Advanced full-automatic inspection of copper interconnects

The early detection of Cu sub-surface voids in nano-interconnects has become a main challenge with the reduction of the critical dimensions of the interconnects. A new methodology for full wafer Cu void inspection with high sensitivity and high speed has been developed using a Multi-Purpose SEM (MP-SEM) using high accelerating voltage, high resolution and multi BSE detectors. This inspection methodology has been used to evaluate the Cu metallization quality in nanointerconnects. The effectiveness of this inspection methodology was proven through the evidence of relations between Cu void density, trench widths, pattern density, and surrounding dummy structures.