Abstract

We have implemented a reflected-light microscope operating in the deep ultraviolet at 193  nm. Many materials absorb strongly at this wavelength, providing greatly enhanced contrast compared with visible and near-ultraviolet microscopes. Polymer films as thin as 1  nm and SiO2 films as thin as 3  nm have been imaged with this nonoptimized instrument. We have also calculated image contrast for several thin-film materials that are important in semiconductor processing, and we show that 193-nm light provides 60485× better contrast than visible light (500  nm) and 495× better contrast than near-ultraviolet light (315  nm) for these materials.

© 2001 Optical Society of America

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References

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  1. M. Pluta, Advanced Light Microscopy (Elsevier, New York, 1988), Vol. 1.
  2. M. Born and E. Wolf, Principles of Optics, 3rd ed. (Pergamon, London, 1965).
  3. R. R. Kunz, V. Liberman, and D. K. Downs, J. Vac. Sci. Technol. B 18, 1306 (2000).
    [CrossRef]
  4. Hamamatsu, Inc.,  “BT-CCD Camera System,” product sheet (2000).
  5. M. Salvermoser, D. E. Murnick, J. Wieser, and A. Ulrich, J. Appl. Phys. 88, 453 (2000).
    [CrossRef]
  6. A. El-Habachi and K. H. Schoenbach, Appl. Phys. Lett. 73, 885 (1998).
    [CrossRef]
  7. A. El-Habachi and K. H. Schoenbach, Appl. Phys. Lett. 72, 22 (1998).
    [CrossRef]
  8. P. A. Heimann and R. Urstadt, Appl. Opt. 29, 495 (1990).
    [CrossRef] [PubMed]

2000 (3)

R. R. Kunz, V. Liberman, and D. K. Downs, J. Vac. Sci. Technol. B 18, 1306 (2000).
[CrossRef]

Hamamatsu, Inc.,  “BT-CCD Camera System,” product sheet (2000).

M. Salvermoser, D. E. Murnick, J. Wieser, and A. Ulrich, J. Appl. Phys. 88, 453 (2000).
[CrossRef]

1998 (2)

A. El-Habachi and K. H. Schoenbach, Appl. Phys. Lett. 73, 885 (1998).
[CrossRef]

A. El-Habachi and K. H. Schoenbach, Appl. Phys. Lett. 72, 22 (1998).
[CrossRef]

1990 (1)

Born, M.

M. Born and E. Wolf, Principles of Optics, 3rd ed. (Pergamon, London, 1965).

Downs, D. K.

R. R. Kunz, V. Liberman, and D. K. Downs, J. Vac. Sci. Technol. B 18, 1306 (2000).
[CrossRef]

El-Habachi, A.

A. El-Habachi and K. H. Schoenbach, Appl. Phys. Lett. 72, 22 (1998).
[CrossRef]

A. El-Habachi and K. H. Schoenbach, Appl. Phys. Lett. 73, 885 (1998).
[CrossRef]

Heimann, P. A.

Kunz, R. R.

R. R. Kunz, V. Liberman, and D. K. Downs, J. Vac. Sci. Technol. B 18, 1306 (2000).
[CrossRef]

Liberman, V.

R. R. Kunz, V. Liberman, and D. K. Downs, J. Vac. Sci. Technol. B 18, 1306 (2000).
[CrossRef]

Murnick, D. E.

M. Salvermoser, D. E. Murnick, J. Wieser, and A. Ulrich, J. Appl. Phys. 88, 453 (2000).
[CrossRef]

Pluta, M.

M. Pluta, Advanced Light Microscopy (Elsevier, New York, 1988), Vol. 1.

Salvermoser, M.

M. Salvermoser, D. E. Murnick, J. Wieser, and A. Ulrich, J. Appl. Phys. 88, 453 (2000).
[CrossRef]

Schoenbach, K. H.

A. El-Habachi and K. H. Schoenbach, Appl. Phys. Lett. 73, 885 (1998).
[CrossRef]

A. El-Habachi and K. H. Schoenbach, Appl. Phys. Lett. 72, 22 (1998).
[CrossRef]

Ulrich, A.

M. Salvermoser, D. E. Murnick, J. Wieser, and A. Ulrich, J. Appl. Phys. 88, 453 (2000).
[CrossRef]

Urstadt, R.

Wieser, J.

M. Salvermoser, D. E. Murnick, J. Wieser, and A. Ulrich, J. Appl. Phys. 88, 453 (2000).
[CrossRef]

Wolf, E.

M. Born and E. Wolf, Principles of Optics, 3rd ed. (Pergamon, London, 1965).

Appl. Opt. (1)

Appl. Phys. Lett. (2)

A. El-Habachi and K. H. Schoenbach, Appl. Phys. Lett. 73, 885 (1998).
[CrossRef]

A. El-Habachi and K. H. Schoenbach, Appl. Phys. Lett. 72, 22 (1998).
[CrossRef]

J. Appl. Phys. (1)

M. Salvermoser, D. E. Murnick, J. Wieser, and A. Ulrich, J. Appl. Phys. 88, 453 (2000).
[CrossRef]

J. Vac. Sci. Technol. B (1)

R. R. Kunz, V. Liberman, and D. K. Downs, J. Vac. Sci. Technol. B 18, 1306 (2000).
[CrossRef]

product sheet (1)

Hamamatsu, Inc.,  “BT-CCD Camera System,” product sheet (2000).

Other (2)

M. Pluta, Advanced Light Microscopy (Elsevier, New York, 1988), Vol. 1.

M. Born and E. Wolf, Principles of Optics, 3rd ed. (Pergamon, London, 1965).

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Figures (3)

Fig. 1
Fig. 1

Calculated reflection contrast χ=R1-R2/R1+R2, where R1 and R2 are, respectively, the reflectivities of the film and the substrate in the absence of height variations for various materials on Si and fused-silica substrates: a, pHOST on Si; b, Si3N4 on Si; c, thermally grown SiO2 on Si; c, pHOST on fused silica. Note the clear advantage of deep-UV illumination compared with near UV and visible in each case.

Fig. 2
Fig. 2

Spectrum of the rf microdischarge lamp operating in an Ar- and F2-containing atmosphere. Inset, schematic drawing of the lamp, showing a small 300μm region of excited gas between two electrodes.

Fig. 3
Fig. 3

Images of thin films taken at 193  nm and in white light; scale bars represent 100 μm. a, 5-nm layer of pHOST upon a Si substrate taken at 193  nm. The pHOST is the darker region. b, Image of the same field but taken in white light. The pHOST is undetectable. Note the Cr alignment feature at the bottom right of these images. c, a 1-nm layer of pHOST upon a transparent quartz substrate. The difficulty of obtaining uniform illumination, particularly for samples with low reflectivity, is apparent in this image. d, 3-nm layer of thermally grown SiO2 upon Si. The theoretical contrast of this image is only 2%.

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