Measurement of Subnanosecond Delay Through Multiwall Carbon-Nanotube Local Interconnects in a CMOS Integrated Circuit

Due to their excellent electrical properties and small size, metallic carbon nanotubes (CNTs) are promising materials for interconnect wires in future integrated circuits. Indeed, simulations have firmly established CNTs as strong contenders for replacing or complementing copper interconnects. In this paper, we analyze the performances of a prototype 0.25-mum CMOS digital integrated circuit with select horizontal multiwall CNT (MWCNT) interconnects. Some local interconnect wires of the prototype chip were implemented, during a post-CMOS assembly process, by single 14-mum -long metallic MWCNT with 30-nm diameter, representative of future requirements for local interconnects. We evaluate the merits and challenges of MWCNT interconnects in a realistic silicon integrated-circuit environment. We experimentally extract the subnanosecond delays of these wires to quantitatively benchmark their future potential for the first time. Furthermore, we compare our experimental results with an existing MWCNT interconnect model, as well as with the expected performances of scaled copper wires. Finally, we discuss the origin of the discrepancies between our experimental results and the modeling projections.