Investigating the microstructure-reliability relationship in Cu damascene lines (original) (raw)
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.
Applied Physics Letters, 2006
Plastic deformation was observed in damascene Cu interconnect test structures during an in situ electromigration experiment and before the onset of visible microstructural damage ͑voiding, hillock formation͒. 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 linewidth. 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. The deformation geometry leads us to conclude that dislocations introduced by plastic flow lie predominantly in the direction of electron flow and may provide additional easy paths for the transport of point defects. Since these findings occur long before any observable voids or hillocks are formed, they may have direct bearing on the final failure stages of electromigration.
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.
Microstructure and reliability of copper interconnects
IEEE Transactions on Electron Devices, 1999
The effects of texture and grain structure on the electromigration lifetime of Cu interconnects are reported. Using different seed layers, (111)-and (200)-textured CVD Cu films with similar grain size distributions are obtained. The electromigration lifetime of (111) CVD Cu is about four times longer than that of (200) CVD Cu. For Damascene CVD Cu interconnects, the electromigration lifetime degrades for linewidths in the deep submicron range because the grains are confined as a result of conformal deposition in narrow trenches. In contrast, electroplated Cu has relatively larger grains in Damascene structure, resulting in longer electromigration lifetime than CVD Cu and no degradation for linewidths in the deep submicron range.
Electromigration failure development in modern dual-damascene interconnects
2009 17th IFIP International Conference on Very Large Scale Integration (VLSI-SoC), 2009
The electromigration failure development in typical copper dual-damascene interconnect structures is analyzed based on numerical simulations. The origin of the lognormal distribution of electromigration times to failure is investigated. Also, electromigration-induced void formation and evolution in advanced 0.18 µm dual-damascene lines are simulated and the results are compared with experiments. It is shown that the lognormal distribution of the grain sizes leads to lognormal distributions of the electromigration lifetimes. Moreover, the void nucleation sites and main features of void development are highly dependent on the microstructure of the interconnect lines.
Electromigration of Cu interconnects under AC, pulsed-DC and DC test conditions
2011
a b s t r a c t Electromigration (EM) of a dual damascene, test vehicle was measured using direct current (DC), alternating current (AC) followed by DC, and three rectangular-wave DC stressing conditions at 598 K. In some of the experiments samples were allowed to cool to room temperature between the 598 K stress cycles.
Reservoir effect on electromigration mechanisms in dual-damascene Cu interconnect structures
Microelectronic Engineering, 2005
Reservoir effect in dual-damascene Cu interconnect structures caused by electromigration was studied by in situ secondary electron microscopy (SEM). Electromigration-induced void nucleation and apparent void movement in opposite direction to electron flow along the Cu/SiNx interface was found to be responsible for the observed reservoir effect. The observed void evolutions seem to be contrary to current understanding of reservoir effect