Universal logic modules based on double-gate carbon nanotube transistors

Abstract

Double-gate carbon nanotube field-effect transistors (DG-CNTFETs) can be controlled in the field to be either n-type or p-type through an extra polarity gate. This results in an embedded XOR behavior, which has inspired several novel circuit designs and architectures. This work makes the following contributions. First, we propose an accurate and efficient semi-classical modeling approach to realize the first SPICE-compatible model for circuit design and optimization of DG-CNTFETs. Second, we design and optimize universal logic modules (ULMs) in two circuit styles based on DG-CNTFETs. The proposed ULMs can leverage the full potential of the embedded XOR through the FPGA-centric lookup table optimization flow. Further, we demonstrate that DG-CNTFET ULMs in the double pass-transistor logic style, which inherently produces dual-rail outputs with balanced delay, are faster than DG-CNTFET circuits in the conventional single-rail static logic style that relies on explicit input inversion. On average across 12 benchmarks, the proposed dual-rail ULMs outperform the best DG-CNTFET fabrics based on tiling patterns by 37%, 12%, and 33% in area, delay, and total power, respectively.