Scaling carbon nanotube field effect transistors to 30 nm channel length on pretreated PET

With the extensive application of flexible circuits to artificial intelligence (AI) and the internet of things (IoT), high requirements have been promoted for the integration and miniaturization of flexible circuits. However, the vast majority of transistors on flexible substrates reported so far have micrometer-level channel length (L_ch), seriously affecting the integration abilities of flexible circuits. In this work, we explore the scaling behaviors of flexible carbon nanotube field effect transistors (CNT FETs) by fabricating p-type flexible CNT FETs with L_ch varying from 2 μm to 70 nm on polyethylene terephthalate (PET) substrates. The improved width-normalized on-state current (I_on/W_ch), transconductance (g_m) and near-constant gate efficiency indicate that CNTs have great potential in constructing ultra-small flexible FETs. Additionally, we fabricate a CNT FET with a 30-nm channel length on a cleaned PET substrate using a self-aligned top-gate structure; this CNT FET can achieve a high on-state performance of 103 μA/μm when V_ds = −0.8 V. The pitch size of the device is 230 nm, which is the smallest size of flexible transistors so far. Even with deep submicron and nanometer channel lengths, the yields of flexible CNT FETs can reach 60% (33/56); which is benefiting from the pretreated substrate, demonstrating the potential for large-scale production.