Ultrathin photoresists for EUV lithography

The strong attenuation of EUV radiation in organic materials has necessitated the use of a thin layer imaging (TLI) resist for lithographic patterning. We have studied several TLI processes for EUV and found the use of an ultra-thin single layer resist (UTR) over a hardmask is a plausible resist system. We have developed new EUV resist systems based on DUV chemical approaches. These EUV resists pattern features as small as 70 nm L/S and 70 nm isolated features. The UTR process shows high sensitivity and low line edge roughness compared to other thin layer imaging resist processes such as top-surface imaging (TSI). The advantage of these UTR resists is the current familiarity in the industry with processing and materials development. We have also been able to address one of the main concerns surrounding such thin resists, and we have found they are sufficient to pattern the hard mask with enough resist remaining.