(Invited) DNA-Directed High-Precision Assembly of CNT FETs

Precise fabrication of semiconducting channel materials into densely-aligned uniformly parallel arrays is one prerequisite to the high-performance ultra-scaled technology nodes, in particular for carbon nanotubes (CNTs). Traditional thin-film-based approaches generally yield CNTs in irregularly-spaced bundles or with wide orientation distribution, and lack a mechanism to effectively eliminate mis-aligned CNTs from the ultra-scaled channel area. Therefore, the averaged pitch value and precision of CNT arrays, the key parameters defining lateral CNT spacing, fail to simultaneously meet all of the patterning requirements for the ultra-scaled technology nodes. Bio-fabrication is promising for patterning CNTls at a resolution beyond the existing lithographic limit. However, impacted by surface charges and sub-micron dimensions of typical bio-templates, current bio-templated electronics exhibit both poor transport performance and array uniformity smaller than 1 micron. We report precise scaling of inter-CNT pitch using a supramolecular assembly method called Spatially Hindered Integration of Nanowire Electronics (SHINE). Specifically, by using nano-trenches to align CNTs and DNA hybridization to stabilize them in place, we constructed parallel CNT arrays with uniform pitch as small as 10.4 nm, at an assembly yield over 95%. The pitch precision improves on that prepared from conventional thin-film approaches by more than two orders of magnitude. Compared to the lithography-patterned Si channels at 10 nm technology node, SHINE simultaneously provides both 70% smaller averaged pitch value and molecular-scale pitch precision in the channel area. By engineering the interfacial compositions, metal ions and surface charges that are destructive to FET performance have been excluded from the channel area without degrading CNT alignment. Under a source-to-drain voltage of -0.5 V, we demonstrate both transconductance more than 0.6 mS/μm with fast on/off switching. And the key FET performance metrics are improved by more than one order of magnitude than previous bio-templated FETs. Furthermore, we demonstrate centimeter-scale alignment of fixed-width CNT arrays. At the interface of high-performance electronics and bio-molecular self-assembly, precise bio-fabrication could provide ultra-scaled devices or circuits compatible with or sensitive to local biological environments.