KIT – University of the State of Baden-Wuerttemberg andNational Research Center of the Helmholtz Association www.kit.edu

Topography and Wafer Mapping

When producing and handling wafers and other products of the semiconductor industry X-ray topography is an es-sential tool for quality control and the development of new materials. With this non-destructive imaging technique, it is possible to characterize defects in the crystal structure quantitatively and with micrometer resolution. Defects may occur in the process of crystal growth already due to thermal stress. Microcracks and other defects may also be caused by thermal and me-chanical stresses during all manufacturing processes, such as slicing, polishing, thermal treatments or wafer handling.

Digital synchrotron X-ray topography is suited well for the rapid metrology measurement of extended defects and strain in large wafers up to 450 mm in diameter as well as in packaged electronic devices. Measurement can be car-ried out in the sectional mode as well as in the large-area transmission or reflection mode. Due to the high brilliance of the synchrotron beam, the exposure time can be reduced drastically without losing information.

ANKA provides one of the best beamlines optimized for white-beam topography. White-beam topography uses the full bandwidth of X-ray wavelengths in the incoming beam, without any wavelength filtering. The technique is parti-cularly useful in combination with synchrotron radiation sources, due to their wide and continuous wavelength spectrum. In contrast to the monochromatic case, in which accurate sample adjustment is needed for diffraction, the Bragg equation is fulfilled always and automatically for

Materials, Structures, Functions Center

ANKA Commercial Services

Karlsruhe Institute of Technology Hermann-von-Helmholtz-Platz 176344 Eggenstein-Leopoldshafen, Germany

Michael Drees Sales Manager ANKA Commercial Services Phone: +49 721 608-26866E-mail: info@anka-cos.kit.edu

Karlsruhe © KIT 2014

a number of wavelengths. White-beam topography is a very fast and non-destructive technique for the analysis of defects, also in polycrystalline wafers. White-beam topogra-phy produces a pattern of several diffraction spots. Each spot contains a full topograph with another angle of view onto the defects. The fine structure of each single topograph is related to defects and distortions in the sample. Deformation of the crystal causes a variation of the shape of the topo-graphs, from which the residual strain in the crystal can be calculated even in encapsulated devices.

Wafer Mapping

Thanks to the cooperation of experts in crystallography, crystallization, X-ray-topography, synchrotron instrumenta-tion, and digital imaging, we can provide topographic over-views of large crystals and complete wafers up to a diameter of 450 mm on a commercial basis.

The detailed high-resolution topographs (resolution up to 2.5 µm per pixel) can be combined by image processing. By zooming in from the overview, it is possible in to find any detail and to localize and characterize even small and dis-persed defects. We can analyze the defect structures in the complete wafer in terms of nature, number and distribution of dislocations, slip bands, stacking faults, and microcracks. The long-term experience of our experts allows a profound and detailed interpretation of these data.

Through ANKA Commercial Services it is possible to plan and organize the complete project, including data processing and assessment of the resulting images by a well-known expert in one step. Non-disclosure can be guaranteed for all parts of the project.