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High aspect ratio metal microcasting by hot embossing for X-ray optics fabrication


Romano, Lucia; Vila-Comamala, Joan; Kagias, Matias; Vogelsang, Konrad; Schift, Helmut; Stampanoni, Marco; Jefimovs, Konstantins (2017). High aspect ratio metal microcasting by hot embossing for X-ray optics fabrication. Microelectronic Engineering, 176:6-10.

Abstract

Metal microstructured optical elements for grating-based X-ray phase-contrast interferometry were fabricated by using an innovative approach of microcasting: hot embossing technology with low melting temperature (280 °C) metal alloy foils and silicon etched templates. A gold-tin alloy (80 wt% Au/20 wt% Sn) was used to cast micro-gratings with pitch sizes in the range of 2 to20 μm and depth of the structures up to 80 μm. The metal filling of the silicon template strongly depends on the wetting properties of the liquid metal on the groove surface. A thin metal wetting layer (20 nm of Ir or Au) was deposited before the casting in order to turn the template surface into hydrophilic with respect of the melted metal alloy. Temperature and pressure of the hot embossing process were optimized for a complete filling of the cavities in a low viscosity regime of the liquid metal, and for minimizing the shear force that might damage the silicon structures for small pitch grating. The new method has relevant advantages, such as being a low cost technique, fast and easily scalable to large area fabrication.

Abstract

Metal microstructured optical elements for grating-based X-ray phase-contrast interferometry were fabricated by using an innovative approach of microcasting: hot embossing technology with low melting temperature (280 °C) metal alloy foils and silicon etched templates. A gold-tin alloy (80 wt% Au/20 wt% Sn) was used to cast micro-gratings with pitch sizes in the range of 2 to20 μm and depth of the structures up to 80 μm. The metal filling of the silicon template strongly depends on the wetting properties of the liquid metal on the groove surface. A thin metal wetting layer (20 nm of Ir or Au) was deposited before the casting in order to turn the template surface into hydrophilic with respect of the melted metal alloy. Temperature and pressure of the hot embossing process were optimized for a complete filling of the cavities in a low viscosity regime of the liquid metal, and for minimizing the shear force that might damage the silicon structures for small pitch grating. The new method has relevant advantages, such as being a low cost technique, fast and easily scalable to large area fabrication.

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Additional indexing

Item Type:Journal Article, not_refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Biomedical Engineering
Dewey Decimal Classification:170 Ethics
610 Medicine & health
Language:English
Date:2017
Deposited On:22 Mar 2018 10:34
Last Modified:13 Apr 2018 11:45
Publisher:Elsevier
ISSN:0167-9317
OA Status:Closed
Publisher DOI:https://doi.org/10.1016/j.mee.2016.12.032

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