The self-formatting barrier characteristics of Cu-Mg/SiO_2 and Cu-Ru/SiO_2 films for Cu interconnects

摘要

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 ℃ for 30 min, the resistivities of the Cu-0.7 at%Mg alloy and Cu-2.2 at%Ru alloy were 2.0 Ωμ cm and 2.5 Ωμ 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/SiO_2 was over 5.0 J/m2, while those of the Cu-Ru/SiO_2 and Cu/ SiO_2 interfaces were 2.2 J/m~2 and 2.4 J/m~2, 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.