Thermal stability, adhesion and electrical studies on (Ti,Zr)Nx thin films as low resistive diffusion barriers between Cu and Si

In this study, we investigated the thermal stability, wettability, adhesion and reliability of (Ti,Zr)N x films used as the diffusion barrier between Cu and Si. (Ti,Zr)N x films were prepared by DC reactive magnetron sputtering from a Ti-5 at. % Zr alloy target in N 2 /Ar gas mixtures. A minimum film resistivity of 59.3 µω cm was obtained at an N 2 /Ar flow ratio of 2.75, which corresponds to the near stoichiometric composition (N/(Ti,Zr) ratio ∼0.95). The sheet resistance of Cu/(Ti,Zr)N 0.95 /Si was not significantly increased until annealing above 750°C, indicating good thermal stability. On the other hand, the adhesion energy between Cu and the (Ti,Zr)Nx film was reduced as the N/Ti ratio was increased. To obtain reliable performance on stress-induced-voiding (SIV) and electromigration (EM) tests, we proposed to use (Ti,Zr)/(Ti,Zr)N x /(Ti,Zr) tri-layers. We suggest that the interfacial adhesion between barrier and Cu plays an important role in reliability. The proposed tri-layer structure may be a promising candidate for a barrier, as it exhibits excellent reliability without increasing resistance.