(Invited) Vlsi Carbon Nanotube Thin-Film Circuits
Authors: Hersam Mark C. 
Published: February 2020

With the availability of large quantities of electronically monodisperse carbon nanotubes (CNTs) [1], homogeneous semiconducting CNT thin films can be produced through a variety of solution-based methods including vacuum filtration [2], dielectrophoresis [3], evaporation-driven self-assembly [4], aerosol jet printing [5], and inkjet printing [6,7].  Through careful integration of these thin films with high-k gate dielectrics [8], CNT thin-film transistors (TFTs) can achieve device metrics that are competitive with polycrystalline silicon and amorphous oxide semiconductors [9]. Furthermore, with appropriate device geometries, doping schemes, and gate electrode materials, threshold voltage can be tuned to enable enhancement-mode p-type and n-type TFTs, resulting in CNT CMOS logic gates with subnanowatt static power dissipation and full rail-to-rail voltage swing [10]. While these results suggest that very-large-scale integration (VLSI) should be possible for CNT thin-film circuits, further improvements are needed in CNT TFT large-area spatial homogeneity and long-term environmental stability. Towards these ends, this talk will introduce encapsulation schemes and automated measurement strategies that yield wafer-scale CNT TFT arrays with sufficiently tight control over on/off ratio, subthreshold swing, and threshold voltage for VLSI CNT thin-film circuits. Using this methodology, large-area arrays of fully functional CNT TFT static random access memory (SRAM) cells are demonstrated with desirable static noise and write margins.

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