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Proceedings Paper

A 3D substrate and buried defect simulator for EUV mask blanks
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Paper Abstract

A new ray-tracing method for assessing buried defect printability in EUVL is thoroughly tested for accuracy and speed. The new ray-tracing approach is shown to produce results in excellent agreement with rigorous electromagnetic simulator results using the FDTD method. The new simulator can be as much as 30,000X faster, and use 40-50X less memory than FDTD. While the ray-tracing approach is very accurate, the Single Surface Approximation (SSA) is shown to underestimate defect printability across various focal regions for many defect sizes. An analysis of the reflected spectra shows that the bottom layers of the multilayer do impact the final reflected spectrum, and shows that it is necessary to use information from all layers to accurately compute the final reflected fields. Defect tolerances are calculated with the new simulator for 2D and 3D buried defects coated with the smoothing process developed at LLNL, establishing guidelines for defect printability in the clear field. Buried 3D defects are shown to be sub-printable in the clear field when their size is smaller than about 70nms, but due to the phase nature of the defects, this size tolerance is dramatically reduced to about 40nms at -1RU defocus. Both size and shape of the buried defect are varied to understand their impact on defect printability. It is shown that Gaussian defects actually print worse than box defects due to an entrenchment effect that occurs during the smoothing process.

Paper Details

Date Published: 6 May 2005
PDF: 11 pages
Proc. SPIE 5751, Emerging Lithographic Technologies IX, (6 May 2005); doi: 10.1117/12.599042
Show Author Affiliations
Michael C. Lam, Univ. of California/Berkeley (United States)
Andrew R. Neureuther, Univ. of California/Berkeley (United States)

Published in SPIE Proceedings Vol. 5751:
Emerging Lithographic Technologies IX
R. Scott Mackay, Editor(s)

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