Feasibility study on the use of Cu(Co) alloy for barrierless copper metallization

In the present study, the properties of Cu(Co) alloy films were studied to evaluate their potential use as alloying elements for copper metallization. The Cu(Co) films were deposited on SiO₂/Si substrates using magnetron sputtering technique. Cu(Co)/SiO₂/Si structures were subsequently annealed in the temperature range of 300–600 °C to determine the diffusion barrier characteristics of the films. Thereafter samples were characterized using four-point probe measurements, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron and transmission electron microscopy. It was found that the Cu(Co) films were preferentially orientated at (111) plane. No copper silicide was detected in the Cu(Co) films annealed up to 500 °C. A Co-containing thin layer was found at the Cu (Co)/SiO₂ interface. In addition, well-defined interfaces were obtained for the sample annealed at 500 °C. There was no evidence of inter-diffusion between Cu and the substrate. - Highlights: • Cu(Co) alloys were studied as candidates for highly reliable interconnects materials. • The 500 °C annealed Cu(Co)/SiO₂/Si structure had well-defined interfaces. • A thin layer rich of Co was initiative formed at the annealed Cu (Co)/SiO₂ interface. • No inter-diffusion can be observed between Cu(Co) alloy layer and SiO₂ layer. • Cu(Co) alloy had low resistivity and high reliability for barrierless metallization.