Optimizing a DUV positive resist for metal layers

Structurally modified acetal resist is designed for lithography on metal layers. The acetal-based polymer used in the resist has intrinsically low post-exposure volatilization and superior metal etch resistance. This resist is designed to have excellent substrate compatibility as indicated by a foot size of less than 10 nm for 250 nm feature size. Lithographic evaluations reveal that this resists is capable of resolving sub-200 nm features on TiN substrates with high photosensitivity, dose latitude and excellent process windows for line and post features. The reduced foot size and enhanced resolution could be achieved by optimizing the resist chemistry and the processing conditions.