Abstract

The increasingly smaller depth of focus of advanced lithographic tools requires that the position of best focus be determined to ensure accuracy and efficiency. We present what we believe is a novel bar in bar that is drawn on a conventional chrome binary mask to translate focal errors into center-to-center shifts of outer and inner bars. An overlay measurement tool can easily measure this shift. A symmetrical center-to-center shift against best focus is created during defocus, and this shift can be well fitted by a second-order polynomial equation. Simply differentiating the fitted equation leads to an accurate and reliable focus value, with a maximum error of less than 0.05 µm. The proposed technique can also be employed to evaluate the tilt, field curvature, and astigmatism of advanced lithographic tools.

© 2001 Optical Society of America

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References

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  1. S. Stalnaker, P. Luehrmann, J. Waelpoel, “Focal plane determination for sub-half micron optical steppers,” Microelectron. Eng. 21, 33–43 (1993).
    [CrossRef]
  2. T. A. Brunner, A. L. Martin, R. M. Martino, C. P. Ausschnitt, T. H. Newman, M. S. Hibbs, “Quantitative stepper metrology using the focus monitor test mask,” in Optical/Laser Microlighography VII, T. A. Brunner, ed., Proc. SPIE2197, 541–549 (1994).
    [CrossRef]
  3. W. H. Arnold, E. Barouch, U. Hollerbach, S. A. Orszag, “A focus vernier for optical lithography,” in Integrated Circuit Metrology, Inspection, and Process Control VII, M. T. Postek, ed., Proc. SPIE1926, 380–392 (1993).
    [CrossRef]
  4. A. D. Katnani, B. J. Lin, “Phase and transmission error study for the alternating element (Levenson) phase-shifting mask,” in Optical/Laser Microlithography V, J. D. Cuthbert, ed., Proc. SPIE1674, 264–270 (1992).
    [CrossRef]
  5. K. Suwa, H. Tateno, N. Irie, S. Hirukawa, “Automatic laser scanning focus detection method using printed focus pattern,” in Optical/Laser Microlithography VIII, T. A. Brunner, ed., Proc. SPIE2440, 712–720 (1995).
    [CrossRef]
  6. Y. C. Kim, G. S. Yeo, J. H. Lee, H. Kim, U. I. Chung, “Automatic in-situ focus monitor using line shortening effect,” in Metrology, Inspection, and Process Control for Microlithography XIII, B. Singh, ed., Proc. SPIE3677, 184–193 (1999).
    [CrossRef]
  7. T. A. Brunner, S. Cheng, A. E. Norton, “A stepper image monitor for precise setup and characterization,” in Fiber Optics Reliability: Benign and Adverse Environments II, R. A. Greenwell, D. K. Paul, S. G. Wadekar, eds., Proc. SPIE922, 366–375 (1988).
  8. T. A. Brunner, J. Lewis, M. Manny, “Stepper self-metrology using automated techniques,” in Optical Fibers in Medicine V, A. Katzir, ed., Proc. SPIE1201, 286–297 (1990).
  9. M. van den Brink, H. Franken, S. Wittekoek, T. Fahner, “Automatic on-line wafer stepper calibration system,” in Integrated Circuit Metrology, Inspection, and Process Control IV, W. H. Arnold, ed., Proc. SPIE1261, 298–314 (1990).
    [CrossRef]
  10. T. Terasawa, N. Hasegawa, T. Kurosaki, T. Tanaka, “0.3 µm optical lithography using a phase-shifting mask,” in Optical/Laser Microlithography II, B. J. Lin, ed., Proc. SPIE1088, 25–33 (1989).
    [CrossRef]
  11. M. D. Levenson, N. S. Viswanathan, R. A. Simpson, “Improving resolution in photolithography with a phase-shifting mask,” IEEE Trans. Electron Devices ED-29, 1828–1836 (1982).
    [CrossRef]

1993 (1)

S. Stalnaker, P. Luehrmann, J. Waelpoel, “Focal plane determination for sub-half micron optical steppers,” Microelectron. Eng. 21, 33–43 (1993).
[CrossRef]

1982 (1)

M. D. Levenson, N. S. Viswanathan, R. A. Simpson, “Improving resolution in photolithography with a phase-shifting mask,” IEEE Trans. Electron Devices ED-29, 1828–1836 (1982).
[CrossRef]

Arnold, W. H.

W. H. Arnold, E. Barouch, U. Hollerbach, S. A. Orszag, “A focus vernier for optical lithography,” in Integrated Circuit Metrology, Inspection, and Process Control VII, M. T. Postek, ed., Proc. SPIE1926, 380–392 (1993).
[CrossRef]

Ausschnitt, C. P.

T. A. Brunner, A. L. Martin, R. M. Martino, C. P. Ausschnitt, T. H. Newman, M. S. Hibbs, “Quantitative stepper metrology using the focus monitor test mask,” in Optical/Laser Microlighography VII, T. A. Brunner, ed., Proc. SPIE2197, 541–549 (1994).
[CrossRef]

Barouch, E.

W. H. Arnold, E. Barouch, U. Hollerbach, S. A. Orszag, “A focus vernier for optical lithography,” in Integrated Circuit Metrology, Inspection, and Process Control VII, M. T. Postek, ed., Proc. SPIE1926, 380–392 (1993).
[CrossRef]

Brunner, T. A.

T. A. Brunner, A. L. Martin, R. M. Martino, C. P. Ausschnitt, T. H. Newman, M. S. Hibbs, “Quantitative stepper metrology using the focus monitor test mask,” in Optical/Laser Microlighography VII, T. A. Brunner, ed., Proc. SPIE2197, 541–549 (1994).
[CrossRef]

T. A. Brunner, S. Cheng, A. E. Norton, “A stepper image monitor for precise setup and characterization,” in Fiber Optics Reliability: Benign and Adverse Environments II, R. A. Greenwell, D. K. Paul, S. G. Wadekar, eds., Proc. SPIE922, 366–375 (1988).

T. A. Brunner, J. Lewis, M. Manny, “Stepper self-metrology using automated techniques,” in Optical Fibers in Medicine V, A. Katzir, ed., Proc. SPIE1201, 286–297 (1990).

Cheng, S.

T. A. Brunner, S. Cheng, A. E. Norton, “A stepper image monitor for precise setup and characterization,” in Fiber Optics Reliability: Benign and Adverse Environments II, R. A. Greenwell, D. K. Paul, S. G. Wadekar, eds., Proc. SPIE922, 366–375 (1988).

Chung, U. I.

Y. C. Kim, G. S. Yeo, J. H. Lee, H. Kim, U. I. Chung, “Automatic in-situ focus monitor using line shortening effect,” in Metrology, Inspection, and Process Control for Microlithography XIII, B. Singh, ed., Proc. SPIE3677, 184–193 (1999).
[CrossRef]

Fahner, T.

M. van den Brink, H. Franken, S. Wittekoek, T. Fahner, “Automatic on-line wafer stepper calibration system,” in Integrated Circuit Metrology, Inspection, and Process Control IV, W. H. Arnold, ed., Proc. SPIE1261, 298–314 (1990).
[CrossRef]

Franken, H.

M. van den Brink, H. Franken, S. Wittekoek, T. Fahner, “Automatic on-line wafer stepper calibration system,” in Integrated Circuit Metrology, Inspection, and Process Control IV, W. H. Arnold, ed., Proc. SPIE1261, 298–314 (1990).
[CrossRef]

Hasegawa, N.

T. Terasawa, N. Hasegawa, T. Kurosaki, T. Tanaka, “0.3 µm optical lithography using a phase-shifting mask,” in Optical/Laser Microlithography II, B. J. Lin, ed., Proc. SPIE1088, 25–33 (1989).
[CrossRef]

Hibbs, M. S.

T. A. Brunner, A. L. Martin, R. M. Martino, C. P. Ausschnitt, T. H. Newman, M. S. Hibbs, “Quantitative stepper metrology using the focus monitor test mask,” in Optical/Laser Microlighography VII, T. A. Brunner, ed., Proc. SPIE2197, 541–549 (1994).
[CrossRef]

Hirukawa, S.

K. Suwa, H. Tateno, N. Irie, S. Hirukawa, “Automatic laser scanning focus detection method using printed focus pattern,” in Optical/Laser Microlithography VIII, T. A. Brunner, ed., Proc. SPIE2440, 712–720 (1995).
[CrossRef]

Hollerbach, U.

W. H. Arnold, E. Barouch, U. Hollerbach, S. A. Orszag, “A focus vernier for optical lithography,” in Integrated Circuit Metrology, Inspection, and Process Control VII, M. T. Postek, ed., Proc. SPIE1926, 380–392 (1993).
[CrossRef]

Irie, N.

K. Suwa, H. Tateno, N. Irie, S. Hirukawa, “Automatic laser scanning focus detection method using printed focus pattern,” in Optical/Laser Microlithography VIII, T. A. Brunner, ed., Proc. SPIE2440, 712–720 (1995).
[CrossRef]

Katnani, A. D.

A. D. Katnani, B. J. Lin, “Phase and transmission error study for the alternating element (Levenson) phase-shifting mask,” in Optical/Laser Microlithography V, J. D. Cuthbert, ed., Proc. SPIE1674, 264–270 (1992).
[CrossRef]

Kim, H.

Y. C. Kim, G. S. Yeo, J. H. Lee, H. Kim, U. I. Chung, “Automatic in-situ focus monitor using line shortening effect,” in Metrology, Inspection, and Process Control for Microlithography XIII, B. Singh, ed., Proc. SPIE3677, 184–193 (1999).
[CrossRef]

Kim, Y. C.

Y. C. Kim, G. S. Yeo, J. H. Lee, H. Kim, U. I. Chung, “Automatic in-situ focus monitor using line shortening effect,” in Metrology, Inspection, and Process Control for Microlithography XIII, B. Singh, ed., Proc. SPIE3677, 184–193 (1999).
[CrossRef]

Kurosaki, T.

T. Terasawa, N. Hasegawa, T. Kurosaki, T. Tanaka, “0.3 µm optical lithography using a phase-shifting mask,” in Optical/Laser Microlithography II, B. J. Lin, ed., Proc. SPIE1088, 25–33 (1989).
[CrossRef]

Lee, J. H.

Y. C. Kim, G. S. Yeo, J. H. Lee, H. Kim, U. I. Chung, “Automatic in-situ focus monitor using line shortening effect,” in Metrology, Inspection, and Process Control for Microlithography XIII, B. Singh, ed., Proc. SPIE3677, 184–193 (1999).
[CrossRef]

Levenson, M. D.

M. D. Levenson, N. S. Viswanathan, R. A. Simpson, “Improving resolution in photolithography with a phase-shifting mask,” IEEE Trans. Electron Devices ED-29, 1828–1836 (1982).
[CrossRef]

Lewis, J.

T. A. Brunner, J. Lewis, M. Manny, “Stepper self-metrology using automated techniques,” in Optical Fibers in Medicine V, A. Katzir, ed., Proc. SPIE1201, 286–297 (1990).

Lin, B. J.

A. D. Katnani, B. J. Lin, “Phase and transmission error study for the alternating element (Levenson) phase-shifting mask,” in Optical/Laser Microlithography V, J. D. Cuthbert, ed., Proc. SPIE1674, 264–270 (1992).
[CrossRef]

Luehrmann, P.

S. Stalnaker, P. Luehrmann, J. Waelpoel, “Focal plane determination for sub-half micron optical steppers,” Microelectron. Eng. 21, 33–43 (1993).
[CrossRef]

Manny, M.

T. A. Brunner, J. Lewis, M. Manny, “Stepper self-metrology using automated techniques,” in Optical Fibers in Medicine V, A. Katzir, ed., Proc. SPIE1201, 286–297 (1990).

Martin, A. L.

T. A. Brunner, A. L. Martin, R. M. Martino, C. P. Ausschnitt, T. H. Newman, M. S. Hibbs, “Quantitative stepper metrology using the focus monitor test mask,” in Optical/Laser Microlighography VII, T. A. Brunner, ed., Proc. SPIE2197, 541–549 (1994).
[CrossRef]

Martino, R. M.

T. A. Brunner, A. L. Martin, R. M. Martino, C. P. Ausschnitt, T. H. Newman, M. S. Hibbs, “Quantitative stepper metrology using the focus monitor test mask,” in Optical/Laser Microlighography VII, T. A. Brunner, ed., Proc. SPIE2197, 541–549 (1994).
[CrossRef]

Newman, T. H.

T. A. Brunner, A. L. Martin, R. M. Martino, C. P. Ausschnitt, T. H. Newman, M. S. Hibbs, “Quantitative stepper metrology using the focus monitor test mask,” in Optical/Laser Microlighography VII, T. A. Brunner, ed., Proc. SPIE2197, 541–549 (1994).
[CrossRef]

Norton, A. E.

T. A. Brunner, S. Cheng, A. E. Norton, “A stepper image monitor for precise setup and characterization,” in Fiber Optics Reliability: Benign and Adverse Environments II, R. A. Greenwell, D. K. Paul, S. G. Wadekar, eds., Proc. SPIE922, 366–375 (1988).

Orszag, S. A.

W. H. Arnold, E. Barouch, U. Hollerbach, S. A. Orszag, “A focus vernier for optical lithography,” in Integrated Circuit Metrology, Inspection, and Process Control VII, M. T. Postek, ed., Proc. SPIE1926, 380–392 (1993).
[CrossRef]

Simpson, R. A.

M. D. Levenson, N. S. Viswanathan, R. A. Simpson, “Improving resolution in photolithography with a phase-shifting mask,” IEEE Trans. Electron Devices ED-29, 1828–1836 (1982).
[CrossRef]

Stalnaker, S.

S. Stalnaker, P. Luehrmann, J. Waelpoel, “Focal plane determination for sub-half micron optical steppers,” Microelectron. Eng. 21, 33–43 (1993).
[CrossRef]

Suwa, K.

K. Suwa, H. Tateno, N. Irie, S. Hirukawa, “Automatic laser scanning focus detection method using printed focus pattern,” in Optical/Laser Microlithography VIII, T. A. Brunner, ed., Proc. SPIE2440, 712–720 (1995).
[CrossRef]

Tanaka, T.

T. Terasawa, N. Hasegawa, T. Kurosaki, T. Tanaka, “0.3 µm optical lithography using a phase-shifting mask,” in Optical/Laser Microlithography II, B. J. Lin, ed., Proc. SPIE1088, 25–33 (1989).
[CrossRef]

Tateno, H.

K. Suwa, H. Tateno, N. Irie, S. Hirukawa, “Automatic laser scanning focus detection method using printed focus pattern,” in Optical/Laser Microlithography VIII, T. A. Brunner, ed., Proc. SPIE2440, 712–720 (1995).
[CrossRef]

Terasawa, T.

T. Terasawa, N. Hasegawa, T. Kurosaki, T. Tanaka, “0.3 µm optical lithography using a phase-shifting mask,” in Optical/Laser Microlithography II, B. J. Lin, ed., Proc. SPIE1088, 25–33 (1989).
[CrossRef]

van den Brink, M.

M. van den Brink, H. Franken, S. Wittekoek, T. Fahner, “Automatic on-line wafer stepper calibration system,” in Integrated Circuit Metrology, Inspection, and Process Control IV, W. H. Arnold, ed., Proc. SPIE1261, 298–314 (1990).
[CrossRef]

Viswanathan, N. S.

M. D. Levenson, N. S. Viswanathan, R. A. Simpson, “Improving resolution in photolithography with a phase-shifting mask,” IEEE Trans. Electron Devices ED-29, 1828–1836 (1982).
[CrossRef]

Waelpoel, J.

S. Stalnaker, P. Luehrmann, J. Waelpoel, “Focal plane determination for sub-half micron optical steppers,” Microelectron. Eng. 21, 33–43 (1993).
[CrossRef]

Wittekoek, S.

M. van den Brink, H. Franken, S. Wittekoek, T. Fahner, “Automatic on-line wafer stepper calibration system,” in Integrated Circuit Metrology, Inspection, and Process Control IV, W. H. Arnold, ed., Proc. SPIE1261, 298–314 (1990).
[CrossRef]

Yeo, G. S.

Y. C. Kim, G. S. Yeo, J. H. Lee, H. Kim, U. I. Chung, “Automatic in-situ focus monitor using line shortening effect,” in Metrology, Inspection, and Process Control for Microlithography XIII, B. Singh, ed., Proc. SPIE3677, 184–193 (1999).
[CrossRef]

IEEE Trans. Electron Devices (1)

M. D. Levenson, N. S. Viswanathan, R. A. Simpson, “Improving resolution in photolithography with a phase-shifting mask,” IEEE Trans. Electron Devices ED-29, 1828–1836 (1982).
[CrossRef]

Microelectron. Eng. (1)

S. Stalnaker, P. Luehrmann, J. Waelpoel, “Focal plane determination for sub-half micron optical steppers,” Microelectron. Eng. 21, 33–43 (1993).
[CrossRef]

Other (9)

T. A. Brunner, A. L. Martin, R. M. Martino, C. P. Ausschnitt, T. H. Newman, M. S. Hibbs, “Quantitative stepper metrology using the focus monitor test mask,” in Optical/Laser Microlighography VII, T. A. Brunner, ed., Proc. SPIE2197, 541–549 (1994).
[CrossRef]

W. H. Arnold, E. Barouch, U. Hollerbach, S. A. Orszag, “A focus vernier for optical lithography,” in Integrated Circuit Metrology, Inspection, and Process Control VII, M. T. Postek, ed., Proc. SPIE1926, 380–392 (1993).
[CrossRef]

A. D. Katnani, B. J. Lin, “Phase and transmission error study for the alternating element (Levenson) phase-shifting mask,” in Optical/Laser Microlithography V, J. D. Cuthbert, ed., Proc. SPIE1674, 264–270 (1992).
[CrossRef]

K. Suwa, H. Tateno, N. Irie, S. Hirukawa, “Automatic laser scanning focus detection method using printed focus pattern,” in Optical/Laser Microlithography VIII, T. A. Brunner, ed., Proc. SPIE2440, 712–720 (1995).
[CrossRef]

Y. C. Kim, G. S. Yeo, J. H. Lee, H. Kim, U. I. Chung, “Automatic in-situ focus monitor using line shortening effect,” in Metrology, Inspection, and Process Control for Microlithography XIII, B. Singh, ed., Proc. SPIE3677, 184–193 (1999).
[CrossRef]

T. A. Brunner, S. Cheng, A. E. Norton, “A stepper image monitor for precise setup and characterization,” in Fiber Optics Reliability: Benign and Adverse Environments II, R. A. Greenwell, D. K. Paul, S. G. Wadekar, eds., Proc. SPIE922, 366–375 (1988).

T. A. Brunner, J. Lewis, M. Manny, “Stepper self-metrology using automated techniques,” in Optical Fibers in Medicine V, A. Katzir, ed., Proc. SPIE1201, 286–297 (1990).

M. van den Brink, H. Franken, S. Wittekoek, T. Fahner, “Automatic on-line wafer stepper calibration system,” in Integrated Circuit Metrology, Inspection, and Process Control IV, W. H. Arnold, ed., Proc. SPIE1261, 298–314 (1990).
[CrossRef]

T. Terasawa, N. Hasegawa, T. Kurosaki, T. Tanaka, “0.3 µm optical lithography using a phase-shifting mask,” in Optical/Laser Microlithography II, B. J. Lin, ed., Proc. SPIE1088, 25–33 (1989).
[CrossRef]

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Figures (12)

Fig. 1
Fig. 1

Binary mask patterns for focus measurement.

Fig. 2
Fig. 2

SEM pictures of different levels of energy: (a) 31 mJ/cm2, (b) 40 mJ/cm2, (c) 49 mJ/cm2.

Fig. 3
Fig. 3

Overlay shift of BIB pattern for various split conditions.

Fig. 4
Fig. 4

Overlay shift of various exposure energy (type 8).

Fig. 5
Fig. 5

Lithographic performance and simulation result.

Fig. 6
Fig. 6

BIB overlay shift measured by SEM methodology.

Fig. 7
Fig. 7

Boundary shift of (a) large holes u and (b) small holes v (measured by SEM).

Fig. 8
Fig. 8

Overlay shift obtained from SEM, overlay measurement system (KLA), and simulation (PROLITH/2).

Fig. 9
Fig. 9

Average aerial intensities of the BIB bar.

Fig. 10
Fig. 10

Fitting curves and derivative results of three energy levels.

Fig. 11
Fig. 11

Measured focus value (plan 1) for five different central focus settings.

Fig. 12
Fig. 12

Three-dimensional view of an exposure field (21 mm × 21 mm).

Tables (2)

Tables Icon

Table 1 Split Conditions of the Novel BIB Patterna

Tables Icon

Table 2 Sampling Plan for 0.4-µm Focus Step

Equations (6)

Equations on this page are rendered with MathJax. Learn more.

u=L1-L2/2,  boundary shift of large holes;
v=S2-S1-u,  boundary shift of small holes.
xBestFocus=v+S1/2,
xDefocus=S2/2.
Δx=xBestFocus-xDefocus=S22-v+S12=12S2-S1-v=u-v2.
u-v=u-S2-S1-u=2u+S1-S2=L1-L2+S1-S2.

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