EUVL mask blanks are ultra-low thermal expansion glass substrates with optical films that are used for extreme ultra-violet lithography (EUVL) suitable for the manufacturing of semiconductor devices with 22nm and smaller nodes. We have been developing EUVL mask blanks by utilizing AGC's core technologies including glass material technologies to precisely control the thermal expansion coefficient with the order of 10-9, glass polishing technologies to realize flat glass surfaces that are <100nm thin, dry coating technologies of highly reflective multi-layer films at 13.5nm wavelength which requires accurate thickness control with the order of 0.01nm.