Relationship between microstructure and electromigration damage in unpassivated PVD copper damascene interconnects

Abstract

The microstructure of unpassivated PVD copper interconnects has been determined by electron backscatter diffraction technique (EBSD) inside a scanning electron microscope (SEM), and the appearance and growth of voids and hillocks during the electromigration testing has been observed in situ inside the SEM. The EBSD measurement indicates a strong <111 > texture for the tested line and a high angle boundary fraction of more than 70%. The comparison of the EBSD maps and the SEM images of the defect formation due to electromigration shows that the voids are formed mainly at the sidewall and after blocking grains. These images indicate that the diffusion paths are both the interface and the grain boundaries.