Electron mean-free path for CNT in vertical interconnects approaches Cu

A carbon nanotube (CNT) contact length scaling is used to derive the electron mean-free path (λ
_CNT
) after full integration. A CNT-to-metal contact resistance of 76 Ω and lower was obtained for 150 nm diameter contacts. By estimating the number of conducting walls in the CNT bundle, a λ
_CNT
of 74 nm is found, which is longer than for Cu. We propose a more conservative approach of calculating λ
_CNT
solely from electrical data. The result is that our CNT interconnects have ballistic transport over 24 nm, which is 5 times longer than reported so far.