Tae Yoon Jeon, Hwan Chul Jeon, Seung-Man Yang and Shin-Hyun Kim, "Hierarchical Nanostructures Created by Interference of High-Order Diffraction Beams," Journal of Materials Chemistry C, Accepted for publication (2015).
We report a novel method to create 2D hierarchical nanopatterns with high structural complexity using phase-shift lithography. With phase masks with large lattice periodicities relative to wavelength of light source, several different diffraction beams are generated from a single grating, which then interfere to form highly complex 3D intensity profile at Fresnel region. We transfer the horizontal slice of the intensity profile into the thin film of negative photoresist, making 2D nanostructures. Because diffraction order determines a length scale of intensity variation in horizontal surface, interference of several different diffraction orders leads to formation of complex and hierarchical nanopatterns, which are difficult to create with conventional phase-shift lithography. In addition, as the 2D profile is modulated along light propagation direction, a variety of complex nanopatterns can be fabricated from single phase mask by adjusting distance between diffraction grating and photoresist film. Full 3D intensity profile formed by interference is calculated with finite-difference time domain (FDTD) method, which enables us to anticipate the shape and morphology of the resulting 2D nanostructures.
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