Self-aligned indium–gallium–zinc oxide thin-film transistors with SiN_x/SiO₂/SiN_x/SiO₂ passivation layers

Self-aligned top-gate amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistors (TFTs) with SiN_x/SiO₂/SiN_x/SiO₂ passivation layers are developed in this paper. The resulting a-IGZO TFT exhibits high reliability against bias stress and good electrical performance including field-effect mobility of 5 cm²/Vs, threshold voltage of 2.5 V, subthreshold swing of 0.63 V/decade, and on/off current ratio of 5 × 10⁶. 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. The proposed a-IGZO TFTs in this paper can act as driving devices in the next generation flat panel displays. - Highlights: • Self-aligned top-gate indium–gallium–zinc oxide thin-film transistor is proposed. • SiN_x/SiO₂/SiN_x/SiO₂ passivation layers are developed. • The source/drain areas are hydrogen-doped by CHF3 plasma. • The devices show good electrical performance and high reliability against bias stress