Abstract

We apply the numerical aperture increasing lens technique to widefield subsurface imaging of silicon integrated circuits. We demonstrate lateral and longitudinal resolutions well beyond the limits of conventional backside imaging. With a simple infrared widefield microscope (λ 0=1.2µm), we demonstrate a lateral spatial resolution of 0.26µm (0.22λ 0) and a longitudinal resolution of 1.24µm (1.03λ 0) for backside imaging through the silicon substrate of an integrated circuit. We present a spatial resolution comparison between widefield and confocal microscopy, which are essential in integrated circuit analysis for emission and excitation microscopy, respectively.

© 2008 Optical Society of America

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  1. C. Xu and W. Denk, "Two-photon optical beam induced current imaging through the backside of integrated circuits," Appl. Phys. Lett. 71, 2578-2580 (1997).
    [CrossRef]
  2. E. Ramsay, D. T. Reid, and K. Wilsher, "Three-dimensional imaging of a silicon flip chip using the two-photon optical-beam induced current effect," Appl. Phys. Lett. 81, 7-9 (2002).
    [CrossRef]
  3. International Technology Roadmap for Semiconductors Update, 2006.
  4. S. B. Ippolito, B. B. Goldberg, and M. S. Unlü, "High spatial resolution subsurface microscopy," Appl. Phys. Lett. 78, 4071-4073 (2001).
    [CrossRef]
  5. S. M. Mansfield and G. S. Kino, "Solid immersion microscope," Appl. Phys. Lett. 57, 2615-2617 (1990).
    [CrossRef]
  6. S. B. Ippolito, S. A. Thorne, M. G. Eraslan, B. B. Goldberg, M. S. Unlü, and Y. Leblebici, "High spatial resolution subsurface thermal emission microscopy," Appl. Phys. Lett. 84, 4529-4531 (2004).
    [CrossRef]
  7. E. Ramsay, N. Pleynet, D. Xiao, R. J. Warburton, and D. T. Reid, "Two-photon optical-beam-induced current solid-immersion imaging if a silicon flip chip with a resolution of 325 nm," Opt. Lett. 30, 26-28 (2005).
    [CrossRef] [PubMed]
  8. E. Ramsay, K. A. Serrels, M. J. Thomson, A. J. Waddie, M. R. Taghizadeh, R. J. Warburton, and D. T. Reid, "Three-dimensional nanoscale subsurface optical imaging of silicon circuits," Appl. Phys. Lett. 90, 131101 (2007).
    [CrossRef]
  9. Z. Liu, B. B. Goldberg, S. B. Ippolito, A. N. Vamivakas, M. S. Unlü, and R. Mirin, "High resolution, high collection efficiency in numerical aperture increasing lens microscopy of individual quantum dots," Appl. Phys. Lett. 87, 071905 (2005).
    [CrossRef]
  10. A. N. Vamivakas, M. Atatüre, S. T. Dreiser, J. Yilmaz, A. Badolato, A. K. Swan, B. B. Goldberg, A. Imamoglu, and M. S. Unlü, "Strong extinction of a far-field laser beam by a single quantum dot," Nano Lett. 7, 2892-2894 (2007).
    [CrossRef] [PubMed]
  11. J. B. Pawley, Handbook of Biological Confocal Microscopy, 3rd ed., (Springer Press, 2006), p. 209.
  12. S. B. Ippolito, B. B. Goldberg, and M. S. Unlü, "Theoretical analysis of numerical aperture increasing lens microscopy," J. Appl. Phys. 97, 053105 (2005).
    [CrossRef]
  13. M. A. Green and M. Keevers, "Optical properties of intrinsic silicon at 300k," Prog. Photovoltaics 3, 189-192 (1995).
    [CrossRef]
  14. T. Wilson and C. Sheppard, Theory and Practice of Scanning Optical Microscopy (Academic Press, 1984) p. 28.
  15. S. B. Ippolito, P. Song, D. L. Miles, and J. D. Sylvestri, "Angular spectrum tailoring in solid immersion microscopy for circuit analysis," Appl. Phys. Lett. 92, 101109 (2008).
    [CrossRef]

2008

S. B. Ippolito, P. Song, D. L. Miles, and J. D. Sylvestri, "Angular spectrum tailoring in solid immersion microscopy for circuit analysis," Appl. Phys. Lett. 92, 101109 (2008).
[CrossRef]

2007

E. Ramsay, K. A. Serrels, M. J. Thomson, A. J. Waddie, M. R. Taghizadeh, R. J. Warburton, and D. T. Reid, "Three-dimensional nanoscale subsurface optical imaging of silicon circuits," Appl. Phys. Lett. 90, 131101 (2007).
[CrossRef]

A. N. Vamivakas, M. Atatüre, S. T. Dreiser, J. Yilmaz, A. Badolato, A. K. Swan, B. B. Goldberg, A. Imamoglu, and M. S. Unlü, "Strong extinction of a far-field laser beam by a single quantum dot," Nano Lett. 7, 2892-2894 (2007).
[CrossRef] [PubMed]

2005

S. B. Ippolito, B. B. Goldberg, and M. S. Unlü, "Theoretical analysis of numerical aperture increasing lens microscopy," J. Appl. Phys. 97, 053105 (2005).
[CrossRef]

Z. Liu, B. B. Goldberg, S. B. Ippolito, A. N. Vamivakas, M. S. Unlü, and R. Mirin, "High resolution, high collection efficiency in numerical aperture increasing lens microscopy of individual quantum dots," Appl. Phys. Lett. 87, 071905 (2005).
[CrossRef]

E. Ramsay, N. Pleynet, D. Xiao, R. J. Warburton, and D. T. Reid, "Two-photon optical-beam-induced current solid-immersion imaging if a silicon flip chip with a resolution of 325 nm," Opt. Lett. 30, 26-28 (2005).
[CrossRef] [PubMed]

2004

S. B. Ippolito, S. A. Thorne, M. G. Eraslan, B. B. Goldberg, M. S. Unlü, and Y. Leblebici, "High spatial resolution subsurface thermal emission microscopy," Appl. Phys. Lett. 84, 4529-4531 (2004).
[CrossRef]

2002

E. Ramsay, D. T. Reid, and K. Wilsher, "Three-dimensional imaging of a silicon flip chip using the two-photon optical-beam induced current effect," Appl. Phys. Lett. 81, 7-9 (2002).
[CrossRef]

2001

S. B. Ippolito, B. B. Goldberg, and M. S. Unlü, "High spatial resolution subsurface microscopy," Appl. Phys. Lett. 78, 4071-4073 (2001).
[CrossRef]

1997

C. Xu and W. Denk, "Two-photon optical beam induced current imaging through the backside of integrated circuits," Appl. Phys. Lett. 71, 2578-2580 (1997).
[CrossRef]

1995

M. A. Green and M. Keevers, "Optical properties of intrinsic silicon at 300k," Prog. Photovoltaics 3, 189-192 (1995).
[CrossRef]

1990

S. M. Mansfield and G. S. Kino, "Solid immersion microscope," Appl. Phys. Lett. 57, 2615-2617 (1990).
[CrossRef]

Atatüre, M.

A. N. Vamivakas, M. Atatüre, S. T. Dreiser, J. Yilmaz, A. Badolato, A. K. Swan, B. B. Goldberg, A. Imamoglu, and M. S. Unlü, "Strong extinction of a far-field laser beam by a single quantum dot," Nano Lett. 7, 2892-2894 (2007).
[CrossRef] [PubMed]

Badolato, A.

A. N. Vamivakas, M. Atatüre, S. T. Dreiser, J. Yilmaz, A. Badolato, A. K. Swan, B. B. Goldberg, A. Imamoglu, and M. S. Unlü, "Strong extinction of a far-field laser beam by a single quantum dot," Nano Lett. 7, 2892-2894 (2007).
[CrossRef] [PubMed]

Denk, W.

C. Xu and W. Denk, "Two-photon optical beam induced current imaging through the backside of integrated circuits," Appl. Phys. Lett. 71, 2578-2580 (1997).
[CrossRef]

Dreiser, S. T.

A. N. Vamivakas, M. Atatüre, S. T. Dreiser, J. Yilmaz, A. Badolato, A. K. Swan, B. B. Goldberg, A. Imamoglu, and M. S. Unlü, "Strong extinction of a far-field laser beam by a single quantum dot," Nano Lett. 7, 2892-2894 (2007).
[CrossRef] [PubMed]

Eraslan, M. G.

S. B. Ippolito, S. A. Thorne, M. G. Eraslan, B. B. Goldberg, M. S. Unlü, and Y. Leblebici, "High spatial resolution subsurface thermal emission microscopy," Appl. Phys. Lett. 84, 4529-4531 (2004).
[CrossRef]

Goldberg, B. B.

A. N. Vamivakas, M. Atatüre, S. T. Dreiser, J. Yilmaz, A. Badolato, A. K. Swan, B. B. Goldberg, A. Imamoglu, and M. S. Unlü, "Strong extinction of a far-field laser beam by a single quantum dot," Nano Lett. 7, 2892-2894 (2007).
[CrossRef] [PubMed]

S. B. Ippolito, B. B. Goldberg, and M. S. Unlü, "Theoretical analysis of numerical aperture increasing lens microscopy," J. Appl. Phys. 97, 053105 (2005).
[CrossRef]

Z. Liu, B. B. Goldberg, S. B. Ippolito, A. N. Vamivakas, M. S. Unlü, and R. Mirin, "High resolution, high collection efficiency in numerical aperture increasing lens microscopy of individual quantum dots," Appl. Phys. Lett. 87, 071905 (2005).
[CrossRef]

S. B. Ippolito, S. A. Thorne, M. G. Eraslan, B. B. Goldberg, M. S. Unlü, and Y. Leblebici, "High spatial resolution subsurface thermal emission microscopy," Appl. Phys. Lett. 84, 4529-4531 (2004).
[CrossRef]

S. B. Ippolito, B. B. Goldberg, and M. S. Unlü, "High spatial resolution subsurface microscopy," Appl. Phys. Lett. 78, 4071-4073 (2001).
[CrossRef]

Green, M. A.

M. A. Green and M. Keevers, "Optical properties of intrinsic silicon at 300k," Prog. Photovoltaics 3, 189-192 (1995).
[CrossRef]

Imamoglu, A.

A. N. Vamivakas, M. Atatüre, S. T. Dreiser, J. Yilmaz, A. Badolato, A. K. Swan, B. B. Goldberg, A. Imamoglu, and M. S. Unlü, "Strong extinction of a far-field laser beam by a single quantum dot," Nano Lett. 7, 2892-2894 (2007).
[CrossRef] [PubMed]

Ippolito, S. B.

S. B. Ippolito, P. Song, D. L. Miles, and J. D. Sylvestri, "Angular spectrum tailoring in solid immersion microscopy for circuit analysis," Appl. Phys. Lett. 92, 101109 (2008).
[CrossRef]

S. B. Ippolito, B. B. Goldberg, and M. S. Unlü, "Theoretical analysis of numerical aperture increasing lens microscopy," J. Appl. Phys. 97, 053105 (2005).
[CrossRef]

Z. Liu, B. B. Goldberg, S. B. Ippolito, A. N. Vamivakas, M. S. Unlü, and R. Mirin, "High resolution, high collection efficiency in numerical aperture increasing lens microscopy of individual quantum dots," Appl. Phys. Lett. 87, 071905 (2005).
[CrossRef]

S. B. Ippolito, S. A. Thorne, M. G. Eraslan, B. B. Goldberg, M. S. Unlü, and Y. Leblebici, "High spatial resolution subsurface thermal emission microscopy," Appl. Phys. Lett. 84, 4529-4531 (2004).
[CrossRef]

S. B. Ippolito, B. B. Goldberg, and M. S. Unlü, "High spatial resolution subsurface microscopy," Appl. Phys. Lett. 78, 4071-4073 (2001).
[CrossRef]

Keevers, M.

M. A. Green and M. Keevers, "Optical properties of intrinsic silicon at 300k," Prog. Photovoltaics 3, 189-192 (1995).
[CrossRef]

Kino, G. S.

S. M. Mansfield and G. S. Kino, "Solid immersion microscope," Appl. Phys. Lett. 57, 2615-2617 (1990).
[CrossRef]

Leblebici, Y.

S. B. Ippolito, S. A. Thorne, M. G. Eraslan, B. B. Goldberg, M. S. Unlü, and Y. Leblebici, "High spatial resolution subsurface thermal emission microscopy," Appl. Phys. Lett. 84, 4529-4531 (2004).
[CrossRef]

Liu, Z.

Z. Liu, B. B. Goldberg, S. B. Ippolito, A. N. Vamivakas, M. S. Unlü, and R. Mirin, "High resolution, high collection efficiency in numerical aperture increasing lens microscopy of individual quantum dots," Appl. Phys. Lett. 87, 071905 (2005).
[CrossRef]

Mansfield, S. M.

S. M. Mansfield and G. S. Kino, "Solid immersion microscope," Appl. Phys. Lett. 57, 2615-2617 (1990).
[CrossRef]

Miles, D. L.

S. B. Ippolito, P. Song, D. L. Miles, and J. D. Sylvestri, "Angular spectrum tailoring in solid immersion microscopy for circuit analysis," Appl. Phys. Lett. 92, 101109 (2008).
[CrossRef]

Mirin, R.

Z. Liu, B. B. Goldberg, S. B. Ippolito, A. N. Vamivakas, M. S. Unlü, and R. Mirin, "High resolution, high collection efficiency in numerical aperture increasing lens microscopy of individual quantum dots," Appl. Phys. Lett. 87, 071905 (2005).
[CrossRef]

Pleynet, N.

Ramsay, E.

E. Ramsay, K. A. Serrels, M. J. Thomson, A. J. Waddie, M. R. Taghizadeh, R. J. Warburton, and D. T. Reid, "Three-dimensional nanoscale subsurface optical imaging of silicon circuits," Appl. Phys. Lett. 90, 131101 (2007).
[CrossRef]

E. Ramsay, N. Pleynet, D. Xiao, R. J. Warburton, and D. T. Reid, "Two-photon optical-beam-induced current solid-immersion imaging if a silicon flip chip with a resolution of 325 nm," Opt. Lett. 30, 26-28 (2005).
[CrossRef] [PubMed]

E. Ramsay, D. T. Reid, and K. Wilsher, "Three-dimensional imaging of a silicon flip chip using the two-photon optical-beam induced current effect," Appl. Phys. Lett. 81, 7-9 (2002).
[CrossRef]

Reid, D. T.

E. Ramsay, K. A. Serrels, M. J. Thomson, A. J. Waddie, M. R. Taghizadeh, R. J. Warburton, and D. T. Reid, "Three-dimensional nanoscale subsurface optical imaging of silicon circuits," Appl. Phys. Lett. 90, 131101 (2007).
[CrossRef]

E. Ramsay, N. Pleynet, D. Xiao, R. J. Warburton, and D. T. Reid, "Two-photon optical-beam-induced current solid-immersion imaging if a silicon flip chip with a resolution of 325 nm," Opt. Lett. 30, 26-28 (2005).
[CrossRef] [PubMed]

E. Ramsay, D. T. Reid, and K. Wilsher, "Three-dimensional imaging of a silicon flip chip using the two-photon optical-beam induced current effect," Appl. Phys. Lett. 81, 7-9 (2002).
[CrossRef]

Serrels, K. A.

E. Ramsay, K. A. Serrels, M. J. Thomson, A. J. Waddie, M. R. Taghizadeh, R. J. Warburton, and D. T. Reid, "Three-dimensional nanoscale subsurface optical imaging of silicon circuits," Appl. Phys. Lett. 90, 131101 (2007).
[CrossRef]

Song, P.

S. B. Ippolito, P. Song, D. L. Miles, and J. D. Sylvestri, "Angular spectrum tailoring in solid immersion microscopy for circuit analysis," Appl. Phys. Lett. 92, 101109 (2008).
[CrossRef]

Swan, A. K.

A. N. Vamivakas, M. Atatüre, S. T. Dreiser, J. Yilmaz, A. Badolato, A. K. Swan, B. B. Goldberg, A. Imamoglu, and M. S. Unlü, "Strong extinction of a far-field laser beam by a single quantum dot," Nano Lett. 7, 2892-2894 (2007).
[CrossRef] [PubMed]

Sylvestri, J. D.

S. B. Ippolito, P. Song, D. L. Miles, and J. D. Sylvestri, "Angular spectrum tailoring in solid immersion microscopy for circuit analysis," Appl. Phys. Lett. 92, 101109 (2008).
[CrossRef]

Taghizadeh, M. R.

E. Ramsay, K. A. Serrels, M. J. Thomson, A. J. Waddie, M. R. Taghizadeh, R. J. Warburton, and D. T. Reid, "Three-dimensional nanoscale subsurface optical imaging of silicon circuits," Appl. Phys. Lett. 90, 131101 (2007).
[CrossRef]

Thomson, M. J.

E. Ramsay, K. A. Serrels, M. J. Thomson, A. J. Waddie, M. R. Taghizadeh, R. J. Warburton, and D. T. Reid, "Three-dimensional nanoscale subsurface optical imaging of silicon circuits," Appl. Phys. Lett. 90, 131101 (2007).
[CrossRef]

Thorne, S. A.

S. B. Ippolito, S. A. Thorne, M. G. Eraslan, B. B. Goldberg, M. S. Unlü, and Y. Leblebici, "High spatial resolution subsurface thermal emission microscopy," Appl. Phys. Lett. 84, 4529-4531 (2004).
[CrossRef]

Unlü, M. S.

A. N. Vamivakas, M. Atatüre, S. T. Dreiser, J. Yilmaz, A. Badolato, A. K. Swan, B. B. Goldberg, A. Imamoglu, and M. S. Unlü, "Strong extinction of a far-field laser beam by a single quantum dot," Nano Lett. 7, 2892-2894 (2007).
[CrossRef] [PubMed]

Z. Liu, B. B. Goldberg, S. B. Ippolito, A. N. Vamivakas, M. S. Unlü, and R. Mirin, "High resolution, high collection efficiency in numerical aperture increasing lens microscopy of individual quantum dots," Appl. Phys. Lett. 87, 071905 (2005).
[CrossRef]

S. B. Ippolito, B. B. Goldberg, and M. S. Unlü, "Theoretical analysis of numerical aperture increasing lens microscopy," J. Appl. Phys. 97, 053105 (2005).
[CrossRef]

S. B. Ippolito, S. A. Thorne, M. G. Eraslan, B. B. Goldberg, M. S. Unlü, and Y. Leblebici, "High spatial resolution subsurface thermal emission microscopy," Appl. Phys. Lett. 84, 4529-4531 (2004).
[CrossRef]

S. B. Ippolito, B. B. Goldberg, and M. S. Unlü, "High spatial resolution subsurface microscopy," Appl. Phys. Lett. 78, 4071-4073 (2001).
[CrossRef]

Vamivakas, A. N.

A. N. Vamivakas, M. Atatüre, S. T. Dreiser, J. Yilmaz, A. Badolato, A. K. Swan, B. B. Goldberg, A. Imamoglu, and M. S. Unlü, "Strong extinction of a far-field laser beam by a single quantum dot," Nano Lett. 7, 2892-2894 (2007).
[CrossRef] [PubMed]

Z. Liu, B. B. Goldberg, S. B. Ippolito, A. N. Vamivakas, M. S. Unlü, and R. Mirin, "High resolution, high collection efficiency in numerical aperture increasing lens microscopy of individual quantum dots," Appl. Phys. Lett. 87, 071905 (2005).
[CrossRef]

Waddie, A. J.

E. Ramsay, K. A. Serrels, M. J. Thomson, A. J. Waddie, M. R. Taghizadeh, R. J. Warburton, and D. T. Reid, "Three-dimensional nanoscale subsurface optical imaging of silicon circuits," Appl. Phys. Lett. 90, 131101 (2007).
[CrossRef]

Warburton, R. J.

E. Ramsay, K. A. Serrels, M. J. Thomson, A. J. Waddie, M. R. Taghizadeh, R. J. Warburton, and D. T. Reid, "Three-dimensional nanoscale subsurface optical imaging of silicon circuits," Appl. Phys. Lett. 90, 131101 (2007).
[CrossRef]

E. Ramsay, N. Pleynet, D. Xiao, R. J. Warburton, and D. T. Reid, "Two-photon optical-beam-induced current solid-immersion imaging if a silicon flip chip with a resolution of 325 nm," Opt. Lett. 30, 26-28 (2005).
[CrossRef] [PubMed]

Wilsher, K.

E. Ramsay, D. T. Reid, and K. Wilsher, "Three-dimensional imaging of a silicon flip chip using the two-photon optical-beam induced current effect," Appl. Phys. Lett. 81, 7-9 (2002).
[CrossRef]

Xiao, D.

Xu, C.

C. Xu and W. Denk, "Two-photon optical beam induced current imaging through the backside of integrated circuits," Appl. Phys. Lett. 71, 2578-2580 (1997).
[CrossRef]

Yilmaz, J.

A. N. Vamivakas, M. Atatüre, S. T. Dreiser, J. Yilmaz, A. Badolato, A. K. Swan, B. B. Goldberg, A. Imamoglu, and M. S. Unlü, "Strong extinction of a far-field laser beam by a single quantum dot," Nano Lett. 7, 2892-2894 (2007).
[CrossRef] [PubMed]

Appl. Phys. Lett.

S. B. Ippolito, B. B. Goldberg, and M. S. Unlü, "High spatial resolution subsurface microscopy," Appl. Phys. Lett. 78, 4071-4073 (2001).
[CrossRef]

S. M. Mansfield and G. S. Kino, "Solid immersion microscope," Appl. Phys. Lett. 57, 2615-2617 (1990).
[CrossRef]

S. B. Ippolito, S. A. Thorne, M. G. Eraslan, B. B. Goldberg, M. S. Unlü, and Y. Leblebici, "High spatial resolution subsurface thermal emission microscopy," Appl. Phys. Lett. 84, 4529-4531 (2004).
[CrossRef]

E. Ramsay, K. A. Serrels, M. J. Thomson, A. J. Waddie, M. R. Taghizadeh, R. J. Warburton, and D. T. Reid, "Three-dimensional nanoscale subsurface optical imaging of silicon circuits," Appl. Phys. Lett. 90, 131101 (2007).
[CrossRef]

Z. Liu, B. B. Goldberg, S. B. Ippolito, A. N. Vamivakas, M. S. Unlü, and R. Mirin, "High resolution, high collection efficiency in numerical aperture increasing lens microscopy of individual quantum dots," Appl. Phys. Lett. 87, 071905 (2005).
[CrossRef]

C. Xu and W. Denk, "Two-photon optical beam induced current imaging through the backside of integrated circuits," Appl. Phys. Lett. 71, 2578-2580 (1997).
[CrossRef]

E. Ramsay, D. T. Reid, and K. Wilsher, "Three-dimensional imaging of a silicon flip chip using the two-photon optical-beam induced current effect," Appl. Phys. Lett. 81, 7-9 (2002).
[CrossRef]

S. B. Ippolito, P. Song, D. L. Miles, and J. D. Sylvestri, "Angular spectrum tailoring in solid immersion microscopy for circuit analysis," Appl. Phys. Lett. 92, 101109 (2008).
[CrossRef]

J. Appl. Phys.

S. B. Ippolito, B. B. Goldberg, and M. S. Unlü, "Theoretical analysis of numerical aperture increasing lens microscopy," J. Appl. Phys. 97, 053105 (2005).
[CrossRef]

Nano Lett.

A. N. Vamivakas, M. Atatüre, S. T. Dreiser, J. Yilmaz, A. Badolato, A. K. Swan, B. B. Goldberg, A. Imamoglu, and M. S. Unlü, "Strong extinction of a far-field laser beam by a single quantum dot," Nano Lett. 7, 2892-2894 (2007).
[CrossRef] [PubMed]

Opt. Lett.

Prog. Photovoltaics

M. A. Green and M. Keevers, "Optical properties of intrinsic silicon at 300k," Prog. Photovoltaics 3, 189-192 (1995).
[CrossRef]

Other

T. Wilson and C. Sheppard, Theory and Practice of Scanning Optical Microscopy (Academic Press, 1984) p. 28.

International Technology Roadmap for Semiconductors Update, 2006.

J. B. Pawley, Handbook of Biological Confocal Microscopy, 3rd ed., (Springer Press, 2006), p. 209.

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Figures (5)

Fig. 1.
Fig. 1.

(Color online) Experimental setup. A sliding mirror provides switching between confocal and widefield microscopes. When the sliding mirror is out, in confocal imaging, illumination and detection is done through the same fiber using a 2×2 optical coupler. When the sliding mirror is in, the sample is illuminated with an LED array and the image is captured using an InGaAs camera.

Fig. 2.
Fig. 2.

(Color online) (a) Drawing of the test structure. The sample has 6 test structures scaled with δ=0.35, 0.6, 0.9, 1.2, 1.5 and 2µm. (b) Front side image of the sample with a commercial visible wavelength optical microscope. (c) Backside image of the sample with the NIR (λ 0=1.2µm) widefield microscope without a NAIL. (d) The magnified frontside images of the test structures with δ=0.9µm (upper) and δ=0.35µm (lower) taken with the visible microscope. (e) The magnified backside images of the test structures with δ=0.9µm (upper) and δ=0.35µm (lower) taken with the NIR microscope without a NAIL. (f) Backside image of the test structures with δ=0.9 and 0.35 µm, respectively, using the NIR widefield microscope and a NAIL with an optimum substrate thickness of 458µm. Notice the upper layers in (b) and (c).

Fig. 3.
Fig. 3.

(a) Data and fit to error function with the line spread function is shown using the widefield microscope for an optimum substrate thickness of 458µm. (b) Same as (a) but with a confocal microscope. (c) Same as (a) but with a non-optimum substrate thickness of 492µm. (d) Same as (c) but with a confocal microscope. All x-axes are normalized to the corresponding wavelengths; λ 0=1.2µm for widefield and λ 0=1.3µm for confocal microscopy.

Fig. 4.
Fig. 4.

(Color online) (a) Frontside image of the test structure with δ=1.5µm taken with the visible wavelength microscope shows all the layers together. (b) Isolated image of the same test structure is easily seen when focused at the poly1 layer. (c) The same area now focused at the metal3 layer. (d) The same area when focused at the metal4 layer. In (b) metal3 and metal4 layers are not seen and in (c) and (d) poly1 layer disappears. However, metal3 and metal4 layers cannot be imaged separately. According to the manufacturer, typical separation between poly1 and metal3 is 2.65µm whereas the separation between metal3 and metal4 is 1µm. In the illustrations, layer and interlayer thicknesses are in scale, but substrate and NAIL thickness and the refraction angles are not.

Fig. 5.
Fig. 5.

Longitudinal linecut taken (a) with the confocal microscope and (b) with the widefield microscope.

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