A comparison between aluminum and copper interactions with high‐temperature oxide and nitride diffusion barriers

A comparative study between the high‐temperature diffusion barriers against either Al or Cu has been made. Several conducting oxides (RuO2, Mo–O) and nitrides (W–N) were examined using cross‐sectional transmission electron microscopy, Auger electron spectroscopy and x‐ray diffraction. Copper was chosen as a less reactive metal than aluminum, and it is widely used in Al–Cu interconnections. Al was found to reduce both oxides to form a thin self‐limiting layer of Al2O3, which hinders interdiffusion between Al and Si. In addition, a localized and nonuniform reaction occurs at the RuO2/SiO2 interface giving rise to the metal‐rich silicide Ru2Si. Cu was fully oxidized by reduction of RuO2 to form Cu2O but did not reduce Mo–O. For Cu on W–N, no reactions occur. However, we observe a significant modification of the Al/W–N interface. A nonuniform reaction giving WAl12 and a continuous thin amorphous layer which appears to be N‐rich aluminum are present. When the W–N is exposed to air before Al deposition, an alum...