EUV mask polarization effects on sub-7nm node imaging

As extreme ultraviolet lithography (EUVL) technology progresses towards and below sub-7nm generations, polarization effects will begin to have an impact. Moving to higher NA will introduce polarization effects at all locations: the mask plane, the optics, and the image plane. Contrast losses at a larger angle can occur from the interference at the image plane that will become significant for smaller geometries approaching the EUVL wavelength. Some of these contrast losses can occur at the mask where the polarized reflectance from an EUV mask is affected by the multilayer reflective stack and patterned features. This paper explores the polarization effects that are induced by EUVL masks for sub-7nm lithography. The results show a polarization-dependent induction and attenuation of current in EUVL mask structures, especially as mask pitch decreases below 6λ.