Carbon nanotubes horizontal interconnects with end-bonded contacts, diameters down to 50 nm and lengths up to 20 μm

This work describes a novel approach to fabricate horizontal nanotube interconnects with dimensions comparable to state-of-the-art copper interconnects. The interconnects consist of carbon nanotubes bundles with wall density ≈1013 cm−2, wire lengths of tens of micrometers and wire diameters scalable to 50 nm. The nanotubes are first grown vertically, inside vias with diameters ranging from 300 to 200 nm, and then flipped on the horizontal direction. Symmetrical contacts are made at the tips of the nanotubes in the so-called end-bonded geometry via a metallization process with a key dry-etch step. The quality of the contacts and the nanotubes is evaluated from the electrical measurements by extracting the specific contact resistivity and the carbon nanotube resistivity, respectively. The measured contact resistivity is 3.9 × 10−8 Ω cm2 with Pd/Au contacts. This is the lowest value ever reported so far for nanotubes contacted in an end-bonded geometry. The nanotube resistivity is as low as 1.1 mΩ cm, a value among the best reported to date and only two decades higher than that of copper.