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Multi-scale X-ray tomography for process and quality control in 3D TSV packaging

: Zschech, Ehrenfried; Niese, Sven; Löffler, Markus; Wolf, M. Jürgen

International Microelectronics and Packaging Society -IMAPS-:
47th International Symposium on Microelectronics, IMAPS 2014. Future of Packaging : San Diego, 13.-16.10.2014
San Diego/Calif., 2014
ISBN: 978-0-9909-0280-5
ISBN: 978-0-9909028-0-5
ISBN: 978-1-63439-992-0 (Ausgabe 2015 bei Curran)
International Symposium on Microelectronics <47, 2014, San Diego/Calif.>
Conference Paper
Fraunhofer IKTS ()
3D TSV; process control; quality control; x-ray tomography

Advanced packaging processes and the resulting 3D products challenge process and quality control. X-ray imaging and X-ray computed tomography (XCT) provide non-destructive characterization capabilities 011 specimens across a range of length scales, observing features with sizes spanning from millimeters over micrometers down to several 10 nanometers. They are the techniques of choice for two- or three- dimensional inspection of medium and small sized objects with a resolution down to several 10 11111. I11 this paper, the potential and the limits of XCT for process development, process monitoring, and failure analysis in 3D TSV stacks are described. It is shown that a multi-scale approach, i.e. using imaging techniques with several resolution ranges, is necessary for these particular tasks. Since sub-micron XCT and nano XCT are very useful techniques with a promising prospect for the future, we focus on the capabilities of two lab- based XCT tools with sub-micron resolution (Zeiss Versa) and with < 50 11111 resolution (Zeiss Ultra). We demonstrate the capabilities for nondestructive imaging of multi-die stacks with TSVs and AgSn microbumps. Major filling defects in TSVs are clearly visualized. A11 analysis of individual bumps reveals mismatches in relative positioning, micron-size pores, and the distribution of intemietallic phases. This information provides important information regarding the respective process steps (process control) and the product quality (quality control). In addition. TSV etch profiles and small voids in Cu TSVs are visualized. Since deviations from the targeted geometry and defects are difficult to locate precisely from a two-dimensional image. X-ray computed tomography has to be applied.