One of the main challenges for EUV mask blank metrology is that most tools are designed for either; 1) wafer handling, 2) off-line characterization, or 3) destructive failure analysis. Few clean room-compatible metrology tools for full EUV mask blanks are commercially available. At International SEMATECH's EUV Mask Blank Development Center (EUV MBDC), in Albany NY, we have partnered closely with both metrology and tool integration vendors to modify tools in order to meet stringent EUV requirements. We have succeeded in integrating SMIF-based mask handling metrology tools in a clean room environment. We have demonstrated seamless mask blank defect identification and characterization by coordinate mapping and transfer from our defect inspection tool to both AFM and FIB-SEM/EDX. Additionally, we have successfully integrated these tools with a software package specifically designed for mask yield improvement- the first deployment of its kind targeted specifically for EUV mask defect reduction. The net result is a state-of-the-art EUV metrology toolset capable of identifying, characterizing, and correlating defects on both EUV mask blanks and bare substrates. The facility is currently capable of analyzing the defects as small as 50 nm, with 30 nm capability forecasted in 2006.
One of the key challenges for the successful implementation of EUV Lithography (EUVL) is the supply of defect free mask blanks. Obviously a reliable defect inspection is a prerequisite to achieve this goal. We report results from a EUVL blank inspection tool developed by Lasertec. The inspection principle of this tool is
based on confocal microscopy at 488nm inspection wavelength. On quartz substrates a sensitivity of 60nm is demonstrated. On buried defects in the multilayer stack a reasonable capture rate down to approximately 25nm defect height has been measured. We compare these results to previously reported data on the wafer version
(M350) of the current M1350.