Improvement of thermal stability of NiAl via employing Al capping layer for advanced interconnect applications

This letter reports on the study of employing an Al capping layer to improve the thermal stability of NiAl films for advanced interconnect applications. We prepare NiAl films with an Al capping layer of various thicknesses. Transmission electron microscopy analysis of NiAl with a 1 nm thick capping layer annealed at 450 degrees C discloses an effective suppression of Al out-diffusion from the NiAl layer and hence enhanced thermal stability. Measurement of thickness-dependent resistivity unravels a much slower resistivity increase for the capping layer sample than that of the sample without capping layer and low resistivity below 10 nm (49.7 mu omega center dot cm for 3.2 nm).