Interfacial phase formation in Cu-Mg alloy films on SiO2

We report the chemical changes and phase formation at the film-SiO2 interface during vacuum annealing of supersaturated Cu-10 at. % Mg alloy films sputter-deposited on SiO2. High-resolution transmission electron microscopy, energy dispersive x-ray spectroscopy and electron energy loss spectroscopy reveal that both Cu and Mg penetrate ∼20-40 nm into silica at ∼400 deg. C. At higher temperatures Mg reduces SiO2 leading to the crystallization of a 35-nm-thick continuous interfacial layer comprised of equiaxed grains of cubic MgO and small amounts (< or approx. 1 vol %) of monoclinic CuMgSi2O6. Manipulating oxide and silicate formation pathways could open up possibilities for the use of Cu alloys to obtain ultra-thin diffusion barriers at Cu-dielectric interfaces for future metallization structures in integrated circuits