Linewidth dependence of grain structure and stress in damascene Cu lines

Damascene Cu interconnects show significant differences in both their microstructural and stress behavior as compared to those of Al interconnects patterned using the etching process. Thermal stresses build up during the successive thermal cycles due to the differences in the coefficients of thermal expansion of the component materials. Other than these thermal stresses, growth stresses originating from grain growth develop in damascene Cu interconnects as well. In this study, the linewidth dependence of the stress in damascene Cu was examined experimentally, as well as by numerical simulation. The stresses of damascene Cu with widths ranging from 0.13to2μm were measured using x-ray diffraction, and the measured hydrostatic stress was found to increase with increasing linewidth, in contrast to the typical behavior of Al interconnects. Microstructure analysis using transmission electron microscopy revealed that the grain sizes increased with increasing line dimensions. The increase in stress in the interco...

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