Investigating the microstructure-reliability relationship in Cu damascene lines (original) (raw)
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Unexpected Mode of Plastic Deformation in Cu Damascene Lines Undergoing Electromigration
MRS Proceedings, 2004
An unexpected mode of plastic deformation was observed in damascene Cu interconnect test structure during an in-situ electromigration experiment and before the onset of visible microstructural damages (void, hillock formation). We show here, using a synchrotron technique of white beam X-ray microdiffraction, that the extent of this electromigration-induced plasticity is dependent on the line width. The grain texture of the line might also play an important role. In wide lines, plastic deformation manifests itself as grain bending and the formation of subgrain structures, while only grain rotation is observed in the narrower lines. This early stage behavior can have a direct bearing on the final failure stage of electromigration.
Application of the Copper Damascene Process for the Preparation of Electromigration Test Structures
The damascene technology is widely used for Cu interconnect structures in integrated circuits. Due to the strong variation of the feature sizes and densities of Cu interconnect lines and contact pads involved in electromigration (EM) test structures, the CMP of the excessive Cu layer is very complicated. This paper will present the challenges of removing of Cu and Ta by CMP and the successful application of well prepared Cu interconnects in life-time experiments.
Journal of Applied Physics, 1999
The texture of electroplated Cu lines of 0.375, 0.5 and 1.5 μm widths with Ta and TiN barrier layers was analyzed using x-ray pole figure and electron backscatter diffraction (EBSD) techniques. Both techniques indicate a strong (111) fiber texture relative to the bottom surface of the trench for samples with a Ta barrier layer and a 400 °C, 30 min, postelectroplating anneal. Samples with a TiN barrier and no anneal exhibit a weak (111) texture. For both barrier layers the quality of the texture, as measured by (111) peak intensity, fraction of randomly oriented grains and (111) peak width, degrades with decreasing linewidth. EBSD data also indicate (111) texture relative to the sidewalls of the trench in samples with a Ta barrier and postelectroplating anneal. Electromigration tests at 300 °C of 0.36 μm damascene Cu lines with the same process conditions show that samples with very weak (111) texture have median time to failures that exceed those of the strongly textured Cu lines. T...
Atomic flux divergence (AFD) based finite element analyses have been performed to show the difference in the electromigration (EM) failure mechanisms at different test conditions for Cu dual damascene line-via test structures. A combined driving force approach adapted in the model consists of driving forces from electron-wind, stressmigration and thermo-migration. It is shown that the failure mechanisms depend on the test condition and the stress free temperature of the structure. As the failure time depends on the failure mechanisms, the life-time prediction from accelerated test would be inaccurate if the invariability of failure mechanisms is assumed. It is also found that the interconnect life-time can be improved by lowering the final annealing temperature of the structure.
12. Electromigration in damascene copper interconnects of line width down to 100 nm
The electromigration reliability of Cu interconnects of line width down to 100 nm is investigated. The activation energy for the electromigration failure of the line width of 150 nm is found to be 1.2 eV, and the Cu/Ta interface is found to be the fast diffusion path for the line widths of 100 nm and 150 nm without any catastrophic void formation in the lines. An atomic flux divergence-based finite element model is used to explain the observed failure sites. Both the resistivity and electromigration reliability of the fabricated interconnects are found to be promising for future technology nodes.