Stresses in copper thin films and silver/nickel multilayers.

摘要

The stresses in substrate-bonded Cu thin films and Ag/Ni multilayers were studied using wafer curvature and x-ray scattering techniques. The biaxial modulus of sputtered Cu films in the as-deposited state is less than that of the dynamic by approximately 15%. After annealing, the modulus increases due to enhanced ⟨111⟩ texture but still remains comparatively low. The deficit increases at higher temperatures, suggesting anelastic processes contribute to the modulus reduction. The annealed Cu films show high flow strengths due to the presence of the rigid substrate. Attempts were made to find a dislocation boundary layer in the plastically strained film by grazing incidence diffraction studies. No confirmation of a strain gradient near the substrate could be found, however, due to the insensitivity of the measurement to strains at buried interfaces. Significant strain relaxation was seen at the surface, however. The effect of interphase boundaries on internal stresses was also studied in Ag/Ni multilayers. The {lcub}111{rcub} interface stress was found to be −2.17 ± 0.15 N m−1, in agreement with previous studies. High and low-angle x-ray scattering experiments show that this value is unaffected by intermixing. The widths of Ag/Ni and Ni/Ag interfaces were determined and correlated to an excess volume that derives from the volume expansion of misfit dislocations. A positive excess volume is consistent with a negative interface stress when accounting for anharmonic terms in the interatomic potential.