Near-field optical lithography using a planar silver lens

A variation of proximity lithography has been proposed using a planar metallic film in a near-field configuration, where metal acts as a near-field "superlens." We report here on experimental evidence of such optical lithography with, a planar silver lens. Silver layers of varying thickness (85-120 nm) placed at specific distances (40-60 nm) below a patterned mask were able to image the mask's features onto a photoresist located after a gap (26-60 nm) below the silver. The entire structure was exposed from above with a mercury lamp. Feature sizes as small as 250 nm (at a 500 nm period) were imaged, demonstrating the lensing ability of the planar silver slab. (C) 2004 American Vacuum Society.