Improved subthreshold swing and gate bias stressing stability of a-IGZO thin-film transistors with HfON/HfO2/HfON tri-stack dielectrics

The electrical characteristics of a-IGZO thin-film transistors (TFTs) with HfO₂ and HfON/HfO₂/HfON (NON) tri-stack gate dielectrics are comparative investigated. Experimental results indicate that NON gate dielectric can effectively improve interface properties and enhance device reliability compared to HfO₂ gate insulator. Bottom gate a-IGZO TFTs with NON gate dielectrics exhibit improved performance with a saturation mobility of 10.2 cm²/V·s, an on-off current ratio of 2.2 × 10⁶, a subthreshold slope of 0.13 V/decade, and a threshold voltage shift of 0.7 V after gate bias stress at 10 V for 300 s, which are ascribed to the inserting of HfON interlayers between substrate and HfO₂, and between HfO₂ and channel film.