Large area gold coated nano-needles fabricated by proximity mask aligner lithography for plasmonic AR-structures

Mask-aligner (MA) lithography is a well-known method for the fabrication of micrometer sized structures on a substrate with a diameter up to 300 mm. In spite of a theoretical resolution below 200 nm, the minimum printable feature sized remained above 1μm due to diffraction effects and limit its utilization to advanced packaging, or MEMS fabrication. Recently, developments in the illumination system and mechanical parts (known as AMALTIH for Advanced MA LITHography) as well as mask design, have permitted to used diffractive based photo-mask, and then reach the resolution limit mentioned above. This opens the possibility to fabricate smaller structures, usually accessible only by ebeam lithography. We propose here to demonstrate a fast and robust fabrication method of large area plasmonic absorber structures based on 2D sub-micrometric (350 nm period) nano-needles in a transparent polymer on a glass substrate and coated with a 50 nm thick gold layer. The interaction of the incoming light with metallic structured surface leads to the small total reflections of the 0th order below 5 %, over a large spectral band (460-660 nm) and a large set of incidence angles with TE and TM polarizations. Those results demonstrate that our fabrication process is a step toward the implementation of plasmonic based effect structures for a wide range of application.