Solid-immersion Lloyd's mirror as a testbed for plasmon-enhanced ultrahigh numerical aperture lithography

摘要

Evanescent-wave imaging is demonstrated using solid-nimmersion Lloyd’smirror interference lithography at λ=325 nmto producen44-nm half-pitch structures (numerical aperture, NA = 1.85). At such annultrahigh NA the image depth is severely compromised due to the evanes-ncent nature of the exposure, and the use of reflections from plasmonicnunderlayers is discussed as a possible solution. Simulations andmodelingnshow that image depths in excess of 100 nm should be possible with suchna system, using silver as the plasmonic material. The concept is scalablento 193 nm illumination using aluminium as the plasmonic reflector, andnsimulation results are shown for 26-nm half-pitch imaging into a 37-nmnthick resist layer using this scheme