Mixed carbon nanotube bundles for interconnect applications

The increasing resistivity of copper with scaling and demands for higher current density are the driving forces behind the ongoing investigation for new wiring solutions for deep nanometer scale VLSI technologies. Metallic carbon nanotubes (CNTs) are promising candidates that can potentially address the challenges faced by copper, and thereby extend the lifetime of electrical interconnects. This article examines the state of the art in CNT applications with focus on CNT interconnect research. It is observed that individually, single-wall carbon nanotubes (SWCNTs) and multi-wall carbon nanotubes (MWCNTs) exhibit characteristics that can be better exploited when a combination of the two is used – in the form of a CNT bundle that plays a vital role in interconnect applications. The focus here is that the usage of a combination of SWCNT (at the centre area of the bundle) and MWCNT (on the outside) provides great performance boost with lower interaction and crosstalk between neighbouring CNT bundles. Simulation results show that the resistance, capacitance, and inductance of a CNT depend on the probability of metallic CNTs present in the bundle and the length of the nanotube. Because Cu is metallic, it indicates that using a higher number of metallic nanotubes in the bundle would aid the CNT bundle performance. In addition, using MWCNT on the outer periphery of the bundle and SWCNT in the centre of the bundle would be the ideal way to maximise the performance of the bundle. Based on the observations we provide an analysis of why a mixed CNT bundle would be highly suitable as interconnections.