Abstract

A noncontact optical technique for the measurement of thin-film thickness and surface roughness with 25-Å and 2-μm vertical and horizontal resolutions, respectively, has been described. It is based on a common-path three-beam shearing interferometer, in which the outer beams act as a reference while the middle beam scans the surface. The results of this technique are comparable with the ones obtained with a stylus instrument.

© 1983 Optical Society of America

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References

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  1. S. Tolansky, Multiple-Beam Interferometry of Surfaces and Films (Clarendon, Oxford, 1943).
  2. J. M. Bennett, Appl. Opt. 15, 2705 (1976).
    [CrossRef] [PubMed]
  3. D. Malacara, Optical Shop Testing (Wiley, New York, 1978), pp. 19, 47, and 130.
  4. At least two famous stylus instruments are available commercially: Detak, manufactured by Sloan Technology Corp., Santa Barbara, Calif.; and Talystep, manufactured by Rank Precision Industries, Ltd., Leicester, England.
  5. F. Zernike, J. Opt. Soc. Am. 40, 326 (1950).
    [CrossRef]
  6. R. E. Kinzly, Appl. Opt. 6, 137 (1967).
    [CrossRef] [PubMed]
  7. P. Hariharan, D. Sen, J. Sci. Instrum. 36, 70 (1959).
    [CrossRef]
  8. R. C. Tyagi, K. Singh, Appl. Opt. 7, 1971 (1968).
    [CrossRef] [PubMed]

1976 (1)

1968 (1)

1967 (1)

1959 (1)

P. Hariharan, D. Sen, J. Sci. Instrum. 36, 70 (1959).
[CrossRef]

1950 (1)

Bennett, J. M.

Hariharan, P.

P. Hariharan, D. Sen, J. Sci. Instrum. 36, 70 (1959).
[CrossRef]

Kinzly, R. E.

Malacara, D.

D. Malacara, Optical Shop Testing (Wiley, New York, 1978), pp. 19, 47, and 130.

Sen, D.

P. Hariharan, D. Sen, J. Sci. Instrum. 36, 70 (1959).
[CrossRef]

Singh, K.

Tolansky, S.

S. Tolansky, Multiple-Beam Interferometry of Surfaces and Films (Clarendon, Oxford, 1943).

Tyagi, R. C.

Zernike, F.

Appl. Opt. (3)

J. Opt. Soc. Am. (1)

J. Sci. Instrum. (1)

P. Hariharan, D. Sen, J. Sci. Instrum. 36, 70 (1959).
[CrossRef]

Other (3)

S. Tolansky, Multiple-Beam Interferometry of Surfaces and Films (Clarendon, Oxford, 1943).

D. Malacara, Optical Shop Testing (Wiley, New York, 1978), pp. 19, 47, and 130.

At least two famous stylus instruments are available commercially: Detak, manufactured by Sloan Technology Corp., Santa Barbara, Calif.; and Talystep, manufactured by Rank Precision Industries, Ltd., Leicester, England.

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Figures (15)

Fig. 1
Fig. 1

Basic three-beam shearing interferometer.

Fig. 2
Fig. 2

Computer plots of a three-beam interference pattern for different phases in the middle beam.

Fig. 3
Fig. 3

(a) Schematic layout of a sample under test, and (b) the three-beam sheared pupils.

Fig. 4
Fig. 4

Experimental layout of He–Ne laser and spatial filters. F2, Ronchi ruling grating 50% duty cycle; S, sample; D, Reticon RG256 detector; L1, L2, lenses; B, beam splitter; M, imaging lens.

Fig. 5
Fig. 5

(a) Interference patterns of sample 1, respectively: (a) three-beam and (b) two-beam.

Fig. 6
Fig. 6

Intensity vs displacement scan of a single fringe on sample 1.

Fig. 7
Fig. 7

Height vs displacement of sample 1 generated by converting the intensity changes in Fig. 5 to height errors using Eq. (5).

Fig. 8
Fig. 8

A mechanical scan of the step on sample 1.

Fig. 9
Fig. 9

Two-beam and three-beam interference pattern of sample 2.

Fig. 10
Fig. 10

Intensity vs displacement scan of a single fringe on sample 2.

Fig. 11
Fig. 11

Height vs displacement of sample 2 generated by converting intensity changes in Fig. 9 to height errors using Eq. (5).

Fig. 12
Fig. 12

Mechanical scan of sample 2.

Fig. 13
Fig. 13

Mechanical scan of sample 3.

Fig. 14
Fig. 14

Two-beam and three-beam interference pattern of sample 3.

Fig. 15
Fig. 15

Height vs displacement of sample 3 generated by converting the intensity changes to height errors using Eq. (5).

Equations (5)

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I ( x , y ) = A 1 exp [ i ϕ ( x , y ) ] + A 2 exp [ i ϕ ( x + Δ x , y ) ] + A 2 exp [ i ϕ ( x - Δ x , y ) ] 2 ,
I ( x , y ) = A 1 2 + 4 A 1 A 2 cos 1 2 [ 2 ϕ ( x , y ) - ϕ ( x + Δ x , y ) - ϕ ( x - Δ x , y ) ] × cos 1 2 [ ϕ ( x + Δ x , y ) - ϕ ( x - Δ x , y ) ] + 4 A 2 2 cos 2 1 2 [ ϕ ( x + Δ x , y ) - ( x - Δ x , y ) ] .
Δ ϕ = N 4 A 1 A 2 sin ϕ             Δ ϕ ~ 1 S / N .
I 1 I 2 = R = 1 + 4 α 2 + 4 α cos ( ϕ ) 1 + 4 α 2 + α ,
cos ϕ = R ( D + 4 α ) - D 4 α , d λ = 1 4 π cos - 1 R ( D + 4 α ) - D 4 α ,

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