| Summary: | In this work, the correlation between SiO<sub>2</sub> deposition thickness and hydrogen content is discussed and the effect of the SiO<sub>2</sub> layer on the properties of synaptic InGaZnO (IGZO) TFTs is analyzed. Three types of IGZO synaptic thin-film transistors (TFTs) were fabricated with different gate insulators, and the effect of SiO<sub>2</sub> as a gate insulator was investigated. XPS analysis confirmed that the hydrogen content in the Al<sub>2</sub>O<sub>3</sub> and SiO<sub>2</sub> layers increased during SiO<sub>2</sub> deposition step for all depth regions. Hydrogen injected by the SiO<sub>2</sub> layer deposition step was confirmed to improve the memory window through more threshold voltage shift under positive bias stress (PBS) and negative bias stress (NBS) conditions. In addition, the retention characteristics were improved due to the low hydrogen movement velocity in the SiO<sub>2</sub> layer. These results contribute to the optimization of the amount of hydrogen, and the proposed device has potential as a synaptic device capable of neuromorphic computing.
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