Abstract

We first discuss an interference microscope’s 3D response in terms of Richards and Wolf’s vector theory. We then report the results we obtained with a 325-nm interference microscope using an ultraviolet transparent beam splitter, short-working-distance Mirau interferometer. The microscope performs at near-ideal definitions with a measured FWHM of the intensity spot at 0.14 μm and a FWHM of the depth envelope intensity at 0.25 μm. Feasibility of a shorter wavelength system operating at 248 nm is demonstrated.

© 1998 Optical Society of America

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References

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  1. G. S. Kino, T. R. Corle, “Confocal scanning optical microscopy,” Phys. Today, 55–62 (September1989).
  2. T. R. Corle, “Real-time scanning confocal microscopy,” Ph.D. dissertation (Stanford University, Stanford, Calif., 1987).
  3. G. S. Kino, S. S. C. Chim, “The Mirau correlation microscope,” Appl. Opt. 29, 3775–3783 (1990).
    [CrossRef] [PubMed]
  4. S. S. C. Chim, G. S. Kino, “Phase measurements using the Mirau correlation microscope,” Appl. Opt. 30, 2197–2201 (1991).
    [CrossRef] [PubMed]
  5. F. C. Chang, G. S. Kino, W. R. Studenmund, S. S. C. Chim, C-H Chou, “Measurement of phase-shift masks,” in Integrated Circuit Metrology, Inspection, and Process Control VII, T. Postek, ed., Proc. SPIE1926, 464–491 (1993).
    [CrossRef]
  6. S. S. C. Chim, P. A. Beck, G. S. Kino, “A novel thin film interferometer,” Rev. Sci. Instrum. 61, 980–983 (1990).
    [CrossRef]
  7. M. Davidson, K. Kaufman, I. Mazor, F. Cohen, “An application of interference microscopy to integrated circuit inspection and metrology,” in Integrated Circuit Metrology, Inspection, and Process Control, K. M. Monahan, ed., Proc. SPIE775, 233–247 (1987).
    [CrossRef]
  8. B. Richards, E. Wolf, “Electromagnetic diffraction in optical systems: II. structure of the image field in an aplanatic system,” Proc. Soc. London Ser. A 253, 358–379 (1959).
    [CrossRef]
  9. J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968).
  10. R. N. Bracewell, The Fourier Transform and Its Applications, 2nd ed. (McGraw-Hill, New York, 1986).
  11. F. C. Chang, G. S. Kino, W. R. Studenmund, “Development of a deep-UV correlation microscope,” in Integrated Circuit Metrology, Inspection, and Process Control VIII, M. H. Bennett, ed., Proc. SPIE2196, 35–46 (1994).
    [CrossRef]
  12. M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1975).
  13. J. W. Goodman, Statistical Optics (Wiley, New York, 1984).
  14. A. Kiermasz, K. Beekman, “Plasma CVD of silicon nitride: process design for increased flexibility,” Semicond. Int. 13, 108–128 (1990).
  15. P. A. Beck, “Micromachined VLSI sensors,” Ph.D. dissertation (Stanford University, Stanford, Calif., 1990).
  16. K. E. Petersen, “Silicon as a mechanical material,” Proc. IEEE 5, 420–457 (1992).
  17. F. C. Chang, G. S. Kino, “Nitrogen-rich silicon nitride thin-films for deep ultraviolet Mirau interferometry,” Opt. Lett. 22, 492–494 (1997).
    [CrossRef] [PubMed]
  18. B. A. Carlson, Communication Systems, 3rd ed. (McGraw-Hill, New York, 1986).

1997

1992

K. E. Petersen, “Silicon as a mechanical material,” Proc. IEEE 5, 420–457 (1992).

1991

1990

A. Kiermasz, K. Beekman, “Plasma CVD of silicon nitride: process design for increased flexibility,” Semicond. Int. 13, 108–128 (1990).

G. S. Kino, S. S. C. Chim, “The Mirau correlation microscope,” Appl. Opt. 29, 3775–3783 (1990).
[CrossRef] [PubMed]

S. S. C. Chim, P. A. Beck, G. S. Kino, “A novel thin film interferometer,” Rev. Sci. Instrum. 61, 980–983 (1990).
[CrossRef]

1989

G. S. Kino, T. R. Corle, “Confocal scanning optical microscopy,” Phys. Today, 55–62 (September1989).

1959

B. Richards, E. Wolf, “Electromagnetic diffraction in optical systems: II. structure of the image field in an aplanatic system,” Proc. Soc. London Ser. A 253, 358–379 (1959).
[CrossRef]

Beck, P. A.

S. S. C. Chim, P. A. Beck, G. S. Kino, “A novel thin film interferometer,” Rev. Sci. Instrum. 61, 980–983 (1990).
[CrossRef]

P. A. Beck, “Micromachined VLSI sensors,” Ph.D. dissertation (Stanford University, Stanford, Calif., 1990).

Beekman, K.

A. Kiermasz, K. Beekman, “Plasma CVD of silicon nitride: process design for increased flexibility,” Semicond. Int. 13, 108–128 (1990).

Born, M.

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1975).

Bracewell, R. N.

R. N. Bracewell, The Fourier Transform and Its Applications, 2nd ed. (McGraw-Hill, New York, 1986).

Carlson, B. A.

B. A. Carlson, Communication Systems, 3rd ed. (McGraw-Hill, New York, 1986).

Chang, F. C.

F. C. Chang, G. S. Kino, “Nitrogen-rich silicon nitride thin-films for deep ultraviolet Mirau interferometry,” Opt. Lett. 22, 492–494 (1997).
[CrossRef] [PubMed]

F. C. Chang, G. S. Kino, W. R. Studenmund, “Development of a deep-UV correlation microscope,” in Integrated Circuit Metrology, Inspection, and Process Control VIII, M. H. Bennett, ed., Proc. SPIE2196, 35–46 (1994).
[CrossRef]

F. C. Chang, G. S. Kino, W. R. Studenmund, S. S. C. Chim, C-H Chou, “Measurement of phase-shift masks,” in Integrated Circuit Metrology, Inspection, and Process Control VII, T. Postek, ed., Proc. SPIE1926, 464–491 (1993).
[CrossRef]

Chim, S. S. C.

S. S. C. Chim, G. S. Kino, “Phase measurements using the Mirau correlation microscope,” Appl. Opt. 30, 2197–2201 (1991).
[CrossRef] [PubMed]

G. S. Kino, S. S. C. Chim, “The Mirau correlation microscope,” Appl. Opt. 29, 3775–3783 (1990).
[CrossRef] [PubMed]

S. S. C. Chim, P. A. Beck, G. S. Kino, “A novel thin film interferometer,” Rev. Sci. Instrum. 61, 980–983 (1990).
[CrossRef]

F. C. Chang, G. S. Kino, W. R. Studenmund, S. S. C. Chim, C-H Chou, “Measurement of phase-shift masks,” in Integrated Circuit Metrology, Inspection, and Process Control VII, T. Postek, ed., Proc. SPIE1926, 464–491 (1993).
[CrossRef]

Chou, C-H

F. C. Chang, G. S. Kino, W. R. Studenmund, S. S. C. Chim, C-H Chou, “Measurement of phase-shift masks,” in Integrated Circuit Metrology, Inspection, and Process Control VII, T. Postek, ed., Proc. SPIE1926, 464–491 (1993).
[CrossRef]

Cohen, F.

M. Davidson, K. Kaufman, I. Mazor, F. Cohen, “An application of interference microscopy to integrated circuit inspection and metrology,” in Integrated Circuit Metrology, Inspection, and Process Control, K. M. Monahan, ed., Proc. SPIE775, 233–247 (1987).
[CrossRef]

Corle, T. R.

G. S. Kino, T. R. Corle, “Confocal scanning optical microscopy,” Phys. Today, 55–62 (September1989).

T. R. Corle, “Real-time scanning confocal microscopy,” Ph.D. dissertation (Stanford University, Stanford, Calif., 1987).

Davidson, M.

M. Davidson, K. Kaufman, I. Mazor, F. Cohen, “An application of interference microscopy to integrated circuit inspection and metrology,” in Integrated Circuit Metrology, Inspection, and Process Control, K. M. Monahan, ed., Proc. SPIE775, 233–247 (1987).
[CrossRef]

Goodman, J. W.

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968).

J. W. Goodman, Statistical Optics (Wiley, New York, 1984).

Kaufman, K.

M. Davidson, K. Kaufman, I. Mazor, F. Cohen, “An application of interference microscopy to integrated circuit inspection and metrology,” in Integrated Circuit Metrology, Inspection, and Process Control, K. M. Monahan, ed., Proc. SPIE775, 233–247 (1987).
[CrossRef]

Kiermasz, A.

A. Kiermasz, K. Beekman, “Plasma CVD of silicon nitride: process design for increased flexibility,” Semicond. Int. 13, 108–128 (1990).

Kino, G. S.

F. C. Chang, G. S. Kino, “Nitrogen-rich silicon nitride thin-films for deep ultraviolet Mirau interferometry,” Opt. Lett. 22, 492–494 (1997).
[CrossRef] [PubMed]

S. S. C. Chim, G. S. Kino, “Phase measurements using the Mirau correlation microscope,” Appl. Opt. 30, 2197–2201 (1991).
[CrossRef] [PubMed]

S. S. C. Chim, P. A. Beck, G. S. Kino, “A novel thin film interferometer,” Rev. Sci. Instrum. 61, 980–983 (1990).
[CrossRef]

G. S. Kino, S. S. C. Chim, “The Mirau correlation microscope,” Appl. Opt. 29, 3775–3783 (1990).
[CrossRef] [PubMed]

G. S. Kino, T. R. Corle, “Confocal scanning optical microscopy,” Phys. Today, 55–62 (September1989).

F. C. Chang, G. S. Kino, W. R. Studenmund, S. S. C. Chim, C-H Chou, “Measurement of phase-shift masks,” in Integrated Circuit Metrology, Inspection, and Process Control VII, T. Postek, ed., Proc. SPIE1926, 464–491 (1993).
[CrossRef]

F. C. Chang, G. S. Kino, W. R. Studenmund, “Development of a deep-UV correlation microscope,” in Integrated Circuit Metrology, Inspection, and Process Control VIII, M. H. Bennett, ed., Proc. SPIE2196, 35–46 (1994).
[CrossRef]

Mazor, I.

M. Davidson, K. Kaufman, I. Mazor, F. Cohen, “An application of interference microscopy to integrated circuit inspection and metrology,” in Integrated Circuit Metrology, Inspection, and Process Control, K. M. Monahan, ed., Proc. SPIE775, 233–247 (1987).
[CrossRef]

Petersen, K. E.

K. E. Petersen, “Silicon as a mechanical material,” Proc. IEEE 5, 420–457 (1992).

Richards, B.

B. Richards, E. Wolf, “Electromagnetic diffraction in optical systems: II. structure of the image field in an aplanatic system,” Proc. Soc. London Ser. A 253, 358–379 (1959).
[CrossRef]

Studenmund, W. R.

F. C. Chang, G. S. Kino, W. R. Studenmund, S. S. C. Chim, C-H Chou, “Measurement of phase-shift masks,” in Integrated Circuit Metrology, Inspection, and Process Control VII, T. Postek, ed., Proc. SPIE1926, 464–491 (1993).
[CrossRef]

F. C. Chang, G. S. Kino, W. R. Studenmund, “Development of a deep-UV correlation microscope,” in Integrated Circuit Metrology, Inspection, and Process Control VIII, M. H. Bennett, ed., Proc. SPIE2196, 35–46 (1994).
[CrossRef]

Wolf, E.

B. Richards, E. Wolf, “Electromagnetic diffraction in optical systems: II. structure of the image field in an aplanatic system,” Proc. Soc. London Ser. A 253, 358–379 (1959).
[CrossRef]

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1975).

Appl. Opt.

Opt. Lett.

Phys. Today

G. S. Kino, T. R. Corle, “Confocal scanning optical microscopy,” Phys. Today, 55–62 (September1989).

Proc. IEEE

K. E. Petersen, “Silicon as a mechanical material,” Proc. IEEE 5, 420–457 (1992).

Proc. Soc. London Ser. A

B. Richards, E. Wolf, “Electromagnetic diffraction in optical systems: II. structure of the image field in an aplanatic system,” Proc. Soc. London Ser. A 253, 358–379 (1959).
[CrossRef]

Rev. Sci. Instrum.

S. S. C. Chim, P. A. Beck, G. S. Kino, “A novel thin film interferometer,” Rev. Sci. Instrum. 61, 980–983 (1990).
[CrossRef]

Semicond. Int.

A. Kiermasz, K. Beekman, “Plasma CVD of silicon nitride: process design for increased flexibility,” Semicond. Int. 13, 108–128 (1990).

Other

P. A. Beck, “Micromachined VLSI sensors,” Ph.D. dissertation (Stanford University, Stanford, Calif., 1990).

M. Davidson, K. Kaufman, I. Mazor, F. Cohen, “An application of interference microscopy to integrated circuit inspection and metrology,” in Integrated Circuit Metrology, Inspection, and Process Control, K. M. Monahan, ed., Proc. SPIE775, 233–247 (1987).
[CrossRef]

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968).

R. N. Bracewell, The Fourier Transform and Its Applications, 2nd ed. (McGraw-Hill, New York, 1986).

F. C. Chang, G. S. Kino, W. R. Studenmund, “Development of a deep-UV correlation microscope,” in Integrated Circuit Metrology, Inspection, and Process Control VIII, M. H. Bennett, ed., Proc. SPIE2196, 35–46 (1994).
[CrossRef]

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1975).

J. W. Goodman, Statistical Optics (Wiley, New York, 1984).

F. C. Chang, G. S. Kino, W. R. Studenmund, S. S. C. Chim, C-H Chou, “Measurement of phase-shift masks,” in Integrated Circuit Metrology, Inspection, and Process Control VII, T. Postek, ed., Proc. SPIE1926, 464–491 (1993).
[CrossRef]

T. R. Corle, “Real-time scanning confocal microscopy,” Ph.D. dissertation (Stanford University, Stanford, Calif., 1987).

B. A. Carlson, Communication Systems, 3rd ed. (McGraw-Hill, New York, 1986).

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Figures (16)

Fig. 1
Fig. 1

System setup of a Mirau correlation/interference microscope.

Fig. 2
Fig. 2

Comparison of PSF’s of a MCM computed with vector and scalar theories.

Fig. 3
Fig. 3

Mirau interferometer closeup.

Fig. 4
Fig. 4

Spectra of conventional 500-Å thin film as a function of wavelength. The solid curve represents transparency equal to the sum of measured transmitted and reflected power (plotted by thick dashed curves); the lossless (or theoretical) transmitted and reflected power spectra are plotted by thin dashed curves.

Fig. 5
Fig. 5

Spectra of thin film as a function of wavelength with different recipes; the anomalous kink around 900 nm is due to a switch to a different detector.

Fig. 6
Fig. 6

Top view of a suspended mirror structure in a Mirau interferometer.

Fig. 7
Fig. 7

Closeup of a 200-μm suspended Al mirror; the rod is a 5-mm pencil lead.

Fig. 8
Fig. 8

Schematic of the short-working-distance Mirau interferometer.

Fig. 9
Fig. 9

Microfabrication steps of the short-distance interferometer (top down and left to right).

Fig. 10
Fig. 10

Infrared images of patterned wafer bonding.

Fig. 11
Fig. 11

325-nm MCM image of the reference mirror of our short-distance Mirau interferometer in correlation with the imaged sample.

Fig. 12
Fig. 12

Correlation signal from our 325-nm short-working-distance Mirau interferometer.

Fig. 13
Fig. 13

Depth intensity envelope from our 325-nm MCM.

Fig. 14
Fig. 14

Edge response of our 325-nm MCM.

Fig. 15
Fig. 15

2D postprocessed images from our 325-nm MCM focused at 0.1 μm apart; left to right: sample is scanned from bottom to top.

Fig. 16
Fig. 16

3D representation of postprocessed phase information extracted from our 325-nm MCM.

Tables (1)

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Table 1 LPCVD Nitride Properties as a Function of Dichlorosilane and Ammonia Gas Mixture Ratio

Equations (22)

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e x ,   y ,   z = - jk 2 π   Ω a s x ,   s y s z   exp jk Φ s x ,   s y + s x x + s y y + s z z d s x d s y , h x ,   y ,   z = - jk 2 π   Ω b s x ,   s y s z   exp jk Φ s x ,   s y + s x x + s y y + s z z d s x d s y ,
e x P e y P e z P = - jA I 0 + I 2   cos   2 ϕ P - jAI 2   sin   2 ϕ P - 2 AI 1   cos   ϕ P ,
h x P h y P h z P = - jAI 2   sin   2 ϕ P - jA I 0 - I 2   cos   2 ϕ P - 2 AI 1   sin   ϕ P ,
I 0 = I 0 ρ P ,   z P = 0 θ 0 cos 1 / 2   θ   sin   θ 1 + cos   θ × J 0 k ρ P   sin   θ     exp jkz P   cos   θ d θ ,
I 1 = I 1 ρ P ,   z P = 0 θ 0 cos 1 / 2   θ   sin 2   θ × J 1 k ρ P   sin   θ exp jkz P   cos   θ d θ ,
I 2 = I 2 ρ P ,   z P = 0 θ 0 cos 1 / 2   θ   sin   θ × 1 - cos   θ J 2 k ρ P   sin   θ exp jkz P   cos   θ d θ ,
V z =   - +   e × h * · z ˆ d x P d y P .
Γ z z = e × h * · z ˆ
= e x h y * - e y h x * ,
e x h y * = e x P 1 + e x P 2 h y * P 1 + h y * P 2 = e x P 1 h y * P 1 + e x P 1 h y * P 2 + e x P 2 h y * P 1 + e x P 2 h y * P 2 ,
e y h x * = e y P 1 h x * P 1 + e y P 1 h x * P 2 + e y P 2 h x * P 1 + e y P 2 h x * P 2 ,
Γ z z = 2 A 2 I 0 P 1 I 0 * P 2 - I 2 P 1 I 2 * P 2 + j 2 A 2 cos   2 ϕ P L I 2 P 1 I 0 * P 2 - I 0 P 1 I 2 * P 2 .
V z =   - +   Γ z z d x P dy P , V z = 2 A 2     - +   I 0 P 1 I 0 * P 2 - I 2 P 1 I 2 * P 2 d x P d y P .
  - +   I 0 P 1 I 0 * P 2 d x d y = 0 θ 0 d θ 1 0 θ 0 d θ 2 exp - j 2 kz   cos   θ 2 cos 1 / 2   θ 1 × sin   θ 1 1 + cos   θ 1 × cos 1 / 2   θ 2   sin   θ 2 1 + cos   θ 2 × 0 2 π d ϕ P 0   J 0 k ρ P   sin   θ 1 J 0 k ρ P   sin   θ 2 ρ p d ρ P .
2 π   0   J 0 k ρ P   sin   θ 1 J 0 k ρ P   sin   θ 2 ρ P d ρ P = 1 k   sin   θ 1   δ k sin   θ 2 - sin   θ 1 = 1 k 2 sin   θ 1   cos   θ 1   δ θ 2 - θ 1 ,
1 k 2 0 θ 0 sin   θ 1 + cos   θ 2 exp - j 2 kz   cos   θ d θ .
- +   I 2 P 1 I 2 * P 2 d x d y = 0 θ 0 d θ 1 0 θ 0 d θ 2 exp - j 2 kz   cos   θ 2 cos 1 / 2   θ 1   ×   sin   θ 1 1 - cos   θ 1 cos 1 / 2   θ 2   sin   θ 2 1 - cos   θ 2 2 π × 0   J 2 k ρ P   sin   θ 1 J 2 k ρ P   sin   θ 2 ρ P d ρ P .
F s = 0   xf x J ν xs d x ,     f x = 0   sF s J ν xs d s .
2 π   0   J 2 k ρ P   sin   θ 1 J 2 k ρ P   sin   θ 2 ρ P d ρ P = 1 k 2   sin   θ 1   cos   θ 1   δ θ 2 - θ 1 .
1 k 2 0 θ 0 sin   θ 1 - cos   θ 2 exp - j 2 kz   cos   θ d θ .
V z = 8 A 2 k 2   0 θ 0 sin   θ   cos   θ   exp - j 2 kz   cos   θ d θ = 8 A 2 k 2 0 θ 0 sin   θ   cos   θ   cos 2 kz   cos   θ d θ .
h PSF ρ P = Γ z ρ P ;   z = 0 = 2 A 2 | I 0 ρ P ;   z P = 0 | 2 - | I 2 ρ P ;   z P = 0 | 2 .

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