Abstract

Real-time monitoring of thin-film deposition with high resolution is important for precise fabrication of thin-film devices in a technological environment with ever-increasing demands for smaller size and better performance. Using photometry, we were able to achieve a real-time optical monitoring resolution of film thickness that is comparable with a single atomic layer scale (i.e., subnanometer). Filtering noise efficiently and compensating for sources of error by use of an appropriate model produced this high resolution. The procedure proved reliable and can be useful in the thin-film-deposition industry.

© 2004 Optical Society of America

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References

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  1. L. Ward, The Optical Constants of Bulk Material and Films2nd ed. (Institute of Physics, London, 1994).
  2. O. Auciello, A. R. Krauss, In Situ Real-Time Characterization of Thin Films (Wiley, New York, 2001).
  3. N. Dietz, K. Ito, “Real-time optical characterization of GaP heterostructures by p-polarized reflectance,” Thin Solid Films, pp. 313–314, 614–619 (1998).
  4. N. Dietz, K. J. Bachman, “Real-time optical monitoring of epitaxial growth processes by p-polarized reflectance spectroscopy,” Mater. Res. Soc. Symp. Proc. 406, 341 (2001).
    [CrossRef]
  5. F. Chen, H. Lu, T. Zhao, Z. Chen, G. Yang, “Optical in situ monitoring of complex oxide thin film laser molecular beam epitaxy,” J. Cryst. Growth 2001(7), 227–228, 950–954.
  6. M. Ruiz-Urbieta, E. M. Sparrow, E. R. Eckert, “Methods for determining film thickness and optical constants of films and substrates,” J. Opt. Soc. Am. 16, 351–359 (1970).
  7. R. Swanepoel, “Determination of the thickness and optical constants of amorphous silicon,” J. Phys. E 16, 1214–1222 (1983).
    [CrossRef]
  8. E. E. Khawaja, “The determination of the refractive index and thickness of a transparent film,” J. Phys. D 9, 1939–1943 (1976).
    [CrossRef]
  9. C. K. Carniglia, “Scalar scattering theory for multiplayer optical coatings,” Opt. Eng. 18, 104 (1979).
    [CrossRef]
  10. J. M. Bennett, L. Mattsson, Introduction to Surface Roughness and Scattering (Optical Society of America, Washington, D.C., 1989), pp. 3–55.

2001

N. Dietz, K. J. Bachman, “Real-time optical monitoring of epitaxial growth processes by p-polarized reflectance spectroscopy,” Mater. Res. Soc. Symp. Proc. 406, 341 (2001).
[CrossRef]

1998

N. Dietz, K. Ito, “Real-time optical characterization of GaP heterostructures by p-polarized reflectance,” Thin Solid Films, pp. 313–314, 614–619 (1998).

1983

R. Swanepoel, “Determination of the thickness and optical constants of amorphous silicon,” J. Phys. E 16, 1214–1222 (1983).
[CrossRef]

1979

C. K. Carniglia, “Scalar scattering theory for multiplayer optical coatings,” Opt. Eng. 18, 104 (1979).
[CrossRef]

1976

E. E. Khawaja, “The determination of the refractive index and thickness of a transparent film,” J. Phys. D 9, 1939–1943 (1976).
[CrossRef]

1970

M. Ruiz-Urbieta, E. M. Sparrow, E. R. Eckert, “Methods for determining film thickness and optical constants of films and substrates,” J. Opt. Soc. Am. 16, 351–359 (1970).

Auciello, O.

O. Auciello, A. R. Krauss, In Situ Real-Time Characterization of Thin Films (Wiley, New York, 2001).

Bachman, K. J.

N. Dietz, K. J. Bachman, “Real-time optical monitoring of epitaxial growth processes by p-polarized reflectance spectroscopy,” Mater. Res. Soc. Symp. Proc. 406, 341 (2001).
[CrossRef]

Bennett, J. M.

J. M. Bennett, L. Mattsson, Introduction to Surface Roughness and Scattering (Optical Society of America, Washington, D.C., 1989), pp. 3–55.

Carniglia, C. K.

C. K. Carniglia, “Scalar scattering theory for multiplayer optical coatings,” Opt. Eng. 18, 104 (1979).
[CrossRef]

Chen, F.

F. Chen, H. Lu, T. Zhao, Z. Chen, G. Yang, “Optical in situ monitoring of complex oxide thin film laser molecular beam epitaxy,” J. Cryst. Growth 2001(7), 227–228, 950–954.

Chen, Z.

F. Chen, H. Lu, T. Zhao, Z. Chen, G. Yang, “Optical in situ monitoring of complex oxide thin film laser molecular beam epitaxy,” J. Cryst. Growth 2001(7), 227–228, 950–954.

Dietz, N.

N. Dietz, K. J. Bachman, “Real-time optical monitoring of epitaxial growth processes by p-polarized reflectance spectroscopy,” Mater. Res. Soc. Symp. Proc. 406, 341 (2001).
[CrossRef]

N. Dietz, K. Ito, “Real-time optical characterization of GaP heterostructures by p-polarized reflectance,” Thin Solid Films, pp. 313–314, 614–619 (1998).

Eckert, E. R.

M. Ruiz-Urbieta, E. M. Sparrow, E. R. Eckert, “Methods for determining film thickness and optical constants of films and substrates,” J. Opt. Soc. Am. 16, 351–359 (1970).

Ito, K.

N. Dietz, K. Ito, “Real-time optical characterization of GaP heterostructures by p-polarized reflectance,” Thin Solid Films, pp. 313–314, 614–619 (1998).

Khawaja, E. E.

E. E. Khawaja, “The determination of the refractive index and thickness of a transparent film,” J. Phys. D 9, 1939–1943 (1976).
[CrossRef]

Krauss, A. R.

O. Auciello, A. R. Krauss, In Situ Real-Time Characterization of Thin Films (Wiley, New York, 2001).

Lu, H.

F. Chen, H. Lu, T. Zhao, Z. Chen, G. Yang, “Optical in situ monitoring of complex oxide thin film laser molecular beam epitaxy,” J. Cryst. Growth 2001(7), 227–228, 950–954.

Mattsson, L.

J. M. Bennett, L. Mattsson, Introduction to Surface Roughness and Scattering (Optical Society of America, Washington, D.C., 1989), pp. 3–55.

Ruiz-Urbieta, M.

M. Ruiz-Urbieta, E. M. Sparrow, E. R. Eckert, “Methods for determining film thickness and optical constants of films and substrates,” J. Opt. Soc. Am. 16, 351–359 (1970).

Sparrow, E. M.

M. Ruiz-Urbieta, E. M. Sparrow, E. R. Eckert, “Methods for determining film thickness and optical constants of films and substrates,” J. Opt. Soc. Am. 16, 351–359 (1970).

Swanepoel, R.

R. Swanepoel, “Determination of the thickness and optical constants of amorphous silicon,” J. Phys. E 16, 1214–1222 (1983).
[CrossRef]

Ward, L.

L. Ward, The Optical Constants of Bulk Material and Films2nd ed. (Institute of Physics, London, 1994).

Yang, G.

F. Chen, H. Lu, T. Zhao, Z. Chen, G. Yang, “Optical in situ monitoring of complex oxide thin film laser molecular beam epitaxy,” J. Cryst. Growth 2001(7), 227–228, 950–954.

Zhao, T.

F. Chen, H. Lu, T. Zhao, Z. Chen, G. Yang, “Optical in situ monitoring of complex oxide thin film laser molecular beam epitaxy,” J. Cryst. Growth 2001(7), 227–228, 950–954.

J. Cryst. Growth

F. Chen, H. Lu, T. Zhao, Z. Chen, G. Yang, “Optical in situ monitoring of complex oxide thin film laser molecular beam epitaxy,” J. Cryst. Growth 2001(7), 227–228, 950–954.

J. Opt. Soc. Am.

M. Ruiz-Urbieta, E. M. Sparrow, E. R. Eckert, “Methods for determining film thickness and optical constants of films and substrates,” J. Opt. Soc. Am. 16, 351–359 (1970).

J. Phys. D

E. E. Khawaja, “The determination of the refractive index and thickness of a transparent film,” J. Phys. D 9, 1939–1943 (1976).
[CrossRef]

J. Phys. E

R. Swanepoel, “Determination of the thickness and optical constants of amorphous silicon,” J. Phys. E 16, 1214–1222 (1983).
[CrossRef]

Mater. Res. Soc. Symp. Proc.

N. Dietz, K. J. Bachman, “Real-time optical monitoring of epitaxial growth processes by p-polarized reflectance spectroscopy,” Mater. Res. Soc. Symp. Proc. 406, 341 (2001).
[CrossRef]

Opt. Eng.

C. K. Carniglia, “Scalar scattering theory for multiplayer optical coatings,” Opt. Eng. 18, 104 (1979).
[CrossRef]

Thin Solid Films

N. Dietz, K. Ito, “Real-time optical characterization of GaP heterostructures by p-polarized reflectance,” Thin Solid Films, pp. 313–314, 614–619 (1998).

Other

L. Ward, The Optical Constants of Bulk Material and Films2nd ed. (Institute of Physics, London, 1994).

O. Auciello, A. R. Krauss, In Situ Real-Time Characterization of Thin Films (Wiley, New York, 2001).

J. M. Bennett, L. Mattsson, Introduction to Surface Roughness and Scattering (Optical Society of America, Washington, D.C., 1989), pp. 3–55.

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Figures (6)

Fig. 1
Fig. 1

(a) One thin film on a bulk substrate. (b) Two thin films on a bulk substrate.

Fig. 2
Fig. 2

Effect of a 4-nm oxide layer with n = 1.5 (top) and a 4-min averaging window (bottom) on the exact curve when a quartz film with n = 1.45 is deposited at a rate of 3 nm/min on a silicon substrate.

Fig. 3
Fig. 3

(a) In-situ real-time monitoring setup of thin-film deposition. (b) Recorded photodetector readings before, during, and after deposition.

Fig. 4
Fig. 4

Fitting analysis without consideration of the extracted film’s optical losses and surface roughness: (a) Data (solid curve) and fit (dashed curve) of the reflection fringes when the 4-nm oxide layer was not considered. (b) Region in the real-refractive-index and deposition-rate space where the minimum fitting error is less than the doubled minimum error and the 4-nm oxide layer was not considered. (c) Data (solid curve) and fit (dashed curve) of the reflection fringes when the 4-nm oxide layer was considered. (d) Region in the real-refractive-index and deposition-rate space where the minimum fitting error is less than the doubled minimum error and the 4-nm oxide layer was considered.

Fig. 5
Fig. 5

(a) Extracted surface roughness rms value and (b) film extinction coefficient versus deposition time when cubic hermite interpolation was used.

Fig. 6
Fig. 6

Fitting analysis with consideration of the extracted film’s optical losses and surface roughness. (a) Data (solid curve) and fit (dashed curve) of the reflection fringes when the 4-nm oxide layer was not considered. (b) Region in the real-refractive-index and deposition-rate space where the minimum fitting error is less than the doubled minimum error and the 4-nm oxide layer was not considered. (c) Data (solid curve) and fit (dashed curve) of the reflection fringes when the 4-nm oxide layer was considered. (d) Region in the real-refractive-index and deposition-rate space where the minimum fitting error is less than the doubled minimum error and the 4-nm oxide layer was considered.

Equations (13)

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

R=|r01|2+|r12|2+2r01r12 cos 2β1+|r01|2|r12|2+2r01r12 cos 2β
β=2πLλN12-sin2 θ,
N=n+jκκ=αλ4π.
δ=1k12ln2r01Rmin+Rmax1/2,
κ=12kLln2r121-r012Rmin-Rmax-1-n2 ln2r01Rmin+Rmax.
r30=r32 expikn2L2+r20 exp-ikn2L2expikn2L2+r32r20 exp-ikn2L2,
r20=r21 expikn1L1+r10 exp-ikn1L1expikn1L1+r21r10 exp-ikn1L1,
rj+1,j=nj+1-njnj+1+nj, j=0, 1, 2,
Δ=1Ww=MWWM+1 Fw-FWM+W2,
En, ρ=iDi-Fin, ρ2
En, ρ=iDi-Δin, ρ-Fin, ρ2,
En, ρ=iFiL1Di-Δin, ρ-Fin, ρ2.
ΔnL=nΔL+LΔn.

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