The evolution of diffusion barriers in copper metallization

Refractory metal nitride thin films have been widely developed as the diffusion barriers for the aluminum or copper interconnects in integrated circuits. This study reviewed the evolution of diffusion barriers in copper metallization. First, materials characteristics and electrical properties of various diffusion barriers, titanium nitride (TiN), tantalum nitride (TaN), and titanium zirconium nitride (TiZrN), were examined. These diffusion barriers were prepared by reactive magnetron sputtering in N-2/Ar gas mixtures. Next, barrier performance was evaluated by annealing the Cu/barrier/Si systems at 400-1,000 degrees C for 60 min. in vacuum as well as the measurements of copper diffusion coefficients. The results suggest that TiZrN films can be used as a diffusion barrier for copper metallization better than the well-known TaN films. Therefore, the evolution of diffusion barriers in copper metallization, from TiN to TaN and then from TaN to TiZrN, is addressed.