Ultrathin (AlCrTaTiZr)N-x/AlCrTaTiZr Bilayer Structures with High Diffusion Resistance for Cu Interconnects

In this study, (AlCrTaTiZr)N-0.7 and (AlCrTaTiZr)(N1) films with quinary metallic elements were developed as diffusion barrier materials for Cu interconnects. To improve the interface adhesion to Cu, an AlCrTaTiZr buffer layer was deposited on the barriers to form (AlCrTaTiZr)N-0.7/AlCrTaTiZr and (AlCrTaTiZr)(N1)/AlCrTaTiZr bilayer structures. The as-deposited AlCrTaTiZr and (AlCrTaTiZr)N-0.7 films were amorphous structures, and (AlCrTaTiZr)N-1 possessed a nanocomposite structure. After annealing at 800 S C, although Cu penetrated into the AlCrTaTiZr buffer layer, the diffusion of Cu was retarded by the (AlCrTaTiZr)N-0.7 and (AlCrTaTiZr)N-1 barriers. During annealing at 900 degrees C, the interdiffusion of Si and Cu occurred through the (AlCrTaTiZr)N-0.7/AlCrTaTiZr bilayer, and Cu silicides formed. However, the (AlCrTaTiZr)N-1/AlCrTaTiZr bilayer remained stable. Neither the interdiffusion of Cu and Si through the (AlCrTaTiZr)N-1/AlCrTaTiZr bilayer nor the silicide formation was identified, indicating the high diffusion resistance of the bilayer structure. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3374194] All rights reserved.