Abstract

Semidirect level monitoring has error compensation capabilities of potential benefit to optical coatings of certain types. A review of the principles of level monitoring using circle diagrams shows how to design a level monitoring scheme for various cases, including the use of precoated monitoring chips. The film thickness sensitivities for various optical monitoring strategies differ considerably. Optimum level trigger point monitoring offers improved sensitivity of change in reflectance vs change in optical thickness. This procedure is also expected to give small thickness errors when optically monitored. Optimum level trigger point monitoring, and its application, is fully described.

© 1987 Optical Society of America

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References

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  1. H. A. Macleod, E. Pelletier, “Error Compensation Mechanisms in Some Thin-Film Monitoring Systems,” Opt. Acta 24, 907 (1977).
    [CrossRef]
  2. F. Zhao, “Monitoring of Periodic Multilayer by the Level Method,” Appl. Opt. 24, 3339 (1985).
    [CrossRef] [PubMed]
  3. H. A. Macleod, “Monitoring of Optical Coatings,” Appl. Opt. 20, 82 (1981).
    [CrossRef] [PubMed]
  4. W. P. Thoni, “Deposition of Optical Coatings: Process Control and Automation,” Thin Solid Films 88, 385 (1982).
    [CrossRef]
  5. B. Vidal, E. Pelletier, “Nonquarterwave Multilayer Filters: Optical Monitoring with a Minicomputer Allowing Correction of Thickness Errors,” Appl. Opt. 18, 3857 (1979).
    [PubMed]
  6. C. Schroedter, “Evaporation Monitoring System Featuring Software Trigger Points and On-Line Evaluation of Refractive Indices,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 15 (1986).
  7. R. R. Willey, “Survey of Computer Numerically Controlled Optical Coating Systems,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 41 (1986).
  8. J. H. Apfel, “Graphics in Optical Coating Design,” Appl. Opt. 11, 1303 (1972).
    [CrossRef] [PubMed]
  9. H. A. Macleod, Thin-Film Optical Filters (Macmillan, New York, 1986), pp. 61, 65.
  10. J. Ward, Vacuum22, 369 (1972).
    [CrossRef]
  11. C. J. van der Laan, “Optical Monitoring of Nonquarterwave Stacks,” Appl. Opt. 25, 753 (1986).
    [CrossRef] [PubMed]
  12. A. Zoller, R. Herrmann, W. Klug, W. Zültzke, “Optical Monitoring: Comparison of Different Monitoring Strategies with Respect to the Resulting Reproducibility to the Completed Layer Systems,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 21 (1986).

1986 (4)

C. Schroedter, “Evaporation Monitoring System Featuring Software Trigger Points and On-Line Evaluation of Refractive Indices,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 15 (1986).

R. R. Willey, “Survey of Computer Numerically Controlled Optical Coating Systems,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 41 (1986).

A. Zoller, R. Herrmann, W. Klug, W. Zültzke, “Optical Monitoring: Comparison of Different Monitoring Strategies with Respect to the Resulting Reproducibility to the Completed Layer Systems,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 21 (1986).

C. J. van der Laan, “Optical Monitoring of Nonquarterwave Stacks,” Appl. Opt. 25, 753 (1986).
[CrossRef] [PubMed]

1985 (1)

1982 (1)

W. P. Thoni, “Deposition of Optical Coatings: Process Control and Automation,” Thin Solid Films 88, 385 (1982).
[CrossRef]

1981 (1)

1979 (1)

1977 (1)

H. A. Macleod, E. Pelletier, “Error Compensation Mechanisms in Some Thin-Film Monitoring Systems,” Opt. Acta 24, 907 (1977).
[CrossRef]

1972 (1)

Apfel, J. H.

Herrmann, R.

A. Zoller, R. Herrmann, W. Klug, W. Zültzke, “Optical Monitoring: Comparison of Different Monitoring Strategies with Respect to the Resulting Reproducibility to the Completed Layer Systems,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 21 (1986).

Klug, W.

A. Zoller, R. Herrmann, W. Klug, W. Zültzke, “Optical Monitoring: Comparison of Different Monitoring Strategies with Respect to the Resulting Reproducibility to the Completed Layer Systems,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 21 (1986).

Macleod, H. A.

H. A. Macleod, “Monitoring of Optical Coatings,” Appl. Opt. 20, 82 (1981).
[CrossRef] [PubMed]

H. A. Macleod, E. Pelletier, “Error Compensation Mechanisms in Some Thin-Film Monitoring Systems,” Opt. Acta 24, 907 (1977).
[CrossRef]

H. A. Macleod, Thin-Film Optical Filters (Macmillan, New York, 1986), pp. 61, 65.

Pelletier, E.

B. Vidal, E. Pelletier, “Nonquarterwave Multilayer Filters: Optical Monitoring with a Minicomputer Allowing Correction of Thickness Errors,” Appl. Opt. 18, 3857 (1979).
[PubMed]

H. A. Macleod, E. Pelletier, “Error Compensation Mechanisms in Some Thin-Film Monitoring Systems,” Opt. Acta 24, 907 (1977).
[CrossRef]

Schroedter, C.

C. Schroedter, “Evaporation Monitoring System Featuring Software Trigger Points and On-Line Evaluation of Refractive Indices,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 15 (1986).

Thoni, W. P.

W. P. Thoni, “Deposition of Optical Coatings: Process Control and Automation,” Thin Solid Films 88, 385 (1982).
[CrossRef]

van der Laan, C. J.

Vidal, B.

Ward, J.

J. Ward, Vacuum22, 369 (1972).
[CrossRef]

Willey, R. R.

R. R. Willey, “Survey of Computer Numerically Controlled Optical Coating Systems,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 41 (1986).

Zhao, F.

Zoller, A.

A. Zoller, R. Herrmann, W. Klug, W. Zültzke, “Optical Monitoring: Comparison of Different Monitoring Strategies with Respect to the Resulting Reproducibility to the Completed Layer Systems,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 21 (1986).

Zültzke, W.

A. Zoller, R. Herrmann, W. Klug, W. Zültzke, “Optical Monitoring: Comparison of Different Monitoring Strategies with Respect to the Resulting Reproducibility to the Completed Layer Systems,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 21 (1986).

Appl. Opt. (5)

Opt. Acta (1)

H. A. Macleod, E. Pelletier, “Error Compensation Mechanisms in Some Thin-Film Monitoring Systems,” Opt. Acta 24, 907 (1977).
[CrossRef]

Proc. Soc. Photo-Opt. Instrum. Eng. (3)

A. Zoller, R. Herrmann, W. Klug, W. Zültzke, “Optical Monitoring: Comparison of Different Monitoring Strategies with Respect to the Resulting Reproducibility to the Completed Layer Systems,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 21 (1986).

C. Schroedter, “Evaporation Monitoring System Featuring Software Trigger Points and On-Line Evaluation of Refractive Indices,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 15 (1986).

R. R. Willey, “Survey of Computer Numerically Controlled Optical Coating Systems,” Proc. Soc. Photo-Opt. Instrum. Eng. 652, 41 (1986).

Thin Solid Films (1)

W. P. Thoni, “Deposition of Optical Coatings: Process Control and Automation,” Thin Solid Films 88, 385 (1982).
[CrossRef]

Other (2)

H. A. Macleod, Thin-Film Optical Filters (Macmillan, New York, 1986), pp. 61, 65.

J. Ward, Vacuum22, 369 (1972).
[CrossRef]

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Figures (32)

Fig. 1
Fig. 1

Addition of amplitude vectors of reflections from the two surfaces of a thin film for various phase angles (thicknesses).

Fig. 2
Fig. 2

Reflectance amplitude diagram for a quarterwave optical thickness of magnesium fluoride on a crown glass substrate.

Fig. 3
Fig. 3

Reflectance spectrum of a QWOT of magnesium fluoride on a crown glass substrate.

Fig. 4
Fig. 4

Optical monitor signal change as the film thickness increases during deposition of a QWOT of magnesium fluoride on a glass substrate.

Fig. 5
Fig. 5

Reflectance diagram of equal percent reflectance intensity contours. The vector represents a reflectance intensity of ~36% and a reflectance amplitude of 0.60.

Fig. 6
Fig. 6

Circle diagram for a classical quarter-half-quarterwave broadband antireflection coating at the design wavelength.

Fig. 7
Fig. 7

Spectral reflectance curve for a quarter-half-quarter antireflection coating showing the design wavelength at 0.520 μm.

Fig. 8
Fig. 8

Optical monitor signal on a single-monitor chip (semidirect monitoring) for the classic quarter-half-quarter antireflection coating.

Fig. 9
Fig. 9

Circle diagram for a QWOT stack of HLHLHLHL on crown glass. At the wavelength at which the layers are QWOTs, the reflectance increases with each layer.

Fig. 10
Fig. 10

Optical monitor curve of the QWOT stack HLHLHLHL on crown glass.

Fig. 11
Fig. 11

Optical monitor curve of the HLHLHLHL QWOT stack to show: the relatively flat spots, that the maximum slopes of the curves are greater for the high-index than the low-index layers, and that the slopes are greatest for layers whose reflectance is in the 20–60% intensity range and diminishes as the reflectance becomes greater or less than this level.

Fig. 12
Fig. 12

Rate of change of reflectance intensity with optical film thickness material of index 1.38 as a function of position on the reflectance circle diagram. Values are symmetric about the real axis.

Fig. 13
Fig. 13

Spectral reflectance of an antireflection coating of design LMHHL QWOTs after Ward,10 which was analyzed by Macleod and Pelletier.1

Fig. 14
Fig. 14

Circle diagram of Ward’s LMHHL antireflection coating without precoating.

Fig. 15
Fig. 15

Optical monitoring curve of Ward’s LMHHL coating without precoating.

Fig. 16
Fig. 16

Circle diagram of Ward’s LMHHL coating with a two-layer precoating described by Macleod and Pelletier as the most satisfactory.

Fig. 17
Fig. 17

Optical monitor curve of Ward’s LMHHL coating with a two-layer precoat.

Fig. 18
Fig. 18

Circle diagram of Ward’s LMHHL coating with a three-layer precoat.

Fig. 19
Fig. 19

Optical monitor curve of Ward’s LMHHL coating with a three-layer precoat.

Fig. 20
Fig. 20

Circle diagram of Ward’s LMHHL coating with a five-layer precoat described by Macleod and Pelletier as the least satisfactory.

Fig. 21
Fig. 21

Optical monitor curve of Ward’s LMHHL coating with a five-layer precoat. Note that the layer terminations are compressed at the high-reflectance values.

Fig. 22
Fig. 22

Circle diagram of a single-layer nonquarterwave precoating for improved sensitivity in monitoring the Ward design.

Fig. 23
Fig. 23

Optical monitor curve of the optimized single-layer precoat for Ward’s LMHHL design.

Fig. 24
Fig. 24

Circle diagram of a four-layer precoat for the four-layer antireflection coating of Ward which maintains the termination points near the optimal sensitivity level.

Fig. 25
Fig. 25

Optical monitor curve of the optimum level precoat for the Ward LMHHL design.

Fig. 26
Fig. 26

Spectral reflectance of Zoller’s12 six-layer antireflection coating.

Fig. 27
Fig. 27

Circle diagram of Zoller’s six layers at the monitoring wavelength.

Fig. 28
Fig. 28

Optical monitor curve used by Zoller et al. which takes advantage of level terminations after turning points.

Fig. 29
Fig. 29

Circle diagram of and optimized single-layer precoat for Zoller’s design.

Fig. 30
Fig. 30

Optical monitor curve for the optimized single-layer precoat for Zoller’s design.

Fig. 31
Fig. 31

Circle diagram of the application of the optimum sensitivity procedure to the design of a four-layer precoating for Zoller’s six-layer antireflection coating.

Fig. 32
Fig. 32

Optical monitor curve of the four-layer precoat which has nearly optimum sensitivity levels for this coating design.

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