Expression of Concern: On the Impact of Process Variations for Carbon Nanotube Bundles for VLSI Interconnect

Bundles of single-walled carbon nanotubes (SWCNTs) have been proposed as a possible replacement for on-chip copper interconnect due to their large conductivity and current-carrying capabilities. Given the manufacturing challenges associated with future nanotube-based interconnect solutions, determining the impact of process variations on this new technology relative to standard copper interconnect is vital for predicting the reliability of nanotube-based interconnect. In this paper, we investigate the impact of process variations on future interconnect solutions based on carbon nanotube bundles. Leveraging an equivalent RLC model for SWCNT bundle interconnect, we calculate the relative impact of ten potential sources of variation in SWCNT bundle interconnect on resistance, capacitance, inductance, and delay. We compare the relative impact of variation for SWCNT bundles and standard copper wires as process technology scales and find that SWCNT bundle interconnect will typically have larger overall three-sigma variations in delay. In order to achieve the same percentage variation in both SWCNT bundles and copper interconnect, the percentage variation in bundle dimensions must be reduced by up to 63% in 22-nm process technology.