Ultra-thin (AlCrTaTiZr)Nx/AlCrTaTiZr Bilayer Structures of High Diffusion Resistance to Cu Metallization

In this study, (AlCrTaTiZr)N0.7 and (AlCrTaTiZr)N1 films of only 10 nm thick have been developed as diffusion barrier materials for Cu interconnects. An AlCrTaTiZr buffer layer of 5 nm thick was deposited on these barriers to form (AlCrTaTiZr)N0.7/AlCrTaTiZr and (AlCrTaTiZr)N1/AlCrTaTiZr bilayer structures, as well as to improve the interface adhesion to Cu layers. The as-deposited AlCrTaTiZr and (AlCrTaTiZr)N0.7 films were amorphous, while the (AlCrTaTiZr)N1 was observed as a nanocomposite structure with nanocrystallites embedded in an amorphous matrix. At a high temperature of 800°C, Cu began to penetrate into the AlCrTaTiZr buffer layer, but its diffusion was retarded by the (AlCrTaTiZr)N0.7 and (AlCrTaTiZr)N1 barriers. At an extremely high temperature of 900°C, the interdiffusion of Si and Cu atoms occurred through the (AlCrTaTiZr)N0.7/AlCrTaTiZr bilayer, and Cu silicides formed; whereas the (AlCrTaTiZr)N1/AlCrTaTiZr bilayer remained stable. No interdiffusion through the (AlCrTaTiZr)N1/AlCrTaTiZr bilayer or formation of any silicides was identified, indicating an excellent diffusion resistance