Abstract

TiO2–SiO2 multilayer dielectric stacks that were deposited by ion-beam sputtering were found to have a granular structure. The grains were in the TiO2 layers rather than in the SiO2 layers. Their formation was due to the heating of the film during deposition. When the apparatus was modified to reduce the substrate temperature, the granularity was eliminated.

© 1996 Optical Society of America

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References

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  1. R. Blazey, “Light scattering by laser mirrors,” Appl. Opt. 6, 831–836 (1964).
    [CrossRef]
  2. J. M. Bennett, “Comparison of the properties of titanium dioxide films prepared by various techniques,” Appl. Opt. 28, 3303–3317 (1989).
    [CrossRef] [PubMed]
  3. C. F. Hickey, C. Amra, E. Pelletier, “Scattering study of single layer titania films,” Appl. Opt. 28, 2754–2761 (1989).
    [CrossRef] [PubMed]
  4. F. Flory, E. Pelletier, G. Albrand, Y. Hu, “Surface optical coatings by ion assisted techniques: study of uniformity,” Appl. Opt. 28, 2952–2959 (1989).
    [CrossRef] [PubMed]
  5. M. Lottiaux, C. Boulesteix, G. Nihoul, F. Varnier, F. Flory, R. Galindo, E. Pelletier, “Morphology and structure of TiO2 layers versus thickness and substrate temperature,” Thin Solid Films 170, 107–126 (1989).
    [CrossRef]
  6. K. H. Guenther, H. L. Gruber, H. K. Pulker, “Morphology and light scattering of dielectric multilayer systems,” Thin Solid Films 34, 363–367 (1976).
    [CrossRef]
  7. K. H. Guenther, “Columnar and nodular growth of thin films,” in Thin Film Technologies and Special Applications, W. R. Hunter, ed., Proc. SPIE346, 9–18 (1982).
  8. K. H. Guenther, “Microstructure of vapor-deposited optical coatings,” Appl. Opt. 23, 3806–3816 (1984).
    [CrossRef] [PubMed]
  9. T. J. Splavins, W. A. Brainard, “Nodular growth in thick-sputtered metallic coatings,” J. Vac. Sci. Technol. 11, 1186–1192 (1974).
    [CrossRef]
  10. J. Elson, “Diffraction and diffuse scattering from dielectric multilayers,” J. Opt. Soc. Am. 69, 48–54 (1979).
    [CrossRef]
  11. A. Kalb, M. Middelbrath, V. Sanders, “Summary abstract: neutral ion beam deposition of high reflectance coatings for use in ring laser gyroscopes,” J. Vac. Sci. Technol. A 4, 436–437 (1986).
    [CrossRef]
  12. See, for example, E. Kusano, “An investigation of hysteresis effects as a function of pumping speed, sputtering current, and O2/Ar ratio in TiO2 reactive sputtering process,” J. Appl. Phys. 70, 7089–7096 (1991).
    [CrossRef]
  13. D. G. Howitt, A. B. Harker, “The oriented growth of anatase in thin films of amorphous titania,” J. Mater. Res. 2, 201–210 (1987).
    [CrossRef]
  14. Ref. 13, Fig. 7b.
  15. F. Varnier, “Ion-assisted deposition effects on the surface structure of a TiO2 thin film,” J. Vac. Sci. Technol. A 8, 2155–2159 (1989).
    [CrossRef]
  16. B. A. Movchan, A. V. Demchishin, “Study of the structure and properties of thick vacuum condensates of nickel, titanium, tungsten, aluminum oxide, and zirconium oxide,” Phys. Met. Metallogr. (USSR) 28, 83 (1969).
  17. R. Messier, A. P. Giri, R. A. Ray, “Revised structure zone model for thin film physical structure,” J. Vac. Sci. Technol. A 2, 500–503 (1984).
    [CrossRef]
  18. H. R. Kaufman, “Material processing with broad-beam ion sources,” Ann. Rev. Mater. Sci. 13, 413–439 (1983); see p. 417.
    [CrossRef]
  19. W. C. Hermann in Optical Thin Films, R. I. Seddon, ed., Proc. SPIE325, 101 (1982).

1991

See, for example, E. Kusano, “An investigation of hysteresis effects as a function of pumping speed, sputtering current, and O2/Ar ratio in TiO2 reactive sputtering process,” J. Appl. Phys. 70, 7089–7096 (1991).
[CrossRef]

1989

M. Lottiaux, C. Boulesteix, G. Nihoul, F. Varnier, F. Flory, R. Galindo, E. Pelletier, “Morphology and structure of TiO2 layers versus thickness and substrate temperature,” Thin Solid Films 170, 107–126 (1989).
[CrossRef]

F. Varnier, “Ion-assisted deposition effects on the surface structure of a TiO2 thin film,” J. Vac. Sci. Technol. A 8, 2155–2159 (1989).
[CrossRef]

C. F. Hickey, C. Amra, E. Pelletier, “Scattering study of single layer titania films,” Appl. Opt. 28, 2754–2761 (1989).
[CrossRef] [PubMed]

F. Flory, E. Pelletier, G. Albrand, Y. Hu, “Surface optical coatings by ion assisted techniques: study of uniformity,” Appl. Opt. 28, 2952–2959 (1989).
[CrossRef] [PubMed]

J. M. Bennett, “Comparison of the properties of titanium dioxide films prepared by various techniques,” Appl. Opt. 28, 3303–3317 (1989).
[CrossRef] [PubMed]

1987

D. G. Howitt, A. B. Harker, “The oriented growth of anatase in thin films of amorphous titania,” J. Mater. Res. 2, 201–210 (1987).
[CrossRef]

1986

A. Kalb, M. Middelbrath, V. Sanders, “Summary abstract: neutral ion beam deposition of high reflectance coatings for use in ring laser gyroscopes,” J. Vac. Sci. Technol. A 4, 436–437 (1986).
[CrossRef]

1984

K. H. Guenther, “Microstructure of vapor-deposited optical coatings,” Appl. Opt. 23, 3806–3816 (1984).
[CrossRef] [PubMed]

R. Messier, A. P. Giri, R. A. Ray, “Revised structure zone model for thin film physical structure,” J. Vac. Sci. Technol. A 2, 500–503 (1984).
[CrossRef]

1983

H. R. Kaufman, “Material processing with broad-beam ion sources,” Ann. Rev. Mater. Sci. 13, 413–439 (1983); see p. 417.
[CrossRef]

1979

1976

K. H. Guenther, H. L. Gruber, H. K. Pulker, “Morphology and light scattering of dielectric multilayer systems,” Thin Solid Films 34, 363–367 (1976).
[CrossRef]

1974

T. J. Splavins, W. A. Brainard, “Nodular growth in thick-sputtered metallic coatings,” J. Vac. Sci. Technol. 11, 1186–1192 (1974).
[CrossRef]

1969

B. A. Movchan, A. V. Demchishin, “Study of the structure and properties of thick vacuum condensates of nickel, titanium, tungsten, aluminum oxide, and zirconium oxide,” Phys. Met. Metallogr. (USSR) 28, 83 (1969).

1964

Albrand, G.

Amra, C.

Bennett, J. M.

Blazey, R.

Boulesteix, C.

M. Lottiaux, C. Boulesteix, G. Nihoul, F. Varnier, F. Flory, R. Galindo, E. Pelletier, “Morphology and structure of TiO2 layers versus thickness and substrate temperature,” Thin Solid Films 170, 107–126 (1989).
[CrossRef]

Brainard, W. A.

T. J. Splavins, W. A. Brainard, “Nodular growth in thick-sputtered metallic coatings,” J. Vac. Sci. Technol. 11, 1186–1192 (1974).
[CrossRef]

Demchishin, A. V.

B. A. Movchan, A. V. Demchishin, “Study of the structure and properties of thick vacuum condensates of nickel, titanium, tungsten, aluminum oxide, and zirconium oxide,” Phys. Met. Metallogr. (USSR) 28, 83 (1969).

Elson, J.

Flory, F.

M. Lottiaux, C. Boulesteix, G. Nihoul, F. Varnier, F. Flory, R. Galindo, E. Pelletier, “Morphology and structure of TiO2 layers versus thickness and substrate temperature,” Thin Solid Films 170, 107–126 (1989).
[CrossRef]

F. Flory, E. Pelletier, G. Albrand, Y. Hu, “Surface optical coatings by ion assisted techniques: study of uniformity,” Appl. Opt. 28, 2952–2959 (1989).
[CrossRef] [PubMed]

Galindo, R.

M. Lottiaux, C. Boulesteix, G. Nihoul, F. Varnier, F. Flory, R. Galindo, E. Pelletier, “Morphology and structure of TiO2 layers versus thickness and substrate temperature,” Thin Solid Films 170, 107–126 (1989).
[CrossRef]

Giri, A. P.

R. Messier, A. P. Giri, R. A. Ray, “Revised structure zone model for thin film physical structure,” J. Vac. Sci. Technol. A 2, 500–503 (1984).
[CrossRef]

Gruber, H. L.

K. H. Guenther, H. L. Gruber, H. K. Pulker, “Morphology and light scattering of dielectric multilayer systems,” Thin Solid Films 34, 363–367 (1976).
[CrossRef]

Guenther, K. H.

K. H. Guenther, “Microstructure of vapor-deposited optical coatings,” Appl. Opt. 23, 3806–3816 (1984).
[CrossRef] [PubMed]

K. H. Guenther, H. L. Gruber, H. K. Pulker, “Morphology and light scattering of dielectric multilayer systems,” Thin Solid Films 34, 363–367 (1976).
[CrossRef]

K. H. Guenther, “Columnar and nodular growth of thin films,” in Thin Film Technologies and Special Applications, W. R. Hunter, ed., Proc. SPIE346, 9–18 (1982).

Harker, A. B.

D. G. Howitt, A. B. Harker, “The oriented growth of anatase in thin films of amorphous titania,” J. Mater. Res. 2, 201–210 (1987).
[CrossRef]

Hermann, W. C.

W. C. Hermann in Optical Thin Films, R. I. Seddon, ed., Proc. SPIE325, 101 (1982).

Hickey, C. F.

Howitt, D. G.

D. G. Howitt, A. B. Harker, “The oriented growth of anatase in thin films of amorphous titania,” J. Mater. Res. 2, 201–210 (1987).
[CrossRef]

Hu, Y.

Kalb, A.

A. Kalb, M. Middelbrath, V. Sanders, “Summary abstract: neutral ion beam deposition of high reflectance coatings for use in ring laser gyroscopes,” J. Vac. Sci. Technol. A 4, 436–437 (1986).
[CrossRef]

Kaufman, H. R.

H. R. Kaufman, “Material processing with broad-beam ion sources,” Ann. Rev. Mater. Sci. 13, 413–439 (1983); see p. 417.
[CrossRef]

Kusano, E.

See, for example, E. Kusano, “An investigation of hysteresis effects as a function of pumping speed, sputtering current, and O2/Ar ratio in TiO2 reactive sputtering process,” J. Appl. Phys. 70, 7089–7096 (1991).
[CrossRef]

Lottiaux, M.

M. Lottiaux, C. Boulesteix, G. Nihoul, F. Varnier, F. Flory, R. Galindo, E. Pelletier, “Morphology and structure of TiO2 layers versus thickness and substrate temperature,” Thin Solid Films 170, 107–126 (1989).
[CrossRef]

Messier, R.

R. Messier, A. P. Giri, R. A. Ray, “Revised structure zone model for thin film physical structure,” J. Vac. Sci. Technol. A 2, 500–503 (1984).
[CrossRef]

Middelbrath, M.

A. Kalb, M. Middelbrath, V. Sanders, “Summary abstract: neutral ion beam deposition of high reflectance coatings for use in ring laser gyroscopes,” J. Vac. Sci. Technol. A 4, 436–437 (1986).
[CrossRef]

Movchan, B. A.

B. A. Movchan, A. V. Demchishin, “Study of the structure and properties of thick vacuum condensates of nickel, titanium, tungsten, aluminum oxide, and zirconium oxide,” Phys. Met. Metallogr. (USSR) 28, 83 (1969).

Nihoul, G.

M. Lottiaux, C. Boulesteix, G. Nihoul, F. Varnier, F. Flory, R. Galindo, E. Pelletier, “Morphology and structure of TiO2 layers versus thickness and substrate temperature,” Thin Solid Films 170, 107–126 (1989).
[CrossRef]

Pelletier, E.

Pulker, H. K.

K. H. Guenther, H. L. Gruber, H. K. Pulker, “Morphology and light scattering of dielectric multilayer systems,” Thin Solid Films 34, 363–367 (1976).
[CrossRef]

Ray, R. A.

R. Messier, A. P. Giri, R. A. Ray, “Revised structure zone model for thin film physical structure,” J. Vac. Sci. Technol. A 2, 500–503 (1984).
[CrossRef]

Sanders, V.

A. Kalb, M. Middelbrath, V. Sanders, “Summary abstract: neutral ion beam deposition of high reflectance coatings for use in ring laser gyroscopes,” J. Vac. Sci. Technol. A 4, 436–437 (1986).
[CrossRef]

Splavins, T. J.

T. J. Splavins, W. A. Brainard, “Nodular growth in thick-sputtered metallic coatings,” J. Vac. Sci. Technol. 11, 1186–1192 (1974).
[CrossRef]

Varnier, F.

F. Varnier, “Ion-assisted deposition effects on the surface structure of a TiO2 thin film,” J. Vac. Sci. Technol. A 8, 2155–2159 (1989).
[CrossRef]

M. Lottiaux, C. Boulesteix, G. Nihoul, F. Varnier, F. Flory, R. Galindo, E. Pelletier, “Morphology and structure of TiO2 layers versus thickness and substrate temperature,” Thin Solid Films 170, 107–126 (1989).
[CrossRef]

Ann. Rev. Mater. Sci.

H. R. Kaufman, “Material processing with broad-beam ion sources,” Ann. Rev. Mater. Sci. 13, 413–439 (1983); see p. 417.
[CrossRef]

Appl. Opt.

J. Appl. Phys.

See, for example, E. Kusano, “An investigation of hysteresis effects as a function of pumping speed, sputtering current, and O2/Ar ratio in TiO2 reactive sputtering process,” J. Appl. Phys. 70, 7089–7096 (1991).
[CrossRef]

J. Mater. Res.

D. G. Howitt, A. B. Harker, “The oriented growth of anatase in thin films of amorphous titania,” J. Mater. Res. 2, 201–210 (1987).
[CrossRef]

J. Opt. Soc. Am.

J. Vac. Sci. Technol.

T. J. Splavins, W. A. Brainard, “Nodular growth in thick-sputtered metallic coatings,” J. Vac. Sci. Technol. 11, 1186–1192 (1974).
[CrossRef]

J. Vac. Sci. Technol. A

F. Varnier, “Ion-assisted deposition effects on the surface structure of a TiO2 thin film,” J. Vac. Sci. Technol. A 8, 2155–2159 (1989).
[CrossRef]

A. Kalb, M. Middelbrath, V. Sanders, “Summary abstract: neutral ion beam deposition of high reflectance coatings for use in ring laser gyroscopes,” J. Vac. Sci. Technol. A 4, 436–437 (1986).
[CrossRef]

R. Messier, A. P. Giri, R. A. Ray, “Revised structure zone model for thin film physical structure,” J. Vac. Sci. Technol. A 2, 500–503 (1984).
[CrossRef]

Phys. Met. Metallogr. (USSR)

B. A. Movchan, A. V. Demchishin, “Study of the structure and properties of thick vacuum condensates of nickel, titanium, tungsten, aluminum oxide, and zirconium oxide,” Phys. Met. Metallogr. (USSR) 28, 83 (1969).

Thin Solid Films

M. Lottiaux, C. Boulesteix, G. Nihoul, F. Varnier, F. Flory, R. Galindo, E. Pelletier, “Morphology and structure of TiO2 layers versus thickness and substrate temperature,” Thin Solid Films 170, 107–126 (1989).
[CrossRef]

K. H. Guenther, H. L. Gruber, H. K. Pulker, “Morphology and light scattering of dielectric multilayer systems,” Thin Solid Films 34, 363–367 (1976).
[CrossRef]

Other

K. H. Guenther, “Columnar and nodular growth of thin films,” in Thin Film Technologies and Special Applications, W. R. Hunter, ed., Proc. SPIE346, 9–18 (1982).

Ref. 13, Fig. 7b.

W. C. Hermann in Optical Thin Films, R. I. Seddon, ed., Proc. SPIE325, 101 (1982).

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Figures (8)

Fig. 1
Fig. 1

Granularity in a MLD film. The illumination was in dark field, and the magnification was 400×.

Fig. 2
Fig. 2

600-nm-thick layer of TiO2 viewed in dark field at 400×. The granular defects are clearly visible.

Fig. 3
Fig. 3

A 900-nm-thick layer of SiO2 as seen in dark field at 400×. The large defects are either dirt particles or defects in the substrate.

Fig. 4
Fig. 4

SEM image of the cross section of the coating of Fig. 1. The thickness of the individual layers and of the stack agreed with the designed thickness and with the thickness as determined from the spectral fringes.

Fig. 5
Fig. 5

SEM image of terracing through the entire stack. The terracing was in pairs, with the TiO2 layer uppermost. The defect density was lower in layers that were closer to the substrate. The granularity appears as depressions.

Fig. 6
Fig. 6

SEM image of the top surface of the topmost TiO2 layer of the coating of Fig. 1. Features that appeared to be point scatterers in the optical microscope are revealed to be nodules. The magnification is 40,000×, and the nodules are ~300 nm in diameter.

Fig. 7
Fig. 7

SEM image of a terraced chip at the top of the coating. The nodules are on the TiO2 surfaces. The intervening SiO2 layer was etched back by HF.

Fig. 8
Fig. 8

SEM image of a terraced chip at the top of a MLD coating that was deposited at a low substrate temperature. By contrast with the coating of Fig. 7, there are no depressions caused by granularity. Dark-field photomicrographs of such coatings were featureless.

Tables (1)

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Table 1 Apparent Effect of Thickness of Granularity

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