Simulation of AFM Tip-Enhanced Near-Field Electromagnetic Responses for Nondestructive Detection of Local Defects in AlN Semiconductors

Near-surface geometric defects and local electrical nonuniformities in semiconductor wafers are difficult to identify simultaneously using conventional far-field inspection methods. In this study, a three-dimensional electromagnetic simulation model based on AFM tip-enhanced near-field coupling was developed to investigate the local defect responses of AlN wide-bandgap semiconductors at 110 GHz. A finite-conductivity Pt80Ir20 metallic AFM probe, a low-loss AlN sample, and a point field probe in CST were used to extract the localized electric-field response near the tip apex. Lateral scanning response and normalized response variation were introduced to evaluate near-field perturbations induced by different defects. The results show that the metallic AFM tip produces a strongly localized electric-field enhancement within the tip–sample gap. Surface cracks, subsurface voids, and local Drude-AlN electrical anomaly blocks all lead to distinguishable near-field response variations. Geometric defects mainly cause local field redistribution and abrupt changes in lateral scanning curves, whereas the Drude-AlN anomaly produces interface transition and depth-dependent attenuation without changing the surface morphology. These findings indicate that AFM-enhanced near-field electromagnetic responses can provide a useful simulation basis for potential nondestructive characterization and signal interpretation of near-surface defects in AlN and related wide-bandgap semiconductors.