Sol-gel-based metal-oxide thin-film transistors for high-performance flexible NMOS inverters

• Published in: Journal of alloys and compounds 2022-08, Vol.912, p.165228, Article 165228
• Main Authors: Park, Sang-Joon, Ha, Tae-Jun
• Format: Article
• Language: English
• Subjects: Annealing; Bending stresses; Charge transport; Current leakage; Flexible NMOS inverter; Gallium; High gain; Indium gallium zinc oxide; Inverters; Leakage current; Metal oxide semiconductors; Non-quasi-static transient measurement; Oxide-TFT; Oxygen annealing; Oxygen enrichment; Semiconducting films; Semiconductor devices; Sol-gel processes; Sol-gel-based metal-oxide films; Substrates; Temperature dependence; Thin film transistors; Threshold voltage; Time constant; Transistors; Velocity distribution; Zinc oxide; Zirconium dioxide; Zirconium oxides
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2022.165228

High-performance metal-oxide thin-film transistors (oxide-TFTs) with high-k zirconium dioxide (ZrO2) dielectric and indium-gallium-zinc oxide (IGZO) semiconducting films were developed on flexible polyimide substrates. The flexible IGZO-TFTs fabricated using a simple and effective sol-gel-based solution-process combined with oxygen-enriched consecutive annealing at 200 °C, exhibited a high field-effect mobility of 13.6 cm2 V−1 s−1 at 5 V, on/off ratio of 1.05 × 106, gate leakage current of 2.7 × 10−11 A, and threshold voltage of 0.44 V. The effects of O2 annealing on the film quality of the sol-gel-based ZrO2 and IGZO were investigated by analyzing the crystallinity, morphology, and degree of metal-oxygen bonding states. Temperature-dependent steady-state direct-current measurements over the temperature range of 90–300 K, and time-domain non-quasi-static transient measurements with a minimized resistance-capacitance time constant were performed. Thus, the activation energy, density of states, interface trap density, and velocity distribution were determined to investigate the charge transport mechanism responsible for the high performance of the oxide- TFTs proposed in this study. An enhancement-load-type N-channel metal-oxide semiconductor (NMOS) inverter consisting of two oxide-TFTs fabricated via O2 annealing was demonstrated. The flexible NMOS inverter exhibited a high gain of 10.8 at 5 V and outstanding mechanical stability against 10,000 cycles of bending stresses at a strain of 30% without a passivation or buffer film. Sol-gel-based metal-oxide TFTs fabricated by oxygen annealing at low temperatures and their applications in high-performance flexible NMOS inverters were developed. [Display omitted] ●Flexible oxide TFTs with sol-gel-based metal-oxide films fabricated by O2 annealing at low temperatures was developed.●Activation energy, density of states, and velocity distribution were obtained for high performance oxide TFTs.●Flexible NMOS inverter exhibiting high inverting performance and mechanical stability was realized.