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Replacement of Cu interconnects with carbon nanotubes (CNTs) has been hindered by the high resistance of the CNTs. In this paper, methods for reducing CNT interconnect sheet resistance are presented. Functionalization with electron accepting molecules decreased sheet resistance up to 60%, giving a minimum sheet resistance of ~55 Ω/sq. Alignment of CNTs within the interconnect further reduced resistance. In contrast to nonaligned fabrics, aligned CNT interconnects maintained a constant resistance as CNT line width decreased, demonstrating a path for scaling to smaller technology nodes. In addition, interconnects made with single-walled CNTs consistently showed lower resistance than those with multiwalled CNTs. Finally, a projected RC delay was calculated that demonstrates improved performance below the 45 nm technology node for CNTs compared to Cu. To achieve the desired RC delay improvement, the aspect ratio of the CNT interconnect should be scaled appropriately and combined with an additional reduction in CNT interconnect sheet resistance to 10 Ω/sq, which is feasible based on the functionalization and alignment methods presented here.
Date of Publication: Jan. 2012