immersion fluid

https://doi.org/10.1351/goldbook.09498
High refractive index liquid medium used in immersion lithography that replaces the air gap between the lens and the resist surface in conventional photolithography.
Source:
PAC, 2020, 92, 1861. (Terminology of polymers in advanced lithography (IUPAC Recommendations 2020)) on page 1876 [Terms] [Paper]