Development status of EUVL mask blanks in AGC - art. no. 67305D

Extreme ultraviolet lithography (EUVL) is a leading candidate for lithographic technology to fabricate the next generation devices with a 32 nm feature size or smaller. The production of the defect-free mask blanks is one of the key technologies to realize the EUVL. The EUV mask blanks requires various kinds of properties such as a low thermal expansion coefficient and an ultra-low flatness of the substrate, a high and uniform reflectivity at EUV wavelength and a ultra-low defectivity down to 30 nm in the reflective multilayer film, and so on. Asahi Glass Company (AGC) has employed its own high quality glass synthetic technology, the glass polishing technology, the glass cleaning technology and film-coating technology acquired for electronic and optical devices to develop the EUV mask blanks. In this paper, we report on the current status of the EUVL mask blank development in AGC. We demonstrated <50 nm flatness on both sides and similar to 10 defects >60 nm on low thermal expansion material (LTEM) substrate. We also demonstrated a Mo/Si multilayer and a Ru capping layer-coated mask blanks with similar to 10defects >83 nm and similar to 65% reflectivity at EUV wavelength. New Ta-based absorber materials and antireflective layers were also developed. Their superior optical properties at the wavelength of the mask pattern inspection light were shown in comparison with the current conventional TAN absorber layer and TaON AR layer. AGC can provide full-stack EUVL mask with this new absorber material for the process developments with the alpha-demo EUV exposure tools.