Thermal Stability and Internal Stress for Strongly (111) Oriented Cu Films

Abstract

Internal stresses and thermal stability of strongly (111) oriented Cu thin films, which are one of promising interconnect materials in advanced ULSI devices, have been studied comparing with those of non-oriented Cu films. Their internal stresses parallel to a film surface were measured by a conventional X-ray diffraction technique (d-spacing vs. sin²ψ method), while the strain distribution with depth by a grazing incidence X-ray scattering (GIXS) methods. Large stress relaxation in strongly (111) oriented Cu films takes place at 200°C without showing any significant grain growth and formation of thermal defects like hillocks. The residual internal stresses of highly oriented (111) Cu films increase almost linearly throughout the thickness up to the substrates. The feature of stress distribution in film depth does not change on annealing. The changes of the residual stresses at each depth are nearly the same as stresses parallel to film surface measured.