Performance enhancements to absorbance-modulation optical lithography. II. Plasmonic superlenses.

The ability to improve the transmission and intensity profiles in absorbance-modulation optical lithography (AMOL) [J. Opt. Soc. Am. A 23, 2290 (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 layer is placed between the absorbance-modulation layer and the photoresist layer. Transmission through this layer is possible due to the ability of thin plasmonic layers to act as near-field analogues of negative refraction materials. The superlens performance is best with a thin layer of 10-20 nm, although this causes a full width at half-maximum increase of ~50%. The introduction of the plasmonic layers allows dichroic filtering of the two wavelengths, with a difference of a factor of 10 in the transmitted intensity ratio, reducing undesirable exposure of the resist. The presented work demonstrates that a plasmonic layer can be interfaced with an AMOL system, but that further optimization and material development are needed to allow substantial performance improvements.