Abstract

Coherence scanning microscopy is a new technique in high resolution imaging. It shares many of the features of confocal microscopy but uses coherence effects to enhance the lateral and longitudinal resolution rather than physical apertures. This approach has two significant implications for profilometry: the longitudinal resolution is decoupled from the lateral resolution, and interference effects can be used to further enhance the longitudinal resolution. We detail the features of coherence scanning profilometry and give some examples.

© 1990 Optical Society of America

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References

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  1. T. C. Strand, “Optical Three-Dimensional Sensing for Machine Vision,” Opt. Eng. 24, 33–40 (1985).
    [CrossRef]
  2. T. C. Strand, Y. Katzir, “Extended Unambiguous Range Interferometry,” Appl. Opt. 26, 4274–4281 (1987).
    [CrossRef] [PubMed]
  3. T. Yoshino, M. Nara, S. Mnatzakanian, B. S. Lee, T. C.. Strand, “Laser Diode Feedback Interferometer for Stabilization and Displacement Measurements,” Appl. Opt. 26, 892–897 (1987).
    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
  5. C. C. Williams, H. K. Wickramasinghe, “Optical Ranging by Wavelength Multiplexed Interferometry,” J. Appl. Phys. 60, 1900–1902 (1986).
    [CrossRef]
  6. K. Creath, “Measuring Step Heights Using an Optical Profiler,” Proc. Soc. Photo-Opt. Instrum. Eng. 661, 296–301 (1986).
  7. M. Davidson, K. Kaufman, I. Mazor, “First Results of a Product Using Coherence Probe Imaging for Wafer Inspection,” Proc. Soc. Photo-Opt. Instrum. Eng. 921, 100–114 (1988).
  8. M. Davidson, K. Kaufman, I. Mazor, F. Cohen, “An Application of Interference Microscopy to Integrated Circuit Inspection and Metrology,” Proc. Soc. Photo-Opt. Instrum. Eng. 775, 233–247 (1987).

1988

M. Davidson, K. Kaufman, I. Mazor, “First Results of a Product Using Coherence Probe Imaging for Wafer Inspection,” Proc. Soc. Photo-Opt. Instrum. Eng. 921, 100–114 (1988).

1987

1986

C. C. Williams, H. K. Wickramasinghe, “Optical Ranging by Wavelength Multiplexed Interferometry,” J. Appl. Phys. 60, 1900–1902 (1986).
[CrossRef]

K. Creath, “Measuring Step Heights Using an Optical Profiler,” Proc. Soc. Photo-Opt. Instrum. Eng. 661, 296–301 (1986).

1985

T. C. Strand, “Optical Three-Dimensional Sensing for Machine Vision,” Opt. Eng. 24, 33–40 (1985).
[CrossRef]

1971

Cohen, F.

M. Davidson, K. Kaufman, I. Mazor, F. Cohen, “An Application of Interference Microscopy to Integrated Circuit Inspection and Metrology,” Proc. Soc. Photo-Opt. Instrum. Eng. 775, 233–247 (1987).

Creath, K.

K. Creath, “Measuring Step Heights Using an Optical Profiler,” Proc. Soc. Photo-Opt. Instrum. Eng. 661, 296–301 (1986).

Davidson, M.

M. Davidson, K. Kaufman, I. Mazor, “First Results of a Product Using Coherence Probe Imaging for Wafer Inspection,” Proc. Soc. Photo-Opt. Instrum. Eng. 921, 100–114 (1988).

M. Davidson, K. Kaufman, I. Mazor, F. Cohen, “An Application of Interference Microscopy to Integrated Circuit Inspection and Metrology,” Proc. Soc. Photo-Opt. Instrum. Eng. 775, 233–247 (1987).

Katzir, Y.

Kaufman, K.

M. Davidson, K. Kaufman, I. Mazor, “First Results of a Product Using Coherence Probe Imaging for Wafer Inspection,” Proc. Soc. Photo-Opt. Instrum. Eng. 921, 100–114 (1988).

M. Davidson, K. Kaufman, I. Mazor, F. Cohen, “An Application of Interference Microscopy to Integrated Circuit Inspection and Metrology,” Proc. Soc. Photo-Opt. Instrum. Eng. 775, 233–247 (1987).

Lee, B. S.

Mazor, I.

M. Davidson, K. Kaufman, I. Mazor, “First Results of a Product Using Coherence Probe Imaging for Wafer Inspection,” Proc. Soc. Photo-Opt. Instrum. Eng. 921, 100–114 (1988).

M. Davidson, K. Kaufman, I. Mazor, F. Cohen, “An Application of Interference Microscopy to Integrated Circuit Inspection and Metrology,” Proc. Soc. Photo-Opt. Instrum. Eng. 775, 233–247 (1987).

Mnatzakanian, S.

Nara, M.

Strand, T. C.

T. C. Strand, Y. Katzir, “Extended Unambiguous Range Interferometry,” Appl. Opt. 26, 4274–4281 (1987).
[CrossRef] [PubMed]

T. C. Strand, “Optical Three-Dimensional Sensing for Machine Vision,” Opt. Eng. 24, 33–40 (1985).
[CrossRef]

Strand, T. C..

Wickramasinghe, H. K.

C. C. Williams, H. K. Wickramasinghe, “Optical Ranging by Wavelength Multiplexed Interferometry,” J. Appl. Phys. 60, 1900–1902 (1986).
[CrossRef]

Williams, C. C.

C. C. Williams, H. K. Wickramasinghe, “Optical Ranging by Wavelength Multiplexed Interferometry,” J. Appl. Phys. 60, 1900–1902 (1986).
[CrossRef]

Wyant, J. C.

Yoshino, T.

Appl. Opt.

J. Appl. Phys.

C. C. Williams, H. K. Wickramasinghe, “Optical Ranging by Wavelength Multiplexed Interferometry,” J. Appl. Phys. 60, 1900–1902 (1986).
[CrossRef]

Opt. Eng.

T. C. Strand, “Optical Three-Dimensional Sensing for Machine Vision,” Opt. Eng. 24, 33–40 (1985).
[CrossRef]

Proc. Soc. Photo-Opt. Instrum. Eng.

K. Creath, “Measuring Step Heights Using an Optical Profiler,” Proc. Soc. Photo-Opt. Instrum. Eng. 661, 296–301 (1986).

M. Davidson, K. Kaufman, I. Mazor, “First Results of a Product Using Coherence Probe Imaging for Wafer Inspection,” Proc. Soc. Photo-Opt. Instrum. Eng. 921, 100–114 (1988).

M. Davidson, K. Kaufman, I. Mazor, F. Cohen, “An Application of Interference Microscopy to Integrated Circuit Inspection and Metrology,” Proc. Soc. Photo-Opt. Instrum. Eng. 775, 233–247 (1987).

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Figures (7)

Fig. 1
Fig. 1

White light interferometer where the object is scanned along the z-axis forms the basis of the coherence scanning microscope. The microscope images the object onto an array detector.

Fig. 2
Fig. 2

Output signal of a white light interferometer as a function of the z-axis position for one point in the image. The envelope of the fringes marks the coherence function.

Fig. 3
Fig. 3

Experimental setup. A commercial microscope and Michelson interferometer attachment form the basis of the equipment. The object to be measured is placed on a stage that scans in the vertical direction. Interference images are collected as the object is scanned vertically.

Fig. 4
Fig. 4

Coherence scanning profile of a 4-μm step. (a) Sketch of object being scanned, consisting of two planar regions vertically displaced by ~4 μm. The steep slope in the transition region precludes imaging that area. (b) Line profile of the step produced with the coherence scanning microscope.

Fig. 5
Fig. 5

Basic interferometer output for three different points along the profile shown in Fig. 4. The first and third scans taken on either side of the transition region show the fringes appearing at the z-axis locations corresponding to the two planar surfaces. The middle scan taken in the transition region shows fringes from both planar surfaces since the PSF overlaps the two surfaces at this point. These fringes have been magnified with respect to the other two scans.

Fig. 6
Fig. 6

Amplitude images showing the edge responses for the two surfaces from the scan used to produce Fig. 4. The solid line indicates the maximum amplitude of the fringes corresponding to the upper surface, and the dashed line is the fringe amplitude for the lower surface. Points A and B indicate the midpoints of the respective edge response functions. These points correspond to the actual edge location and are used to define the transition region width.

Fig. 7
Fig. 7

Coherence scanning profile of a multilayer target consisting of a metallic layer under a transparent dielectric layer: (a) the top trace corresponds to the transparent dielectric layer, and the bottom trace is thee metallic layer; (b) expanded view of the top dielectric layer profile from (a); (c) expanded view of the bottom metallic layer profile from (a).

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