Glass Lenses

Equations (5)

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r = 0.6 λ N . A . ,
d = λ 2 N . A . 2 ,
f ( λ ) f 0 = [ n 0 - 1 n ( λ ) - 1 ] ,
Δ f = f 0 Δ n n 0 - 1 .
1 f = 1 x 1 + 1 x 2 ,

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