A modified bilayer resist approach for 45 nm flash lithography

Advancing technology nodes in semiconductor manufacturing require more demanding lithographic performance for patterning. The advent of 45 nm development necessitated dual damascene lithography moving from a KrF-based bilayer approach to one that includes an ArF photoresist for higher resolution. There are multiple methods for an ArF dual damascene (via first, trench last) system, including bilayer, trilayer and hard mask approaches. Flash manufacturing demands are sensitive to process cost of ownership, so more complex approaches such as trilayer and hard mask film stacks were not as attractive. One method examined as an ArF dual damascene solution was a so-called "modified bilayer" approach, which is a combination of both KrF and ArF resist materials; in particular, this film stack allows for the use of ArF silicon-containing resists along with a variety of anti-reflective and gap fill underlayer materials. The modified bilayer approach afforded many advantages, including chemical compatibility, etch performance and process robustness. The modified bilayer approach represents a culmination of learning that has enabled 45 nm back end of the line (BEOL) dual damascene processing with ArF silicon-containing photoresists.