Low-temperature bottom-up integration of carbon nanotubes for vertical interconnects in monolithic 3D integrated circuits

Carbon nanotubes (CNT) can be an attractive candidate for vertical interconnects in 3D monolithic integration, due to their excellent thermal and electrical properties. In this paper we investigate the use of a true bottom-up approach to fabricate CNT vias, for application in 3D monolithic integration. This circumvents metal deposition in high aspect ratio holes, and also allows the use of bundle densification techniques to increase CNT density. Using this approach we fabricated four-point probe electrical measurement structures for both as-grown and densified CNT bundles, and performed I-V measurements. The resulting I-V curves display non-linearities due to a non-Ohmic top contact. The measured resistivities of 10-20 mΩ-cm are among the better values found in literature.