Flexible In-Ga-Zn-O thin-film transistors with sub-300-nm channel lengths defined by two-photon direct laser writing

In this work, the low-temperature (= 150 °C) fabrication and characterization of flexible Indium-Gallium-ZincOxide (IGZO) top-gate thin-film transistors (TFTs) with channel lengths down to 280 nm is presented. Such extremely short channel lengths in flexible IGZO TFTs were realized with a novel manufacturing process combining two-photon direct laser writing (DLW) photolithography with Ti/Au/Ti source/drain e-beam evaporation and lift-off. The resulting flexible IGZO TFTs exhibit a saturation field-effect mobility of 1.1 cm2V -1 s -1 and a threshold voltage of 3 V. Thanks to the short channel lengths (280 nm) and the small gate to source/drain overlap (5.2 µm), the TFTs yield a transit frequency of 80 MHz (at 8.5 V gate-source voltage) extracted from the measured S-parameters. Furthermore, the devices are fully functional when wrapped around a cylindrical rod with 6 mm radius, corresponding to 0.4 % tensile strain in the TFT channel. These results demonstrate a new methodology to realize entirely flexible nano-structures, and prove its suitability for the fabrication of short-channel transistors on polymer substrates for future wearable communication electronics.