Abstract

The use of optical metrology techniques in process control for microelectronic manufacturing has become widespread. These techniques are fast and non-destructive, allowing a higher sampling rate than non-optical methods like scanning electron or atomic force microscopy. One drawback of most optical metrology tools is the requirement that special measurement structures be fabricated in the scribe line between chips. This poses significant limitations regarding the characterization of lithography processes that may be overcome via in-chip measurements. In this paper we present experimental results for an in-chip optical metrology technique that allows direct measurement of both critical dimensions and overlay displacement errors in the DRAM manufacturing process. This technique does not require special target structures and is performed on the actual semiconductor devices.

© 2009 OSA

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References

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  1. C. J. Raymond, “Scatterometry for Semiconductor Metrology,” Handbook of silicon semiconductor metrology, A.C. Diebold, ed., (Academic press 2001), Chap. 18, p.477–514.
  2. N. P. Smith, “Overlay metrology at the crossroads,” Proc. SPIE 6922, 0277–0286 (2008).
  3. C. Hedlund, H.-O. Blom, and S. Berg, “Microloading effect in reactive ion etching,” J. Vac. Sci. Technol. A 12(4), 1962–1965 (1994).
    [CrossRef]
  4. K. Rochford, “Polarization and polarimetry,” NIST publication, http://boulder.nist.gov/div815/81503_pubs/PPMDocs/Rochford-EPST-02.pdf
  5. R. W. Collins, Handbook of Ellipsometry, H. G. Tompkins and E. A. Irene, eds., (William Andrew Publishing & Springer-Verlag, 2005), Chap. 7.3.3, p 546–566.
  6. L. Li, “New formulation of the Fourier modal method for crossed surface relief gratings,” J. Opt. Soc. Am. A 14(10), 2758–2767 (1997).
    [CrossRef]
  7. L. Li, “Symmetries of cross-polarization diffraction coefficients of gratings,” J. Opt. Soc. Am. A 17(5), 881–887 (2000).
    [CrossRef]
  8. P. Vagos, J. Hu, Z. Liu, and S. Rabello, “Uncertainty and Sensitivity Analysis and its application in OCD measurements,” Proc. of SPIE 7272, 72721N–72721N–9 (2009)

2000 (1)

1997 (1)

1994 (1)

C. Hedlund, H.-O. Blom, and S. Berg, “Microloading effect in reactive ion etching,” J. Vac. Sci. Technol. A 12(4), 1962–1965 (1994).
[CrossRef]

Berg, S.

C. Hedlund, H.-O. Blom, and S. Berg, “Microloading effect in reactive ion etching,” J. Vac. Sci. Technol. A 12(4), 1962–1965 (1994).
[CrossRef]

Blom, H.-O.

C. Hedlund, H.-O. Blom, and S. Berg, “Microloading effect in reactive ion etching,” J. Vac. Sci. Technol. A 12(4), 1962–1965 (1994).
[CrossRef]

Hedlund, C.

C. Hedlund, H.-O. Blom, and S. Berg, “Microloading effect in reactive ion etching,” J. Vac. Sci. Technol. A 12(4), 1962–1965 (1994).
[CrossRef]

Li, L.

J. Opt. Soc. Am. A (2)

J. Vac. Sci. Technol. A (1)

C. Hedlund, H.-O. Blom, and S. Berg, “Microloading effect in reactive ion etching,” J. Vac. Sci. Technol. A 12(4), 1962–1965 (1994).
[CrossRef]

Other (5)

K. Rochford, “Polarization and polarimetry,” NIST publication, http://boulder.nist.gov/div815/81503_pubs/PPMDocs/Rochford-EPST-02.pdf

R. W. Collins, Handbook of Ellipsometry, H. G. Tompkins and E. A. Irene, eds., (William Andrew Publishing & Springer-Verlag, 2005), Chap. 7.3.3, p 546–566.

P. Vagos, J. Hu, Z. Liu, and S. Rabello, “Uncertainty and Sensitivity Analysis and its application in OCD measurements,” Proc. of SPIE 7272, 72721N–72721N–9 (2009)

C. J. Raymond, “Scatterometry for Semiconductor Metrology,” Handbook of silicon semiconductor metrology, A.C. Diebold, ed., (Academic press 2001), Chap. 18, p.477–514.

N. P. Smith, “Overlay metrology at the crossroads,” Proc. SPIE 6922, 0277–0286 (2008).

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Figures (7)

Fig. 1
Fig. 1

Broadband spectroscopic rotating compensator ellipsometer used in this paper.

Fig. 2
Fig. 2

TEM cross-section image along the long axis of STI island.

Fig. 3
Fig. 3

Second lithographic step in the RCAT DRAM manufacture. (a) STI islands etched in silicon. (b) Photo resist lines printed over the SiO2 filled STI silicon islands (c). Top view of the structure with photo resist lines over the STI islands. The unit cell of the repeating pattern is outlined in white. (d) TEM image of the AEI structure showing the misalignment of the photo resist lines with respect to the silicon islands, the overlay error is δx = (x1-x2)/2.

Fig. 4
Fig. 4

Experimental spectra of the combination of two MM-SE elements, M13 + M31, from the center die horizontally across the wafer. Each curve correspond to a different overlay shift in the +/− 15 nm range.

Fig. 5
Fig. 5

Average response (over wavelengths in the 245-265 nm range) of the sum M13 + M31 vs. overlay shift.

Fig. 6
Fig. 6

RCWA fit to the experimental Mueller matrix data.

Fig. 7
Fig. 7

Correlation between MM SE in-chip overlay measurement and imaging overlay measurement on the scribe line. The insert shows the correlation of the OCD PR line width measurement to CDSEM.

Equations (6)

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S o u t = [ M A R ( A ) ] M S a m p l e [ R 1 ( C ) M C R ( C ) ] [ R 1 ( P ) M P ] S i n
J = ( r s s r s p r p s r p p )
M s a m p l e = T J J * T 1
T = ( 1 0 0 1 1 0 0 1 0 1 1 0 0 i i 0 )
M 13 + M 31 = 0 M 23 + M 32 = 0
M 13 + M 31 = C 1 δ x M 23 + M 32 = C 2 δ x

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