The influence of pulse plating frequency and duty cycle on the microstructure and stress state of electroplated copper films

In this work, the impact of pulse electroplating parameters on the cross-sectional and surface microstructures of blanket copper films were studied using electron backscattering diffraction and x-ray diffraction. The films evaluated were highly (111) textured in the direction perpendicular to the film surface. The degree of preferential orientation was found to decrease with longer pulse on-times, due to strain energy density driven growth of other grain orientations. Residual biaxial stresses were also measured in the films and higher pulse frequencies during deposition led to smaller biaxial stresses in the films. Film stress was also found to correlate with the amount of twinning in the copper film cross-sections. This has been attributed to the twins' thermal stability and mechanical properties.