High-resolution 3D Inspection of Bonding Defects in HBM using Optically-coupled X-ray Computed Laminography

This is the authors' abstract. We don't add key points for this paper.

The rapid growth of artificial intelligence and high-performance computing has accelerated demand for high-bandwidth memory (HBM), in which dozens of DRAM dies are vertically stacked and interconnected through through-silicon vias (TSVs) and micro-bumps. Bonding defects such as bump voids, non-wets, and misalignment in these interconnects critically affect device yield and reliability, making nondestructive three-dimensional (3D) inspection essential. Conventional X-ray imaging systems rely on geometric magnification, which forces the use of low-power nano- or micro-focus sources and results in scan times exceeding 30 minutes per HBM module. In this work, we present an optically-coupled X-ray computed laminography (CL) system that decouples spatial resolution from the X-ray focal spot size by placing a scintillator in direct contact with the object and acquiring images through an optical magnification stage. This configuration allows the use of a high-power X-ray tube with a large focal spot without sacrificing resolution. A sub-micrometer spatial resolution was achieved using a 11-μm-thick CsI:Tl scintillator and a 10× optical lens, and 3D reconstruction of an HBM module from 1600 projections clearly resolved DRAM-to-DRAM and DRAM-to-logic micro-bumps along with bump voids. The proposed system establishes a practical route toward high-throughput, high-resolution in-line inspection of advanced 2.5D/3D semiconductor packages.