US Patent 7875408 Bleachable materials for lithography

Compositions comprising photobleachable organic materials can be bleached by 193 nm light, and brought back to their original state by stimuli after exposure. (reversible photobleaching). We use these compositions in art-known contrast enhancement layers and as a part of a photoresist, especially in optical lithography processes for semiconductor fabrication. They may comprise polymers such as organo-silicon polymers, polymers comprising polymers of aromatic hydroxyl compounds such as phenol and naphthol such as phenol formaldehyde polymers and naphthol formaldehyde polymers styrene polymers and phenolic acrylate polymers or cyclic materials comprising: