Abstract

In a basic study to identify low-loss optics for applications in F2 lithography, five potential coating materials (AlF3, Na3AlF6, MgF2, LaF3, and GdF3) and three deposition methods (thermal evaporation by a resistance heater and by electron beam and ion-beam sputtering) were investigated in the vacuum ultraviolet (VUV) region. Samples were supplied as single-layer coatings on CaF2 substrates by four Japanese coating suppliers. Refractive indices (n) and extinction coefficients (k) of these coatings at 157 nm were evaluated; the transmittance and the reflectance were measured by a VUV spectrometer and were compared. As a result, resistance heating thermal evaporation is seen to be the optimal method for achieving low-loss antireflection coatings. The relation among optical constants, microstructures, and stoichiometry is discussed.

© 2002 Optical Society of America

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References

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  1. J. Kolbe, H. Schink, “Optical losses of dielectric VUV-mirrors deposited by conventional evaporation, IAD, and IBS,” in Thin Films for Optical Systems, K. H. Guenther, ed, Proc. SPIE1782, 435–446 (1993).
  2. L. J. Lingg, J. D. Targove, J. P. Lehan, H. A. Macleod, “Ion-assisted deposition of lanthanide trifluorides for VUV applications,” in Current Developments in Optical Engineering II: R. E. Fischer, W. J. Smith, eds., Proc. SPIE818, 86–92 (1987).
  3. J. Kolbe, H. Schink, D. Ristau, “Optical losses of fluoride coatings for UV/VUV applications deposited by reactive IAD and IBS processes,” presented at the Society of Vacuum Coaters Thirty-Sixth Annual Technical Conference, 1993.
  4. International Organization for Standardization, “Optics and optical instruments, lasers and laser related equipment, test method for absorptance of optical laser components,” standard ISO 11551 (ISO, Geneva, Switzerland, 1997).
  5. International Organization for Standardization/DIS, “Optics and optical instruments, test methods for radiation scattered by optical components,” ISO/DIS standard 13696 (ISO, Geneva, Switzerland, 1999).
  6. U. Kaiser, N. Kaiser, P. WeiBbrodt, U. Mademann, E. Hacker, H. Muller, “Structure of thin fluoride films deposited on amorphous substrates,” Thin Solid Films 217, 7–16 (1992).
    [CrossRef]

1992

U. Kaiser, N. Kaiser, P. WeiBbrodt, U. Mademann, E. Hacker, H. Muller, “Structure of thin fluoride films deposited on amorphous substrates,” Thin Solid Films 217, 7–16 (1992).
[CrossRef]

D. Targove, J.

L. J. Lingg, J. D. Targove, J. P. Lehan, H. A. Macleod, “Ion-assisted deposition of lanthanide trifluorides for VUV applications,” in Current Developments in Optical Engineering II: R. E. Fischer, W. J. Smith, eds., Proc. SPIE818, 86–92 (1987).

Hacker, E.

U. Kaiser, N. Kaiser, P. WeiBbrodt, U. Mademann, E. Hacker, H. Muller, “Structure of thin fluoride films deposited on amorphous substrates,” Thin Solid Films 217, 7–16 (1992).
[CrossRef]

J. Lingg, L.

L. J. Lingg, J. D. Targove, J. P. Lehan, H. A. Macleod, “Ion-assisted deposition of lanthanide trifluorides for VUV applications,” in Current Developments in Optical Engineering II: R. E. Fischer, W. J. Smith, eds., Proc. SPIE818, 86–92 (1987).

Kaiser, N.

U. Kaiser, N. Kaiser, P. WeiBbrodt, U. Mademann, E. Hacker, H. Muller, “Structure of thin fluoride films deposited on amorphous substrates,” Thin Solid Films 217, 7–16 (1992).
[CrossRef]

Kaiser, U.

U. Kaiser, N. Kaiser, P. WeiBbrodt, U. Mademann, E. Hacker, H. Muller, “Structure of thin fluoride films deposited on amorphous substrates,” Thin Solid Films 217, 7–16 (1992).
[CrossRef]

Kolbe, J.

J. Kolbe, H. Schink, D. Ristau, “Optical losses of fluoride coatings for UV/VUV applications deposited by reactive IAD and IBS processes,” presented at the Society of Vacuum Coaters Thirty-Sixth Annual Technical Conference, 1993.

J. Kolbe, H. Schink, “Optical losses of dielectric VUV-mirrors deposited by conventional evaporation, IAD, and IBS,” in Thin Films for Optical Systems, K. H. Guenther, ed, Proc. SPIE1782, 435–446 (1993).

Macleod, H. A.

L. J. Lingg, J. D. Targove, J. P. Lehan, H. A. Macleod, “Ion-assisted deposition of lanthanide trifluorides for VUV applications,” in Current Developments in Optical Engineering II: R. E. Fischer, W. J. Smith, eds., Proc. SPIE818, 86–92 (1987).

Mademann, U.

U. Kaiser, N. Kaiser, P. WeiBbrodt, U. Mademann, E. Hacker, H. Muller, “Structure of thin fluoride films deposited on amorphous substrates,” Thin Solid Films 217, 7–16 (1992).
[CrossRef]

Muller, H.

U. Kaiser, N. Kaiser, P. WeiBbrodt, U. Mademann, E. Hacker, H. Muller, “Structure of thin fluoride films deposited on amorphous substrates,” Thin Solid Films 217, 7–16 (1992).
[CrossRef]

P. Lehan, J.

L. J. Lingg, J. D. Targove, J. P. Lehan, H. A. Macleod, “Ion-assisted deposition of lanthanide trifluorides for VUV applications,” in Current Developments in Optical Engineering II: R. E. Fischer, W. J. Smith, eds., Proc. SPIE818, 86–92 (1987).

Ristau, D.

J. Kolbe, H. Schink, D. Ristau, “Optical losses of fluoride coatings for UV/VUV applications deposited by reactive IAD and IBS processes,” presented at the Society of Vacuum Coaters Thirty-Sixth Annual Technical Conference, 1993.

Schink, H.

J. Kolbe, H. Schink, “Optical losses of dielectric VUV-mirrors deposited by conventional evaporation, IAD, and IBS,” in Thin Films for Optical Systems, K. H. Guenther, ed, Proc. SPIE1782, 435–446 (1993).

J. Kolbe, H. Schink, D. Ristau, “Optical losses of fluoride coatings for UV/VUV applications deposited by reactive IAD and IBS processes,” presented at the Society of Vacuum Coaters Thirty-Sixth Annual Technical Conference, 1993.

WeiBbrodt, P.

U. Kaiser, N. Kaiser, P. WeiBbrodt, U. Mademann, E. Hacker, H. Muller, “Structure of thin fluoride films deposited on amorphous substrates,” Thin Solid Films 217, 7–16 (1992).
[CrossRef]

Thin Solid Films

U. Kaiser, N. Kaiser, P. WeiBbrodt, U. Mademann, E. Hacker, H. Muller, “Structure of thin fluoride films deposited on amorphous substrates,” Thin Solid Films 217, 7–16 (1992).
[CrossRef]

Other

J. Kolbe, H. Schink, “Optical losses of dielectric VUV-mirrors deposited by conventional evaporation, IAD, and IBS,” in Thin Films for Optical Systems, K. H. Guenther, ed, Proc. SPIE1782, 435–446 (1993).

L. J. Lingg, J. D. Targove, J. P. Lehan, H. A. Macleod, “Ion-assisted deposition of lanthanide trifluorides for VUV applications,” in Current Developments in Optical Engineering II: R. E. Fischer, W. J. Smith, eds., Proc. SPIE818, 86–92 (1987).

J. Kolbe, H. Schink, D. Ristau, “Optical losses of fluoride coatings for UV/VUV applications deposited by reactive IAD and IBS processes,” presented at the Society of Vacuum Coaters Thirty-Sixth Annual Technical Conference, 1993.

International Organization for Standardization, “Optics and optical instruments, lasers and laser related equipment, test method for absorptance of optical laser components,” standard ISO 11551 (ISO, Geneva, Switzerland, 1997).

International Organization for Standardization/DIS, “Optics and optical instruments, test methods for radiation scattered by optical components,” ISO/DIS standard 13696 (ISO, Geneva, Switzerland, 1999).

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Figures (9)

Fig. 1
Fig. 1

Schematic of the VUV spectrometer. The sample and the detector can be rotated. The sample chamber was purged of nitrogen during measurement to prevent the samples’ being contaminated in vacuum. There is a MgF2 window between the sample chamber and the chopper chamber to seal the vacuum.

Fig. 2
Fig. 2

Steps in calculation of the optical constants.

Fig. 3
Fig. 3

Data for calculation of optical constants AlF3 and Na3AlF6 on the top, plano substrates and on the bottom, wedged substrates. A–D identify the suppliers.

Fig. 4
Fig. 4

Data for calculation of optical constant MgF2 on the top, plano substrates and on the bottom, wedged substrates. A–D identify the suppliers.

Fig. 5
Fig. 5

Data for calculation of optical constant GdF3 on the top, plano substrates and on the bottom, wedged substrates. A–D identify the suppliers.

Fig. 6
Fig. 6

Data for calculation of optical constant LaF3 on the top, plano substrates and on the bottom, wedged substrates. A–D identify the suppliers.

Fig. 7
Fig. 7

Comparison of refractive indices and extinction coefficients of five materials and four coating methods. A–D identify the suppliers of coatings.

Fig. 8
Fig. 8

Scanning electron microscope images of the films. White lines show the growth directions of the column structures.

Fig. 9
Fig. 9

X-ray diffraction (XRD) data. GdF3 was grown epitaxially with (111) orientation upon a CaF2 substrate regardless of which coating process was used. The substrate of the IBS-generated coating has only (111) orientation, and the substrate of the RH-generated film has a 26° offset. No peak was observed at θ–2θ scan and pole-figure, as was also the case for AlF3 coatings.

Tables (2)

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Table 1 Properties and Results of Three Kinds of Coating Process

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Table 2 Comparison of the Ratio of Fluorine to Metal Analyzed by X-Ray Photoelectron Spectroscopya

Equations (2)

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nλ=A+Bλ2+Cλ4,
Loss=1-Transmittance-Reflectance

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