Nondestructive 3D Metrology of Through-Glass Via Geometry and Internal Wall Texture Using Holotomography

Abstract

Through-glass vias (TGVs) are increasingly important for semiconductor packaging, yet their internal geometry and wall texture remain difficult to characterize nondestructively. Here, we use holotomography (HT) to inspect the three-dimensional (3D) geometry and internal wall texture of intact, unfilled TGVs before metallization. HT reconstructs the refractive index (RI) distribution of the glass and via. Maps of RI and spatially filtered RI then localize the internal boundary. Geometric fitting quantifies via dimensions and taper, while spatial filtering separates slowly varying wall form from finer texture. The reconstructed surface supports volumetric visualization, dimensional measurements and spatial characterization of wall texture within one optical inspection workflow. These measurements reveal internal features inaccessible from surface views and provide quantitative descriptors to evaluate TGVs