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

Abstract

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.