Abstract

Various reports state that Line Edge/Width Roughness (LER/LWR) has a significant impact on the integrated circuits fabricated by means of lithography, hence there is a need to determine the LER in–line so that it never exceeds certain specified limits. In our work we deal with the challenge of measuring LER on 50nm resist gratings using scatterometry. We show by simulation that there is a difference between LER and no–LER scatter signatures which first: depends on the polarization and second: is proportional to the amount of LER. Moreover, we show that the mentioned difference is very specific, that is — a grating with LER acts like a grating without LER but showing another width (CD, Critical Dimension), which we refer–to as effective–CD.

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References

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  1. K. Shibata, N. Izumi, and K. Tsujita, “Influence of line–edge roughness on MOSFET devices with sub–50nm gates,” Proc. SPIE 5375, 865–873 (2004).
    [CrossRef]
  2. International Technology Roadmap for Semiconductors, www.itrs.net .
  3. A. C. Diebold, Handbook of Silicon Semiconductor Metrology (CRC Press, 2001).
    [CrossRef]
  4. A. E. Braun, “How CD–SEMs Complement Scatterometry,” Semicond. Int. Mag. (June2009).
  5. G. Gallatin, “SPIE Short Course 886: Line Edge Roughness.”
  6. W. Osten, V. Ferreras Paz, K. Frenner, T. Schuster, and H. Bloess, “Simulations of scatterometry down to 22nm structure sizes and beyond with special emphasis on LER,” in Frontiers of Characterization and Metrology for Nanoelectronics: 2009, E. M. Secula, D. G. Seiler, R. P. Khosla, D. Herr, C. M. Garner, R. McDonald, and A. C. Diebold, eds. (AIP Conference Proceedings, 2009). Vol. 1173, pp. 371–378.
  7. B. C. Bergner, T. A. Germer, and T. J. Suleski, “Effect of line–width roughness on optical scatterometry measurements,” Proc. SPIE 7272, 72720U (2009).
    [CrossRef]
  8. B. C. Bergner, T. A. Germer, and T. J. Suleski, “Effective medium approximations for modeling optical reflectance from gratings with rough edges,” J. Opt. Soc. Am. A 5, 1083–1090 (2010).
    [CrossRef]
  9. M. Totzeck, “Numerical simulation of high–NA quantitative polarization microscopy and corresponding near–fields,” Optik 112, 399–406 (2001).

2010 (1)

B. C. Bergner, T. A. Germer, and T. J. Suleski, “Effective medium approximations for modeling optical reflectance from gratings with rough edges,” J. Opt. Soc. Am. A 5, 1083–1090 (2010).
[CrossRef]

2009 (1)

B. C. Bergner, T. A. Germer, and T. J. Suleski, “Effect of line–width roughness on optical scatterometry measurements,” Proc. SPIE 7272, 72720U (2009).
[CrossRef]

2004 (1)

K. Shibata, N. Izumi, and K. Tsujita, “Influence of line–edge roughness on MOSFET devices with sub–50nm gates,” Proc. SPIE 5375, 865–873 (2004).
[CrossRef]

2001 (1)

M. Totzeck, “Numerical simulation of high–NA quantitative polarization microscopy and corresponding near–fields,” Optik 112, 399–406 (2001).

Bergner, B. C.

B. C. Bergner, T. A. Germer, and T. J. Suleski, “Effective medium approximations for modeling optical reflectance from gratings with rough edges,” J. Opt. Soc. Am. A 5, 1083–1090 (2010).
[CrossRef]

B. C. Bergner, T. A. Germer, and T. J. Suleski, “Effect of line–width roughness on optical scatterometry measurements,” Proc. SPIE 7272, 72720U (2009).
[CrossRef]

Bloess, H.

W. Osten, V. Ferreras Paz, K. Frenner, T. Schuster, and H. Bloess, “Simulations of scatterometry down to 22nm structure sizes and beyond with special emphasis on LER,” in Frontiers of Characterization and Metrology for Nanoelectronics: 2009, E. M. Secula, D. G. Seiler, R. P. Khosla, D. Herr, C. M. Garner, R. McDonald, and A. C. Diebold, eds. (AIP Conference Proceedings, 2009). Vol. 1173, pp. 371–378.

Braun, A. E.

A. E. Braun, “How CD–SEMs Complement Scatterometry,” Semicond. Int. Mag. (June2009).

Diebold, A. C.

A. C. Diebold, Handbook of Silicon Semiconductor Metrology (CRC Press, 2001).
[CrossRef]

Ferreras Paz, V.

W. Osten, V. Ferreras Paz, K. Frenner, T. Schuster, and H. Bloess, “Simulations of scatterometry down to 22nm structure sizes and beyond with special emphasis on LER,” in Frontiers of Characterization and Metrology for Nanoelectronics: 2009, E. M. Secula, D. G. Seiler, R. P. Khosla, D. Herr, C. M. Garner, R. McDonald, and A. C. Diebold, eds. (AIP Conference Proceedings, 2009). Vol. 1173, pp. 371–378.

Frenner, K.

W. Osten, V. Ferreras Paz, K. Frenner, T. Schuster, and H. Bloess, “Simulations of scatterometry down to 22nm structure sizes and beyond with special emphasis on LER,” in Frontiers of Characterization and Metrology for Nanoelectronics: 2009, E. M. Secula, D. G. Seiler, R. P. Khosla, D. Herr, C. M. Garner, R. McDonald, and A. C. Diebold, eds. (AIP Conference Proceedings, 2009). Vol. 1173, pp. 371–378.

Gallatin, G.

G. Gallatin, “SPIE Short Course 886: Line Edge Roughness.”

Germer, T. A.

B. C. Bergner, T. A. Germer, and T. J. Suleski, “Effective medium approximations for modeling optical reflectance from gratings with rough edges,” J. Opt. Soc. Am. A 5, 1083–1090 (2010).
[CrossRef]

B. C. Bergner, T. A. Germer, and T. J. Suleski, “Effect of line–width roughness on optical scatterometry measurements,” Proc. SPIE 7272, 72720U (2009).
[CrossRef]

Izumi, N.

K. Shibata, N. Izumi, and K. Tsujita, “Influence of line–edge roughness on MOSFET devices with sub–50nm gates,” Proc. SPIE 5375, 865–873 (2004).
[CrossRef]

Osten, W.

W. Osten, V. Ferreras Paz, K. Frenner, T. Schuster, and H. Bloess, “Simulations of scatterometry down to 22nm structure sizes and beyond with special emphasis on LER,” in Frontiers of Characterization and Metrology for Nanoelectronics: 2009, E. M. Secula, D. G. Seiler, R. P. Khosla, D. Herr, C. M. Garner, R. McDonald, and A. C. Diebold, eds. (AIP Conference Proceedings, 2009). Vol. 1173, pp. 371–378.

Schuster, T.

W. Osten, V. Ferreras Paz, K. Frenner, T. Schuster, and H. Bloess, “Simulations of scatterometry down to 22nm structure sizes and beyond with special emphasis on LER,” in Frontiers of Characterization and Metrology for Nanoelectronics: 2009, E. M. Secula, D. G. Seiler, R. P. Khosla, D. Herr, C. M. Garner, R. McDonald, and A. C. Diebold, eds. (AIP Conference Proceedings, 2009). Vol. 1173, pp. 371–378.

Shibata, K.

K. Shibata, N. Izumi, and K. Tsujita, “Influence of line–edge roughness on MOSFET devices with sub–50nm gates,” Proc. SPIE 5375, 865–873 (2004).
[CrossRef]

Suleski, T. J.

B. C. Bergner, T. A. Germer, and T. J. Suleski, “Effective medium approximations for modeling optical reflectance from gratings with rough edges,” J. Opt. Soc. Am. A 5, 1083–1090 (2010).
[CrossRef]

B. C. Bergner, T. A. Germer, and T. J. Suleski, “Effect of line–width roughness on optical scatterometry measurements,” Proc. SPIE 7272, 72720U (2009).
[CrossRef]

Totzeck, M.

M. Totzeck, “Numerical simulation of high–NA quantitative polarization microscopy and corresponding near–fields,” Optik 112, 399–406 (2001).

Tsujita, K.

K. Shibata, N. Izumi, and K. Tsujita, “Influence of line–edge roughness on MOSFET devices with sub–50nm gates,” Proc. SPIE 5375, 865–873 (2004).
[CrossRef]

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

B. C. Bergner, T. A. Germer, and T. J. Suleski, “Effective medium approximations for modeling optical reflectance from gratings with rough edges,” J. Opt. Soc. Am. A 5, 1083–1090 (2010).
[CrossRef]

Optik (1)

M. Totzeck, “Numerical simulation of high–NA quantitative polarization microscopy and corresponding near–fields,” Optik 112, 399–406 (2001).

Proc. SPIE (2)

B. C. Bergner, T. A. Germer, and T. J. Suleski, “Effect of line–width roughness on optical scatterometry measurements,” Proc. SPIE 7272, 72720U (2009).
[CrossRef]

K. Shibata, N. Izumi, and K. Tsujita, “Influence of line–edge roughness on MOSFET devices with sub–50nm gates,” Proc. SPIE 5375, 865–873 (2004).
[CrossRef]

Other (5)

International Technology Roadmap for Semiconductors, www.itrs.net .

A. C. Diebold, Handbook of Silicon Semiconductor Metrology (CRC Press, 2001).
[CrossRef]

A. E. Braun, “How CD–SEMs Complement Scatterometry,” Semicond. Int. Mag. (June2009).

G. Gallatin, “SPIE Short Course 886: Line Edge Roughness.”

W. Osten, V. Ferreras Paz, K. Frenner, T. Schuster, and H. Bloess, “Simulations of scatterometry down to 22nm structure sizes and beyond with special emphasis on LER,” in Frontiers of Characterization and Metrology for Nanoelectronics: 2009, E. M. Secula, D. G. Seiler, R. P. Khosla, D. Herr, C. M. Garner, R. McDonald, and A. C. Diebold, eds. (AIP Conference Proceedings, 2009). Vol. 1173, pp. 371–378.

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Figures (7)

Fig. 1
Fig. 1

Power spectral density (PSD) of a typical (per data available, [5]) rough edge (a) and a realistic rough line it yields as an example (b). The two important parameters of the PSD are cut-off frequency ξ0 (here 0.011/nm) and the log–log slope m (here −3).

Fig. 2
Fig. 2

Investigated set–ups. One needs to note that s–polarized incidence (E⃗s) in Θ00 is y–polarized while in Θ90x–polarized.

Fig. 3
Fig. 3

Although in the big picture (3a) the signatures of CD50+LER gratings (oe-19-21-19967-i001.jpg) are indistinguishable from CD50’s signature (oe-19-21-19967-i002.jpg), taking a closer look (3b–2) one can observe an offset between the two. For instance the σ = 3 LER+CD50’s signature oe-19-21-19967-i003.jpg follows the signature of CD49.3. The family of gradient bands is scatter signatures of CD49.0, . . . , CD51.0 no–LER gratings. As one can observe, the two windows (1, 2) in 3a have the same size, yet they yield different local sensitivities (3b).

Fig. 4
Fig. 4

The effective–CD interpolated from CD+LERs’ signatures recorded by variable–angle scatterometry. Figure shares the legend with Fig. 5. Discontinuities roughly correspond to the areas of low local sensitivity in scatter signatures, see Fig. 2. As such, those areas are of little interest from the point of view of metrology and erroneous (discontinuous) effective–CD they deliver may easily be disregarded.

Fig. 5
Fig. 5

The effective–CD interpolated from CD+LERs’ signatures recorded by fixed–angle scatterometry.

Fig. 6
Fig. 6

The relationship between the effective–CD and LER. It seems to be uniform for (at least) all CDs of approximately 50nm.

Fig. 7
Fig. 7

Effective–CD surfaces. While two parameters of the roughness are varying, the third one is fixed at its most typical value (indicated above the surfaces). As can be expected, the upper surfaces correspond to results from E⃗x, the bottom ones – from E⃗y.

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