Nanofabrication of sub-wavelength size aperture array for near field optical probe array

Recently there have been tremendous interests about near field optical lithographic techniques for the next generation gigabyte information storage devices. The near field optical lithographic technique will circumvent the classical diffraction limit and can provide the sub-wavelength size patterns less than 100 nm and the parallel data processing has been examined. Therefore, several parallel processing techniques such as multi-cantilever array and the nano-size aperture array have been previously reported. In this work, the nano-fabrication technique for the sub-wavelength size aperture array is presented. Initially, the (50x50) dot array was patterned on the SiO₂ thermally grown on Si (100) substrate. Each dot has (5x5) μm² pattern size. The anisotropic TMAH etching of the Si substrate was performed and followed by anisotropic stress-dependent thermal oxidation at 1000°C and backside Si etching using TMAH solution. The opening of the nano-size aperture on the oxide pyramid array was carried out using water-diluted (50:1) HF solution. The uniformity of the (50x50) nano-size aperture array was examined carefully on the four corners of the array patterns. The average diameter of the aperture was -260 nm and its deviation was found to be ∼10%. The optical characterization for the oxide pyramidal array was performed and its diffraction pattern was revealed. In addition, the 50 nm thick Al thin film for the near field probe was deposited and the result of its characterization is reported.