To investigate the effect of hydrogen diffusion from the silicon oxide etch-stopper (SiO x ES) layer into the amorphous In-Ga-Zn-O (a-IGZO) on thin-film transistor (TFT) properties and stabilities, we fabricated a-IGZO TFTs with a SiO x ES layer deposited by plasma-enhanced chemical vapor deposition at various silane (SiH 4 ) partial pressures (P[SiH 4 ]). Then, quantitative analysis was performed to investigate the relationship between the hydrogen content of the a-IGZO and electrical properties and stability of the TFTs. We found that a low resistance region was formed at the backchannel of the TFT, when the SiO x ES layer was deposited at higher P[SiH 4 ], leading to a drastic negative threshold voltage (V th ) shift. In addition, it was also found that at the frontchannel, the increase in the carrier concentration of a-IGZO was proportional to the increase in the amount of hydrogen in a-IGZO. On the other hand, when P[SiH 4 ] was increased, the subthreshold swing, hysteresis, and gate-bias stability of the TFT improved. The results indicate that hydrogen diffused from the SiO x ES layer passivates the electron traps at the a-IGZO and/or gate insulator/a-IGZO interface, and almost all of the hydrogen also acts as shallow-donor in a-IGZO.Index Terms-Amorphous In-Ga-Zn-O (a-IGZO), etchstopper (ES), hydrogen diffusion, silane (SiH 4 ) partial pressure, silicon oxide (SiO x ), thin-film transistor (TFT).
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