Investigations of the interactions of silicon dioxide with copper-aluminum alloy used as an adhesion promoter and diffusion barrier for copper metallization on silicon dioxide.

摘要

This study explores the concept of alloying copper with Al in order to impart properties that will make Cu useful for interconnect applications in ICs. The advantages of using Al as the alloying element lies in the thermodynamically favored interaction of Al with the underlying dielectric and with the O ₂ at the surface of pure Cu thus achieving both the adhesion and passivation. This approach has been shown to generate an ultra thin interfacial layer, which acts as an adhesion promoter and diffusion barrier against Cu migration in the dielectric, without significantly affecting the resistivity of Cu. An emphasis has been placed to examine (a) the interaction of Al (from the Cu-Al alloy) with SiO₂ at the alloy-SiO₂ interface, (b) the Al migration to surface of the alloy or pure Cu if used, and (c) the impact of such migration on the bulk Cu film and passivation on the surface.; In this work, sputtered Cu-Al (1–5 at%), with a resistivity in the range of 5–6 μΩ-cm, were studied as diffusion barriers/adhesion promoters between SiO₂ and pure Cu. The films were examined in as-deposited state and after anneal at different temperatures for varying times and in different ambients by the use of surface and interface characterization techniques, Rutherford backscattering spectrometry (RBS) and secondary ion mass spectroscopy (SIMS), and resistance measurements together with metal-oxide-silicon (MOS) capacitor studies. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were also used to elucidate the structure.; The results elucidate the mechanisms of Al movement and interaction with the interface SiO₂ and O₂ on surface and indicate that films of Cu doped with Al do act as a suitable diffusion barrier and adhesion promoter between SiO₂ and Cu.