Abstract

An innovative method of in situ real-time optical monitoring of thin film deposition and etching is presented. In this technique, intensity maps of a thin film corresponding to a series of wavelengths selected by a monochromator (300800  nm) are recorded by a CCD camera. From the maps the reflectance spectra at individual points of the sample surface can be extracted. By fitting the reflectance spectra to the theoretical ones, the maps of a thin film morphology (including optical parameters) and their temporal development during technological processes can be obtained. The method was tested by in situ observation of the growth of silicon nitride and silicon oxide thin films prepared by ion beam sputtering and by the monitoring of etching of thermally grown SiO2 thin films.

© 2007 Optical Society of America

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References

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  1. H. G. Tompkins and W. A. McGahan, Spectroscopic Ellipsometry and Reflectometry: a User's Guide (Wiley, 1999), pp. 14-61.
  2. G. Jin, R. Jansson, and H. Arwina, "Imaging ellipsometry revisited: developments for visualization of thin transparent layers on silicon substrates," Rev. Sci. Instrum. 67, 2930-2936 (1996).
    [CrossRef]
  3. C.-Y. Han and Y.-F. Chao, "Photoelastic modulated imaging ellipsometry by stroboscopic illumination technique," Rev. Sci. Instrum. 77, 023107 (2006).
    [CrossRef]
  4. Y.-S. Ghim and S.-W. Kim, "Thin-film thickness profile and its refractive index measurements by dispersive white-light interferometry," Opt. Express 14, 11885-11891 (2006).
    [CrossRef] [PubMed]
  5. O. S. Heavens, Optical Properties of Thin Solid Films (Dover, 1991), pp. 46-95.
  6. E. D. Palik, Handbook of Optical Constants of Solids (Academic, 1991), pp. 719-772.
  7. D. Poelman and P. F. Smet, "Methods for the determination of the optical constants of thin films from single transmission measurements: a critical review," J. Phys. D: Appl. Phys. 36, 1850-1857 (2003).
    [CrossRef]
  8. W. D. Marquardt, "An algorithm for least-squares estimation of nonlinear parameters," J. Soc. Ind. Appl. Math. 11, 431-441 (1963).
    [CrossRef]
  9. J. Spousta, M. Urbánek, R. Chmelík, J. Jiruse, J. Zlámal, K. Navrátil, A. Nebojsa, and T. Šikola, "In situ measurements of surface homogeneity of optical parameters of weakly absorbing thin films," Surf. Interface Anal. 34, 664-667 (2002).
    [CrossRef]
  10. E. Schmidt, "Optical properties of GeSi alloys in the energy region from 1 to 13 eV," Phys. Status Solidi B 27, 57-67 (1968).
    [CrossRef]

2006 (2)

C.-Y. Han and Y.-F. Chao, "Photoelastic modulated imaging ellipsometry by stroboscopic illumination technique," Rev. Sci. Instrum. 77, 023107 (2006).
[CrossRef]

Y.-S. Ghim and S.-W. Kim, "Thin-film thickness profile and its refractive index measurements by dispersive white-light interferometry," Opt. Express 14, 11885-11891 (2006).
[CrossRef] [PubMed]

2003 (1)

D. Poelman and P. F. Smet, "Methods for the determination of the optical constants of thin films from single transmission measurements: a critical review," J. Phys. D: Appl. Phys. 36, 1850-1857 (2003).
[CrossRef]

2002 (1)

J. Spousta, M. Urbánek, R. Chmelík, J. Jiruse, J. Zlámal, K. Navrátil, A. Nebojsa, and T. Šikola, "In situ measurements of surface homogeneity of optical parameters of weakly absorbing thin films," Surf. Interface Anal. 34, 664-667 (2002).
[CrossRef]

1999 (1)

H. G. Tompkins and W. A. McGahan, Spectroscopic Ellipsometry and Reflectometry: a User's Guide (Wiley, 1999), pp. 14-61.

1996 (1)

G. Jin, R. Jansson, and H. Arwina, "Imaging ellipsometry revisited: developments for visualization of thin transparent layers on silicon substrates," Rev. Sci. Instrum. 67, 2930-2936 (1996).
[CrossRef]

1991 (2)

O. S. Heavens, Optical Properties of Thin Solid Films (Dover, 1991), pp. 46-95.

E. D. Palik, Handbook of Optical Constants of Solids (Academic, 1991), pp. 719-772.

1968 (1)

E. Schmidt, "Optical properties of GeSi alloys in the energy region from 1 to 13 eV," Phys. Status Solidi B 27, 57-67 (1968).
[CrossRef]

1963 (1)

W. D. Marquardt, "An algorithm for least-squares estimation of nonlinear parameters," J. Soc. Ind. Appl. Math. 11, 431-441 (1963).
[CrossRef]

Arwina, H.

G. Jin, R. Jansson, and H. Arwina, "Imaging ellipsometry revisited: developments for visualization of thin transparent layers on silicon substrates," Rev. Sci. Instrum. 67, 2930-2936 (1996).
[CrossRef]

Chao, Y.-F.

C.-Y. Han and Y.-F. Chao, "Photoelastic modulated imaging ellipsometry by stroboscopic illumination technique," Rev. Sci. Instrum. 77, 023107 (2006).
[CrossRef]

Chmelík, R.

J. Spousta, M. Urbánek, R. Chmelík, J. Jiruse, J. Zlámal, K. Navrátil, A. Nebojsa, and T. Šikola, "In situ measurements of surface homogeneity of optical parameters of weakly absorbing thin films," Surf. Interface Anal. 34, 664-667 (2002).
[CrossRef]

Ghim, Y.-S.

Han, C.-Y.

C.-Y. Han and Y.-F. Chao, "Photoelastic modulated imaging ellipsometry by stroboscopic illumination technique," Rev. Sci. Instrum. 77, 023107 (2006).
[CrossRef]

Heavens, O. S.

O. S. Heavens, Optical Properties of Thin Solid Films (Dover, 1991), pp. 46-95.

Jansson, R.

G. Jin, R. Jansson, and H. Arwina, "Imaging ellipsometry revisited: developments for visualization of thin transparent layers on silicon substrates," Rev. Sci. Instrum. 67, 2930-2936 (1996).
[CrossRef]

Jin, G.

G. Jin, R. Jansson, and H. Arwina, "Imaging ellipsometry revisited: developments for visualization of thin transparent layers on silicon substrates," Rev. Sci. Instrum. 67, 2930-2936 (1996).
[CrossRef]

Jiruše, J.

J. Spousta, M. Urbánek, R. Chmelík, J. Jiruse, J. Zlámal, K. Navrátil, A. Nebojsa, and T. Šikola, "In situ measurements of surface homogeneity of optical parameters of weakly absorbing thin films," Surf. Interface Anal. 34, 664-667 (2002).
[CrossRef]

Kim, S.-W.

Marquardt, W. D.

W. D. Marquardt, "An algorithm for least-squares estimation of nonlinear parameters," J. Soc. Ind. Appl. Math. 11, 431-441 (1963).
[CrossRef]

McGahan, W. A.

H. G. Tompkins and W. A. McGahan, Spectroscopic Ellipsometry and Reflectometry: a User's Guide (Wiley, 1999), pp. 14-61.

Navrátil, K.

J. Spousta, M. Urbánek, R. Chmelík, J. Jiruse, J. Zlámal, K. Navrátil, A. Nebojsa, and T. Šikola, "In situ measurements of surface homogeneity of optical parameters of weakly absorbing thin films," Surf. Interface Anal. 34, 664-667 (2002).
[CrossRef]

Nebojsa, A.

J. Spousta, M. Urbánek, R. Chmelík, J. Jiruse, J. Zlámal, K. Navrátil, A. Nebojsa, and T. Šikola, "In situ measurements of surface homogeneity of optical parameters of weakly absorbing thin films," Surf. Interface Anal. 34, 664-667 (2002).
[CrossRef]

Palik, E. D.

E. D. Palik, Handbook of Optical Constants of Solids (Academic, 1991), pp. 719-772.

Poelman, D.

D. Poelman and P. F. Smet, "Methods for the determination of the optical constants of thin films from single transmission measurements: a critical review," J. Phys. D: Appl. Phys. 36, 1850-1857 (2003).
[CrossRef]

Schmidt, E.

E. Schmidt, "Optical properties of GeSi alloys in the energy region from 1 to 13 eV," Phys. Status Solidi B 27, 57-67 (1968).
[CrossRef]

Šikola, T.

J. Spousta, M. Urbánek, R. Chmelík, J. Jiruse, J. Zlámal, K. Navrátil, A. Nebojsa, and T. Šikola, "In situ measurements of surface homogeneity of optical parameters of weakly absorbing thin films," Surf. Interface Anal. 34, 664-667 (2002).
[CrossRef]

Smet, P. F.

D. Poelman and P. F. Smet, "Methods for the determination of the optical constants of thin films from single transmission measurements: a critical review," J. Phys. D: Appl. Phys. 36, 1850-1857 (2003).
[CrossRef]

Spousta, J.

J. Spousta, M. Urbánek, R. Chmelík, J. Jiruse, J. Zlámal, K. Navrátil, A. Nebojsa, and T. Šikola, "In situ measurements of surface homogeneity of optical parameters of weakly absorbing thin films," Surf. Interface Anal. 34, 664-667 (2002).
[CrossRef]

Tompkins, H. G.

H. G. Tompkins and W. A. McGahan, Spectroscopic Ellipsometry and Reflectometry: a User's Guide (Wiley, 1999), pp. 14-61.

Urbánek, M.

J. Spousta, M. Urbánek, R. Chmelík, J. Jiruse, J. Zlámal, K. Navrátil, A. Nebojsa, and T. Šikola, "In situ measurements of surface homogeneity of optical parameters of weakly absorbing thin films," Surf. Interface Anal. 34, 664-667 (2002).
[CrossRef]

Zlámal, J.

J. Spousta, M. Urbánek, R. Chmelík, J. Jiruse, J. Zlámal, K. Navrátil, A. Nebojsa, and T. Šikola, "In situ measurements of surface homogeneity of optical parameters of weakly absorbing thin films," Surf. Interface Anal. 34, 664-667 (2002).
[CrossRef]

J. Phys. D: Appl. Phys. (1)

D. Poelman and P. F. Smet, "Methods for the determination of the optical constants of thin films from single transmission measurements: a critical review," J. Phys. D: Appl. Phys. 36, 1850-1857 (2003).
[CrossRef]

J. Soc. Ind. Appl. Math. (1)

W. D. Marquardt, "An algorithm for least-squares estimation of nonlinear parameters," J. Soc. Ind. Appl. Math. 11, 431-441 (1963).
[CrossRef]

Opt. Express (1)

Phys. Status Solidi B (1)

E. Schmidt, "Optical properties of GeSi alloys in the energy region from 1 to 13 eV," Phys. Status Solidi B 27, 57-67 (1968).
[CrossRef]

Rev. Sci. Instrum. (2)

G. Jin, R. Jansson, and H. Arwina, "Imaging ellipsometry revisited: developments for visualization of thin transparent layers on silicon substrates," Rev. Sci. Instrum. 67, 2930-2936 (1996).
[CrossRef]

C.-Y. Han and Y.-F. Chao, "Photoelastic modulated imaging ellipsometry by stroboscopic illumination technique," Rev. Sci. Instrum. 77, 023107 (2006).
[CrossRef]

Surf. Interface Anal. (1)

J. Spousta, M. Urbánek, R. Chmelík, J. Jiruse, J. Zlámal, K. Navrátil, A. Nebojsa, and T. Šikola, "In situ measurements of surface homogeneity of optical parameters of weakly absorbing thin films," Surf. Interface Anal. 34, 664-667 (2002).
[CrossRef]

Other (3)

H. G. Tompkins and W. A. McGahan, Spectroscopic Ellipsometry and Reflectometry: a User's Guide (Wiley, 1999), pp. 14-61.

O. S. Heavens, Optical Properties of Thin Solid Films (Dover, 1991), pp. 46-95.

E. D. Palik, Handbook of Optical Constants of Solids (Academic, 1991), pp. 719-772.

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Figures (7)

Fig. 1
Fig. 1

Reflections from a thin film.

Fig. 2
Fig. 2

(Color online) Flowchart of the fitting procedure.

Fig. 3
Fig. 3

(Color online) Imaging reflectometry setup. The sample is sequentially illuminated by monochromatic light of various wavelengths, and the point P on the sample surface is imaged by a mirror into the point P′. The map of intensities of the reflected light at a given wavelength is then recorded by a CCD camera.

Fig. 4
Fig. 4

(Color online) Time development of reflectance spectra recorded by one pixel of the CCD camera.

Fig. 5
Fig. 5

(Color online) Experimental and best-fitting theoretical reflectance spectra.

Fig. 6
Fig. 6

(Color online) Thickness and refractive index ( λ = 500   nm ) map of SiO x thin film at two different deposition times. In the pictures ( 85 min ) the unhomogeneity of the deposited thin film is clearly seen.

Fig. 7
Fig. 7

(Color online) Thickness of SiO 2 thin film at different stages of etching by HF. Steps 1, 2, 3, and 4 were made by etching of the corresponding parts of the film for 4, 8, 12, and 16 min, respectively.

Equations (3)

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R = I I std R std .
r 12 = N 1 N 2 N 1 + N 2 .
r = r 12 + r 23 exp ( i 2 β ) 1 + r 12 r 23 exp ( i 2 β ) ,

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