OSA's Digital Library

Optics Express

Optics Express

  • Editor: Michael Duncan
  • Vol. 13, Iss. 18 — Sep. 5, 2005
  • pp: 6699–6708

Through-focus technique for nano-scale grating pitch and linewidth analysis

Yi-Sha Ku, An-Shun Liu, and Nigel Smith  »View Author Affiliations

Optics Express, Vol. 13, Issue 18, pp. 6699-6708 (2005)

View Full Text Article

Acrobat PDF (485 KB)

Browse Journals / Lookup Meetings

Browse by Journal and Year


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools



We report results of experimental investigations into a through-focus method relevant to sub-wavelength feature dimension measurement. The method linearizes the partial derivative values of a focus indicator with respect to minimum intensity order, and hence permits determination of pitch using a classical linear method. By evaluating the variations in focus indicator of the different captured images obtained at various focal positions, the through-focus curves show a response to sub-resolution changes in the grating structure. The results suggest that sub-wavelength feature dimensions can be evaluated using regular optical microscopes by implementing the through focus method.

© 2005 Optical Society of America

OCIS Codes
(050.1950) Diffraction and gratings : Diffraction gratings
(120.3940) Instrumentation, measurement, and metrology : Metrology

ToC Category:
Research Papers

Original Manuscript: July 1, 2005
Revised Manuscript: August 10, 2005
Published: September 5, 2005

Yi-Sha Ku, An-Shun Liu, and Nigel Smith, "Through-focus technique for nano-scale grating pitch and linewidth analysis," Opt. Express 13, 6699-6708 (2005)

Sort:  Journal  |  Reset


  1. S. Fox, R. M. Silver, E. Kornegay and M. Dagenais., �??Focus and Edge Detection Algorithm and their Relevance to the Development of an Optical Overlay Calibration Standard,�?? Proc. SPIE 3677, 95-106 (1999).
  2. R. Attota, R. M. Silver, M. Stocker, E. Marx, J. Jun, M. Davidson and R. Larrabee., �??A New Method to Enhance Overlay Tool Performance,�?? Proc. SPIE 5038, 428-436 (2003).
  3. R. M. Silver, R. Attota, M. Stocker, M. Bishop, J. Jun, E. Marx, M. Davison and R. Larrabee, �??High-resolution Optical Overlay Metrology,�?? Proc. SPIE 5375, 78-95 (2004).
  4. Murali Subbarao, Tae Choi, and Arman Nikzad, �??Focusing Techniques,�?? Proc. SPIE Optical Engineering, 32, 2824-2836 (1994).
  5. Je-Ho Lee, et al., �??Implementation of a Passive Automatic Focusing Algorithm for Digital Still Camera,�?? IEEE Transactions on Consumer Electronics, 41, 449-454 (1995).
  6. Minori Noguchi and Shree K. Nayar, �??Microscopic Shape from Focus Using Active Illumination,�?? in Proceedings of the International Conference on Pattern Recognition, 147-152 (1994).
  7. Helmy A. Eltoukhy and Sam Kavusi, �??A Computationally Efficient Algorithm for Multi-Focus Image Reconstruction,�?? Proc. SPIE Int. Soc. Opt. Eng. 5017, 332-341 (2003).
  8. Murali Subbarao and Jenn-Kwei Tyan, �??Selecting the Optimal Focus Measure for Autofocusing and Depth-From-Focus�?? IEEE Transaction on Pattern Analysis and Machine Intelligence, 20, 864-869 (1998).
  9. R.M. Sliver, J. Jun, S. Fox, E. Kornegay, �??Overlay Metrology: Recent Advances and Future Solutions,�?? Future Fab Intl., 11, 2001.
  10. Bravo-Zanoguera, Miguel, et al., �??High-performance autofocus circuit for biological microscopy,�?? Rev. Sci. Instrum. 69, 3966-3977(1998). [CrossRef]
  11. Berizzi, Fabrizio, and Corsini, Giovanni, �??Autofocusing of Inverse Synthetic Aperture Radar Images Using Contrast Optimization�?? IEEE Trans. Aerosp. Electron. Syst, 32, 118-1191 (1996).
  12. Krotkov, Eric, �??Focusing?�?? International J. Computer Vision 1, 223-237 (1987).
  13. R. M. Silver, R. Attota, M. Stocker, M. Bishop, J. Jun, E. Marx, M. Davison and R. Larrabee, �??High-resolution Optical Metrology,�?? Proc. SPIE 5752, 67-79 (2005).
  14. R. Attota, R. M. Silver, T. A. Germer and M. Bishop, �??Application of Through-focus Focus-metric Analysis in High Resolution Optical Metrology,�?? Proc. SPIE 5752, 1441-1449(2005).

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited