Combining X-ray Nano Tomography with focused ion beam serial section imaging — Application of correlative tomography to integrated circuits

Abstract In this research we show the combination of two sub-micrometer imaging techniques, namely focused ion beam (FIB) and scanning electron microscope (SEM)-based X-ray nano tomography, on the exact same sample, a fragment of a central processing unit (CPU). Based on its three-dimensional structure, we compare the volumetric measurement results in terms of scanned volume, spatial resolution, visible details, and artifacts. For comparability reasons we limit the acquisition time to 24 h for both imaging modalities. By this comparison we evaluate the capability of our self-developed laboratory nano-computed tomography system (XRM-II nano-CT) as its performance and usability was increased by the recent upgrades. The nano-computed tomography (nano-CT) offers a 12 times larger scanned sample volume than the FIB tomography on the one hand, but a lower volumetric resolution combined with a factor of 5 lower sampling on the other. The main artifacts of the nano-CT are blurred structures caused by incomplete alignment during the reconstruction process, while in the FIB tomography curtain artifacts lead to distorted structures in the reconstructed volume. We give an outlook to combine the benefits of the two methods, where the nano-CT is used as a navigational scan for the FIB tomography to achieve the best resolution on a given part of a sample.