Enhancement of pattern quality with loss modulation: Applying plasmonic lithography in sub-20 nm technology node and beyond

Abstract

Abstract Plasmonic lithography, which uses the evanescent electromagnetic (EM) fields to image beyond the diffraction limit, has been successfully demonstrated as a main candidate for recording integrated circuits (IC) with sub-10 nm resolution. However, as the feature size continuously down-scaling, the corresponding photoresist profile in general exhibits a very poor pattern fidelity due to the near-field optical proximity effect (OPE), far below the minimum requirement for nanofabrication. The importance of the near-field OPE formation and its minimization for nanodevice fabrication with high dense feature and fidelity necessitates a systematic study of the phenomenon and its origins. In this work, a point-spread function (PSF) generated by a plasmonic bowtie nanoridge aperture (BNA) is employed to account for all physical and chemical phenomena involved in the near-field patterning process. The achievable resolution of plasmonic lithography has successfully been enhanced to approximately 4 nm with numerical simulations. A field enhancement factor (F) as a function of gap size is defined to quantitatively evaluate the strong near-field enhancement effect excited by a plasmonic BNA, which also revels that the high enhancement of evanescent field is due to the strong resonant coupling between the plasmonic waveguide and the surface plasmon waves (SPWs). However, based on the investigation of the physical origin of the near-field OPE, and the theoretical calculations indicate that the evanescent-field-induced high-k information loss is the main optical contributor for the near-field OPE. Furthermore, an analytic formula is introduced to quantitatively analyze the effect of the rapidly decaying feature of the evanescent field on the final exposure pattern profile. Notably, a fast and effective optimization method based on the compensation principle of exposure dose is proposed to relax the pattern distortion by modulating the exposure map with dose leveling. The proposed pattern quality enhancement method can open new possibilities in the manufacture of nanostructures with ultrahigh pattern quality via plasmonic lithography, which would find potentially promising applications in high density optical storage, biosensors, plasmonic nanofocusing, and so forth.