Abstract

An interferometer for planeness testing of technical surfaces is described and real-time interferometric evaluations of 10-cm (4-in.) diam silicon wafers were carried out. The interferometer, using the principles of phase sampling interferometry, is a combination of an oblique incidence Fizeau interferometer with a moire interferometer. The interference pattern is a pure two-beam pattern. To get low frequency moire fringes the live interference fringes must have about the same spatial frequency as the moving grating used for reference phase stepping. Assuming that an automatic alignment device is included in the design, up to three wafers per minute could be measured and classified.

© 1986 Optical Society of America

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  1. N. Abramson, “The Interferoscope—a New Type of Interferometer with Variable Fringe Separation,” Optik 30, 56 (1969).
  2. K. J. Birch, “Oblique Incidence Interferometry Applicated to Non-Optical Surfaces,” J. Phys. E. 6, 1045 (1973).
    [CrossRef]
  3. J. Schwider, K.-E. Elssner, R. Spolaczyk, K. Merkel, “Echtzeitinterferometrie,” Opt. Appl. (Wrocław) 15, 255 (1985).
  4. J. H. Bruning, D. R. Herriott, J. E. Gallagher, D. P. Rosenfeld, A. D. White, D. J. Brangaccio, “Digital Wavefront Measuring Interferometer for Testing Optical Surfaces and Lenses,” Appl. Opt. 13, 2693 (1974).
    [CrossRef] [PubMed]
  5. J. Schwider, R. Burow, K.-E. Elssner, K. Föllmer, J. Grzanna, R. Spolaczyk, S. Wallburg, K. Merkel, “Echtzeitinterferometer für die Optikprüfung,” Opt. Appl. (Wrocław) 15, 359 (1985).
  6. J. Schwider, R. Burow, K.-E. Elssner, J. Grzanna, R. Spolaczyk, K. Merkel, “Digital Wave-Front Measuring Interferometry: Some Systematic Error Sources,” Appl. Opt. 22, 3421 (1983).
    [CrossRef] [PubMed]
  7. J. Schwider, R. Spolaczyk, K.-E. Elssner, “Anordnung zur interferometrischen Ebenheitsprüfung technischer Oberflächen,” DDR-Wirtschaftspatent WP-219 565 A1 (5Dec.1983).
  8. M. Born, E. Wolf, Principles of Optics (Pergamon, Oxford, 1975), p. 352.
  9. A. Slomba, J. Figoski, “A Coaxial Interferometer with Low Mapping Distortion,” Proc. Soc. Photo-Opt. Instrum. Eng. 153, 156 (1978).
  10. B. J. Biddles, “A Non-Contacting Interferometer for Testing Steeply Curved Surfaces,” Opt. Acta 16, 137 (1969).
    [CrossRef]
  11. K.-E. Elssner, S. Wallburg, “Abbildung im Twyman-Green-Interferometer,” Beiträge zur Optik und Quantenelektronik (Phys. Ges. der DDR, Berlin, 1982), p. 142.
  12. J. Robinson, “Wafer Flatness Testing,” Semicond. Int., p. 57 (Jan./Feb.1979).
  13. T. C. Bettes, “Wafer Flatness Testing,” Semicond. Int., p. 77 (Feb.1982).
  14. P. Tigreat, “Eurostep 2000: New Steps in Wafer Steppers,” Proc. Soc. Photo-Opt. Instrum. Eng. 334, 90 (1982).

1985

J. Schwider, K.-E. Elssner, R. Spolaczyk, K. Merkel, “Echtzeitinterferometrie,” Opt. Appl. (Wrocław) 15, 255 (1985).

J. Schwider, R. Burow, K.-E. Elssner, K. Föllmer, J. Grzanna, R. Spolaczyk, S. Wallburg, K. Merkel, “Echtzeitinterferometer für die Optikprüfung,” Opt. Appl. (Wrocław) 15, 359 (1985).

1983

J. Schwider, R. Burow, K.-E. Elssner, J. Grzanna, R. Spolaczyk, K. Merkel, “Digital Wave-Front Measuring Interferometry: Some Systematic Error Sources,” Appl. Opt. 22, 3421 (1983).
[CrossRef] [PubMed]

J. Schwider, R. Spolaczyk, K.-E. Elssner, “Anordnung zur interferometrischen Ebenheitsprüfung technischer Oberflächen,” DDR-Wirtschaftspatent WP-219 565 A1 (5Dec.1983).

1982

T. C. Bettes, “Wafer Flatness Testing,” Semicond. Int., p. 77 (Feb.1982).

P. Tigreat, “Eurostep 2000: New Steps in Wafer Steppers,” Proc. Soc. Photo-Opt. Instrum. Eng. 334, 90 (1982).

1979

J. Robinson, “Wafer Flatness Testing,” Semicond. Int., p. 57 (Jan./Feb.1979).

1978

A. Slomba, J. Figoski, “A Coaxial Interferometer with Low Mapping Distortion,” Proc. Soc. Photo-Opt. Instrum. Eng. 153, 156 (1978).

1974

1973

K. J. Birch, “Oblique Incidence Interferometry Applicated to Non-Optical Surfaces,” J. Phys. E. 6, 1045 (1973).
[CrossRef]

1969

N. Abramson, “The Interferoscope—a New Type of Interferometer with Variable Fringe Separation,” Optik 30, 56 (1969).

B. J. Biddles, “A Non-Contacting Interferometer for Testing Steeply Curved Surfaces,” Opt. Acta 16, 137 (1969).
[CrossRef]

Abramson, N.

N. Abramson, “The Interferoscope—a New Type of Interferometer with Variable Fringe Separation,” Optik 30, 56 (1969).

Bettes, T. C.

T. C. Bettes, “Wafer Flatness Testing,” Semicond. Int., p. 77 (Feb.1982).

Biddles, B. J.

B. J. Biddles, “A Non-Contacting Interferometer for Testing Steeply Curved Surfaces,” Opt. Acta 16, 137 (1969).
[CrossRef]

Birch, K. J.

K. J. Birch, “Oblique Incidence Interferometry Applicated to Non-Optical Surfaces,” J. Phys. E. 6, 1045 (1973).
[CrossRef]

Born, M.

M. Born, E. Wolf, Principles of Optics (Pergamon, Oxford, 1975), p. 352.

Brangaccio, D. J.

Bruning, J. H.

Burow, R.

J. Schwider, R. Burow, K.-E. Elssner, K. Föllmer, J. Grzanna, R. Spolaczyk, S. Wallburg, K. Merkel, “Echtzeitinterferometer für die Optikprüfung,” Opt. Appl. (Wrocław) 15, 359 (1985).

J. Schwider, R. Burow, K.-E. Elssner, J. Grzanna, R. Spolaczyk, K. Merkel, “Digital Wave-Front Measuring Interferometry: Some Systematic Error Sources,” Appl. Opt. 22, 3421 (1983).
[CrossRef] [PubMed]

Elssner, K.-E.

J. Schwider, R. Burow, K.-E. Elssner, K. Föllmer, J. Grzanna, R. Spolaczyk, S. Wallburg, K. Merkel, “Echtzeitinterferometer für die Optikprüfung,” Opt. Appl. (Wrocław) 15, 359 (1985).

J. Schwider, K.-E. Elssner, R. Spolaczyk, K. Merkel, “Echtzeitinterferometrie,” Opt. Appl. (Wrocław) 15, 255 (1985).

J. Schwider, R. Burow, K.-E. Elssner, J. Grzanna, R. Spolaczyk, K. Merkel, “Digital Wave-Front Measuring Interferometry: Some Systematic Error Sources,” Appl. Opt. 22, 3421 (1983).
[CrossRef] [PubMed]

J. Schwider, R. Spolaczyk, K.-E. Elssner, “Anordnung zur interferometrischen Ebenheitsprüfung technischer Oberflächen,” DDR-Wirtschaftspatent WP-219 565 A1 (5Dec.1983).

K.-E. Elssner, S. Wallburg, “Abbildung im Twyman-Green-Interferometer,” Beiträge zur Optik und Quantenelektronik (Phys. Ges. der DDR, Berlin, 1982), p. 142.

Figoski, J.

A. Slomba, J. Figoski, “A Coaxial Interferometer with Low Mapping Distortion,” Proc. Soc. Photo-Opt. Instrum. Eng. 153, 156 (1978).

Föllmer, K.

J. Schwider, R. Burow, K.-E. Elssner, K. Föllmer, J. Grzanna, R. Spolaczyk, S. Wallburg, K. Merkel, “Echtzeitinterferometer für die Optikprüfung,” Opt. Appl. (Wrocław) 15, 359 (1985).

Gallagher, J. E.

Grzanna, J.

J. Schwider, R. Burow, K.-E. Elssner, K. Föllmer, J. Grzanna, R. Spolaczyk, S. Wallburg, K. Merkel, “Echtzeitinterferometer für die Optikprüfung,” Opt. Appl. (Wrocław) 15, 359 (1985).

J. Schwider, R. Burow, K.-E. Elssner, J. Grzanna, R. Spolaczyk, K. Merkel, “Digital Wave-Front Measuring Interferometry: Some Systematic Error Sources,” Appl. Opt. 22, 3421 (1983).
[CrossRef] [PubMed]

Herriott, D. R.

Merkel, K.

J. Schwider, R. Burow, K.-E. Elssner, K. Föllmer, J. Grzanna, R. Spolaczyk, S. Wallburg, K. Merkel, “Echtzeitinterferometer für die Optikprüfung,” Opt. Appl. (Wrocław) 15, 359 (1985).

J. Schwider, K.-E. Elssner, R. Spolaczyk, K. Merkel, “Echtzeitinterferometrie,” Opt. Appl. (Wrocław) 15, 255 (1985).

J. Schwider, R. Burow, K.-E. Elssner, J. Grzanna, R. Spolaczyk, K. Merkel, “Digital Wave-Front Measuring Interferometry: Some Systematic Error Sources,” Appl. Opt. 22, 3421 (1983).
[CrossRef] [PubMed]

Robinson, J.

J. Robinson, “Wafer Flatness Testing,” Semicond. Int., p. 57 (Jan./Feb.1979).

Rosenfeld, D. P.

Schwider, J.

J. Schwider, K.-E. Elssner, R. Spolaczyk, K. Merkel, “Echtzeitinterferometrie,” Opt. Appl. (Wrocław) 15, 255 (1985).

J. Schwider, R. Burow, K.-E. Elssner, K. Föllmer, J. Grzanna, R. Spolaczyk, S. Wallburg, K. Merkel, “Echtzeitinterferometer für die Optikprüfung,” Opt. Appl. (Wrocław) 15, 359 (1985).

J. Schwider, R. Burow, K.-E. Elssner, J. Grzanna, R. Spolaczyk, K. Merkel, “Digital Wave-Front Measuring Interferometry: Some Systematic Error Sources,” Appl. Opt. 22, 3421 (1983).
[CrossRef] [PubMed]

J. Schwider, R. Spolaczyk, K.-E. Elssner, “Anordnung zur interferometrischen Ebenheitsprüfung technischer Oberflächen,” DDR-Wirtschaftspatent WP-219 565 A1 (5Dec.1983).

Slomba, A.

A. Slomba, J. Figoski, “A Coaxial Interferometer with Low Mapping Distortion,” Proc. Soc. Photo-Opt. Instrum. Eng. 153, 156 (1978).

Spolaczyk, R.

J. Schwider, R. Burow, K.-E. Elssner, K. Föllmer, J. Grzanna, R. Spolaczyk, S. Wallburg, K. Merkel, “Echtzeitinterferometer für die Optikprüfung,” Opt. Appl. (Wrocław) 15, 359 (1985).

J. Schwider, K.-E. Elssner, R. Spolaczyk, K. Merkel, “Echtzeitinterferometrie,” Opt. Appl. (Wrocław) 15, 255 (1985).

J. Schwider, R. Spolaczyk, K.-E. Elssner, “Anordnung zur interferometrischen Ebenheitsprüfung technischer Oberflächen,” DDR-Wirtschaftspatent WP-219 565 A1 (5Dec.1983).

J. Schwider, R. Burow, K.-E. Elssner, J. Grzanna, R. Spolaczyk, K. Merkel, “Digital Wave-Front Measuring Interferometry: Some Systematic Error Sources,” Appl. Opt. 22, 3421 (1983).
[CrossRef] [PubMed]

Tigreat, P.

P. Tigreat, “Eurostep 2000: New Steps in Wafer Steppers,” Proc. Soc. Photo-Opt. Instrum. Eng. 334, 90 (1982).

Wallburg, S.

J. Schwider, R. Burow, K.-E. Elssner, K. Föllmer, J. Grzanna, R. Spolaczyk, S. Wallburg, K. Merkel, “Echtzeitinterferometer für die Optikprüfung,” Opt. Appl. (Wrocław) 15, 359 (1985).

K.-E. Elssner, S. Wallburg, “Abbildung im Twyman-Green-Interferometer,” Beiträge zur Optik und Quantenelektronik (Phys. Ges. der DDR, Berlin, 1982), p. 142.

White, A. D.

Wolf, E.

M. Born, E. Wolf, Principles of Optics (Pergamon, Oxford, 1975), p. 352.

Appl. Opt.

DDR-Wirtschaftspatent WP-219 565 A1

J. Schwider, R. Spolaczyk, K.-E. Elssner, “Anordnung zur interferometrischen Ebenheitsprüfung technischer Oberflächen,” DDR-Wirtschaftspatent WP-219 565 A1 (5Dec.1983).

J. Phys. E.

K. J. Birch, “Oblique Incidence Interferometry Applicated to Non-Optical Surfaces,” J. Phys. E. 6, 1045 (1973).
[CrossRef]

Opt. Acta

B. J. Biddles, “A Non-Contacting Interferometer for Testing Steeply Curved Surfaces,” Opt. Acta 16, 137 (1969).
[CrossRef]

Opt. Appl. (Wroclaw)

J. Schwider, K.-E. Elssner, R. Spolaczyk, K. Merkel, “Echtzeitinterferometrie,” Opt. Appl. (Wrocław) 15, 255 (1985).

J. Schwider, R. Burow, K.-E. Elssner, K. Föllmer, J. Grzanna, R. Spolaczyk, S. Wallburg, K. Merkel, “Echtzeitinterferometer für die Optikprüfung,” Opt. Appl. (Wrocław) 15, 359 (1985).

Optik

N. Abramson, “The Interferoscope—a New Type of Interferometer with Variable Fringe Separation,” Optik 30, 56 (1969).

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

A. Slomba, J. Figoski, “A Coaxial Interferometer with Low Mapping Distortion,” Proc. Soc. Photo-Opt. Instrum. Eng. 153, 156 (1978).

P. Tigreat, “Eurostep 2000: New Steps in Wafer Steppers,” Proc. Soc. Photo-Opt. Instrum. Eng. 334, 90 (1982).

Semicond. Int.

J. Robinson, “Wafer Flatness Testing,” Semicond. Int., p. 57 (Jan./Feb.1979).

T. C. Bettes, “Wafer Flatness Testing,” Semicond. Int., p. 77 (Feb.1982).

Other

K.-E. Elssner, S. Wallburg, “Abbildung im Twyman-Green-Interferometer,” Beiträge zur Optik und Quantenelektronik (Phys. Ges. der DDR, Berlin, 1982), p. 142.

M. Born, E. Wolf, Principles of Optics (Pergamon, Oxford, 1975), p. 352.

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Figures (10)

Fig. 1
Fig. 1

Oblique incidence Fizeau interferometer with anamorphic prism for squeezing and desqueezing the light bundle illuminating the surface under test.

Fig. 2
Fig. 2

Fizeau prism interferometer combined with a moire grating interferometer enabling the phase sampling technique.

Fig. 3
Fig. 3

Multiple beam fringes. The reference surface of the prism and the wafer are in contact. Note the dissymmetries of the fringes. Surface deviations from fringe to fringe equal 7 μm.

Fig. 4
Fig. 4

Multiple beam fringes caused by a mean distance of the reference and the test surfaces of ∼200 μm. Note the strong phase mismatch.

Fig. 5
Fig. 5

Optical ray path for multiple reflection between reference and test surfaces. Definition of symbols of Eq. (1): α, wedge angle; ρ, distance of observation point P from edge O; N1,… Np, wavefront normals of waves W1,… Wp; θ, incidence angle outside the wedge; θ′, incidence angle inside the wedge.

Fig. 6
Fig. 6

Moire fringes directly behind the grating (for comparison see Fig. 2) (left) and in the detector plane after spatial filtering by a low pass for one order of diffraction (right). The pure two-beam interference pattern directly in front of the grating (not shown here) has the same mean spatial frequency of 5 lines per mm as the grating itself. The height difference corresponding to one fringe distance is 7 μm.

Fig. 7
Fig. 7

Lateral shear between reference and test beams due to grazing incidence and the distance between the surfaces.

Fig. 8
Fig. 8

Pseudo 3-D plot and contour lines of mean plane deviation (MPD) of a silicon wafer of 100-mm diameter; 1λ ≜ 7-μm surface deviation.

Fig. 9
Fig. 9

Pseudo 3-D plot and contour lines of focal plane deviation (FPD). 1λ ≜ 7-μm surface deviation.

Fig. 10
Fig. 10

Percent usable area (PUA). The threshold limit of the surface deviations is 7 μm. A 3-mm wide section of the rim region was excluded from the calculation of the PUA value.

Equations (9)

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Δ = n ( PN p PN 1 ) = n ρ ( sin θ p sin θ 1 ) , δ = k Δ = 2 kn h cos θ sin [ ( p 1 ) α ] [ cos ( p 1 ) α tan θ sin ( p 1 ) α ] / tan α + 2 ( p 1 ) χ ,
u g = { a 1 + a 2 exp [ j ( Φ kx sin 2 α ) ] } n = cn × exp [ jkn ( x x ) sin 2 α ] ,
u g 01 = c 0 a 1 + c 1 a 2 exp [ j ( Φ kx sin 2 α ) ] ,
u g 01 = c 0 a 2 exp [ j ( Φ kx sin 2 α ) ] + c 1 a 1 × exp [ jk ( x x ) sin 2 α ]
I = | u g 01 | 2 = ( c 0 a 2 ) 2 + ( c 1 a 1 ) 2 + 2 c 0 c 1 a 1 a 2 × cos ( Φ kx sin 2 α ) .
Φ ( x , y ) = arctan 2 I ( x , y ; φ = π / 2 ) 2 I ( x , y ; φ = 3 π / 2 ) I ( x , y ; φ = 0 ) 2 I ( x , y ; φ = π ) + I ( x , y ; φ = 2 π ) .
s 2 d tan θ .
δ W ( x , y ) = W ( x + s , y ) W ( x , y ) s ( W / x ) .
Δ x = f ( W / x ) f ( δ W / s ) .

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