Abstract

A method to measure thin-film thickness, refractive index, and dispersion constants based on white-light interferometry is described. The thin-film property is retrieved from the Fourier amplitude of the white-light correlogram. The sources of errors in Fourier amplitude, which include the accuracy of wave number, light source variation in time, and illumination nonuniformity, are investigated. With all these errors reduced, the film thicknesses and refractive indices of four samples measured by white-light interferometry are within 1% of the ellipsometry results.

© 2012 Optical Society of America

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References

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    [CrossRef]
  4. L. Deck, and P. de Groot, “High-speed noncontact profiler based on scanning white-light interferometry,” Appl. Opt. 33, 7334–7338 (1994).
    [CrossRef]
  5. G. S. Kino, and S. S. C. Chim, “Mirau correlation microscope,” Appl. Opt. 29, 3775–3783 (1990).
    [CrossRef]
  6. A. Pförtner, and J. Schwider, “Dispersion error in white-light Linnik interferometers and its implications for evaluation procedures,” Appl. Opt. 40, 6223–6228 (2001).
    [CrossRef]
  7. P. de Groot, X. C. de Lega, J. Kramer, and M. Turzhitsky, “Determination of fringe order in white-light interference microscopy,” Appl. Opt. 41, 4571–4578 (2002).
    [CrossRef]
  8. J. C. Wyant, “White light interferometry,” Proc. SPIE 4737, 98–107 (2002).
    [CrossRef]
  9. T. Li, A. Wang, K. Murphy, and R. Claus, “White-light scanning fiber Michelson interferometer for absolute position-distance measurement,” Opt. Lett. 20, 785–787 (1995).
    [CrossRef]
  10. P. de Groot, and L. Deck, “Surface profiling by analysis of white-light interferograms in the spatial frequency,” J. Mod. Opt. 42, 389–401 (1995).
    [CrossRef]
  11. A. Olszak, “Lateral scanning white-light interferometer,” Appl. Opt. 39, 3906–3913 (2000).
    [CrossRef]
  12. S. W. Kim, and G. H. Kim, “Thickness-profile measurement of transparent thin film layers by white-light scanning interferometry,” Appl. Opt. 38, 5968–5973 (1999).
    [CrossRef]
  13. M. Roy, I. Cooper, P. Moore, C. J. R. Sheppard, and P. Hariharan, “White-light interference microscopy: effects of multiple reflections within a surface film,” Opt. Express 13, 164–170 (2005).
    [CrossRef]
  14. D. S. Wan, “Measurement of thin films using Fourier amplitude,” US patent 7612891 (3November2009).
  15. F. L. McCrackin, E. Passaglia, R. R. Stromberg, and H. L. Steinberg, “Measurement of the thickness and refractive index of very thin films and the optical properties of surfaces by ellipsometry,” J. Res. Natl. Bur. Stan. Sect. A 67, 363–377 (1963).
    [CrossRef]
  16. R. A. Synowicki, “Spectroscopic ellipsometry characterization of indium tin oxide film microstructure and optical constants,” Thin Solid Films 313–314, 394–397 (1998).
    [CrossRef]
  17. H. A. Macleod, Thin Film Optical Filters (Macmillan, 1986).

2005 (1)

2002 (2)

2001 (1)

2000 (1)

1999 (1)

1998 (1)

R. A. Synowicki, “Spectroscopic ellipsometry characterization of indium tin oxide film microstructure and optical constants,” Thin Solid Films 313–314, 394–397 (1998).
[CrossRef]

1995 (2)

P. de Groot, and L. Deck, “Surface profiling by analysis of white-light interferograms in the spatial frequency,” J. Mod. Opt. 42, 389–401 (1995).
[CrossRef]

T. Li, A. Wang, K. Murphy, and R. Claus, “White-light scanning fiber Michelson interferometer for absolute position-distance measurement,” Opt. Lett. 20, 785–787 (1995).
[CrossRef]

1994 (1)

1992 (1)

1990 (2)

1972 (1)

1963 (1)

F. L. McCrackin, E. Passaglia, R. R. Stromberg, and H. L. Steinberg, “Measurement of the thickness and refractive index of very thin films and the optical properties of surfaces by ellipsometry,” J. Res. Natl. Bur. Stan. Sect. A 67, 363–377 (1963).
[CrossRef]

Chim, S. S. C.

Claus, R.

Cooper, I.

de Groot, P.

de Lega, X. C.

Deck, L.

P. de Groot, and L. Deck, “Surface profiling by analysis of white-light interferograms in the spatial frequency,” J. Mod. Opt. 42, 389–401 (1995).
[CrossRef]

L. Deck, and P. de Groot, “High-speed noncontact profiler based on scanning white-light interferometry,” Appl. Opt. 33, 7334–7338 (1994).
[CrossRef]

Dresel, T.

Flourney, P. A.

Hariharan, P.

Häusler, G.

Kim, G. H.

Kim, S. W.

Kino, G. S.

Kramer, J.

Lee, B. S.

Li, T.

Macleod, H. A.

H. A. Macleod, Thin Film Optical Filters (Macmillan, 1986).

McClure, R. W.

McCrackin, F. L.

F. L. McCrackin, E. Passaglia, R. R. Stromberg, and H. L. Steinberg, “Measurement of the thickness and refractive index of very thin films and the optical properties of surfaces by ellipsometry,” J. Res. Natl. Bur. Stan. Sect. A 67, 363–377 (1963).
[CrossRef]

Moore, P.

Murphy, K.

Olszak, A.

Passaglia, E.

F. L. McCrackin, E. Passaglia, R. R. Stromberg, and H. L. Steinberg, “Measurement of the thickness and refractive index of very thin films and the optical properties of surfaces by ellipsometry,” J. Res. Natl. Bur. Stan. Sect. A 67, 363–377 (1963).
[CrossRef]

Pförtner, A.

Roy, M.

Schwider, J.

Sheppard, C. J. R.

Steinberg, H. L.

F. L. McCrackin, E. Passaglia, R. R. Stromberg, and H. L. Steinberg, “Measurement of the thickness and refractive index of very thin films and the optical properties of surfaces by ellipsometry,” J. Res. Natl. Bur. Stan. Sect. A 67, 363–377 (1963).
[CrossRef]

Strand, T. C.

Stromberg, R. R.

F. L. McCrackin, E. Passaglia, R. R. Stromberg, and H. L. Steinberg, “Measurement of the thickness and refractive index of very thin films and the optical properties of surfaces by ellipsometry,” J. Res. Natl. Bur. Stan. Sect. A 67, 363–377 (1963).
[CrossRef]

Synowicki, R. A.

R. A. Synowicki, “Spectroscopic ellipsometry characterization of indium tin oxide film microstructure and optical constants,” Thin Solid Films 313–314, 394–397 (1998).
[CrossRef]

Turzhitsky, M.

Venzke, H.

Wan, D. S.

D. S. Wan, “Measurement of thin films using Fourier amplitude,” US patent 7612891 (3November2009).

Wang, A.

Wyant, J. C.

J. C. Wyant, “White light interferometry,” Proc. SPIE 4737, 98–107 (2002).
[CrossRef]

Wyntjes, G.

Appl. Opt. (9)

J. Mod. Opt. (1)

P. de Groot, and L. Deck, “Surface profiling by analysis of white-light interferograms in the spatial frequency,” J. Mod. Opt. 42, 389–401 (1995).
[CrossRef]

J. Res. Natl. Bur. Stan. Sect. A (1)

F. L. McCrackin, E. Passaglia, R. R. Stromberg, and H. L. Steinberg, “Measurement of the thickness and refractive index of very thin films and the optical properties of surfaces by ellipsometry,” J. Res. Natl. Bur. Stan. Sect. A 67, 363–377 (1963).
[CrossRef]

Opt. Express (1)

Opt. Lett. (1)

Proc. SPIE (1)

J. C. Wyant, “White light interferometry,” Proc. SPIE 4737, 98–107 (2002).
[CrossRef]

Thin Solid Films (1)

R. A. Synowicki, “Spectroscopic ellipsometry characterization of indium tin oxide film microstructure and optical constants,” Thin Solid Films 313–314, 394–397 (1998).
[CrossRef]

Other (2)

H. A. Macleod, Thin Film Optical Filters (Macmillan, 1986).

D. S. Wan, “Measurement of thin films using Fourier amplitude,” US patent 7612891 (3November2009).

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Figures (8)

Fig. 1.
Fig. 1.

Schematic diagram of WLSI thin-film measurement.

Fig. 2.
Fig. 2.

Correlation points of thin film measurement: (a) uncoated substrate and (b) thin film sample.

Fig. 3.
Fig. 3.

Flow chart describing our method for finding thickness and refractive index of a transparent dielectric thin film by WLSI.

Fig. 4.
Fig. 4.

Reflection amplitudes of ten regions for (a) Ta2O5 and (b) SiO2 thin films.

Fig. 5.
Fig. 5.

Spectrum ratios of edge filter to blank window at frame interval 71 nm and at 71±3.55nm, the same ratio measured by a standard spectrometer in solid curve.

Fig. 6.
Fig. 6.

Comparison of film spectrum with a monitor (solid curve) and without a monitor (dashed curve) for (a) sample Ta2O5, (b) sample SiO2, difference in spectrum for (c) Ta2O5, and (d) SiO2.

Fig. 7.
Fig. 7.

Comparison of film spectrum with uniformity adjustment (solid curve) and without uniformity adjustment, (dashed curve) for (a) sample Ta2O5 and (b) sample SiO2 thin films, difference in spectrum for (c) Ta2O5 and (d) SiO2.

Fig. 8.
Fig. 8.

Comparison of film spectrum with (solid curve) and without substrate dispersion data (dashed curve) for (a) sample Ta2O5 and (b) sample SiO2, difference in spectrum for (c) Ta2O5 and (d) SiO2.

Tables (2)

Tables Icon

Table 1. Film Thickness, Cauchy Constants, and Refractive Index at Wavelength 550 nm of the 10 Regions for Ta2O5 and SiO2 Thin Film

Tables Icon

Table 2. Comparison of WLSI Measurements of Four Samples with Ellipsometry Measurements

Equations (12)

Equations on this page are rendered with MathJax. Learn more.

Er=a·r·Ar(k)·exp[j·(4πkz0)],
Es=a·ρ(k)·Ar(k)·exp{j·[4πk(z+h)+ϕ]},
I(z)=IDC+k2a2rAr2(k)ρ(k)·cos{2πk[2(zz0+h)]+ϕ}.
|FT(I(z))|=2a2rAr2ρ(k).
[BC]=[cosδisinδninsinδcosδ][1nS].
ρmodel(k;n,d)=BCB+C,
n=C1+C2·k2+C3·k4,
|FT(Is(z))|=2a2rAr2ρs(k).
ρ(k)=FT(D)FT(C)ρs(k)·1FT(B)FT(A).
Error(n,d)=k(ρ(k)|ρmodel(k;n,d)|)2.
ρ(k)=FT(D)FT(B)ρs(k).
ρ(k)=FT(D)FT(C)ρs(k).

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