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49. Fabrication and Theoretical Evaluation of Thermo- Mechanical Durability of Cu-CNT Composites



Carbon Nanotubes (CNTs) have exceptional electrical and mechanical properties. However, these exceptional properties cannot be realized due to challenges involved with their integration with other materials. Specifically, the interface electrical and thermal resistances between CNTs and other metallic material is the prohibiting issue that has delayed integration of CNTs with other conductive materials. On the other hand, Copper has been the common material for interconnects in microelectronics. However, due to issues such as electro-migration and increased resistivity at nanoscale, Cu is being reevaluated for next generation of microelectronics. The need for new advanced material, has prompted a new trend in creating composites using combination of Cu and CNT. Integration of CNTs with Cu will facilitate easy adaption of these materials in microelectronic manufacturing processes. The research presented here deals with fabrication of this type of composite material specifically for nanoscale interconnects used for through silicon vias (TSVs). CNTs are grown using both thermal Chemical Vapor Deposition (CVD) and Plasma Enhanced Chemical Vapor Deposition (PECVD) techniques. Several techniques such as electroplating, electro- less plating, and sputtering are used to deposit copper on highly dense, highly oriented CNTs to create the composite structure. PECVD was found to be the most appropriate technique for CNT growth and deposition of Cu was found to be feasible using sputtering on CNTs and electro-less plating on Carbon Nanofibers (CNFs). Mechanical integrity of this composite material is evaluated through extensive multiscale modeling approach where Molecular Dynamics (MD) simulation is used to evaluate the interfacial behavior of CNTs and Cu material inside TSVs. Finite element (FE) simulation is then used to evaluate the mechanical and long term thermo-mechanical behavior of the TSVs. The hybrid Cu-CNT material was found to have longer life than pure Copper TSVs.

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