Entwicklung eines Nanoimprint-Prozesses zur Herstellung von dreidimensional strukturierten Nanopartikeln mit erhöhter mechanischer Stabilität

The nanoimprint technology realizes already the production of two-dimensional (2D) shaped nanoparticles of different shapes and materials. These nanoparticles can be applied in advanced applications in material engineering, as well as in biology and particularly in drug-delivery systems. This work presents three-dimensional (3D) shaped nanoparticles with T-, L- and step-like cross-sections, implemented by substrate conformal imprint lithography (SCIL) and a manual soft-imprint technique. Further, 2D shaped nanoparticles of different lengths were imprinted for direct comparison. It was shown that particles of same cross-section size, but different shape, exhibit different properties in mechanical stiffness. 3D shaped particles present a higher stiffness than 2D shaped particles with the same absolute height. Additionally, particles of very low heights build curls in water solution. These nanoparticles were successfully imprinted and harvested using fluorescent AMONIL, which was mixed with fluorophor. Throughout the whole process (UV-SCIL, residual layer etching and harvesting) the functionality of the particles was maintained. The entire process leads to a decrease of the particle geometries defined initially in the master template. Thereby, the nanoimprint process leads to a polymer shrinkage of 12%. The resulting residual layers of 100-150 nm in combination with a not fully anisotropic etching process lead to additional reduction of particle widths and heights. The polymer etching rate depend strongly on the coating process and was not ideally controllable. Finally, the geometry of the resulting nanoparticles is approx. 50% smaller than the master template structures. Final widths and heights are in the range of 50-200 nm. The particle lengths equal 2 μm or 20 μm. The master template, with structured areas up to 3 cm^2, was implemented by standard electron-beam lithography in high quality. Further, grey-scale electron-beam lithography was applied for 3D structuring. Additionally, a process for increasing the structured stamp area via step-and-flash SCIL was presented complementary. With this process the structured stamp area was increased by the factor of 4 to 6.