Performance enhancements to absorbance-modulation optical lithography. I. Plasmonic reflector layers

The ability to improve the transmission and intensity profiles in absorbance-modulation optical lithography [J. Opt. Soc. Am. A 23, 2290-2294 (2006) and Phys. Rev. Lett. 98, 043905 (2007)] through the introduction of a plasmonic metal layer is investigated. In this part of the work, a plasmonic reflector layer (PRL) is placed beneath the photoresist layer. Improvement is expected due to surface plasmons being induced on the plasmonic layer and supporting the transmission of the image deeper into the imaging layer. The introduction of the plasmonic reflector improves the depth of focus markedly, with the image confinement extended up to 60 nm but with a penalty of up to a 50% increase in the minimum full width at half-maximum of the intensity profile. The presented work demonstrates that a PRL can be a valuable tool for near-field lithography.