Contrast measurement of reflection mask with Cr and Ta absorber for Extreme Ultraviolet Lithography

We chose chromium, Cr, and tantalum, Ta, metals as a new absorbing material for extreme ultraviolet lithography (EUVL) reflection mask. These metals are frequently used in photomask or X-ray mask for lithography and their fabrication processes are well investigated. This paper shows the calculated transmittance of EUV light for various metals at the wavelength of 13.5 nm. Thee transmittance (or absorbing ability) of Cr and Ta metals for the EUV light is nearly equal to that of tungsten, W. We have fabricated the reflection masks with Cr or Ta metal absorbers deposited on top of Mo/Si multilayer reflectors.