Journal
IEEE TRANSACTIONS ON ELECTRON DEVICES
Volume 61, Issue 11, Pages 3762-3767Publisher
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/TED.2014.2359739
Keywords
Amorphous In-Ga-Zn-O (a-IGZO); etchstopper (ES); hydrogen diffusion; silane (SiH4) partial pressure; silicon oxide (SiOx); thin-film transistor (TFT)
Funding
- Japan Society for the Promotion of Science, Tokyo, Japan [23560408, 2611657]
- Ministry of Education, Culture, Sports, Science and Technology, Japan
- Grants-in-Aid for Scientific Research [14J11657] Funding Source: KAKEN
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To investigate the effect of hydrogen diffusion from the silicon oxide etch-stopper (SiOx 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 SiOx ES layer deposited by plasma-enhanced chemical vapor deposition at various silane (SiH4) partial pressures (P[SiH4]). 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 SiOx ES layer was deposited at higher P[SiH4], 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[SiH4] was increased, the subthreshold swing, hysteresis, and gate-bias stability of the TFT improved. The results indicate that hydrogen diffused from the SiOx 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.
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