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

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 on 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 nm. In 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 nm resoluti...