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

•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.

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.