Defect classification and characterization on mask substrates and blanks can be used to the identify defect sources within the tool and process. Defect reduction has been achieved in SEMATECH’s EUV Mask Blank Development Center (MBDC), aided by successful classifications of defect populations. Failure analysis of EUV substrate and blank defects in the MBDC begins with automatic classification of defects detected by M1350 and M7360 Lasertec inspection tools. Two sets of defect images and classification emerge from the two detection tools. The M1350 provides a more variegated set of 13 defect class types, while the M7360 provides eight. During manual review of the classifications, the defect class sets for both tools are often collapsed to only two major classes of interests with respect to production and failure analysis: particles and pits. This leaves various other classes ignored before subsequent characterization steps like SEM classification and composition analysis. The usefulness of tracking and verifying more detailed classes of defect needs to be explored. SEM analysis can be used to validate the relative size comparison yielded from inspection data alone, beyond the calibrated comparison of inspection signals from well-understood polystyrene latex spheres. The accuracy of rule-based defect classification of inspection tool data must be quantified by statistical tracking and validation SEM analysis. Classification of false counts increases as sensitivity of detection tools are increased to ensure the capture of smallest defects. The validity of calling a defect “false” is usually a manual review of pixel images created on the detection tool.
Extreme ultraviolet lithography (EUVL) mask blanks must be free of printable defects. The SEMATECH Mask Blank
Development Center (MBDC) is focused on driving down the defect density of EUVL mask blanks by providing a
collaborative environment for EUVL mask substrate and equipment suppliers and a state-of-the-art analytical toolset for
them to improve their products. Multilayer (ML) coating, substrate cleaning, and substrate suppliers are on site
improving their products with a toolset that includes defect inspection, multilayer deposition, and substrate cleaning
capabilities. X-ray diffraction (XRD) and EUV reflectance measurement capability as well as focused ion beam
scanning electron microscopy/energy-dispersive X-ray (FIBSEM/EDX) and atomic force microscopy (AFM) for defect
characterization are on site.
The SEMATECH MBDC has just installed a Lasertec M7360, an advanced EUV mask blank inspection tool. The
M7360 operates at a much shorter wavelength than the previous generation of confocal scanning inspection tools
(266nm vs. 488nm for the M1350). The M7360 represents a significant improvement in our defect detection
sensitivity. This paper will center on the capabilities of this new tool and show initial inspection results on EUV
multilayer at sensitivities well below those that have been previously reported.
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