Front- and backside structuring of gratings for phase contrast imaging with x-ray tubes

J. Kenntner; T. Grund; B. Matthis; M. Boerner; J. Mohr; T. Scherer; M. Walter; M. Willner; A. Tapfer; M. Bech; F. Pfeiffer; I. Zanette; T. Weitkamp

doi:10.1117/12.859666

2 September 2010 Front- and backside structuring of gratings for phase contrast imaging with x-ray tubes

J. Kenntner, T. Grund, B. Matthis, M. Boerner, J. Mohr, T. Scherer, M. Walter, M. Willner, A. Tapfer, M. Bech, F. Pfeiffer, I. Zanette, T. Weitkamp

Author Affiliations +

Proceedings Volume 7804, Developments in X-Ray Tomography VII; 780408 (2010) https://doi.org/10.1117/12.859666
Event: SPIE Optical Engineering + Applications, 2010, San Diego, California, United States

Abstract

Phase contrast imaging with conventional X-ray tubes as e.g. in computer tomography scanners (CTscanners) requires a setup of three different types of optical gratings. One grating is used to obtain a spatially coherent radiation, the second grating defines a periodic phase shift and the third is used as a periodic absorption grating. In order to absorb high energy radiation, absorption gratings with periods of a few microns only and extreme aspect ratios (>80) are fabricated, employing a modified LIGA process. However, above a critical structural height, structures collapse due to e.g. capillary effects. To overcome this limitation a new variant of the LIGA process has been developed. It is characterized by structuring of a resist on both sides of a membrane, resulting in a moderate aspect ratio on both sides of the membrane instead of an extreme aspect ratio on one side. To get a perfect overlay of both structures the grating structure on the front side of a membrane patterned by the standard LIGA-process is used as the mask for structuring the second resist layer on the backside of the membrane. A second electroforming step fills the gaps on the backside.

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J. Kenntner, T. Grund, B. Matthis, M. Boerner, J. Mohr, T. Scherer, M. Walter, M. Willner, A. Tapfer, M. Bech, F. Pfeiffer, I. Zanette, and T. Weitkamp "Front- and backside structuring of gratings for phase contrast imaging with x-ray tubes", Proc. SPIE 7804, Developments in X-Ray Tomography VII, 780408 (2 September 2010); https://doi.org/10.1117/12.859666

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