Abstract

The use of optical differential phase-contrast microscopy to obtain the surface profile of samples is outlined. The range of accurate feature height determination was calculated as a function of steepness of the side of the feature. Heights of thin features (height <0.1 μm) were accurately determined experimentally. Sample tilting and oblique stage scanning were required in order to determine the heights of thicker samples. Reconstructed profile heights were measured as a function of defocus.

© 1992 Optical Society of America

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References

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  1. J. B. DeVelis, G. O. Reynolds, Theory and Applications of Holography (Addison-Wesley, Reading, Mass., 1967), pp. 161–162.
  2. R. A. Sprague, B. J. Thompson, “Quantitative visualization of large phase objects,” Appl. Opt. 11, 1469–1479 (1972).
    [CrossRef] [PubMed]
  3. R. J. Whitefield, “Noncontact optical profilometer,” Appl. Opt. 14, 2480–2485 (1975).
    [CrossRef] [PubMed]
  4. G. M. Robinson, D. M. Perry, R. W. Peterson, “Optical interferometry of surfaces,” Sci. Am. 265(7), 66–71 (July1991).
    [CrossRef]
  5. D. Kermisch, “Visualization of large variation phase objects,” in Image Processing, J. C. Urbach, ed. Proc. Soc. Photo-Opt. Instrum. Eng.74, 126–129 (1976).
  6. N. H. Dekkers, H. de Lang, “Differential phase contrast in a STEM,” Optik 41, 452–456 (1974).
  7. N. H. Dekkers, H. de Lang, “A detection method for producing phase and amplitude images simultaneously in a scanning transmission electron microscope,” Philips Tech. Rev. 37, 1–9 (1977).
  8. D. K. Hamilton, T. Wilson, “Two-dimensional phase imaging in the scanning optical microscope,” Appl. Opt. 23, 348–352 (1984).
    [CrossRef] [PubMed]
  9. D. K. Hamilton, T. Wilson, “Edge enhancement in scanning optical microscopy by differential detection,” J. Opt. Soc. Am. A. 1, 322–323 (1984).
    [CrossRef]
  10. J. P. H. Benschop, “Phase detection using scanning optical microscopy,” in Integrated Circuit Metrology, Inspection, and Process Control II, K. M. Monahan, ed. Proc. Soc. Photo-Opt. Instrum. Eng.921, 123–130 (1988).
  11. A. E. Dixon, S. Damaskinos, M. R. Atkinson, “A new transmission and double reflection scanning beam confocal microscope: applications in transmission,” in Scanning Microscopy Instrumentation, Proc. Soc. Photo-Opt. Instrum. Eng. 1556, 144–153 (1992).
  12. M. R. Atkinson, “Confocal microscopy applied to metrology of integrated circuits,” Ph.D. dissertation (University of Waterloo, Waterloo, Ontario N2L 3G1, Canada, 1991).

1992 (1)

A. E. Dixon, S. Damaskinos, M. R. Atkinson, “A new transmission and double reflection scanning beam confocal microscope: applications in transmission,” in Scanning Microscopy Instrumentation, Proc. Soc. Photo-Opt. Instrum. Eng. 1556, 144–153 (1992).

1991 (1)

G. M. Robinson, D. M. Perry, R. W. Peterson, “Optical interferometry of surfaces,” Sci. Am. 265(7), 66–71 (July1991).
[CrossRef]

1984 (2)

D. K. Hamilton, T. Wilson, “Edge enhancement in scanning optical microscopy by differential detection,” J. Opt. Soc. Am. A. 1, 322–323 (1984).
[CrossRef]

D. K. Hamilton, T. Wilson, “Two-dimensional phase imaging in the scanning optical microscope,” Appl. Opt. 23, 348–352 (1984).
[CrossRef] [PubMed]

1977 (1)

N. H. Dekkers, H. de Lang, “A detection method for producing phase and amplitude images simultaneously in a scanning transmission electron microscope,” Philips Tech. Rev. 37, 1–9 (1977).

1975 (1)

1974 (1)

N. H. Dekkers, H. de Lang, “Differential phase contrast in a STEM,” Optik 41, 452–456 (1974).

1972 (1)

Atkinson, M. R.

A. E. Dixon, S. Damaskinos, M. R. Atkinson, “A new transmission and double reflection scanning beam confocal microscope: applications in transmission,” in Scanning Microscopy Instrumentation, Proc. Soc. Photo-Opt. Instrum. Eng. 1556, 144–153 (1992).

M. R. Atkinson, “Confocal microscopy applied to metrology of integrated circuits,” Ph.D. dissertation (University of Waterloo, Waterloo, Ontario N2L 3G1, Canada, 1991).

Benschop, J. P. H.

J. P. H. Benschop, “Phase detection using scanning optical microscopy,” in Integrated Circuit Metrology, Inspection, and Process Control II, K. M. Monahan, ed. Proc. Soc. Photo-Opt. Instrum. Eng.921, 123–130 (1988).

Damaskinos, S.

A. E. Dixon, S. Damaskinos, M. R. Atkinson, “A new transmission and double reflection scanning beam confocal microscope: applications in transmission,” in Scanning Microscopy Instrumentation, Proc. Soc. Photo-Opt. Instrum. Eng. 1556, 144–153 (1992).

de Lang, H.

N. H. Dekkers, H. de Lang, “A detection method for producing phase and amplitude images simultaneously in a scanning transmission electron microscope,” Philips Tech. Rev. 37, 1–9 (1977).

N. H. Dekkers, H. de Lang, “Differential phase contrast in a STEM,” Optik 41, 452–456 (1974).

Dekkers, N. H.

N. H. Dekkers, H. de Lang, “A detection method for producing phase and amplitude images simultaneously in a scanning transmission electron microscope,” Philips Tech. Rev. 37, 1–9 (1977).

N. H. Dekkers, H. de Lang, “Differential phase contrast in a STEM,” Optik 41, 452–456 (1974).

DeVelis, J. B.

J. B. DeVelis, G. O. Reynolds, Theory and Applications of Holography (Addison-Wesley, Reading, Mass., 1967), pp. 161–162.

Dixon, A. E.

A. E. Dixon, S. Damaskinos, M. R. Atkinson, “A new transmission and double reflection scanning beam confocal microscope: applications in transmission,” in Scanning Microscopy Instrumentation, Proc. Soc. Photo-Opt. Instrum. Eng. 1556, 144–153 (1992).

Hamilton, D. K.

D. K. Hamilton, T. Wilson, “Edge enhancement in scanning optical microscopy by differential detection,” J. Opt. Soc. Am. A. 1, 322–323 (1984).
[CrossRef]

D. K. Hamilton, T. Wilson, “Two-dimensional phase imaging in the scanning optical microscope,” Appl. Opt. 23, 348–352 (1984).
[CrossRef] [PubMed]

Kermisch, D.

D. Kermisch, “Visualization of large variation phase objects,” in Image Processing, J. C. Urbach, ed. Proc. Soc. Photo-Opt. Instrum. Eng.74, 126–129 (1976).

Perry, D. M.

G. M. Robinson, D. M. Perry, R. W. Peterson, “Optical interferometry of surfaces,” Sci. Am. 265(7), 66–71 (July1991).
[CrossRef]

Peterson, R. W.

G. M. Robinson, D. M. Perry, R. W. Peterson, “Optical interferometry of surfaces,” Sci. Am. 265(7), 66–71 (July1991).
[CrossRef]

Reynolds, G. O.

J. B. DeVelis, G. O. Reynolds, Theory and Applications of Holography (Addison-Wesley, Reading, Mass., 1967), pp. 161–162.

Robinson, G. M.

G. M. Robinson, D. M. Perry, R. W. Peterson, “Optical interferometry of surfaces,” Sci. Am. 265(7), 66–71 (July1991).
[CrossRef]

Sprague, R. A.

Thompson, B. J.

Whitefield, R. J.

Wilson, T.

D. K. Hamilton, T. Wilson, “Edge enhancement in scanning optical microscopy by differential detection,” J. Opt. Soc. Am. A. 1, 322–323 (1984).
[CrossRef]

D. K. Hamilton, T. Wilson, “Two-dimensional phase imaging in the scanning optical microscope,” Appl. Opt. 23, 348–352 (1984).
[CrossRef] [PubMed]

Appl. Opt. (3)

J. Opt. Soc. Am. A. (1)

D. K. Hamilton, T. Wilson, “Edge enhancement in scanning optical microscopy by differential detection,” J. Opt. Soc. Am. A. 1, 322–323 (1984).
[CrossRef]

Optik (1)

N. H. Dekkers, H. de Lang, “Differential phase contrast in a STEM,” Optik 41, 452–456 (1974).

Philips Tech. Rev. (1)

N. H. Dekkers, H. de Lang, “A detection method for producing phase and amplitude images simultaneously in a scanning transmission electron microscope,” Philips Tech. Rev. 37, 1–9 (1977).

Scanning Microscopy Instrumentation (1)

A. E. Dixon, S. Damaskinos, M. R. Atkinson, “A new transmission and double reflection scanning beam confocal microscope: applications in transmission,” in Scanning Microscopy Instrumentation, Proc. Soc. Photo-Opt. Instrum. Eng. 1556, 144–153 (1992).

Sci. Am. (1)

G. M. Robinson, D. M. Perry, R. W. Peterson, “Optical interferometry of surfaces,” Sci. Am. 265(7), 66–71 (July1991).
[CrossRef]

Other (4)

D. Kermisch, “Visualization of large variation phase objects,” in Image Processing, J. C. Urbach, ed. Proc. Soc. Photo-Opt. Instrum. Eng.74, 126–129 (1976).

M. R. Atkinson, “Confocal microscopy applied to metrology of integrated circuits,” Ph.D. dissertation (University of Waterloo, Waterloo, Ontario N2L 3G1, Canada, 1991).

J. B. DeVelis, G. O. Reynolds, Theory and Applications of Holography (Addison-Wesley, Reading, Mass., 1967), pp. 161–162.

J. P. H. Benschop, “Phase detection using scanning optical microscopy,” in Integrated Circuit Metrology, Inspection, and Process Control II, K. M. Monahan, ed. Proc. Soc. Photo-Opt. Instrum. Eng.921, 123–130 (1988).

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Figures (11)

Fig. 1
Fig. 1

Unfolded diagram of a reflection DPC microscope. The field in the ith plane is Ui.

Fig. 2
Fig. 2

Field in the detector plane when the beam is focused on a tilted sample. The hatched area indicates the region of nonzero field.

Fig. 3
Fig. 3

Description of a line object with sloped sides: (a) line profile; (b) and (c) amplitude and phase portions of the reflection function t(x) = A(x)exp[jϕ(x)], respectively.

Fig. 4
Fig. 4

Infinity-corrected scanning beam DPC microscope. The interferometer behind the sample holder measures the axial motion of the sample.

Fig. 5
Fig. 5

Reconstructed object heights compared with actual object heights. The accuracy of the object reconstruction is investigated as a function of the thickness of the object and the slope of the side of the object. The calculations are based on a system with a 0.9-NA objective lens and λ = 633 nm.

Fig. 6
Fig. 6

Differential signal calibration of the microscope by using a 0.7-NA objective. Discrete points correspond to measured values.

Fig. 7
Fig. 7

Images of a boron phosphide film: (a) conventional, (b) DPC.

Fig. 8
Fig. 8

Reconstruction of chrome lines: (a) DPC signal; (b) reconstructed profile of lines. The height was measured using a Talysurf profilometer and was found to be 80 ± 5 nm.

Fig. 9
Fig. 9

Sample tilting applied to DPC: (a) untilted; (b) optimally tilted (note the change to oblique stage scanning); θm = maximum unambiguously measurable slope = ±(0.5)sin−1(NA).

Fig. 10
Fig. 10

Reconstructed profiles of a 0.41-μm step as a function of sample tilt. The 0°, −2°, −4°, and −6° tilt curves have been offset laterally by 1 μm. The tilt of the sample was removed from the measured profiles before they were plotted.

Fig. 11
Fig. 11

Reconstructed step height as a function of defocus: *, no sample tilting; ○, 14° sample tilt.

Equations (7)

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U 3 = exp ( j k 2 f ) / ( λ f ) 2 P 1 ( x 1 , y 1 ) P 3 ( x 3 , y 3 ) × t ( x 2 - x off , y 2 - y off ) exp { - j k [ x 2 ( x 1 + x 3 ) + y 2 ( y 1 + y 3 ) ] / f 1 } d x 1 d y 1 d x 2 d y 2 ,
t ( x 2 ) - x off , y 2 - y off ) = F - 1 { T ( m , n ) } × exp { - j 2 π ( m x off + n y off ) } ,
U 3 = exp ( j k 2 f ) / ( λ f ) 2 P 1 ( x 1 , y 1 ) P 3 ( x 3 , y 3 ) × T ( m , n ) exp ( j 2 π { x 2 [ m - ( x 1 + x 3 ) / λ f 1 ] + y 2 [ n - ( y 1 + y 3 ) / λ f 1 ] } ) × exp [ - j 2 π ( m x off + n y off ) ] d x 1 d y 1 d x 2 d y 2 d m d n .
U 3 = exp ( j k 2 f ) / ( λ f ) 2 P 1 ( x 3 , y 3 ) × P 3 ( λ f 1 m - x 3 , λ f 1 n - y 3 ) T ( m , n ) × exp [ - j 2 π ( m x off + n y off ) ] d m d n .
T ( m , n ) = F { exp ( j a x 2 ) } = δ ( a + 2 π m ) δ ( 2 π n ) ,
U 3 = exp ( j k 2 f ) / ( λ f ) 2 P 1 ( x 3 , y 3 ) × P 3 ( - a f 1 / k - x 3 , - a f 1 / k - y 3 ) exp ( j a x off ) .
T ( m ) = r δ ( m ) - 2 b r sinc ( 2 b m ) + 2 t exp ( j p ) sinc ( 2 t m ) + { exp [ j ( p + 2 π m t ) ] - exp [ j ( 2 π m b ) ] } × { j [ p / ( b - t ) - 2 π m ] } - 1 + { exp [ j ( - 2 π m t ) ] - exp [ j ( p - 2 π m b ) ] } × { j [ - p / ( b - t ) - 2 π m ] } - 1 ,

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