Triangular Carbon Nanotube Bundle Interconnects for Subthreshold VLSI Circuits
Triangular carbon nanotube (T-CNT) bundles are proposed as long interconnects for subthreshold VLSI circuits. The performance of subthreshold interconnects depends on the intrinsic quantum and electrostatic coupling capacitances of the interconnects. Proposed T-CNT bundles have the most optimum geometry that give least possible coupling capacitance between adjacent wires in an IC. First, we describe the T-CNT bundle models and of traditionally used square/rectangular CNT bundles for comparison. The subthreshold output current of an inverter is modelled, and hence, we find the optimum transistor widths for nFET and pFET that drives the subthreshold interconnects. This is carried out by the current-over-capacitance ratio approach, where the subthreshold current and the transistor output capacitance are considered. Then, we model the interconnects using equivalent single conductor models and find their propagation delay and power dissipated. The performance factors such as crosstalk-induced delay, power delay product and victim noise levels of capacitive coupled interconnects of T-CNT bundles are compared to traditionally used square/rectangular CNT bundles for lengths ranging from 500 μm to 2000 μm. We find that T-CNT bundles outperform square/rectangular CNT bundles.