30-nm Contacted Gate Pitch Back-Gate Carbon Nanotube FETs for Sub-3-nm Nodes

Carbon nanotube FETs (CNFETs) promise significant energy efficiency benefits versus silicon for digital systems. While these projected benefits are for CNFETs with similar geometries as silicon FETs (e.g., top-gate FETs, with the FET gate on top of the channel), the majority of the demonstrated CNFETs leverage back-gate geometries due to ease of fabrication (i.e., the gate is fabricated before and underneath the FET channel). Although back-gate CNFETs have already been experimentally demonstrated, importantly, there lacks any rigorous analysis of their benefits for digital very-large-scale integrated (VLSI) circuits. Here, we rigorously quantify, for the first time, the benefits of back-gate geometries: both for enabling aggressive device scaling as well as VLSI circuit energy-delay product (EDP) benefits. The key contributions of this paper are: 1) first analysis of back-gate FET geometries for digital VLSI circuits, showing they enable >1.6× additional EDP benefit for CNFETs due to reduced parasitic capacitances (versus top-gate CNFETs), 2) our analysis shows that leveraging back-gate FETs enables aggressive FET scaling to sub-3-nm technology nodes, and 3) as a feasibility case study, we experimentally realize digital logic circuits that fit within the world's smallest contacted gate pitch to date (CGP, a key metric defining the area of an FET and consequently the technology node) of 30 nm.