Abstract

We present a novel method for determining both the thickness and the optical constants of a weakly absorbing thin film upon a nearly transparent substrate through analysis of transmittance measured at various incident angles with coherent light. We demonstrate this method for a polymer thin film. The refractive indices and extinction coefficients of poly(DRI-anthranilic acid) at wavelengths of 1064, 632.8, and 532 nm were determined for the first time to our knowledge. We also confirmed the validity of our method with a polystyrene thin film whose optical constant was known. It was found that a thickness of a few hundred nanometers can easily be measured and that this method offers simplicity as well as the capability of in situ measurement.

© 2002 Optical Society of America

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References

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  1. S. Y. Kim, “Simultaneous determination of refractive index, extinction coefficient, and void distribution of titanium dioxide thin film by optical methods,” Appl. Opt. 35, 6703–6707 (1996).
    [CrossRef] [PubMed]
  2. S. Y. Kim, “Determination of the complex refractive index and thickness of MNA/PMMA thin film,” Journal of the Optical Society of Korea 7, 357–362 (1996).
  3. C. Caliendo, E. Verona, G. Saggio, “An integrated optical method for measuring the thickness and refractive index of birefringent thin films,” Thin Solid Films 292, 255–259 (1997).
    [CrossRef]
  4. H. Wang, “Determination of optical constants of absorbing crystalline thin films from reflectance and transmittance measurements with oblique incidence,” J. Opt. Soc. Am. A 11, 2331–2337 (1994).
    [CrossRef]
  5. R. M. A. Azzam, N. M. Bashara, Ellipsometry and Polarized Light (North-Holland, Amsterdam, 1977).
  6. K. Vedam, S. Y. Kim, “Simultaneous determination of refractive index, its dispersion and depth-profile of magnesium oxide thin film by spectroscopic ellipsometry,” Appl. Opt. 18, 2691–2694 (1989).
    [CrossRef]
  7. G. Bader, P. V. Ashrit, F. E. Girouard, V. -V. Truong, “Reflection-transmission photoellipsometry: theory and experiments,” Appl. Opt. 34, 1684–1691 (1995).
    [CrossRef] [PubMed]
  8. X. Rusli, G. A. J. Amaratunga, “Determination of the optical constants and thickness of thin films on slightly absorbing substrates,” Appl. Opt. 34, 7914–7924 (1995).
  9. J. A. Dobrowolski, F. C. Ho, A. Waldorf, “Determination of optical constants of thin film coating materials based on inverse synthesis,” Appl. Opt. 22, 3191–3200 (1983).
    [CrossRef] [PubMed]
  10. Y. Wang, M. Miyagi, “Simultaneous measurement of optical constants of dispersive material at visible and infrared wavelengths,” Appl. Opt. 36, 877–884 (1997).
    [CrossRef] [PubMed]
  11. J. I. Cisneros, “Optical characterization of dielectric and semiconductor thin films by use of transmission data,” Appl. Opt. 37, 5262–5270 (1998).
    [CrossRef]
  12. B. Harbecke, “Coherent and incoherent reflection and transmission of multilayerstructures,” Appl. Phys. B 39, 165–170 (1986).
    [CrossRef]
  13. H. A. Macleod, Thin-Film Optical Filters (Macmillan, New York, 1986).
    [CrossRef]
  14. Z. Knittl, Optics of Thin Films (Wiley, London, 1976).
  15. J. C. Seferis, “Refractive indices of polymers,” in Polymer Handbook, J. Brandrup, E. H. Immergut, eds. (Wiley, New York, 1989), Chap. VI, pp. VI/451–VI/461.

1998 (1)

1997 (2)

C. Caliendo, E. Verona, G. Saggio, “An integrated optical method for measuring the thickness and refractive index of birefringent thin films,” Thin Solid Films 292, 255–259 (1997).
[CrossRef]

Y. Wang, M. Miyagi, “Simultaneous measurement of optical constants of dispersive material at visible and infrared wavelengths,” Appl. Opt. 36, 877–884 (1997).
[CrossRef] [PubMed]

1996 (2)

S. Y. Kim, “Simultaneous determination of refractive index, extinction coefficient, and void distribution of titanium dioxide thin film by optical methods,” Appl. Opt. 35, 6703–6707 (1996).
[CrossRef] [PubMed]

S. Y. Kim, “Determination of the complex refractive index and thickness of MNA/PMMA thin film,” Journal of the Optical Society of Korea 7, 357–362 (1996).

1995 (2)

1994 (1)

1989 (1)

K. Vedam, S. Y. Kim, “Simultaneous determination of refractive index, its dispersion and depth-profile of magnesium oxide thin film by spectroscopic ellipsometry,” Appl. Opt. 18, 2691–2694 (1989).
[CrossRef]

1986 (1)

B. Harbecke, “Coherent and incoherent reflection and transmission of multilayerstructures,” Appl. Phys. B 39, 165–170 (1986).
[CrossRef]

1983 (1)

Amaratunga, G. A. J.

Ashrit, P. V.

Azzam, R. M. A.

R. M. A. Azzam, N. M. Bashara, Ellipsometry and Polarized Light (North-Holland, Amsterdam, 1977).

Bader, G.

Bashara, N. M.

R. M. A. Azzam, N. M. Bashara, Ellipsometry and Polarized Light (North-Holland, Amsterdam, 1977).

Caliendo, C.

C. Caliendo, E. Verona, G. Saggio, “An integrated optical method for measuring the thickness and refractive index of birefringent thin films,” Thin Solid Films 292, 255–259 (1997).
[CrossRef]

Cisneros, J. I.

Dobrowolski, J. A.

Girouard, F. E.

Harbecke, B.

B. Harbecke, “Coherent and incoherent reflection and transmission of multilayerstructures,” Appl. Phys. B 39, 165–170 (1986).
[CrossRef]

Ho, F. C.

Kim, S. Y.

S. Y. Kim, “Simultaneous determination of refractive index, extinction coefficient, and void distribution of titanium dioxide thin film by optical methods,” Appl. Opt. 35, 6703–6707 (1996).
[CrossRef] [PubMed]

S. Y. Kim, “Determination of the complex refractive index and thickness of MNA/PMMA thin film,” Journal of the Optical Society of Korea 7, 357–362 (1996).

K. Vedam, S. Y. Kim, “Simultaneous determination of refractive index, its dispersion and depth-profile of magnesium oxide thin film by spectroscopic ellipsometry,” Appl. Opt. 18, 2691–2694 (1989).
[CrossRef]

Knittl, Z.

Z. Knittl, Optics of Thin Films (Wiley, London, 1976).

Macleod, H. A.

H. A. Macleod, Thin-Film Optical Filters (Macmillan, New York, 1986).
[CrossRef]

Miyagi, M.

Rusli, X.

Saggio, G.

C. Caliendo, E. Verona, G. Saggio, “An integrated optical method for measuring the thickness and refractive index of birefringent thin films,” Thin Solid Films 292, 255–259 (1997).
[CrossRef]

Seferis, J. C.

J. C. Seferis, “Refractive indices of polymers,” in Polymer Handbook, J. Brandrup, E. H. Immergut, eds. (Wiley, New York, 1989), Chap. VI, pp. VI/451–VI/461.

Truong, V. -V.

Vedam, K.

K. Vedam, S. Y. Kim, “Simultaneous determination of refractive index, its dispersion and depth-profile of magnesium oxide thin film by spectroscopic ellipsometry,” Appl. Opt. 18, 2691–2694 (1989).
[CrossRef]

Verona, E.

C. Caliendo, E. Verona, G. Saggio, “An integrated optical method for measuring the thickness and refractive index of birefringent thin films,” Thin Solid Films 292, 255–259 (1997).
[CrossRef]

Waldorf, A.

Wang, H.

Wang, Y.

Appl. Opt. (7)

Appl. Phys. B (1)

B. Harbecke, “Coherent and incoherent reflection and transmission of multilayerstructures,” Appl. Phys. B 39, 165–170 (1986).
[CrossRef]

J. Opt. Soc. Am. A (1)

Journal of the Optical Society of Korea (1)

S. Y. Kim, “Determination of the complex refractive index and thickness of MNA/PMMA thin film,” Journal of the Optical Society of Korea 7, 357–362 (1996).

Thin Solid Films (1)

C. Caliendo, E. Verona, G. Saggio, “An integrated optical method for measuring the thickness and refractive index of birefringent thin films,” Thin Solid Films 292, 255–259 (1997).
[CrossRef]

Other (4)

R. M. A. Azzam, N. M. Bashara, Ellipsometry and Polarized Light (North-Holland, Amsterdam, 1977).

H. A. Macleod, Thin-Film Optical Filters (Macmillan, New York, 1986).
[CrossRef]

Z. Knittl, Optics of Thin Films (Wiley, London, 1976).

J. C. Seferis, “Refractive indices of polymers,” in Polymer Handbook, J. Brandrup, E. H. Immergut, eds. (Wiley, New York, 1989), Chap. VI, pp. VI/451–VI/461.

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Figures (6)

Fig. 1
Fig. 1

Laser beams with a specific radius transmitting a thin film upon a glass substrate obliquely without interference.

Fig. 2
Fig. 2

Experimental setup for measuring transmittance with three different laser beams: B. S., beam splitter; NDF; neutral density filter.

Fig. 3
Fig. 3

Interval L b between two adjacent transmitted beams owing to multiple reflections in the substrate.

Fig. 4
Fig. 4

Measured transmittance (open circles) as a function of incident angle for the glass substrate at wavelengths of 1064, 632.8, and 532 nm. All solid curves are least-squares fits to the corresponding experimental data.

Fig. 5
Fig. 5

Measured transmittance (open circles) as a function of incident angle of the PDR1ANA thin film at wavelengths of 1064, 632.8, and 532 nm. All solid curves are least-squares fits to the corresponding experimental data.

Fig. 6
Fig. 6

Measured transmittance (open circles) as a function of incident angle of the polystyrene thin film at wavelengths of 1064 and 532 nm. All solid curves are least-squares fits to the corresponding experimental data.

Tables (3)

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Table 1 Experimental Values of Optical Constants for Glass at Three Wavelengths

Tables Icon

Table 2 Experimental Values of Optical Constants for the PDR1ANA Thin Film at Three Wavelengths

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Table 3 Experimental Values of Optical Constants for the Thin Film of Polystyrene at Two Wavelengths

Equations (2)

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T=|tafbexp-βtba|2+ |tafbexp-βtbarba exp-2βrbfa|2 +|tafbexp-βtbarba exp-2βrbfa2|2 + =|tba|2|tafb|2 exp-2β1-|rba|2|rbfa|2 exp-4β,
ΔT=i=1NTfitsθi-Texpsθi2N+i=1NTfitpθi-Texppθi2N1/2,

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