Metrology challenges and trends for through-glass vias in advanced semiconductor packaging

Abstract Through-glass vias (TGVs) are emerging as a key technology for three-dimensional heterogeneous integration and advanced semiconductor packaging because of their low electrical loss, tailorable thermal expansion, and compatibility with large-format panel-level processing. However, the optical transparency, refractive properties, and brittleness of glass create significant inspection challenges, making reliable high-throughput metrology a major barrier to TGV manufacturing. This review presents a requirements-driven framework for TGV metrology that links fabrication processes and defect mechanisms to quantitative measurement needs. Key defects associated with laser ablation, laser-induced deep etching, and metallization including microcracks, nanovoids, sidewall roughness, via taper, copper protrusion, and thermomechanical cracking are examined. Representative metrology requirements include detection of sub-1-µm microcracks and sub-2-µm voids, characterization of sidewall roughness below 50 nm, taper-angle uncertainty below 0.1°, and panel-scale inspection at thousands of vias per second. Established and emerging techniques, including shadowgraphy, optical coherence tomography (OCT), spectral reflectometry, digital holographic microscopy (DHM), and two-photon fluorescence, are compared in terms of measurement capability, uncertainty, calibration, traceability, and throughput. No single technique currently meets the combined requirements for resolution, field of view, defect sensitivity, and high-volume throughput. Multimodal inspection, AI-assisted defect classification, physics-informed reconstruction, virtual metrology, and TGV-specific reference artefacts and standards are therefore identified as key directions toward robust, traceable, and scalable TGV metrology.