Evanescent-field-controlled nano-pattern transfer and micro-manipulation

Utilizing evanescent fields (optical near field), we demonstrate a novel processing beyond the diffraction limits of lights. One is relating to a pattern transfer in a nano-scale dimension. The other is a manipulation of micro-objects. The nano-scaled patterns beyond the diffraction limits were successfully transferred by using evanescent field generated near metal slits. For this purpose, masks having the metal slits and apertures were fabricated by using an electron beam (EB) and an atomic force microscope (AFM). AFM-based fabrication method was applied to fabricate nano-apertures of which diameters are below 50 nm. UV was irradiated using a mercury lamp keeping the mask in contact with a wafer on which conventional photo-resist was coated. For obtaining a small pattern, it is required to come the mask into contact with the substrate completely. Deformable silicon membrane was effective for this purpose. The nano-scale patterns having a size below 200 nm were successfully obtained by transferring the mask pattern onto the conventional photo-resist. On the other hands, fundamental experiments about the manipulation of particles with the evanescent field were made by using a patterned thin metal. It was confirmed experimentally that the evanescent field created on the metal-slits and thin metal film gives the particles a force. By using this force, trappings, arrangements and movements were demonstrated.