Concurrent optimization of binary phase mask for 3D nanopatterning by inverse design of electric field

Abstract

The technique for a high-resolution three-dimensional (3D) nanostructure has been a big interest in the nanotechnology field. Proximity-field nanopatterning (PnP), which fabricates 3D nanostructure based on interference pattern by phase shift through phase shifting mask, has been applied to various nanotechnology fields due to its rapid and stable fabrication. The previous optimization of PnP for high-resolution was based on diffraction order control, controlling the height of phase mask. To overcome the single variable optimization, which was a limitation of previous optimization, the concurrent optimization was proceeded with particle swarm optimization, controlling the height and width of phase mask concurrently. In addition, we adopted the inverse design to directly control the electric field distribution, different from the previous optimization, which controlled the diffraction order to modulate the electric field. The optimum design calculated by the inverse design showed high electric field intensity contrast and also succeeded to fabricate a highly uniformed nanochannel array. The inverse design method used in this thesis is expected to enlarge the symmetry of nanostructure from PnP. Further optimization will be concentrated on pillar array phase mask design and non-intuitive design mask which can fabricate optimum structure for each application field.