Nanoscale X-ray Tomography of Integrated Circuits using a Hybrid Electron/X-ray Microscope: Results and Prospects

Accurate characterization of subsurface features in integrated circuits (ICs) is essential for defect detection, quality assurance, and supply chain security. The interiors of ICs are challenging to probe post-manufacturing due to the presence of many close-packed and nanoscale subsurface features of multiple material compositions, often spread over square millimeters of chip area. X-ray computed tomography (CT) has historically been a powerful tool for 3-dimensional imaging of buried features, but modern instruments are unable to achieve the spatial resolution, elemental sensitivity, or scan areas required to fully characterize ICs. Advanced imaging of ICs is possible at synchrotron beamlines, but such methods are not easily accessible and could not reside directly at a semiconductor foundry or security agency. A need exists for compact, laboratory-scale instrumentation that can image nanoscale features in 3-dimensions over large areas, with sensitivity to feature size, shape, and composition. We describe an approach to x-ray CT which merges a focused electron beam with high magnification system geometry and a combination of high efficiency and high resolving power x-ray detection. This achieves nanoscale, element-sensitive imaging of ICs in a compact instrument footprint. A proof-of-concept has been demonstrated and current imaging capabilities are discussed. The path forward is described, with opportunity for advances in spatial resolution, imaging speed, and spectral imaging capabilities beyond conventional laboratory CT instruments.