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6 May 2005 A 3D substrate and buried defect simulator for EUV mask blanks
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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.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Michael C. Lam and Andrew R. Neureuther "A 3D substrate and buried defect simulator for EUV mask blanks", Proc. SPIE 5751, Emerging Lithographic Technologies IX, (6 May 2005);

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