LabAdviser/Technology Research/Microfabrication of X-ray optical elements

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Microfabrication of X-ray optical elements

• Project type: Ph.D project
• Project responsible: Chantal Silvestre
• Supervisors: Ole Hansen, Henri Jansen
• Partners involved: DTU Physics, Teknologiske Institut
• Full thesis: https://orbit.dtu.dk/en/publications/microfabrication-technologies-of-x-ray-optical-elements

Project description

DTU Nanolab has been very active in development of microfabrication technology for a wide range of applications. Microfabrication technology for X-ray optical elements is rather challenging, but the potential in terms of applications is rapidly increasing. The present project aims at improving the microfabrication technology for X-ray optical elements as well as specifically realizing X-ray gratings for dark field X-ray imaging. The project was carried out at DTU Nanolab, with a close collaboration with DTU Physics and DMRI Teknologisk Institut. Deep reactive ion etching (DRIE) of silicon has already proven to be a useful approach for fabrication of high performance refractive optical elements for shaping and focussing X-ray beams, as clearly demonstrated in a very successful previous PhD project (Frederik Stöhr) where DTU Physics, DTU Danchip and DTU Nanotech collaborated to produce excellent results. In this project we shall further improve the fabrication technology to enhance the aspect ratio of the etched structures and improve the side-wall morphology to enhance the performance of the optical elements. The etched silicon structures may also be used as moulds for replication in other materials, and in this project technology for replication in materials with high X-ray absorption will be developed and used to produce high-contrast X-ray gratings, which will benefit from high aspect ratio structuring of silicon. The X-ray gratings will be used in a Modular Dark Field Detector (MDD) system developed in collaboration with external partners: DMRI Teknologisk Institut, Niels Bohr Institutet, InnospeXion, X-Novo, FOSS and Tican. The system design, hardware and software will be provided by the external partners, while the PhD project is responsible for development and realization of a set of X-ray gratings that are key elements in the system. The purpose of the X-ray system is online detection of foreign bodies in food products, and in particular bodies that cannot be detected in conventional X-ray absorption systems for the same purpose, due to low X-ray contrast. Thus, the PhD project is partly funded by Innovationsfonden, while the remaining funding is covered by DTU Nanolab (formely : jointly by DTU Danchip and DTU Nanotech). In the PhD project we will also develop fabrication technology aimed at other X-ray optical elements. In addition, the targeted improvements in aspect ratio and surface morphology of etched silicon structures will greatly benefit also a wide range of other MEMS applications.

Publications

Publication as first author

• Microfabrication of high aspect ratio X-ray gratings using laser ablation of tungsten

Silvestre, Chantal M. , Hemmingsen, Jens H., Dreier, Erik S., Kehres, J. and Hansen, O.,

Microelectronic Engineering, 209, pp.60-65 (2019) [1]

• Deep reactive ion etching of ‘grass-free’ widely-spaced periodic 2D arrays, using sacrificial structures

Silvestre, Chantal M. , Jansen, H., Hansen, O.,

Microelectronic Engineering, 223, 111228 (2020) [2]

Publication as co-author

• Virtual subpixel approach for single-mask phase-contrast imaging using Timepix3

Dreier, E.S., Silvestre, Chantal M. , Kehres, J., Turecek, D, Khalil M., Hemmingsen, J.H., Hansen, O., Jakubek, J., Feidenhans'l, R. and Olsen, U.L.

Journal of Instrumentation, 14,(2019), C01011, [3]

• Single-shot, omni-directional X-ray scattering imaging on a laboratory source using single-photon subpixel localization

Dreier, E.S., Silvestre, Chantal M. , Kehres, J., Turecek, D, Khalil M., Hemmingsen, J.H., Hansen, O., Jakubek, J., Feidenhans'l, R. and Olsen, U.L.

Optics Letters, 45,(2020), 1021-1024, [4]

• The CORE Sequence : A Nanoscale Fluorocarbon-Free Silicon Plasma Etch Process Based on SF6/O Cycles with Excellent 3D Profile Control at Room Temperature.

Nguyen H., T. V. , Silvestre, C. M. , Shi, P. , Cork, R., Jensen, F., Hubner, J., Ma, K., Leussink, P., De Boer, M., Jansen, H.

ECS J. Solid State Sci Technology, 9,(2020), 024002, [5]

Fabrication process flows

This fabrication process flow has been used to fabricated linear and two-dimensional gold grating.

Process flow for gold grating (pdf format): Process flow gold grating.