Effects of Fluoride Residue on Thermal Stability in Cu/Porous Low-k Interconnects

摘要

We have investigated the effects of fluoride residue on the thermal stability of a Cu/barrier metal (BM)/porous low-k film (k < 2.3) structure. We confirmed that the Cu agglomerated more on a BM/inter layer dielectric (ILD) with a fluoride residue. To consider the effect of fluoride residue on Cu agglomeration, the structural state at the Cu/BM interface was evaluated with a cross-section transmission electron microscope (TEM) and atomic force microscope (AFM). In addition, the chemical bonding state at the Cu/BM interface was evaluated with the interface peeling-off method and X-ray photoelectron spectroscopy (XPS). Moreover, we confirmed the ionization of fluoride residue and oxidation of Cu with fluoride and moisture to clarify the effect of fluoride residue on Cu. Our experimental results indicated that the thermal stability in Cu/porous low-k interconnects was degraded by enhancement of Cu oxidation with fluoride ions diffusion as an oxidizing catalyst.