Cross-correlation between actinic and visible defect inspection tool for extreme ultraviolet lithography

Abstract
We present recent experimental results from an actinic (operates at the EUV wavelength) defect inspection system for extreme ultraviolet lithography mask blanks. A method to cross-register and cross-correlate between the actinic inspection system and a commercial visible-light scattering defect inspection system is demonstrated. Thus, random, real defects detected using the visible-light scattering inspection tool can be found and studied by our actinic inspection tool. Several defects with sub-100 nm size (as classified by the visible scattering tool) are found with the actinic inspection tool with a good signal to noise ratio. This result demonstrates the capability of the actinic inspection tool for independent defect counting experiments at a sub-100 nm defect sensitivity level.

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