OSA's Digital Library

Applied Optics

Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

  • Editor: James C. Wyant
  • Vol. 47, Iss. 4 — Feb. 1, 2008
  • pp: 495–503

Linewidth measurement technique using through-focus optical images

Ravikiran Attota, Richard Silver, and Ronald Dixson  »View Author Affiliations


Applied Optics, Vol. 47, Issue 4, pp. 495-503 (2008)
http://dx.doi.org/10.1364/AO.47.000495


View Full Text Article

Enhanced HTML    Acrobat PDF (2040 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

We present a detailed experimental study of a new through-focus technique to measure critical dimension linewidth with nanometer sensitivity using a bright field optical microscope. This method relies on analyzing intensity gradients in optical images at different focus positions, here defined as the focus metric (FM) signature. The contrast of an optical image of a structured target, where a particular structure is repeated several times, varies greatly as it is moved through-focus if the spacing between the structures is such that the scattered field from the features interferes. Complex, distinguishable through-focus optical response occurs under this condition giving rise to the formation of several cyclic high and low contrast images. As a result it exhibits several FM signature peaks as opposed to a single FM peak for structures nearly isolated. This complex optical behavior is very sensitive to the dimensions of the target geometry. By appropriately analyzing the through-focus optical image, information can be obtained regarding the target. An array of lines is used as a structured target. Linewidth measurements were made by using experimental through-focus optical data obtained using a bright field microscope and simulated optical data. The optical results are compared with reference metrology tools such as a critical dimension atomic force microscope and critical dimension scanning electron microscope.

© 2008 Optical Society of America

OCIS Codes
(110.6760) Imaging systems : Talbot and self-imaging effects
(120.3940) Instrumentation, measurement, and metrology : Metrology
(180.6900) Microscopy : Three-dimensional microscopy
(290.3700) Scattering : Linewidth
(350.2770) Other areas of optics : Gratings

ToC Category:
Instrumentation, Measurement, and Metrology

History
Original Manuscript: July 2, 2007
Revised Manuscript: December 10, 2007
Manuscript Accepted: December 11, 2007
Published: January 23, 2008

Citation
Ravikiran Attota, Richard Silver, and Ronald Dixson, "Linewidth measurement technique using through-focus optical images," Appl. Opt. 47, 495-503 (2008)
http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-47-4-495


Sort:  Year  |  Journal  |  Reset  

References

  1. C. J. Raymond, S. S. H. Naqvi, and J. R. McNeil, "Scatterometry for CD measurements of etched structures," Proc. SPIE 2725, 720-728 (1996).
  2. R. Attota, R. M. Silver, M. Bishop, E. Marx, J. Jun, M. Stocker, M. Davidson, and R. Larrabee, "Evaluation of new in-chip and arrayed line overlay target designs," Proc. SPIE 5375, 395-402 (2004).
  3. Y.-S. Ku, A.-S. Liu, and N. Smith, "Through-focus technique for nano-scale grating pitch and linewidth analysis," Opt. Express 13, 6699-6708 (2005). [PubMed]
  4. A.-S. Liu, Y.-S. Ku, and N. Smith, "Through-focus algorithm to improve overlay tool performance," Proc. SPIE 5908, 383-391 (2005).
  5. Y.-S. Ku, A.-S. Liu, and N. Smith, "Through-focus technique for grating linewidth analysis with nanometer sensitivity," Opt. Eng. 45, 123602 (2006).
  6. E. Krotkov, "Focusing," Int. J. Comput. Vis. 1, 223-237 (1987).
  7. S. Fox, R. M. Silver, E. Kornegay, and M. Dagenais, "Focus and edge detection algorithms and their relevance to the development of an optical overlay calibration standard," Proc. SPIE 3677, 95-106 (1999).
  8. R. M. Silver, R. Attota, M. Stocker, M. Bishop, J. Jun, E. Marx, M. Davidson, and R. Larrabee, "High resolution optical overlay metrology," Proc. SPIE 5375, 78-95 (2004).
  9. R. Attota, R. M. Silver, and J. Potzick, "Optical illumination and critical dimension analysis using the through-focus focus metric," Proc. SPIE 6289, 62890Q (2006).
  10. H. F. Talbot, "Facts relating to optical science, No. IV," Philos. Mag. 9, 401-407 (1836).
  11. P. Latimer and R. F. Crouse, "Talbot effect reinterpreted," Appl. Opt. 31, 80-89 (1992). [PubMed]
  12. P. Latimer, "Talbot plane patterns: grating images or interference effects?," Appl. Opt. 32, 1078-1083 (1993). [PubMed]
  13. M. Davidson, "Analytic waveguide solutions and the coherence probe microscope," Microelectron. Eng. 13, 523-526 (1991).
  14. E. Marx, "Images of strips on and trenches in substrates," Appl. Opt. 46, 5571-5587 (2007). [PubMed]
  15. T. A. Germer and E. Marx, "Simulations of optical microscope images," Proc. SPIE 6152, 61520I (2006).
  16. T. V. Pistor, "Electromagnetic simulation and modeling with applications in lithography," Ph.D. dissertation (University of California at Berkeley, 2001).
  17. R. Attota, R. M. Silver, T. A. Germer, M. Bishop, R. Larrabee, M. T. Stocker, and L. Howard, "Application of through-focus focus-metric analysis in high resolution optical metrology," Proc. SPIE 5752, 1441-1449 (2005).
  18. R. M. Silver, B. M. Barnes, R. Attota, J. Jun, J. Filliben, J. Soto, M. Stocker, P. Lipscomb, E. Marx, H. J. Patrick, R. Dixson, and R. Larrabee, "The limits of image-based optical metrology," Proc. SPIE 6152, 61520Z (2006).
  19. R. G. Dixson, R. A. Allen, W. F. Guthrie, and M. W. Cresswell, "Traceable calibration of critical-dimension atomic force microscope linewidth measurements with nanometer uncertainty," J. Vac. Sci. Technol. B 23, 3028-3032 (2005).
  20. N. Orji, A. Martinez, R. Dixson, and J. Allgair, "Progress on implementation of a CD-AFM based reference measurement system," Proc. SPIE 6152, 61520O (2006).
  21. N. G. Orji and R. G. Dixson, "Higher order tip effects in traceable CD-AFM based linewidth measurements," Meas. Sci. and Technol. 18, 448-455 (2007).

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