Kinetics of interfacial reaction in Cu–Mg alloy films on SiO2

Abstract

We report the kinetics of Mg reduction of SiO2 at the Cu–Mg/SiO2 interface during vacuum annealing. Annealing supersaturated Cu–Mg films to T>∼400 °C results in the interfacial segregation of Mg and the formation of cubic MgO on the silica side of the interface. At ∼475 °C, the film sheet resistance (RS) increases a factor of 3 concurrent with Mg interfacial segregation, MgO formation, and Si release into the Cu film. Analysis of RS–T signatures obtained at different annealing rates reveals that the Mg reduction of SiO2 is the rate-limiting step, with an activation energy Ea=2.7±0.1 eV. The Si released from SiO2 diffuses into the top Cu layer with Ea=2.2±0.1 eV, consistent with the lattice diffusion of Si in Cu. These activation energy values would be important for designing and evaluating annealing treatments to controllably form interfacial isolation layers from Cu–Mg alloy films for device metallization structures.