Crystallization and failure behavior of Ta-TM (TM = Fe, Co) nanostructured/amorphous diffusion barriers for copper metallization

This work examined the thin-film properties and diffusion barrier behavior of sputtered Ta-TM (TM = Fe, Co) films, aiming at depositing a highly crystallization-resistant and conductive diffusion barrier film for Cu metallization. Four-point probe measurement, x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and a secondary ion mass spectrometer (SIMS) were used to examine the barrier properties. Structural examination indicated that intermetallic-compound-free amorphous Ta-TM films were obtained by magnetron sputtering, thus giving a resistivity of 146.82 mu Omega-cm and 247.01 mu Omega-cm for Ta0.5Fe0.5 and Ta0.5Co0.5 films, respectively. The Si/Ta0.5Fe0.5/Cu and Si/Ta0.5Co0.5/Cu stacked samples were observed to fail completely at temperature above 650 degrees C and 700 degrees C because of the formation Of CU3Si protrusions between silicon and the Ta-TM interface. Ta0.5Co0.5 is thus superior to Ta0.5Fe0.5 in preventing copper from diffusion. Highly thermally stabilized amorphous Ta-TM thin film can thus be potentially adopted as a diffusion barrier for Cu metallization.