Abstract

An interferometric method is presented that has been successfully used to measure the alignment precision of different mask patterns superimposed on a silicon wafer in the lithographic process. Based on an extremely precise electrooptical phase measurement technique this method is capable of measuring the relative pattern displacement with precision in the nanometer region. The principle of the measurement technique is described. Results of experiments are discussed including suggestions for improving the measurement precision.

© 1984 Optical Society of America

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References

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  1. H. Bohlen, J. Greschner, J. Keyser, W. Kulcke, P. NehmizIBM J. Res. Dev. 26, 568 (1982).
    [CrossRef]
  2. G. Makosch, B. Solf, Proc. Soc. Photo-Opt. Instrum. Eng. 316, 42 (1981).

1982 (1)

H. Bohlen, J. Greschner, J. Keyser, W. Kulcke, P. NehmizIBM J. Res. Dev. 26, 568 (1982).
[CrossRef]

1981 (1)

G. Makosch, B. Solf, Proc. Soc. Photo-Opt. Instrum. Eng. 316, 42 (1981).

Bohlen, H.

H. Bohlen, J. Greschner, J. Keyser, W. Kulcke, P. NehmizIBM J. Res. Dev. 26, 568 (1982).
[CrossRef]

Greschner, J.

H. Bohlen, J. Greschner, J. Keyser, W. Kulcke, P. NehmizIBM J. Res. Dev. 26, 568 (1982).
[CrossRef]

Keyser, J.

H. Bohlen, J. Greschner, J. Keyser, W. Kulcke, P. NehmizIBM J. Res. Dev. 26, 568 (1982).
[CrossRef]

Kulcke, W.

H. Bohlen, J. Greschner, J. Keyser, W. Kulcke, P. NehmizIBM J. Res. Dev. 26, 568 (1982).
[CrossRef]

Makosch, G.

G. Makosch, B. Solf, Proc. Soc. Photo-Opt. Instrum. Eng. 316, 42 (1981).

Nehmiz, P.

H. Bohlen, J. Greschner, J. Keyser, W. Kulcke, P. NehmizIBM J. Res. Dev. 26, 568 (1982).
[CrossRef]

Solf, B.

G. Makosch, B. Solf, Proc. Soc. Photo-Opt. Instrum. Eng. 316, 42 (1981).

IBM J. Res. Dev. (1)

H. Bohlen, J. Greschner, J. Keyser, W. Kulcke, P. NehmizIBM J. Res. Dev. 26, 568 (1982).
[CrossRef]

Proc. Soc. Photo-Opt. Instrum. Eng. (1)

G. Makosch, B. Solf, Proc. Soc. Photo-Opt. Instrum. Eng. 316, 42 (1981).

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Figures (8)

Fig. 1
Fig. 1

Generation of two diffraction orders m,m′ propagating in a common direction by illuminating a grating with two laser beams at angles θ and θ′.

Fig. 2
Fig. 2

Optical arrangement of the DOG for overlay measurement.

Fig. 3
Fig. 3

DOG response as a result of continuous lateral displacement of a grating (g = 10 μm). The full period of the sawtooth corresponds to a displacement of g/2.

Fig. 4
Fig. 4

Overlay measurement procedure.

Fig. 5
Fig. 5

DOG calibration curve: reflection grating on a silicon wafer (g = 12 μm), microscope lens adapted to the grating constant.

Fig. 6
Fig. 6

DOG calibration curve: unfavorable conditions of collimation. The focal length of the microscope lens is 9/8 times greater than that of Fig. 5.

Fig. 7
Fig. 7

Overlay scans from three different initial positions of the same grating. The adjustment conditions of the DOG correspond to that of the calibration curve shown in Fig. 6. The step height of the DOG response varies from scan to scan.

Fig. 8
Fig. 8

Overlay scans at proper microscope adaptation to the grating. ΔH corresponds to the difference of the DOG reading between position B and the average of the two A positions in units of 1/2048 of the full period. Corrected values are written in brackets.

Equations (4)

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Δ φ = 2 π ( m - m ) Δ x g ,
Δ φ M = 4 π · Δ x g .
φ M = tan - 1 ( 2 J s - J R - J T 3 ( J R - J T ) ) mod 2 π .
Δ x = g 4 π Δ φ M , Δ φ M = φ M B - φ M A 1 + φ M A 2 2 .

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