Fabrication of High-aspect-ratio Nano-structures for X-ray Microscopy Applications
Recent efforts of x-ray microscopy research and development are pushing the resolution of state-of-the-art x-ray microscopes toward single digit of nanometer region. Among all the x-ray focusing optics, Fresnel zone plates are superior considering their nature of two-dimensional focusing and a resolution close to diffraction limit. However, high-resolution zone plates operated at x-ray wavelengths, especially in hard x-ray region, require a high-aspect-ratio geometry for their concentric metal zones to efficiently diffract lightwave, a challenge to nanofabrication researchers.
In this talk, I will discuss three different approaches for fabricating high-aspect-ratio metallic nanostructures, including methods utilizing stressless electroforming molds, double-patterning, and zone-doubling techniques. Using these techniques we demonstrated hard-x-ray zone plates with 19:1 aspect-ratio and 30 nm outermost zone width, as well as a platinum resolution test pattern featuring 17-nm-wide, 255-nm-tall gratings.