Beam settings optimization for active voltage contrast of copper and aluminum wiring

Active Voltage Contrast (AVC) is increasingly applied as a quantitative measurement technique for resolving electrostatic potential differences in semiconductor structures using low-energy secondary-electron imaging. This study evaluates how beam landing energy, working distance, and scan speed influence AVC measurement sensitivity on copper interconnects biased at controlled voltage levels. Voltage discriminability was quantified using detectability-index analysis derived from pixel-intensity distributions. Low landing energies, particularly 250 eV, produced the strongest separability, while increasing working distance resulted in reduced contrast efficiency due to broader intensity distributions. Surface roughness introduced additional variance that limited achievable precision, emphasizing the role of sample preparation in voltage-contrast metrology. Pixel-count analysis further showed that low landing energies and short working distances substantially decrease the number of electrons required for high-confidence classification. These results provide a quantitative framework for selecting SEM operating parameters that maximize AVC sensitivity and support reliable, high-throughput voltage-contrast metrology for device-level diagnostics.