Abstract
In this study, (AlCrTaTiZr)N 0.7 and (AlCrTaTiZr)N 1 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)N 0.7 /AlCrTaTiZr and (AlCrTaTiZr)N 1 /AlCrTaTiZr bilayer structures, as well as to improve the interface adhesion to Cu layers. The as-deposited AlCrTaTiZr and (AlCrTaTiZr)N 0.7 films were amorphous, while the (AlCrTaTiZr)N 1 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)N 0.7 and (AlCrTaTiZr)N 1 barriers. At an extremely high temperature of 900°C, the interdiffusion of Si and Cu atoms occurred through the (AlCrTaTiZr)N 0.7 /AlCrTaTiZr bilayer, and Cu silicides formed; whereas the (AlCrTaTiZr)N 1 /AlCrTaTiZr bilayer remained stable. No interdiffusion through the (AlCrTaTiZr)N 1 / AlCrTaTiZr bilayer or formation of any silicides was identified, indicating an excellent diffusion resistance. ©The Electrochemical Society.