Carbon nanotubes (CNTs) are made by rolling up of sheet of graphene into
a cylinder. These nanostructures are constructed with length-to-diameter ratio
of up to (1.32 × 108):1 (Wang 2009) that is significantly larger than any other
material. As their name suggests, the diameter of nanotube is in the order of few
nanometers, while they can be up to 18 centimeters in length (Javey and Kong,
2009). CNTs are most promising candidates in the field of nanoelectronics, especially
for interconnect applications. Metallic CNTs have aroused a lot of research
interest for their applicability as VLSI interconnects due to high thermal stability,
high thermal conductivity, and large current carrying capability. A CNT can
carry current density in excess of 103 MA/cm2, which can enhance the electrical
performance as well as eliminate electromigration reliability concerns that plagues
current nanoscale Cu interconnects (Wei et al., 2001). Recent modeling works
have revealed that CNT bundle interconnects can potentially offer added advantages
over Cu. Moreover, recent experiments have demonstrated that the resistance
values as small as 200 Ω can be achieved in CNT bundles.
2.2 Structure