Very Thin Extreme Ultraviolet Mask Absorber Material for Extremely Fine Pitch Patterning

In this report, we propose palladium oxide (PdO) as an absorber material for an EUV mask that can print line-and-space patterns with a half pitch down to 14 nm. In our simulations, because of its low refractive index (n = 0.8634) and high extinction coefficient (k = 0.0536), an attenuated phase shift mask with a very thin (∼20 nm) PdO absorber can provide an EUV contrast as high as 88% at a 14 nm half pitch under dipole illumination. This results in a very limited horizontal–vertical critical dimension bias (≤2.6 nm) and a sufficiently high normalized image log slope (≥2.78) down to a 14 nm half pitch.