Abstract

In the case of extreme ultraviolet (EUV) lithography, modeling has shown that reflector phase roughness on the lithographic mask is a significant concern due to the image plane speckle it causes and the resulting line-edge roughness on imaged features. Modeling results have recently been used to determine the requirements for future production worthy masks yielding the extremely stringent specification of 50pmrms roughness. Owing to the scale of the problem in terms of memory requirements, past modeling results have been based on the thin mask appro ximation in this application. EUV masks, however, are inherently three-dimensional (3D) in nature and thus the question arises as to the validity of the thin mask approximation. Here, we directly compare the image plane speckle calculation results using the fast two-dimensional thin mask model to rigorous finite-difference time-domain results and find the two methods to agree to within 10% in the computation of the speckle magnitude and 20% in the computation of the line-edge roughness limited depth of focus. For both types of computation, the two-dimensional method provides a conservative estimate. The 3D modeling is also used to show that layer-to-layer correlated roughness is indeed the roughness metric of most concern.

© 2011 Optical Society of America

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References

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  1. P. Naulleau and G. Gallatin, “The line-edge roughness transfer function and its application to determining mask effects in EUV resist characterization,” Appl. Opt. 42, 3390–3397 (2003).
    [CrossRef] [PubMed]
  2. N. Beaudry and T. Milster, “Effects of mask roughness and condenser scattering in EUVL systems,” Proc. SPIE. 3676, 653–662 (1999).
    [CrossRef]
  3. P. Naulleau, “The relevance of mask-roughness-induced printed line-edge roughness in recent and future EUV lithography tests,” Appl. Opt. 43, 4025–4032 (2004).
    [CrossRef] [PubMed]
  4. P. Naulleau, D. Niakoula, and G. Zhang, “System-level line-edge roughness limits in extreme ultraviolet lithography,” J. Vac. Sci. Technol. B Microelectron. Process. Phenom. 26, 1289–1293 (2008).
    [CrossRef]
  5. P. Naulleau, “Correlation method for the measure of mask-induced line-edge roughness in extreme ultraviolet lithography,” Appl. Opt. 48, 3302–3307 (2009).
    [CrossRef] [PubMed]
  6. P. Naulleau and S. George, “Implications of image plane line-edge roughness requirements on extreme ultraviolet mask specifications,” Proc. SPIE 7379, 73790O(2009).
    [CrossRef]
  7. J. W. Goodman, Statistical Optics (Wiley, 1985), Chap. 7, pp. 286–360.
  8. Prolith is a registered trademark of KLA-Tencor Corporation, 160 Rio Robles, San Jose, California 95134.
  9. EM-Suite is a registered trademark of Panoramic Technologies, www.panoramictech.com.
  10. B. McClinton and P. Naulleau, “Mask-roughness-induced line-edge roughness: rule of thumb,” J. Micro/Nanolith. MEMS MOEMS 9, 041208 (2010).
    [CrossRef]

2010 (1)

B. McClinton and P. Naulleau, “Mask-roughness-induced line-edge roughness: rule of thumb,” J. Micro/Nanolith. MEMS MOEMS 9, 041208 (2010).
[CrossRef]

2009 (2)

P. Naulleau, “Correlation method for the measure of mask-induced line-edge roughness in extreme ultraviolet lithography,” Appl. Opt. 48, 3302–3307 (2009).
[CrossRef] [PubMed]

P. Naulleau and S. George, “Implications of image plane line-edge roughness requirements on extreme ultraviolet mask specifications,” Proc. SPIE 7379, 73790O(2009).
[CrossRef]

2008 (1)

P. Naulleau, D. Niakoula, and G. Zhang, “System-level line-edge roughness limits in extreme ultraviolet lithography,” J. Vac. Sci. Technol. B Microelectron. Process. Phenom. 26, 1289–1293 (2008).
[CrossRef]

2004 (1)

2003 (1)

1999 (1)

N. Beaudry and T. Milster, “Effects of mask roughness and condenser scattering in EUVL systems,” Proc. SPIE. 3676, 653–662 (1999).
[CrossRef]

Beaudry, N.

N. Beaudry and T. Milster, “Effects of mask roughness and condenser scattering in EUVL systems,” Proc. SPIE. 3676, 653–662 (1999).
[CrossRef]

Gallatin, G.

George, S.

P. Naulleau and S. George, “Implications of image plane line-edge roughness requirements on extreme ultraviolet mask specifications,” Proc. SPIE 7379, 73790O(2009).
[CrossRef]

Goodman, J. W.

J. W. Goodman, Statistical Optics (Wiley, 1985), Chap. 7, pp. 286–360.

McClinton, B.

B. McClinton and P. Naulleau, “Mask-roughness-induced line-edge roughness: rule of thumb,” J. Micro/Nanolith. MEMS MOEMS 9, 041208 (2010).
[CrossRef]

Milster, T.

N. Beaudry and T. Milster, “Effects of mask roughness and condenser scattering in EUVL systems,” Proc. SPIE. 3676, 653–662 (1999).
[CrossRef]

Naulleau, P.

B. McClinton and P. Naulleau, “Mask-roughness-induced line-edge roughness: rule of thumb,” J. Micro/Nanolith. MEMS MOEMS 9, 041208 (2010).
[CrossRef]

P. Naulleau, “Correlation method for the measure of mask-induced line-edge roughness in extreme ultraviolet lithography,” Appl. Opt. 48, 3302–3307 (2009).
[CrossRef] [PubMed]

P. Naulleau and S. George, “Implications of image plane line-edge roughness requirements on extreme ultraviolet mask specifications,” Proc. SPIE 7379, 73790O(2009).
[CrossRef]

P. Naulleau, D. Niakoula, and G. Zhang, “System-level line-edge roughness limits in extreme ultraviolet lithography,” J. Vac. Sci. Technol. B Microelectron. Process. Phenom. 26, 1289–1293 (2008).
[CrossRef]

P. Naulleau, “The relevance of mask-roughness-induced printed line-edge roughness in recent and future EUV lithography tests,” Appl. Opt. 43, 4025–4032 (2004).
[CrossRef] [PubMed]

P. Naulleau and G. Gallatin, “The line-edge roughness transfer function and its application to determining mask effects in EUV resist characterization,” Appl. Opt. 42, 3390–3397 (2003).
[CrossRef] [PubMed]

Niakoula, D.

P. Naulleau, D. Niakoula, and G. Zhang, “System-level line-edge roughness limits in extreme ultraviolet lithography,” J. Vac. Sci. Technol. B Microelectron. Process. Phenom. 26, 1289–1293 (2008).
[CrossRef]

Zhang, G.

P. Naulleau, D. Niakoula, and G. Zhang, “System-level line-edge roughness limits in extreme ultraviolet lithography,” J. Vac. Sci. Technol. B Microelectron. Process. Phenom. 26, 1289–1293 (2008).
[CrossRef]

Appl. Opt. (3)

J. Micro/Nanolith. MEMS MOEMS (1)

B. McClinton and P. Naulleau, “Mask-roughness-induced line-edge roughness: rule of thumb,” J. Micro/Nanolith. MEMS MOEMS 9, 041208 (2010).
[CrossRef]

J. Vac. Sci. Technol. B Microelectron. Process. Phenom. (1)

P. Naulleau, D. Niakoula, and G. Zhang, “System-level line-edge roughness limits in extreme ultraviolet lithography,” J. Vac. Sci. Technol. B Microelectron. Process. Phenom. 26, 1289–1293 (2008).
[CrossRef]

Proc. SPIE (1)

P. Naulleau and S. George, “Implications of image plane line-edge roughness requirements on extreme ultraviolet mask specifications,” Proc. SPIE 7379, 73790O(2009).
[CrossRef]

Proc. SPIE. (1)

N. Beaudry and T. Milster, “Effects of mask roughness and condenser scattering in EUVL systems,” Proc. SPIE. 3676, 653–662 (1999).
[CrossRef]

Other (3)

J. W. Goodman, Statistical Optics (Wiley, 1985), Chap. 7, pp. 286–360.

Prolith is a registered trademark of KLA-Tencor Corporation, 160 Rio Robles, San Jose, California 95134.

EM-Suite is a registered trademark of Panoramic Technologies, www.panoramictech.com.

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Figures (9)

Fig. 1
Fig. 1

HyperLith screen capture of the top 10 layers in the modeled surface, where the dark layers represent molybdenum and the light layers represent silicon.

Fig. 2
Fig. 2

Direct comparison of 2D and 3D modeling methods for the computation of image plane speckle assuming an AOI of 0 ° at various numerical apertures.

Fig. 3
Fig. 3

Direct comparison of 2D and 3D modeling methods for various mask conditions. Case 1: correlation length = 125 nm and surface roughness = 100 pm , Case 2: correlation length = 75 nm and surface roughness = 230 pm , and Case 3: correlation length = 75 nm and surface roughness = 100 pm .

Fig. 4
Fig. 4

Computed speckle contrast using the 3D method as a function of NA and AOI. Results are relatively insensitive to the AOI for all considered NAs.

Fig. 5
Fig. 5

Direct comparison of 2D and 3D modeling methods for the computation of image plane LER.

Fig. 6
Fig. 6

Image of the multilayer stack generated using an uncorrelated layer thickness model. Aspect ratio is greatly exaggerated for visualization purposes.

Fig. 7
Fig. 7

Speckle through-focus for uncorrelated layer thickness roughness using 3D modeling.

Fig. 8
Fig. 8

Image of the multilayer stack generated using an un correlated interface roughness model. Aspect ratio is greatly exaggerated for visualization purposes.

Fig. 9
Fig. 9

Speckle through-focus for an uncorrelated interface roughness using 3D modeling.

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