The self-formatting barrier characteristics of Cu–Mg/SiO2 and Cu–Ru/SiO2 films for Cu interconnects

To substitute or to supplement diffusion barrier as reducing lateral dimension of interconnects, the alloying Mg and Ru to Cu was investigated as a self-formatting barrier in terms of their resistivity, adhesion, and barrier characteristics After annealing at 400 °C for 30 min, the resistivities of the Cu–0.7 at%Mg alloy and Cu–2.2 at%Ru alloy were 2.0 μΩ cm and 2.5 μΩ cm, respectively, which are comparable to that of Cu films. The adhesion was investigated by means of a sandwiched structure using the four point bending test. The interfacial debonding energy, which represents the adhesion, of Cu–Mg/SiO2 was over 5.0 J/m2, while those of the Cu–Ru/SiO2 and Cu/SiO2 interfaces were 2.2 J/m2 and 2.4 J/m2, respectively. The barrier characteristics of the alloy films were also investigated by the time-dependent dielectric breakdown test, using a metal–oxide–semiconductor structure, under bias-temperature stress. It was shown that the alloying of Mg made the lifetime seven times longer, as opposed to the alloying of Ru which made it shorter.