Subwavelength pattern transfer by near-field photolithography

The subwavelength patterns beyond the diffraction limits were successfully transferred by using an evanescent field generated near metal slits. For this purpose, masks having metal slits and apertures were fabricated using an electron beam (EB) and an atomic force microscope (AFM). An AFM-based fabrication method was applied to fabricate small apertures of which the minimum diameter was below 50 nm. UV light was illuminated using a mercury lamp by keeping the mask in contact with a wafer on which a conventional photoresist was coated. To obtain a small pattern, close contact between the mask and the substrate was required. A deformable silicon diaphragm was effective for this purpose. Subwavelength patterns having a size below 200 nm were successfully transferred onto the conventional photoresist beyond the diffraction limits of light. Furthermore, it was found that the polarized light decreased the size of transferred patterns due to enhancement of near-field localization and reduction of far-field effect.