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Proceedings Paper

High-aspect ratio zone plate fabrication for hard x-ray nanoimaging
Author(s): Karolis Parfeniukas; Stylianos Giakoumidis; Rabia Akan; Ulrich Vogt
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Paper Abstract

We present our results in fabricating Fresnel zone plate optics for the NanoMAX beamline at the fourth-generation synchrotron radiation facility MAX IV, to be used in the energy range of 6–10 keV. The results and challenges of tungsten nanofabrication are discussed, and an alternative approach using metal-assisted chemical etching (MACE) of silicon is showcased. We successfully manufactured diffraction-limited zone plates in tungsten with 30 nm outermost zone width and an aspect ratio of 21:1. These optics were used for nanoimaging experiments at NanoMAX. However, we found it challenging to further improve resolution and diffraction efficiency using tungsten. High efficiency is desirable to fully utilize the advantage of increased coherence on the optics at MAX IV. Therefore, we started to investigate MACE of silicon for the nanofabrication of high-resolution and high-efficiency zone plates. The first type of structures we propose use the silicon directly as the phase-shifting material. We have achieved 6 μm deep dense vertical structures with 100 nm linewidth. The second type of optics use iridium as the phase material. The structures in the silicon substrate act as a mold for iridium coating via atomic layer deposition (ALD). A semi-dense pattern is used with line-to-space ratio of 1:3 for a so-called frequency-doubled zone plate. This way, it is possible to produce smaller structures with the tradeoff of the additional ALD step. We have fabricated 45 nm-wide and 3.6 μm-tall silicon/iridium structures.

Paper Details

Date Published: 23 August 2017
PDF: 8 pages
Proc. SPIE 10386, Advances in X-Ray/EUV Optics and Components XII, 103860S (23 August 2017); doi: 10.1117/12.2272695
Show Author Affiliations
Karolis Parfeniukas, KTH Royal Institute of Technology (Sweden)
Stylianos Giakoumidis, KTH Royal Institute of Technology (Sweden)
Rabia Akan, KTH Royal Institute of Technology (Sweden)
Ulrich Vogt, KTH Royal Institute of Technology (Sweden)

Published in SPIE Proceedings Vol. 10386:
Advances in X-Ray/EUV Optics and Components XII
Christian Morawe; Ali M. Khounsary; Shunji Goto, Editor(s)

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