Carbon nanotube transistor compact model for circuit design and performance optimization

Abstract

In this paper, we describe the development of the Stanford University Carbon Nanotube FET (CNFET) Compact Model. The CNFET Model is a circuit-compatible, compact model which describes enhancement-mode, CMOS-like CNFETs. It can be used to simulate both functionality and performance of large-scale circuits with hundreds of CNFETs. To produce realistic and relevant results, the model accounts for several practical non-idealities such as scattering in the near-ballistic channel, effects of the source/drain extension region, and charge-screening for multiple-nanotube CNFETs. The model also includes a full transcapacitance network for more accurate transient and AC results. The Stanford University CNFET Model is implemented in both HSPICE macro language and VerilogA. The VerilogA implementation shows speedups of roughly 7x∼15x over HSPICE. Applications of the model suggest that n- and p-CNFETs will have 6x and 13x speed advantage over Si n- and p-MOSFETs respectively at the 32nm node, and that a CNT density of 250 CNTs/um is ideal for multiple-nanotube gates. Such a compact CNFET model will be absolutely essential in ushering in the Design Era of CNFET circuits as carbon nanotube technology outgrows its “science discovery” phase.