Self-aligned top-gate InGaZnO thin film transistors using SiO₂/Al₂O₃ stack gate dielectric

Self-aligned top-gate amorphous indium–gallium–zinc oxide (a-IGZO) thin film transistors (TFTs) utilizing SiO₂/Al₂O₃ stack thin films as gate dielectric are developed in this paper. Due to high quality of the high-k Al₂O₃ and good interface between active layer and gate dielectric, the resulting a-IGZO TFT exhibits good electrical performance including field-effect mobility of 9 cm²/Vs, threshold voltage of 2.2 V, subthreshold swing of 0.2 V/decade, and on/off current ratio of 1 × 10⁷. With scaling down of the channel length, good characteristics are also obtained with a small shift of the threshold voltage and no degradation of subthreshold swing. - Highlights: • Self-aligned top-gate indium–gallium–zinc oxide thin-film transistor is proposed. • SiO₂/Al₂O₃ stack gate dielectric is proposed. • The source/drain areas are hydrogen-doped by CHF₃ plasma. • The devices show good electrical performance and scaling down behavior