In this work we studied the impact of pulse electroplating parameters on the cross-sectional and surface microstructures of blanket copper films 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 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.

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Organic additives are typically used in the pulse electrodeposition of copper (Cu) to prevent void formation during the filling of high aspect ratio features. In this work, the role of bath chemistry as modified by organic additives was investigated for its effects on Cu trench microstructure. Polyethylene glycol (PEG), bis(3-sulfopropyl) disulfide (SPS), and Janus green b (JGB) concentrations were varied in the Cu electrodeposition bath. Results indicated a correlation between the JGB/SPS ratio and the surface roughness and residual stresses in the Cu. Electron backscattering diffraction (EBSD) and transmission Kikuchi diffraction (TKD) were used to study the cross-sectional microstructure in the trenches. Finer grain morphologies appeared in trenches filled with organic additives as compared to additive-free structures. Cu trench (111) texture also decreased with increasing organic additive concentrations due to more pronounced influence of sidewall seed layers on trench features. Twin density in the microstructure closely tracked calculated stresses in the Cu trenches. A comprehensive microstructural analysis was conducted in this study, on an area of focus that has garnered little attention from the literature, yet can have a major impact on microelectronic reliability.