Abstract

Rigorous coupled wave analysis (RCWA) interprets 3D white-light interference microscopy profiles and reveals the dimensions of optically-unresolved surface features. Measurements of silicon etch depth of a 450-nm pitch grating structure correlate to atomic force microscopy with R2 = 0.995 and a repeatability of 0.11nm. This same technique achieves a <1nm sensitivity to 80-nm lateral widths of 190-nm pitch gratings using a 570-nm mean wavelength.

© 2008 Optical Society of America

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References

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  1. P. de Groot and L. Deck, "Surface profiling by analysis of white-light interferograms in the spatial frequency domain," J. Mod. Opt. 42, 389-401 (1995).
    [CrossRef]
  2. M. G. Moharam and T. K. Gaylord, "Diffraction analysis of dielectric surface-relief gratings," J. Opt. Soc. Am. 72, 1385-1392, (1982).
    [CrossRef]
  3. M. G. Moharam, E. B. Grann, and D. A. Pommet, "Formulation for stable and efficient implementation of the rigorous coupled-wave analysis of binary gratings," J. Opt. Soc. Am. A 12, 1068 - 1076 (1995)
    [CrossRef]
  4. C. J. Raymond, "Scatterometry for Semiconductor Metrology," in Handbook of Silicon Semiconductor Metrology, A. J. Deibold, ed., (Marcel Dekker, Inc., New York, 2001)
    [CrossRef]
  5. A. Tavrov, J. Schmit, N. Kerwien, W. Osten, and H. Tiziani, "Diffraction-induced coherence levels," Appl. Opt. 44, 2202-2212 (2005)
    [CrossRef] [PubMed]
  6. M. Totzeck, "Numerical simulation of high-NA quantitative polarization microscopy and corresponding near-fields," Optik 112 (2001) 381-390
    [CrossRef]
  7. P. de Groot, R. Stoner, and X. Colonna De Lega, "Profiling complex surface structures using height scanning interferometry," US Patent No. 7,151,607 (2006).

2005 (1)

2001 (1)

M. Totzeck, "Numerical simulation of high-NA quantitative polarization microscopy and corresponding near-fields," Optik 112 (2001) 381-390
[CrossRef]

1995 (2)

M. G. Moharam, E. B. Grann, and D. A. Pommet, "Formulation for stable and efficient implementation of the rigorous coupled-wave analysis of binary gratings," J. Opt. Soc. Am. A 12, 1068 - 1076 (1995)
[CrossRef]

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

1982 (1)

de Groot, P.

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

Deck, L.

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

Gaylord, T. K.

Grann, E. B.

Kerwien, N.

Moharam, M. G.

Osten, W.

Pommet, D. A.

Schmit, J.

Tavrov, A.

Tiziani, H.

Totzeck, M.

M. Totzeck, "Numerical simulation of high-NA quantitative polarization microscopy and corresponding near-fields," Optik 112 (2001) 381-390
[CrossRef]

Appl. Opt. (1)

J. Mod. Opt. (1)

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

J. Opt. Soc. Am. (1)

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

Optik (1)

M. Totzeck, "Numerical simulation of high-NA quantitative polarization microscopy and corresponding near-fields," Optik 112 (2001) 381-390
[CrossRef]

Other (2)

P. de Groot, R. Stoner, and X. Colonna De Lega, "Profiling complex surface structures using height scanning interferometry," US Patent No. 7,151,607 (2006).

C. J. Raymond, "Scatterometry for Semiconductor Metrology," in Handbook of Silicon Semiconductor Metrology, A. J. Deibold, ed., (Marcel Dekker, Inc., New York, 2001)
[CrossRef]

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Figures (7)

Fig. 1.
Fig. 1.

Optical step-height measurement on a surface structure that includes transparent film layers with optically unresolved features. The measured profile does not resolve the features but is influenced by linewidth and etch depth.

Fig. 2.
Fig. 2.

White light interference surface profiler adapted for parameter metrology of sub-wavelength structures.

Fig. 3.
Fig. 3.

Left: Example RCWA calculation of a white-light interference signal for a 200-nm pitch, optically-unresolved grating, showing the intensity distribution at each scan position z (vertical axis) and at each object-space pixel position x (horizontal axis). Right: electron microscope image of a similar structure.

Fig. 4.
Fig. 4.

Predicted measured step according to RCWA modeling as a function of the Si etch depth for the structure shown in Fig. 1 with a 450-nm feature pitch. The illumination polarization in the pupil plane is orthogonal to the grating lines.

Fig. 5.
Fig. 5.

Silicon etch depth measured using the technique of this paper with the prediction graph of Fig. 4 compared to an independent AFM measurement.

Fig. 6.
Fig. 6.

Predicted step height measurement values for the structure of Fig. 1, assuming a 190-nm pitch and a polarization parallel to the grating lines. This configuration shows high sensitivity to feature width (left-hand graph) and low sensitivity to etch depth (right-hand graph), making this configuration ideal for parameter metrology of grating line widths.

Fig. 7.
Fig. 7.

Wafer map showing the experimentally-measured variation in the nominal 80-nm linewidth for a 190-nm pitch grating printed at different locations on the wafer.

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