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 degrees C for 30 min, the resistivities of the Cu-0.7 at%Mg alloy and Cu-2.2 at%Ru alloy were 2.0 mu Omega cm and 2.5 mu Omega 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/m(2), while those of the Cu-Ru/SiO2 and Cu/SiO2 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. (C) 2008 Elsevier Ltd. All rights reserved.