Naomasa Suzuki

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.

SEM imaging capability for advanced nano-structures and its application to metrology

In recent trend of semiconductor manufacturing, accurate critical dimension (CD) metrology is required to realize miniaturized three-dimensional (3D) structures. However, the conventional edge contrast of scanning electron microscopy (SEM) is often suppressed when imaging the deep bottom of the 3D structures. In this paper, we propose effective approaches realizing the improved SEM image contrast for such metrology targets. Our approach utilizes the principle of the SEM contrast, and optimizes the three major influencing factors of SEM contrast; signal generation, signal propagation inside the specimen, and signal detection by the detectors. We show the examples of improved image contrast including, embedded voids imaging by high landing beam energy, contact-hole bottom imaging by angular selective detections, and precise edge position extraction realized by energy-angular selective imaging.