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Proceedings Paper

Fundamental limits of optical critical dimension metrology: a simulation study
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Paper Abstract

This paper is a comprehensive summary and analysis of a SEMATECH funded project to study the limits of optical critical dimension scatterometry (OCD). The project was focused on two primary elements: 1) the comparison, stability, and validity of industry models and 2) a comprehensive analysis of process stacks to evaluate the ultimate sensitivity and limits of OCD. Modeling methods are a requirement for the interpretation and quantitative analysis of scatterometry data. The four models evaluated show good agreement over a range of targets and geometries for zero order specular reflection as well as higher order diffraction. A number of process stacks and geometries representing semiconductor manufacturing nodes from the 45 nm node to the 18 nm node were simulated using several measurement modalities including angle-resolved scatterometry and spectrally-resolved scatterometry, measuring various combinations of intensity and polarization. It is apparent in the results that large differences are observed between those methods that rely upon unpolarized and single polarization measurements. Using the three parameter fits and assuming that the sensitivity of scatterometry must meet the criterion that the 3σ uncertainty in the bottom dimension must be less than 2% of the linewidth, specular scatterometry solutions exist for all but the isolated lines at 18 nm node. Scatterometry does not have sufficient sensitivity for isolated and semi-isolated lines at the 18 nm node unless the measurement uses wavelengths as short as 200 nm or 150 nm and scans over large angle ranges.

Paper Details

Date Published: 5 April 2007
PDF: 17 pages
Proc. SPIE 6518, Metrology, Inspection, and Process Control for Microlithography XXI, 65180U (5 April 2007); doi: 10.1117/12.716604
Show Author Affiliations
Richard Silver, National Institute of Standards and Technology (United States)
Thomas Germer, National Institute of Standards and Technology (United States)
Ravikiran Attota, National Institute of Standards and Technology (United States)
Bryan M. Barnes, National Institute of Standards and Technology (United States)
Benjamin Bunday, International Sematech Manufacturing Initiative (United States)
John Allgair, International Sematech Manufacturing Initiative (United States)
Egon Marx, National Institute of Standards and Technology (United States)
Jay Jun, National Institute of Standards and Technology (United States)


Published in SPIE Proceedings Vol. 6518:
Metrology, Inspection, and Process Control for Microlithography XXI
Chas N. Archie, Editor(s)

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