Extension of 193-nm immersion optical lithography to the 22-nm half-pitch node

Initial volume manufacturing of the 16- to 22-nm half-pitch integrated circuit node is targeted for the year 2018. Lithography is under tremendous pressure to extend its capabilities to meet this deadline. Recently, immersion lithography, particularly using water as an immersion fluid at 193 nm, has attracted much attention as a promising optical lithography extension. However based on simple optical bandwidth considerations, 193-nm-based optical lithography alone will not have the bandwidth necessary for printing the 22-nm half-pitch mode with any foreseeable combination of immersion liquids and conventional resolution enhancement techniques (RETs). The approach to reaching this node presented here is to combine all available RETs with processing nonlinearities and spatial-frequency doubling using two photoresist layers and an image storage layer. Appropriate combinations of multiple exposures/processes can access the 22-nm node; thus reaching current end-of-roadmap values for half-pitch while retaining the current 193-nm lithography infrastructure. A detailed simulation (PROLITH(TM) 8) study of this approach is reported.