Association of Defects and Local Crystallization with Electrical Insulation Degradation in Anodic Tantalum Oxide...

Ta₂O₅ thin films exhibit excellent insulating properties for capacitor-related applications; however, locally formed circular defects can significantly degrade their electrical reliability. In this study, the relationship between the structural characteristics of circular defects and the insulating performance of anodized Ta₂O₅ thin films was investigated by correlating site-specific electrical measurements, which distinguish defect-free and defective regions, with structural characterization by four-dimensional scanning transmission electron microscopy (4D-STEM) and synchrotron X-ray diffraction. Defect-free regions exhibited negligible leakage currents and high dielectric robustness, maintaining stable behavior even under prolonged constant-voltage stress, whereas regions containing circular defects showed enhanced leakage conduction, reduced voltage endurance, and time-dependent degradation. The higher leakage in defective regions was reproducibly observed at multiple locations. Spatially resolved 4D-STEM analysis revealed localized crystalline domains within a representative circular defect and near the delamination front, whereas the surrounding oxide was predominantly amorphous. Together, these electrical and structural observations support an association among circular-defect morphology, localized crystallinity, delamination, and degraded electrical insulation in anodic Ta₂O₅ thin films. This work provides microstructural insight into how localized crystallinity is associated with insulation degradation in anodic oxide dielectric films.