Synchrotron radiation-based characterization of interconnections in microelectronics: recent 3D results

摘要

In microelectronics, more and more attention is paid to the physical characterization of interconnections, to get a better understanding of reliability issues like voiding, cracking and performance degradation. Those interconnections have a 3D architecture with features in the deep sub-μm range, requiring a probe with high spatial resolution and high penetration depth. Third generation synchrotron sources are the ideal candidate for that, and we show hereafter the potential of synchrotron radiation-based hard x-ray nanotomography to investigate the 2D and 3D morphology of through silicon vias (TSVs) and copper pillars, using projection (holotomography) and scanning (fluorescence) 2D and 3D imaging, based on a series of experiments performed at the ESRF. In particular, we highlight the benefits of the method to characterize voids, but also the distribution of intermetallics in copper pillars, which play a critical role for the device reliability. Beyond morphological imaging, an original acquisition scheme based on scanning Laue tomography is introduced. It consists in performing a raster scan (z,θ) of a sample illuminated by a synchrotron polychromatic radiation while recording diffraction data. After processing and image reconstruction, it allows for 3D reconstruction of grain orientation, strain and stress in copper TSV and also in the surrounding Si matrix.