Scanning-electron-microscope image processing for accurate analysis of line-edge and line-width roughness

Atsushi Hiraiwa, Akio Nishida

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

Abstract

The control of line-edge or line-width roughness (LER/LWR) is a challenge especially for future devices that are fabricated using extreme-ultraviolet lithography. Accurate analysis of the LER/LWR plays an essential role in this challenge and requires the noise involved in scanning-electron-microscope (SEM) images to be reduced by appropriate image processing prior to analyses. In order to achieve this, the authors simulated SEM images using the Monte-Carlo method and detected line edges in experimental and these theoretical images after noise filtering using new image-analysis software. The validity of these simulation and software was confirmed by a good agreement between the experimental and theoretical results. In the case when the image pixels aligned perpendicular (crosswise) to line edges were averaged, the variance var(φ) that was additionally induced by the image noise decreased with the number N PIX,X of averaged pixels but turned to increase for relatively large N PIX,X's. Real LER/LWR, however, remained unaffected. On the other hand, averaging image pixels aligned parallel (longitudinal) to line edges not only reduced var(φ) but smoothed the real LER/LWR. As a result, the nominal variance of real LWR, obtained using simple arithmetic, monotonically decreased with the number N PIX, L of averaged pixels. Artifactual oscillations were additionally observed in power spectral densities. var(φ) in this case decreased in an inverse proportion to the square root of N PIX,L according to the statistical mechanism clarified here. In this way, image processing has a marked effect on the LER/LWR analysis and needs to be much more cared and appropriately applied. All the aforementioned results not only constitute a solid basis of but improve previous empirical instructions for accurate analyses. The most important instruction is to avoid the longitudinal averaging and to crosswise average an optimized number of image pixels consulting the equation derived in this study.

Original languageEnglish
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
Volume8324
DOIs
Publication statusPublished - 2012
EventMetrology, Inspection, and Process Control for Microlithography XXVI - San Jose, CA
Duration: 2012 Feb 132012 Feb 16

Other

OtherMetrology, Inspection, and Process Control for Microlithography XXVI
CitySan Jose, CA
Period12/2/1312/2/16

Fingerprint

Scanning Electron Microscope
Linewidth
Roughness
image processing
Image Processing
Image processing
Electron microscopes
roughness
plasma interaction experiment
electron microscopes
Surface roughness
Pixels
Scanning
Pixel
scanning
Line
pixels
Base of a solid
Real Line
Averaging

Keywords

  • Filtering
  • LER
  • Line edge roughness
  • Line width roughness
  • LWR
  • Noise
  • Power spectral density
  • PSD
  • Scanning electron microscope
  • SEM
  • Standard deviation
  • Variance

ASJC Scopus subject areas

  • Applied Mathematics
  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Hiraiwa, A., & Nishida, A. (2012). Scanning-electron-microscope image processing for accurate analysis of line-edge and line-width roughness. In Proceedings of SPIE - The International Society for Optical Engineering (Vol. 8324). [83241D] https://doi.org/10.1117/12.914230

Scanning-electron-microscope image processing for accurate analysis of line-edge and line-width roughness. / Hiraiwa, Atsushi; Nishida, Akio.

Proceedings of SPIE - The International Society for Optical Engineering. Vol. 8324 2012. 83241D.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Hiraiwa, A & Nishida, A 2012, Scanning-electron-microscope image processing for accurate analysis of line-edge and line-width roughness. in Proceedings of SPIE - The International Society for Optical Engineering. vol. 8324, 83241D, Metrology, Inspection, and Process Control for Microlithography XXVI, San Jose, CA, 12/2/13. https://doi.org/10.1117/12.914230
Hiraiwa A, Nishida A. Scanning-electron-microscope image processing for accurate analysis of line-edge and line-width roughness. In Proceedings of SPIE - The International Society for Optical Engineering. Vol. 8324. 2012. 83241D https://doi.org/10.1117/12.914230
Hiraiwa, Atsushi ; Nishida, Akio. / Scanning-electron-microscope image processing for accurate analysis of line-edge and line-width roughness. Proceedings of SPIE - The International Society for Optical Engineering. Vol. 8324 2012.
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abstract = "The control of line-edge or line-width roughness (LER/LWR) is a challenge especially for future devices that are fabricated using extreme-ultraviolet lithography. Accurate analysis of the LER/LWR plays an essential role in this challenge and requires the noise involved in scanning-electron-microscope (SEM) images to be reduced by appropriate image processing prior to analyses. In order to achieve this, the authors simulated SEM images using the Monte-Carlo method and detected line edges in experimental and these theoretical images after noise filtering using new image-analysis software. The validity of these simulation and software was confirmed by a good agreement between the experimental and theoretical results. In the case when the image pixels aligned perpendicular (crosswise) to line edges were averaged, the variance var(φ) that was additionally induced by the image noise decreased with the number N PIX,X of averaged pixels but turned to increase for relatively large N PIX,X's. Real LER/LWR, however, remained unaffected. On the other hand, averaging image pixels aligned parallel (longitudinal) to line edges not only reduced var(φ) but smoothed the real LER/LWR. As a result, the nominal variance of real LWR, obtained using simple arithmetic, monotonically decreased with the number N PIX, L of averaged pixels. Artifactual oscillations were additionally observed in power spectral densities. var(φ) in this case decreased in an inverse proportion to the square root of N PIX,L according to the statistical mechanism clarified here. In this way, image processing has a marked effect on the LER/LWR analysis and needs to be much more cared and appropriately applied. All the aforementioned results not only constitute a solid basis of but improve previous empirical instructions for accurate analyses. The most important instruction is to avoid the longitudinal averaging and to crosswise average an optimized number of image pixels consulting the equation derived in this study.",
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