Metallic-CNT and Non-uniform CNTs Tolerant Design of CNFET-based Circuits Using Independent N2-Transistor Structures

Carbon Nanotube Field Effect Transistors (CNFETs), consisting of semi conducting Carbon Nanotubes (CNTs), show great promise as extensions to silicon CMOS. However, imperfections related to CNT growth process result in metallic and non-uniform CNTs leading to CNFET failures. This paper investigates a defect tolerant technique for CNFETs which adds redundancy at the transistor level to provide a built-in immunity to metallic and non-uniform CNTs. The proposed technique is based on replacing each transistor by independent N2 series-parallel/parallel-series transistor structures. The technique is adopted to use single directional independence inherent in CNTs to guarantee immunity to both open and short defects as validated by theoretical analysis and experimental results. As demonstrated by extensive simulation results, the proposed technique achieves 1-part-per-bilion failure rate in a typical CNFET fabrication process.