Optimization procedures for metal-coated NSOM aperture array

Recently, there has been tremendous interest in near-field optical lithographic techniques for gigabyte portable information storage devices. The near-field optical lithographic technique will circumvent the classical diffraction limit and therefore can provide sub-wavelength-size patterns. For a potential near-field optical probe, a novel technique for the nano-fabrication of sub-wavelength-size aperture arrays has been developed based on semiconductor batch fabrication technology. Hollow pyramidal type 50x50 and 25x25 SiO2 nano-aperture arrays have been fabricated through the following procedures: square-dot array patterning, V-groove formation, thermal oxidation at a concave Si surface, backside Si etching, and nano-aperture opening by SiO2 etching using HF solution. The average diameter of the fabricated 50x50 nano-size aperture array was measured to be similar to260 nm and the deviation to be less than 10%. For the purpose of completing a metal-coated array, metal deposition including Ti and Al was carried out. Next, thermal annealing and preliminary laser annealing experiments were performed in order to obtain better surface characteristics such as adhesion and better surface morphology around the metal-coated apertures.