Synergistic Enhancement of a-IGZTO TFTs via Hydrogen-Tuned Bilayer Gate-Stack Engineering

초록

We report high-performance top-gate amorphous indium-gallium-zinc-tin-oxide (a-IGZTO) thin-film transistors (TFTs) incorporating a hydrogen (H)-tuned bilayer gate insulator (GI) consisting of SiO2 and Al2O3. The bilayer stack integrates the H-rich SiO2 interlayer and Al2O3 top layer with relatively high dielectric constant, enabling concurrent control of H doping and interface trap states. By adjusting the O-2 plasma density (PO2) during plasma-enhanced atomic layer deposition (PEALD), H incorporation and oxygen vacancy (V-O) suppression were simultaneously optimized. The optimized device exhibited a high field-effect mobility of 71.8 cm(2)/V.s, near-zero threshold voltage V-TH of 0.12 V, and sharp subthreshold swing of 0.25 V/decade. Chemical profiling revealed that Sn-H and In-H bonding played a dominant role in carrier transport, while excess H and V-O-related trap states were effectively mitigated through PO2 tuning. The device also showed excellent bias stress stability, exhibiting a V-TH shift of +0.08 and +0.02 V under positive and negative stress, respectively. These results demonstrate that the synergistic modulation of H incorporation and gate-stack composition is an effective strategy to realize reliable and high-mobility oxide TFTs for advanced display backplane applications.

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