The distribution of triaxial stresses within single damascene Cu/organosilicate interconnect structures as a function of linewidth, ranging from 45 to 250 nm, was measured using x-ray diffraction. Least-squares minimization techniques were employed to determine the volume-averaged stress tensors of the Cu features. Longitudinal Cu stress values increased for linewidths below 100 nm, while transverse stresses decreased with decreasing linewidth below 100 nm due to the interplay between the Cu microstructure and the feature geometry. Large tensile out-of-plane stresses were observed in all of the lines demonstrating the constraint imposed by the barrier layers that encapsulate the Cu. © 2011 American Institute of Physics.