Photolithography is widely used to transfer a geometric pattern from a mask to a photoresist film, but the minimum feature sizes are limited by diffraction through the mask. Focused ion beam and electron beam lithography can be used when higher resolution is desired, but the write times are long and costly. Deep ultraviolet interference lithography, which is a maskless technique, can be used as an alternative to produce high resolution patterns with feature sizes as small as 100 nm. Since double negative metamaterial superlenses can be used for super-resolving and imaging subwavelength objects, there is a need for fabricating such objects to characterize the performance of these metamaterials. In this paper, simulations using standard finite element methods are first used to verify super-resolution and near-field imaging at 405 nm for such objects using a metamaterial superlens previously fabricated from silver and silicon carbide nanoparticles. Thereafter, results of fabrication and characterization of sub-wavelength objects using molybdenum of typical thickness 50 nm initially sputtered on a glass substrate is presented. A deep ultraviolet laser source at 266 nm is used. An anti-reflection layer followed by a high resolution negative tone photoresist is coated on the top of the molybdenum film. The cross-linked photoresist created after the development and bake processes is used as a mask for etching. Fabrication of the sub-wavelength object is completed using reactive ion etching in fluorinated plasma. Both 1D and 2D patterns are fabricated. The quality of the sub-wavelength objects during fabrication is checked using scanning electron microscopy, and the 1D object is characterized using TE and TM polarized illumination.

Date Published: 10 September 2014
PDF: 8 pages
Proc. SPIE 9163, Plasmonics: Metallic Nanostructures and Their Optical Properties XII, 91631D (10 September 2014); doi: 10.1117/12.2063102

Published in SPIE Proceedings Vol. 9163:
Plasmonics: Metallic Nanostructures and Their Optical Properties XII
Allan D. Boardman, Editor(s)