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Proceedings Paper

WSi2/Si multilayer sectioning by reactive ion etching for multilayer Laue lens fabrication
Author(s): N. Bouet; R. Conley; J. Biancarosa; R. Divan; A. T. Macrander
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Paper Abstract

Reactive ion etching (RIE) has been employed in a wide range of fields such as semiconductor fabrication, MEMS (microelectromechanical systems), and refractive x-ray optics with a large investment put towards the development of deep RIE. Due to the intrinsic differing chemistries related to reactivity, ion bombardment, and passivation of materials, the development of recipes for new materials or material systems can require intense effort and resources. For silicon in particular, methods have been developed to provide reliable anisotropic profiles with good dimensional control and high aspect ratios1,2,3, high etch rates, and excellent material to mask etch selectivity. A multilayer Laue lens4 is an x-ray focusing optic, which is produced by depositing many layers of two materials with differing electron density in a particular stacking sequence where the each layer in the stack satisfies the Fresnel zone plate law. When this stack is sectioned to allow side-illumination with radiation, the diffracted exiting radiation will constructively interfere at the focal point. Since the first MLLs were developed at Argonne in the USA in 20064, there have been published reports of MLL development efforts in Japan5, and, very recently, also in Germany6. The traditional technique for sectioning multilayer Laue lens (MLL) involves mechanical sectioning and polishing7, which is labor intensive and can induce delamination or structure damage and thereby reduce yield. If a non-mechanical technique can be used to section MLL, it may be possible to greatly shorten the fabrication cycle, create more usable optics from the same amount of deposition substrate, and perhaps develop more advanced structures to provide greater stability or flexibility. Plasma etching of high aspect-ratio multilayer structures will also expand the scope for other types of optics fabrication (such as gratings, zone plates, and so-on). However, well-performing reactive ion etching recipes have been developed for only a small number of materials, and even less recipes exist for concurrent etching of more than one element so a fully material specific process needs to be developed. In this paper, sectioning of WSi2/Si multilayers for MLL fabrication using fluorinated gases is investigated. The main goals were to demonstrate the feasibility of this technique, achievement of high anisotropy, adequate sidewall roughness control and high etching rates. We note that this development for MLL sidewalls should be distinguished from work on improving aspect ratios in traditional Fresnel zone plates. Aspect ratios for MLL sidewalls are not similarly constrained.

Paper Details

Date Published: 29 September 2010
PDF: 5 pages
Proc. SPIE 7802, Advances in X-Ray/EUV Optics and Components V, 780203 (29 September 2010); doi: 10.1117/12.865306
Show Author Affiliations
N. Bouet, Brookhaven National Lab. (United States)
R. Conley, Brookhaven National Lab. (United States)
Argonne National Lab. (United States)
J. Biancarosa, Brookhaven National Lab. (United States)
R. Divan, Argonne National Lab. (United States)
A. T. Macrander, Argonne National Lab. (United States)

Published in SPIE Proceedings Vol. 7802:
Advances in X-Ray/EUV Optics and Components V
Shunji Goto; Ali M. Khounsary; Christian Morawe, Editor(s)

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