The increasing demand for faster and more reliable integrated circuits (ICs)
has promoted the integration of Copper-based metallization. Electroplated Cu
films demonstrate a microstructural transition at room temperature, known as
self annealing. In this paper we intend to investigate the annealing
behavior of electroplated Cu films grown on a seed Cu layer on top of the
barrier layers over a single crystal silicon substrate. All the samples were
undergone through a multistep annealing process. Grazing incident x-ray
diffraction pattern shows stronger x-ray reflections from Cu (111) and (220)
planes but weaker reflections from (200), (311) and (222) planes in all the
electroplated Cu samples. Transmission electron microscopy was performed on
the cross section of the samples and the diffraction pattern showed the
crystalline behavior of both seed layer and electroplated Cu.
Nanoindentation was performed on all the samples using the continuous
stiffness measurement (CSM) technique and it was found that the elastic
modulus varies from 110 to 130 GPa while the hardness varies from 1 to 1.6
GPa depending on the annealing conditions. The tribological properties of
all the copper films were also measured using the Bench Top CMP tester.
Subsequently, Nanoindentation was performed on the samples after polishing
the top surface in order to investigate the work hardening and an increase
in hardness and modulus was observed. Finite Element Modeling was performed
in order to investigate the stress behavior during nanoindentation.