Thermal stability, adhesion and electrical studies on (Ti,Zr)N x 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.