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EUV mask blanks reach pilot-line defect levels |
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Feb 14, 2006 at 06:13 PM |
 SEMATECH North, an external program of Austin-based SEMATECH, located at Albany NanoTech have been able to remove all particles as small as 43nm from EUV mask blanks, close to the 40nm target that would enable pilot-line use of the masks.
"This achievement is a critical and necessary step in generating a zero-defect mask blank," said David Krick, program manager for SEMATECH North's Mask Blank Development Center (MBDC). "It demonstrates that the MBDC now has world-class cleaning capability in addition to our world-class deposition expertise."
The qualified cleaning process paves the way to the final step of depositing a multi-layered reflective coating on the substrate, allowing the resulting photomask to effectively reflect EUV energy.
Krick said the MBDC's cleaning project was challenged by the limitations of metrology, since even the most powerful commercial mask inspection microscopes cannot reliably detect particles smaller than 50 nm. The SEMATECH team, using an upgraded confocal microscope from Lasertec, compensated with a repetitive cleaning and overlay methodology that effectively "enlarged" the sub-50 nm particles so that they could be detected.
"Cleaning of defects is a critical and necessary step in generating a zero-defect mask blank, because defects in the substrate become defects in the multilayer, which ruins the mask blank," Krick noted. A related challenge involves working with suppliers to produce mask substrates with no nonremovable defects larger than 25 nm, he added.
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