Abstract

Beam deviation in the polarizing elements is identified as a significant source of error in existing ellipsometer alignment procedures. A high precision alignment procedure that eliminates these errors is described. This procedure is less time consuming than previous methods, and its accuracy is comparable to the limit of resolution of the ellipsometer (typically 0.01–0.005°). A further advantage of this procedure is that it provides a precise method for the alignment of specimens and lasers with the ellipsometer.

© 1974 Optical Society of America

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  1. R. M. A. Azzam, N. M. Bashara, J. Opt. Soc. Am. 61, 600, 1118, 1236, 1380 (1971); J. Opt. Soc. Am. 62, 700 (1972).
    [CrossRef]
  2. D. E. Aspnes, J. Opt. Soc. Am. 61, 1077 (1971).
    [CrossRef]
  3. D. E. Aspnes, A. A. Studna, Appl. Opt. 10, 1024 (1971).
    [CrossRef] [PubMed]
  4. F. L. McCrackin, J. Opt. Soc. Am. 60, 57 (1970).
    [CrossRef]
  5. W. R. Hunter, D. H. Eaton, C. T. Sah, Surf. Sci. 20, 355 (1970).
    [CrossRef]
  6. M. Ghezzo, Brit. J. Appl. Phys. 2, 1483 (1969).
  7. G. Forgacs, Brit. J. Appl. Phys. 3, 1513 (1970).
  8. M. J. Dingham, M. Moskovits, Appl. Opt. 9, 1868 (1970).
  9. Some ambiguity exists in the previous literature due to the indiscriminate use of the term, alignment, to describe both the alignment of the telescope axes and the calibration of the azimuthal scales of the ellipsometer. In this paper, alignment implies the alignment of the telescope axes, and calibration implies the calibration of the azimuthal scales.
  10. F. L. McCrackin, E. Passaglia, R. R. Stromberg, H. L. Steinberg, J. Res. Nat. Bur. Stand. 67A, 363 (1963).
    [CrossRef]
  11. M. R. Steel, Appl. Opt. 10, 2370 (1971).
    [CrossRef] [PubMed]
  12. A. B. Winterbottom, Optical Studies of Metal Surfaces, The Royal Norwegian Sci. Soc. Rept. 1 (F Bruns, Trondheim, 1955).
  13. R. J. Archer, Manual of Ellipsometry (Gaertner Scientific Corp., Chicago, 1968).
  14. A. T. Fromhold, Ph.D. Dissertation, Department of Physics, Cornell University (1961).
  15. J. M. Bennett, H. E. Bennett, in Handbook of Optics, W. G. Driscoll, W. Vaughan, Eds. (McGraw-Hill, New York, to be published).
  16. Since the standard sample tables of many commercial ellipsometers do not allow an independent horizontal adjustment of the sample position, a special sample table (e.g., one with linear translation adjustments) may be necessary.
  17. A transparent slide with only one coated slide could be used, but the optical quality of the beam reflected from the back side of the coating is generally unsatisfactory due to interference between the beams reflected from the slide and the coating.
  18. If a source other than the alignment laser is to be used in the measurements, it may be advisable to align the source before the sample table is removed (see Sec. II F).
  19. W. R. Hunter, J. Opt. Soc. Am. 63, 951 (1973).
    [CrossRef]
  20. J. R. Zeidler, N. M. Bashara, unpublished.

1973 (1)

1971 (4)

1970 (4)

G. Forgacs, Brit. J. Appl. Phys. 3, 1513 (1970).

M. J. Dingham, M. Moskovits, Appl. Opt. 9, 1868 (1970).

F. L. McCrackin, J. Opt. Soc. Am. 60, 57 (1970).
[CrossRef]

W. R. Hunter, D. H. Eaton, C. T. Sah, Surf. Sci. 20, 355 (1970).
[CrossRef]

1969 (1)

M. Ghezzo, Brit. J. Appl. Phys. 2, 1483 (1969).

1963 (1)

F. L. McCrackin, E. Passaglia, R. R. Stromberg, H. L. Steinberg, J. Res. Nat. Bur. Stand. 67A, 363 (1963).
[CrossRef]

Archer, R. J.

R. J. Archer, Manual of Ellipsometry (Gaertner Scientific Corp., Chicago, 1968).

Aspnes, D. E.

Azzam, R. M. A.

R. M. A. Azzam, N. M. Bashara, J. Opt. Soc. Am. 61, 600, 1118, 1236, 1380 (1971); J. Opt. Soc. Am. 62, 700 (1972).
[CrossRef]

Bashara, N. M.

R. M. A. Azzam, N. M. Bashara, J. Opt. Soc. Am. 61, 600, 1118, 1236, 1380 (1971); J. Opt. Soc. Am. 62, 700 (1972).
[CrossRef]

J. R. Zeidler, N. M. Bashara, unpublished.

Bennett, H. E.

J. M. Bennett, H. E. Bennett, in Handbook of Optics, W. G. Driscoll, W. Vaughan, Eds. (McGraw-Hill, New York, to be published).

Bennett, J. M.

J. M. Bennett, H. E. Bennett, in Handbook of Optics, W. G. Driscoll, W. Vaughan, Eds. (McGraw-Hill, New York, to be published).

Dingham, M. J.

Eaton, D. H.

W. R. Hunter, D. H. Eaton, C. T. Sah, Surf. Sci. 20, 355 (1970).
[CrossRef]

Forgacs, G.

G. Forgacs, Brit. J. Appl. Phys. 3, 1513 (1970).

Fromhold, A. T.

A. T. Fromhold, Ph.D. Dissertation, Department of Physics, Cornell University (1961).

Ghezzo, M.

M. Ghezzo, Brit. J. Appl. Phys. 2, 1483 (1969).

Hunter, W. R.

W. R. Hunter, J. Opt. Soc. Am. 63, 951 (1973).
[CrossRef]

W. R. Hunter, D. H. Eaton, C. T. Sah, Surf. Sci. 20, 355 (1970).
[CrossRef]

McCrackin, F. L.

F. L. McCrackin, J. Opt. Soc. Am. 60, 57 (1970).
[CrossRef]

F. L. McCrackin, E. Passaglia, R. R. Stromberg, H. L. Steinberg, J. Res. Nat. Bur. Stand. 67A, 363 (1963).
[CrossRef]

Moskovits, M.

Passaglia, E.

F. L. McCrackin, E. Passaglia, R. R. Stromberg, H. L. Steinberg, J. Res. Nat. Bur. Stand. 67A, 363 (1963).
[CrossRef]

Sah, C. T.

W. R. Hunter, D. H. Eaton, C. T. Sah, Surf. Sci. 20, 355 (1970).
[CrossRef]

Steel, M. R.

Steinberg, H. L.

F. L. McCrackin, E. Passaglia, R. R. Stromberg, H. L. Steinberg, J. Res. Nat. Bur. Stand. 67A, 363 (1963).
[CrossRef]

Stromberg, R. R.

F. L. McCrackin, E. Passaglia, R. R. Stromberg, H. L. Steinberg, J. Res. Nat. Bur. Stand. 67A, 363 (1963).
[CrossRef]

Studna, A. A.

Winterbottom, A. B.

A. B. Winterbottom, Optical Studies of Metal Surfaces, The Royal Norwegian Sci. Soc. Rept. 1 (F Bruns, Trondheim, 1955).

Zeidler, J. R.

J. R. Zeidler, N. M. Bashara, unpublished.

Appl. Opt. (3)

Brit. J. Appl. Phys. (2)

M. Ghezzo, Brit. J. Appl. Phys. 2, 1483 (1969).

G. Forgacs, Brit. J. Appl. Phys. 3, 1513 (1970).

J. Opt. Soc. Am. (4)

J. Res. Nat. Bur. Stand. (1)

F. L. McCrackin, E. Passaglia, R. R. Stromberg, H. L. Steinberg, J. Res. Nat. Bur. Stand. 67A, 363 (1963).
[CrossRef]

Surf. Sci. (1)

W. R. Hunter, D. H. Eaton, C. T. Sah, Surf. Sci. 20, 355 (1970).
[CrossRef]

Other (9)

A. B. Winterbottom, Optical Studies of Metal Surfaces, The Royal Norwegian Sci. Soc. Rept. 1 (F Bruns, Trondheim, 1955).

R. J. Archer, Manual of Ellipsometry (Gaertner Scientific Corp., Chicago, 1968).

A. T. Fromhold, Ph.D. Dissertation, Department of Physics, Cornell University (1961).

J. M. Bennett, H. E. Bennett, in Handbook of Optics, W. G. Driscoll, W. Vaughan, Eds. (McGraw-Hill, New York, to be published).

Since the standard sample tables of many commercial ellipsometers do not allow an independent horizontal adjustment of the sample position, a special sample table (e.g., one with linear translation adjustments) may be necessary.

A transparent slide with only one coated slide could be used, but the optical quality of the beam reflected from the back side of the coating is generally unsatisfactory due to interference between the beams reflected from the slide and the coating.

If a source other than the alignment laser is to be used in the measurements, it may be advisable to align the source before the sample table is removed (see Sec. II F).

J. R. Zeidler, N. M. Bashara, unpublished.

Some ambiguity exists in the previous literature due to the indiscriminate use of the term, alignment, to describe both the alignment of the telescope axes and the calibration of the azimuthal scales of the ellipsometer. In this paper, alignment implies the alignment of the telescope axes, and calibration implies the calibration of the azimuthal scales.

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Figures (5)

Fig. 1
Fig. 1

Alignment errors due to beam deviation in the optical elements. Point P is the apex of the cone of the deviated beam, and C is the axis of rotation of the ellipsometer. The error in the tilt angles of the analyzer telescope is related to the central axis of the instrument, and thus the alignment error produced by a prism whose angular deviation is δ is given by β1 at the entrance pinhole to the analyzer arm and β2 at the exit pinhole. d0 is the distance from C to P, and d1 and d2 are the distances from C to the entrance and exit pinholes of the analyzer arm, respectively.

Fig. 2
Fig. 2

Positioning of the sample so that it is parallel to the central axis of the ellipsometer. B1 and B2 are the beams reflected from the sample in positions (a) and (b), respectively. Sample position (b) is obtained from (a) by a 180° rotation of the sample table. As illustrated in Fig. 2(b), alignment is complete when B1 and B2 are parallel. C is the central axis.

Fig. 3
Fig. 3

Vertical tilt adjustments of the alignment slide. F is the position on the viewing screen of the beam reflected from the slide at the initial setting of the tilt adjust screws. B1 is the position of the back reflected beam at the initial setting. The tilt is then adjusted to bring the back reflected beam to B2, half of the vertical distance y1 between F1 and B1. The sample table is then rotated 180°, and the front reflected beam F2 is marked. The tilt is then adjusted to bring the beam to F3, half of the vertical distance y2 between F2 and B2. This procedure is repeated until the vertical separation yi is minimized.

Fig. 4
Fig. 4

Positioning of the sample so that it is centered on the central axis of the ellipsometer. B1 and B2 are the beams reflected from the sample in positions (a) and (b), respectively. (b) is obtained from (a) by a 180° rotation of the sample table. C is the central axis. Δx is the distance between C and the center of the sample. Alignment is complete when Δx = 0. At this point B1 and B2 coincide for a plane parallel sample.

Fig. 5
Fig. 5

End-on-view of the intersection of the beam B with the sample S and the axis of rotation C when the beam is properly positioned at grazing incidence. M indicates the sample table mounting that holds the sample in place.

Equations (1)

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β = ( 1 + d 0 / d ) δ ,

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