Abstract

A new scanning common-path interferometric profiler capable of absolute-phase measurement is described. The key element is a computer-generated hologram, which acts as the beam-splitting element. Unlike most absolute phase systems, it can be made entirely common path with respect to piston microphonics and is thus exceptionally stable. In addition to operating in scanning mode, the optical configuration permits simultaneous operation as a single-shot phase measuring interferometer and is thus capable of simultaneous form and texture measurements. The operation and stability of the scanning profiler are demonstrated experimentally.

© 1998 Optical Society of America

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References

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  1. G. E. Sommargren, “Optical heterodyne profilometry,” Appl. Opt. 20, 610–618 (1981).
    [CrossRef] [PubMed]
  2. H. K. Wickramasinghe, S. Ameri, C. W. See, “Differential phase contrast microscope with 1Å depth resolution,” Electron. Lett. 18, 973–975 (1982).
    [CrossRef]
  3. M. B. Suddendorf, M. G. Somekh, C. W. See, “Single-probe-beam differential amplitude and phase scanning interferometer,” Appl. Opt. 36, 6202–6210 (1997).
    [CrossRef]
  4. C. C. Huang, “Optical heterodyne profilometer,” Opt. Eng. 23, 365–370 (1984).
    [CrossRef]
  5. M. J. Offside, M. G. Somekh, “Interferometric scanning optical microscope for surface characterization,” Appl. Opt. 31, 6772–6782 (1992).
    [CrossRef] [PubMed]
  6. Inasmuch as only a portion of the interferogram was used, the effective reference area was approximately 800 μm by 100 μm. This area was found to be satisfactory for our purposes, but by using several similar regions or a single larger region one could readily use a larger reference area.
  7. K. Creath, “Calibration of numerical aperture effects in interferometric microscope objectives,” Appl. Opt. 28, 3333–3338 (1989).
    [CrossRef] [PubMed]
  8. M. G. Somekh, M. S. Valera, R. K. Appel, “Scanning heterodyne confocal differential phase and intensity microscope,” Appl. Opt. 34, 4857–4868 (1995).
    [CrossRef] [PubMed]
  9. M. Takeda, H. Ina, S. Kobayashi, “Fourier transform method of fringe-pattern analysis for computer-based topography and interferometry,” J. Opt. Soc. Am. 72, 156–160 (1982).
    [CrossRef]

1997 (1)

1995 (1)

1992 (1)

1989 (1)

1984 (1)

C. C. Huang, “Optical heterodyne profilometer,” Opt. Eng. 23, 365–370 (1984).
[CrossRef]

1982 (2)

H. K. Wickramasinghe, S. Ameri, C. W. See, “Differential phase contrast microscope with 1Å depth resolution,” Electron. Lett. 18, 973–975 (1982).
[CrossRef]

M. Takeda, H. Ina, S. Kobayashi, “Fourier transform method of fringe-pattern analysis for computer-based topography and interferometry,” J. Opt. Soc. Am. 72, 156–160 (1982).
[CrossRef]

1981 (1)

Ameri, S.

H. K. Wickramasinghe, S. Ameri, C. W. See, “Differential phase contrast microscope with 1Å depth resolution,” Electron. Lett. 18, 973–975 (1982).
[CrossRef]

Appel, R. K.

Creath, K.

Huang, C. C.

C. C. Huang, “Optical heterodyne profilometer,” Opt. Eng. 23, 365–370 (1984).
[CrossRef]

Ina, H.

Kobayashi, S.

Offside, M. J.

See, C. W.

M. B. Suddendorf, M. G. Somekh, C. W. See, “Single-probe-beam differential amplitude and phase scanning interferometer,” Appl. Opt. 36, 6202–6210 (1997).
[CrossRef]

H. K. Wickramasinghe, S. Ameri, C. W. See, “Differential phase contrast microscope with 1Å depth resolution,” Electron. Lett. 18, 973–975 (1982).
[CrossRef]

Somekh, M. G.

Sommargren, G. E.

Suddendorf, M. B.

Takeda, M.

Valera, M. S.

Wickramasinghe, H. K.

H. K. Wickramasinghe, S. Ameri, C. W. See, “Differential phase contrast microscope with 1Å depth resolution,” Electron. Lett. 18, 973–975 (1982).
[CrossRef]

Appl. Opt. (5)

Electron. Lett. (1)

H. K. Wickramasinghe, S. Ameri, C. W. See, “Differential phase contrast microscope with 1Å depth resolution,” Electron. Lett. 18, 973–975 (1982).
[CrossRef]

J. Opt. Soc. Am. (1)

Opt. Eng. (1)

C. C. Huang, “Optical heterodyne profilometer,” Opt. Eng. 23, 365–370 (1984).
[CrossRef]

Other (1)

Inasmuch as only a portion of the interferogram was used, the effective reference area was approximately 800 μm by 100 μm. This area was found to be satisfactory for our purposes, but by using several similar regions or a single larger region one could readily use a larger reference area.

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Figures (5)

Fig. 1
Fig. 1

Schematic diagram of the system: (a) illumination path and (b) imaging path.

Fig. 2
Fig. 2

(a) Image of the fringe pattern detected on a CCD camera. (b) Single-line output from the CCD and the associated Fourier transform taken across the line shown in (a). (c) Cumulative line scan and associated Fourier transform obtained by vertical summation of the signal in the rectangular box shown in (a).

Fig. 3
Fig. 3

Scans obtained with the common-path profiler: (a) long-range scan taken with a 0.13-N.A. objective over a sample with 17-nm-high tracks, (b) scan taken with a 0.95-N.A. objective close to the one of the track edges, (c) scans taken with a 0.95-N.A. objective at 2-h intervals (the traces are displaced by 5 nm for clarity).

Fig. 4
Fig. 4

Plots of common-path variation versus defocus for reference-beam incident angles of 11.3 deg (open circles) and 18.3 deg (filled circles). The results were obtained with the nominally 0.95-N.A. objective lens.

Fig. 5
Fig. 5

Measured common-path factor versus angle of incidence of the reference beam for a 0.95-N.A. objective.

Equations (1)

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cpf = 1 - | common-path   phase   fluctuation | absolute-phase   fluctuation = 1 - | cos   θ inc - cos   θ | cos   θ .

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