Abstract

We present a new method for in situ monitoring of a grating profile during the development process to control the critical dimensions of surface-relief rectangular photoresist gratings on transparent substrates. A He–Ne laser of visible wavelength is employed as the monitoring light source. We determine the height of the grating ridges from the first minimum value of the diffraction intensity curve of the zeroth transmission order and then obtain the duty cycle of the grating from the diffraction intensity of the 1st transmission order. The effectiveness of our method has been demonstrated through the fabrication of rectangular photoresist gratings of 1200, 2200, and 3000  lines/mm on glass substrates. The experimental results are statistically compared with results extracted from scanning electron micrographs. Good agreement between the online, real-time measured results and the scanning electron microscopy results is obtained.

© 2010 Optical Society of America

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  1. H. Lin and L. Li, “Fabrication of extreme-ultraviolet blazed gratings by use of direct argon-oxygen ion-beam etching through a rectangular photoresist mask,” Appl. Opt. 47, 6212-6218 (2008).
    [CrossRef]
  2. L. Li, M. Xu, G. I. Stegeman, and C. T. Seaton, “Fabrication of photoresist masks for submicrometer surface relief gratings,” Proc. SPIE 835, 72-82 (1987).
  3. Y. Nakano and K. Tada, “In situ monitoring technique for fabrication of high-quality diffraction gratings,” Opt. Lett. 13, 7-9 (1988).
    [CrossRef]
  4. J. A. Britten, R. D. Boyd, and B. W. Shore, “In situ end-point detection during development of submicrometer grating structures in photoresist,” Opt. Eng. 34, 474-479 (1995).
  5. P. Chapados and A. Paranjpe, “In situ monitoring of sub-micron polysilicon linewidths using diffraction gratings,” Proc. SPIE 1803, 283-289 (1992).
  6. P. Chapados, “Diffraction image processing algorithms for in-situ monitoring of sub-micron polysilicon linewidths,” Proc. SPIE 1907, 250-257 (1993).
  7. M. Neviere and E. Popov, Light Propagation in Periodic Media: Differential Theory and Design (Marcel Dekker, 2003).
  8. J. Zhao, L. Li, and Z. Wu, “Method for controlling groove depth and duty cycle of rectangular photoresist gratings,” Acta Opt. Sin. 24, 1285-1291 (2004), in Chinese.
  9. L. Li and L. Zeng, “Measurement of duty cycles of photoresist grating masks made on top of multilayer dielectric stacks,” Appl. Opt. 44, 4494-4500 (2005).
    [CrossRef]
  10. J. R. Marciante, N. O. Farmiga, J. I. Hirsh, M. S. Evans, and H. T. Ta, “Optical measurement of depth and duty cycle for binary diffraction gratings with subwavelength features,” Appl. Opt. 42, 3234-3240 (2003).
    [CrossRef]
  11. H. Huang and F. L. Terry, “Spectroscopic ellipsometry and reflectometry from gratings (scatterometry) for critical dimension measurement and in situ, real-time process monitoring,” Thin Solid Films 455, 828-836 (2004).
    [CrossRef]
  12. J. Zhao, L. Li, and Z. Wu, “Modeling of in-situ monitoring curves during development of holographic gratings,” Acta Opt. Sin. 24, 1146-1150 (2004), in Chinese.
  13. S. Wei and L. Li, “Measurement of photoresist grating profiles based on multiwavelength scatterometry and artificial neural network,” Appl. Opt. 47, 2524-2532 (2008).
    [CrossRef]

2008

2005

2004

J. Zhao, L. Li, and Z. Wu, “Method for controlling groove depth and duty cycle of rectangular photoresist gratings,” Acta Opt. Sin. 24, 1285-1291 (2004), in Chinese.

H. Huang and F. L. Terry, “Spectroscopic ellipsometry and reflectometry from gratings (scatterometry) for critical dimension measurement and in situ, real-time process monitoring,” Thin Solid Films 455, 828-836 (2004).
[CrossRef]

J. Zhao, L. Li, and Z. Wu, “Modeling of in-situ monitoring curves during development of holographic gratings,” Acta Opt. Sin. 24, 1146-1150 (2004), in Chinese.

2003

1995

J. A. Britten, R. D. Boyd, and B. W. Shore, “In situ end-point detection during development of submicrometer grating structures in photoresist,” Opt. Eng. 34, 474-479 (1995).

1993

P. Chapados, “Diffraction image processing algorithms for in-situ monitoring of sub-micron polysilicon linewidths,” Proc. SPIE 1907, 250-257 (1993).

1992

P. Chapados and A. Paranjpe, “In situ monitoring of sub-micron polysilicon linewidths using diffraction gratings,” Proc. SPIE 1803, 283-289 (1992).

1988

1987

L. Li, M. Xu, G. I. Stegeman, and C. T. Seaton, “Fabrication of photoresist masks for submicrometer surface relief gratings,” Proc. SPIE 835, 72-82 (1987).

Boyd, R. D.

J. A. Britten, R. D. Boyd, and B. W. Shore, “In situ end-point detection during development of submicrometer grating structures in photoresist,” Opt. Eng. 34, 474-479 (1995).

Britten, J. A.

J. A. Britten, R. D. Boyd, and B. W. Shore, “In situ end-point detection during development of submicrometer grating structures in photoresist,” Opt. Eng. 34, 474-479 (1995).

Chapados, P.

P. Chapados, “Diffraction image processing algorithms for in-situ monitoring of sub-micron polysilicon linewidths,” Proc. SPIE 1907, 250-257 (1993).

P. Chapados and A. Paranjpe, “In situ monitoring of sub-micron polysilicon linewidths using diffraction gratings,” Proc. SPIE 1803, 283-289 (1992).

Evans, M. S.

Farmiga, N. O.

Hirsh, J. I.

Huang, H.

H. Huang and F. L. Terry, “Spectroscopic ellipsometry and reflectometry from gratings (scatterometry) for critical dimension measurement and in situ, real-time process monitoring,” Thin Solid Films 455, 828-836 (2004).
[CrossRef]

Li, L.

S. Wei and L. Li, “Measurement of photoresist grating profiles based on multiwavelength scatterometry and artificial neural network,” Appl. Opt. 47, 2524-2532 (2008).
[CrossRef]

H. Lin and L. Li, “Fabrication of extreme-ultraviolet blazed gratings by use of direct argon-oxygen ion-beam etching through a rectangular photoresist mask,” Appl. Opt. 47, 6212-6218 (2008).
[CrossRef]

L. Li and L. Zeng, “Measurement of duty cycles of photoresist grating masks made on top of multilayer dielectric stacks,” Appl. Opt. 44, 4494-4500 (2005).
[CrossRef]

J. Zhao, L. Li, and Z. Wu, “Method for controlling groove depth and duty cycle of rectangular photoresist gratings,” Acta Opt. Sin. 24, 1285-1291 (2004), in Chinese.

J. Zhao, L. Li, and Z. Wu, “Modeling of in-situ monitoring curves during development of holographic gratings,” Acta Opt. Sin. 24, 1146-1150 (2004), in Chinese.

L. Li, M. Xu, G. I. Stegeman, and C. T. Seaton, “Fabrication of photoresist masks for submicrometer surface relief gratings,” Proc. SPIE 835, 72-82 (1987).

Lin, H.

Marciante, J. R.

Nakano, Y.

Neviere, M.

M. Neviere and E. Popov, Light Propagation in Periodic Media: Differential Theory and Design (Marcel Dekker, 2003).

Paranjpe, A.

P. Chapados and A. Paranjpe, “In situ monitoring of sub-micron polysilicon linewidths using diffraction gratings,” Proc. SPIE 1803, 283-289 (1992).

Popov, E.

M. Neviere and E. Popov, Light Propagation in Periodic Media: Differential Theory and Design (Marcel Dekker, 2003).

Seaton, C. T.

L. Li, M. Xu, G. I. Stegeman, and C. T. Seaton, “Fabrication of photoresist masks for submicrometer surface relief gratings,” Proc. SPIE 835, 72-82 (1987).

Shore, B. W.

J. A. Britten, R. D. Boyd, and B. W. Shore, “In situ end-point detection during development of submicrometer grating structures in photoresist,” Opt. Eng. 34, 474-479 (1995).

Stegeman, G. I.

L. Li, M. Xu, G. I. Stegeman, and C. T. Seaton, “Fabrication of photoresist masks for submicrometer surface relief gratings,” Proc. SPIE 835, 72-82 (1987).

Ta, H. T.

Tada, K.

Terry, F. L.

H. Huang and F. L. Terry, “Spectroscopic ellipsometry and reflectometry from gratings (scatterometry) for critical dimension measurement and in situ, real-time process monitoring,” Thin Solid Films 455, 828-836 (2004).
[CrossRef]

Wei, S.

Wu, Z.

J. Zhao, L. Li, and Z. Wu, “Method for controlling groove depth and duty cycle of rectangular photoresist gratings,” Acta Opt. Sin. 24, 1285-1291 (2004), in Chinese.

J. Zhao, L. Li, and Z. Wu, “Modeling of in-situ monitoring curves during development of holographic gratings,” Acta Opt. Sin. 24, 1146-1150 (2004), in Chinese.

Xu, M.

L. Li, M. Xu, G. I. Stegeman, and C. T. Seaton, “Fabrication of photoresist masks for submicrometer surface relief gratings,” Proc. SPIE 835, 72-82 (1987).

Zeng, L.

Zhao, J.

J. Zhao, L. Li, and Z. Wu, “Method for controlling groove depth and duty cycle of rectangular photoresist gratings,” Acta Opt. Sin. 24, 1285-1291 (2004), in Chinese.

J. Zhao, L. Li, and Z. Wu, “Modeling of in-situ monitoring curves during development of holographic gratings,” Acta Opt. Sin. 24, 1146-1150 (2004), in Chinese.

Acta Opt. Sin.

J. Zhao, L. Li, and Z. Wu, “Method for controlling groove depth and duty cycle of rectangular photoresist gratings,” Acta Opt. Sin. 24, 1285-1291 (2004), in Chinese.

J. Zhao, L. Li, and Z. Wu, “Modeling of in-situ monitoring curves during development of holographic gratings,” Acta Opt. Sin. 24, 1146-1150 (2004), in Chinese.

Appl. Opt.

Opt. Eng.

J. A. Britten, R. D. Boyd, and B. W. Shore, “In situ end-point detection during development of submicrometer grating structures in photoresist,” Opt. Eng. 34, 474-479 (1995).

Opt. Lett.

Proc. SPIE

L. Li, M. Xu, G. I. Stegeman, and C. T. Seaton, “Fabrication of photoresist masks for submicrometer surface relief gratings,” Proc. SPIE 835, 72-82 (1987).

P. Chapados and A. Paranjpe, “In situ monitoring of sub-micron polysilicon linewidths using diffraction gratings,” Proc. SPIE 1803, 283-289 (1992).

P. Chapados, “Diffraction image processing algorithms for in-situ monitoring of sub-micron polysilicon linewidths,” Proc. SPIE 1907, 250-257 (1993).

Thin Solid Films

H. Huang and F. L. Terry, “Spectroscopic ellipsometry and reflectometry from gratings (scatterometry) for critical dimension measurement and in situ, real-time process monitoring,” Thin Solid Films 455, 828-836 (2004).
[CrossRef]

Other

M. Neviere and E. Popov, Light Propagation in Periodic Media: Differential Theory and Design (Marcel Dekker, 2003).

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Figures (10)

Fig. 1
Fig. 1

SEM image of the typical rectangular photoresist grating mask profiled in this study.

Fig. 2
Fig. 2

Trajectory of geometric parameters of the photoresist gratings shown as the bold W X Y Z curve in three-dimensional (H, T, DC) space during the development process: H, the height of the grating ridges; T, the thickness of the undeveloped photoresist; DC, the duty cycle of the grating profile; h, the thickness of the photoresist layer. The right view is the 1 st-order transmission diffraction efficiency curve versus H.

Fig. 3
Fig. 3

Transmission 1 st-order diffraction efficiency versus height of grating ridges and DC of a 1200   lines / mm rectangular photoresist grating on a glass substrate during monitoring. The detailed parameters are given in Subsection 2B. Note that there is no photoresist in the grating troughs, i.e., T = 0 . The white line represents the trajectory of the maximum value of the 1 st-order diffraction efficiency as a function of DC.

Fig. 4
Fig. 4

Schematic illustration of the experimental setup.

Fig. 5
Fig. 5

Typical in situ monitoring curves of our method.

Fig. 6
Fig. 6

Data measured from SEM pictures and data obtained with our method for the 1200   lines / mm grating. The two data points in each data pair are connected by a vertical line to aid reading.

Fig. 7
Fig. 7

Same as Fig. 6 but for the 2200   lines / mm grating.

Fig. 8
Fig. 8

Same as Fig. 6 but for the 3000   lines / mm grating.

Fig. 9
Fig. 9

Minimum of the 0th-order transmission diffraction efficiency with respect to DC versus height of the grating ridges of a 1200   lines / mm rectangular photoresist grating on a glass substrate during monitoring. The solid curve represents the theoretical values; the efficiency values of the dashed curves are 2% corrected relative to those of the solid curve.

Fig. 10
Fig. 10

Same as Fig. 3 except the grating line density is 1740   lines / mm and the substrate is chromium.

Equations (3)

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eff t 0 = V 0 m V 0 b V 0 i V 0 b 1 η a s ,
eff t 1 = V 1 e V 1 b V 1 m V 1 b V 1 m ( cal ) ,
Δ h d h d ε Δ ε ,

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