Actinic inspection of multilayer defects on EUV masks

Anton Barty; Yanwei Liu; Eric Gullikson; John S. Taylor; Obert Wood

doi:10.1117/12.598488

6 May 2005 Actinic inspection of multilayer defects on EUV masks

Anton Barty, Yanwei Liu, Eric Gullikson, John S. Taylor, Obert Wood

Proceedings Volume 5751, Emerging Lithographic Technologies IX; (2005) https://doi.org/10.1117/12.598488
Event: Microlithography 2005, 2005, San Jose, California, United States

Abstract

The production of defect-free mask blanks, and the development of techniques for inspecting and qualifying EUV mask blanks, remains a key challenge for EUV lithography. In order to ensure a reliable supply of defect-free mask blanks, it is necessary to develop techniques to reliably and accurately detect defects on un-patterned mask blanks. These inspection tools must be able to accurately detect all critical defects whilst simultaneously having the minimum possible false-positive detection rate. There continues to be improvement in high-speed non-actinic mask blank inspection tools, and it is anticipated that these tools can and will be used by industry to qualify EUV mask blanks. However, the outstanding question remains one of validating that non-actinic inspection techniques are capable of detecting all printable EUV defects. To qualify the performance of non-actinic inspection tools, a unique dual-mode EUV mask inspection system has been installed at the Advanced Light Source (ALS) synchrotron at Lawrence Berkeley National Laboratory. In high-speed inspection mode, whole mask blanks are scanned for defects using 13.5-nm wavelength light to identify and map all locations on the mask that scatter a significant amount of EUV light. In imaging, or defect review mode, a zone plate is placed in the reflected beam path to image a region of interest onto a CCD detector with an effective resolution on the mask of 100-nm or better. Combining the capabilities of the two inspection tools into one system provides the unique capability to determine the coordinates of native defects that can be used to compare actinic defect inspection with visible light defect inspection tools under commercial development, and to provide data for comparing scattering models for EUV mask defects.

Citation Download Citation

Anton Barty, Yanwei Liu, Eric Gullikson, John S. Taylor, and Obert Wood "Actinic inspection of multilayer defects on EUV masks", Proc. SPIE 5751, Emerging Lithographic Technologies IX, (6 May 2005); https://doi.org/10.1117/12.598488

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