Editing Immersion lithography (section)

==Multiple patterning==
[[File:Pitch splitting.png|thumb|left|180px|'''Double patterning by pitch splitting.''' Double patterning by pitch splitting involves assigning adjacent features to different masks, indicated by different colors.]]
[[File:LELELE_patterning.png|thumb|right|180px|'''Triple patterning by pitch splitting.''' Triple patterning by pitch splitting involves assigning adjacent features to 3 different masks, using three colors.]]
{{unreferenced section|date=November 2022}}

The resolution limit for a 1.35 NA immersion tool operating at 193 nm wavelength is 36 nm. Going beyond this limit to sub-[[20nm]] nodes  requires [[multiple patterning]].<ref>Haley, G. (2023). 193i Lithography Takes Center Stage...Again. Semiconductor Engineering. Retrieved from <nowiki>https://semiengineering.com/193i-lithography-takes-center-stage-again</nowiki></ref> At the 20nm foundry and memory nodes and beyond, double patterning and triple patterning are already being used{{when|date=November 2022}} with immersion lithography for the densest layers.