Texture and stress analysis in as-deposited and annealed damascene Cu interconnects using XRD & OIM

Abstract

Texture variations were investigated as a function of linewidth in as‐deposited and annealed damascene Cu interconnect lines using x‐ray diffraction (XRD) and orientation imaging microscopy (OIM). Texture was predominantly {111} fiber in narrower lines in as‐deposited condition with some contribution from {111}〈110〉 component in narrower linewidths and {111}〈112〉 component in the higher linewidths. Texture became sharper with decreasing linewidth in case of as‐deposited specimens and became more random upon annealing. The decrease in texture strength was attributed to the increased twinning upon annealing. The role of linewidth to pitch distance ratio on influencing the texture strength was identified. Electron back scatter diffraction (EBSD) investigations revealed variations in texture of the local grain population. Presence of sidewall {111} component was identified in the 0.4 and 0.5 μm lines in as‐deposited condition and persisted upon annealing but was absent in the 0.35 μm lines. Presence of {110} grains parallel to the surface became more dominant upon annealing in the narrowest 0.35 μm lines with a sidewall {100} component. Residual stresses measured in the lines were tensile in all the three principal directions with very low values in the normal direction for higher linewidths.