Abstract

To improve the resolution and the sensitivity of optical metrology, we have constructed an interferometer for vacuum-ultraviolet wavelengths. To examine the influence of the wavelength, especially with regard to the period of the object’s structure, we chose an apochromatic design. With reflective optics, wavelengths from 157 to 900 nm can be employed for interferometric measurements. The benefits and also the technological problems that accompany the use of vacuum-ultraviolet wavelengths are discussed. The design of this interferometer and measuring results with different wavelengths are presented.

© 1999 Optical Society of America

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References

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  1. J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968), pp. 129–131.
  2. J. Schwider, R. Burow, K.-E. Elssner, J. Grzanna, R. Spolaczyk, K. Merkel, “Digital wave-front measuring interferometry: some systematic error sources,” Appl. Opt. 22, 3421–3432 (1983).
    [CrossRef] [PubMed]
  3. U. Krackhardt, J. Schwider, M. Schrader, N. Streibl, “Synthetic holograms written by a laser pattern generator,” Opt. Eng. 32, 781–785 (1993).
    [CrossRef]
  4. R. Petit, Electromagnetic Theory of Gratings (Springer, New York, 1980).
    [CrossRef]
  5. G. Schulz, “Ein einfaches Interferenzmikroskop für Auflicht,” Naturwissenschaften 48, 565 (1961).
    [CrossRef]
  6. U. Minor, “Ein Dreistrahl-Interferenzmikroskop ohne materielle Vergleichsfläche,” Ph.D. dissertation (Humbold Universität, Berlin, 1967).
  7. K. Schwarzschild, Theorie der Spiegeltelescope (Weidmann, Berlin, 1905).
  8. T. Dresel, A. Horstmann, A. Otto, J. Schwider, “UV interferometry for microstructure measurements,” Pure Appl. Opt. 1, 241–249 (1992).
    [CrossRef]
  9. M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1980), pp. 306–309.
  10. H. E. Bennett, J. O. Porteus, “Relation between surface roughness and specular reflectance at normal incidence,” J. Opt. Soc. Am. 51, 123–129 (1961).
    [CrossRef]
  11. N. Lindlein, raytrace, V. 6.3, distributed by the Chair of Optics, University of Erlangen, Staudtstrasse 7/BII, D-91058 Erlangen, Germany.
  12. K. Watanabe, E. C. Y. Inn, M. Zelikoff, “Absorption coefficients of oxygen in the vacuum ultraviolet,” J. Chem. Phys. 21, 1026–1030 (1953).
    [CrossRef]
  13. K. Watanabe, M. Zelikoff, “Absorption coefficients of water vapor in the vacuum ultraviolet,” J. Opt. Soc. Am. 43, 753–755 (1953).
    [CrossRef]
  14. J. Schwider, O. Falkensdörfer, H. Schreiber, A. Zöller, N. Streibl, “New compensating four-phase algorithm for phase-shift interferometry,” Opt. Eng. 32, 1883–1885 (1993).
    [CrossRef]

1993 (2)

U. Krackhardt, J. Schwider, M. Schrader, N. Streibl, “Synthetic holograms written by a laser pattern generator,” Opt. Eng. 32, 781–785 (1993).
[CrossRef]

J. Schwider, O. Falkensdörfer, H. Schreiber, A. Zöller, N. Streibl, “New compensating four-phase algorithm for phase-shift interferometry,” Opt. Eng. 32, 1883–1885 (1993).
[CrossRef]

1992 (1)

T. Dresel, A. Horstmann, A. Otto, J. Schwider, “UV interferometry for microstructure measurements,” Pure Appl. Opt. 1, 241–249 (1992).
[CrossRef]

1983 (1)

1961 (2)

1953 (2)

K. Watanabe, E. C. Y. Inn, M. Zelikoff, “Absorption coefficients of oxygen in the vacuum ultraviolet,” J. Chem. Phys. 21, 1026–1030 (1953).
[CrossRef]

K. Watanabe, M. Zelikoff, “Absorption coefficients of water vapor in the vacuum ultraviolet,” J. Opt. Soc. Am. 43, 753–755 (1953).
[CrossRef]

Bennett, H. E.

Born, M.

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1980), pp. 306–309.

Burow, R.

Dresel, T.

T. Dresel, A. Horstmann, A. Otto, J. Schwider, “UV interferometry for microstructure measurements,” Pure Appl. Opt. 1, 241–249 (1992).
[CrossRef]

Elssner, K.-E.

Falkensdörfer, O.

J. Schwider, O. Falkensdörfer, H. Schreiber, A. Zöller, N. Streibl, “New compensating four-phase algorithm for phase-shift interferometry,” Opt. Eng. 32, 1883–1885 (1993).
[CrossRef]

Goodman, J. W.

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968), pp. 129–131.

Grzanna, J.

Horstmann, A.

T. Dresel, A. Horstmann, A. Otto, J. Schwider, “UV interferometry for microstructure measurements,” Pure Appl. Opt. 1, 241–249 (1992).
[CrossRef]

Inn, E. C. Y.

K. Watanabe, E. C. Y. Inn, M. Zelikoff, “Absorption coefficients of oxygen in the vacuum ultraviolet,” J. Chem. Phys. 21, 1026–1030 (1953).
[CrossRef]

Krackhardt, U.

U. Krackhardt, J. Schwider, M. Schrader, N. Streibl, “Synthetic holograms written by a laser pattern generator,” Opt. Eng. 32, 781–785 (1993).
[CrossRef]

Merkel, K.

Minor, U.

U. Minor, “Ein Dreistrahl-Interferenzmikroskop ohne materielle Vergleichsfläche,” Ph.D. dissertation (Humbold Universität, Berlin, 1967).

Otto, A.

T. Dresel, A. Horstmann, A. Otto, J. Schwider, “UV interferometry for microstructure measurements,” Pure Appl. Opt. 1, 241–249 (1992).
[CrossRef]

Petit, R.

R. Petit, Electromagnetic Theory of Gratings (Springer, New York, 1980).
[CrossRef]

Porteus, J. O.

Schrader, M.

U. Krackhardt, J. Schwider, M. Schrader, N. Streibl, “Synthetic holograms written by a laser pattern generator,” Opt. Eng. 32, 781–785 (1993).
[CrossRef]

Schreiber, H.

J. Schwider, O. Falkensdörfer, H. Schreiber, A. Zöller, N. Streibl, “New compensating four-phase algorithm for phase-shift interferometry,” Opt. Eng. 32, 1883–1885 (1993).
[CrossRef]

Schulz, G.

G. Schulz, “Ein einfaches Interferenzmikroskop für Auflicht,” Naturwissenschaften 48, 565 (1961).
[CrossRef]

Schwarzschild, K.

K. Schwarzschild, Theorie der Spiegeltelescope (Weidmann, Berlin, 1905).

Schwider, J.

U. Krackhardt, J. Schwider, M. Schrader, N. Streibl, “Synthetic holograms written by a laser pattern generator,” Opt. Eng. 32, 781–785 (1993).
[CrossRef]

J. Schwider, O. Falkensdörfer, H. Schreiber, A. Zöller, N. Streibl, “New compensating four-phase algorithm for phase-shift interferometry,” Opt. Eng. 32, 1883–1885 (1993).
[CrossRef]

T. Dresel, A. Horstmann, A. Otto, J. Schwider, “UV interferometry for microstructure measurements,” Pure Appl. Opt. 1, 241–249 (1992).
[CrossRef]

J. Schwider, R. Burow, K.-E. Elssner, J. Grzanna, R. Spolaczyk, K. Merkel, “Digital wave-front measuring interferometry: some systematic error sources,” Appl. Opt. 22, 3421–3432 (1983).
[CrossRef] [PubMed]

Spolaczyk, R.

Streibl, N.

J. Schwider, O. Falkensdörfer, H. Schreiber, A. Zöller, N. Streibl, “New compensating four-phase algorithm for phase-shift interferometry,” Opt. Eng. 32, 1883–1885 (1993).
[CrossRef]

U. Krackhardt, J. Schwider, M. Schrader, N. Streibl, “Synthetic holograms written by a laser pattern generator,” Opt. Eng. 32, 781–785 (1993).
[CrossRef]

Watanabe, K.

K. Watanabe, E. C. Y. Inn, M. Zelikoff, “Absorption coefficients of oxygen in the vacuum ultraviolet,” J. Chem. Phys. 21, 1026–1030 (1953).
[CrossRef]

K. Watanabe, M. Zelikoff, “Absorption coefficients of water vapor in the vacuum ultraviolet,” J. Opt. Soc. Am. 43, 753–755 (1953).
[CrossRef]

Wolf, E.

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1980), pp. 306–309.

Zelikoff, M.

K. Watanabe, M. Zelikoff, “Absorption coefficients of water vapor in the vacuum ultraviolet,” J. Opt. Soc. Am. 43, 753–755 (1953).
[CrossRef]

K. Watanabe, E. C. Y. Inn, M. Zelikoff, “Absorption coefficients of oxygen in the vacuum ultraviolet,” J. Chem. Phys. 21, 1026–1030 (1953).
[CrossRef]

Zöller, A.

J. Schwider, O. Falkensdörfer, H. Schreiber, A. Zöller, N. Streibl, “New compensating four-phase algorithm for phase-shift interferometry,” Opt. Eng. 32, 1883–1885 (1993).
[CrossRef]

Appl. Opt. (1)

J. Chem. Phys. (1)

K. Watanabe, E. C. Y. Inn, M. Zelikoff, “Absorption coefficients of oxygen in the vacuum ultraviolet,” J. Chem. Phys. 21, 1026–1030 (1953).
[CrossRef]

J. Opt. Soc. Am. (2)

Naturwissenschaften (1)

G. Schulz, “Ein einfaches Interferenzmikroskop für Auflicht,” Naturwissenschaften 48, 565 (1961).
[CrossRef]

Opt. Eng. (2)

U. Krackhardt, J. Schwider, M. Schrader, N. Streibl, “Synthetic holograms written by a laser pattern generator,” Opt. Eng. 32, 781–785 (1993).
[CrossRef]

J. Schwider, O. Falkensdörfer, H. Schreiber, A. Zöller, N. Streibl, “New compensating four-phase algorithm for phase-shift interferometry,” Opt. Eng. 32, 1883–1885 (1993).
[CrossRef]

Pure Appl. Opt. (1)

T. Dresel, A. Horstmann, A. Otto, J. Schwider, “UV interferometry for microstructure measurements,” Pure Appl. Opt. 1, 241–249 (1992).
[CrossRef]

Other (6)

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1980), pp. 306–309.

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968), pp. 129–131.

N. Lindlein, raytrace, V. 6.3, distributed by the Chair of Optics, University of Erlangen, Staudtstrasse 7/BII, D-91058 Erlangen, Germany.

R. Petit, Electromagnetic Theory of Gratings (Springer, New York, 1980).
[CrossRef]

U. Minor, “Ein Dreistrahl-Interferenzmikroskop ohne materielle Vergleichsfläche,” Ph.D. dissertation (Humbold Universität, Berlin, 1967).

K. Schwarzschild, Theorie der Spiegeltelescope (Weidmann, Berlin, 1905).

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Figures (10)

Fig. 1
Fig. 1

Interferometric head (after Schulz5 and Minor6).

Fig. 2
Fig. 2

Fringe contrast versus reflectivity for several wavelengths and beam-splitter materials. Reflectivity of the object, R quartz for TM polarization of ≈0.4; reflectivity of the mirror, R Al+65 nm MgF2 for TM polarization of ≈0.9.

Fig. 3
Fig. 3

Definition of direction angles for calculation of the Brewster fringe pattern.

Fig. 4
Fig. 4

Schematic for correction of a wedge angle of the beam-splitter plate.

Fig. 5
Fig. 5

Calculated wave fronts in the detector plane for defocused objects.

Fig. 6
Fig. 6

Illumination and imaging apertures of the reflective optical system and the resultant MTF for 193 nm.

Fig. 7
Fig. 7

Sketch of the glove box with experimental setup and gas supply.

Fig. 8
Fig. 8

Gray-scale representations of interferograms of a binary grating recorded at three wavelengths (grating etched in quartz glass; 10-µm period; depth, 36 nm; aspect ratio, 1). Phase changes that are due to the object structure are marked.

Fig. 9
Fig. 9

Section through the measured structure of a grating (period, 10 µm; depth, 36 nm; aspect ratio, 1).

Fig. 10
Fig. 10

Perspective plot of a measured grating (period, 10 µm; depth, 36 nm; aspect ratio, 1). Interferograms evaluated with phase shifting.

Tables (3)

Tables Icon

Table 1 Object Shift Δz To Correct for the Influence of the Dispersive Beam Splitter When the Wavelength Is Changed (Δz > 0 ⇔ Object Closer to Objective) and Spectral Area ±Δλ for Diffraction-Limited Imaging at Several Wavelengths without Change of the Object’s Position

Tables Icon

Table 2 Calculated Reflectivities for Several Wavelengths λ and Angles of Incidence φin a

Tables Icon

Table 3 Specifications of the ICCD Detector

Equations (5)

Equations on this page are rendered with MathJax. Learn more.

rlat=K×λ/N.A.,
OPD=α×Aψ, ϕ+β×Bψ, ϕ,
Aψ, ϕ=4d sin ψ cos ψ cos ϕ/n2-1+cos2 ψ cos2 ϕ1/2, Bψ, ϕ=4d cos2 ψ sin ϕ cos ϕ/n2-1+cos2 ψ cos2 ϕ1/2,
N=ΔOPD/λ, ΔOPDA×D/f tilt about the y axis, ΔOPDB×D/f tilt about the x axis.
L>5×109×IDet×ADetRObj×1m2×sr,

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