Rapid trench initiated recrystallization and stagnation in narrow Cu interconnect lines

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Authors
O'Brien, Brendan
Rizzolo, Michael
Prestowitz, Luke
Dunn, Kathleen
Issue Date
2015-09-01
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Article
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Recrystallization , Interconnects , Microstructure , Transmission Electron Microscopy , Thermodynamics
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Abstract
Understanding and ultimately controlling the self-annealing of Cu in narrow interconnect lines has remained a top priority in order to continue down-scaling of back-end of the line interconnects. Recently, it was hypothesized that a bottom-up microstructural transformation process in narrow interconnect features competes with the surface-initiated overburden transformation. Here, a set of transmission electron microscopy images which captures the grain coarsening process in 48 nm lines in a time resolved manner is presented, supporting such a process. Grain size measurements taken from these images have demonstrated that the Cu microstructural transformation in 48 nm interconnect lines stagnates after only 1.5 h at room temperature. This stubborn metastable structure remains stagnant, even after aggressive elevated temperature anneals, suggesting that a limited internal energy source such as dislocation content is driving the transformation. As indicated by the extremely low defect density found in 48 nm trenches, a rapid recrystallization process driven by annihilation of defects in the trenches appears to give way to a metastable microstructure in the trenches.
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O'Brien, B. B., Rizzolo, M., Prestowitz, L. C., & Dunn, K. k. (2015). Rapid trench initiated recrystallization and stagnation in narrow Cu interconnect lines. Applied Physics Letters, 107(17), 1-5. DOI: 10.1063/1.4932577.
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American Institute of Physics
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00036951
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