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High-aspect ratio zone plate fabrication for hard x-ray nanoimaging

DOI: 10.1117/12.2272695 DOI Help

Authors: Karolis Parfeniukas (KTH Royal Institute of Technology (Sweden)) , Stylianos Giakoumidis (KTH Royal Institute of Technology (Sweden)) , Ulrich Vogt (KTH Royal Institute of Technology (Sweden)) , Rabia Akan (KTH Royal Institute of Technology (Sweden)) , Christian Morawe (KTH Royal Institute of Technology (Sweden)) , Ali M. Khounsary (KTH Royal Institute of Technology (Sweden)) , Shunji Goto (KTH Royal Institute of Technology (Sweden))
Co-authored by industrial partner: No

Type: Conference Paper
Conference: Advances in X-Ray/EUV Optics and Components XII
Peer Reviewed: No

State: Published (Approved)
Published: August 2017
Diamond Proposal Number(s): 12046

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.

Journal Keywords: zone plate; high-aspect ratio; etching; RIE; MACE; tungsten; silicon; gold

Subject Areas: Physics

Instruments: I13-1-Coherence

Other Facilities: MAX IV

Added On: 08/11/2017 14:19

Discipline Tags:

Optics Physics

Technical Tags:

Imaging Tomography