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

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