Control of fabrication processes for a gate stack structure with a ZnO thin channel layer and an Al2O3 gate insulator has been examined for enhancing the performance of a top-gate ZnO thin film transistor (TFT). The Al2O3/ZnO interface and the ZnO layer are defective just after the Al2O3 layer formation by atomic layer deposition. Post treatments such as plasma oxidation, annealing after the Al2O3 deposition, and gate metal formation (PMA) are promising to improve the interfacial and channel layer qualities drastically. Post-plasma oxidation effectively reduces the interfacial defect density and eliminates Fermi level pinning at the Al2O3/ZnO interface, which is essential for improving the cut-off of the drain current of TFTs. A thermal effect of post-Al2O3 deposition annealing at 350 °C can improve the crystalline quality of the ZnO layer, enhancing the mobility. On the other hand, impacts of post-Al2O3 deposition annealing and PMA need to be optimized because the annealing can also accompany the increase in the shallow-level defect density and the resulting electron concentration, in addition to the reduction in the deep-level defect density. The development of the interfacial control technique has realized the excellent TFT performance with a large ON/OFF ratio, steep subthreshold characteristics, and high field-effect mobility.
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16 April 2018
Research Article|
April 17 2018
TiN/Al2O3/ZnO gate stack engineering for top-gate thin film transistors by combination of post oxidation and annealing
Kimihiko Kato;
Kimihiko Kato
a)
1
Department of Electrical Engineering and Information Systems, The University of Tokyo
, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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Hiroaki Matsui;
Hiroaki Matsui
1
Department of Electrical Engineering and Information Systems, The University of Tokyo
, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
2
Department of Bioengineering, The University of Tokyo
, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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Hitoshi Tabata
;
Hitoshi Tabata
1
Department of Electrical Engineering and Information Systems, The University of Tokyo
, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
2
Department of Bioengineering, The University of Tokyo
, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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Mitsuru Takenaka;
Mitsuru Takenaka
1
Department of Electrical Engineering and Information Systems, The University of Tokyo
, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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Shinichi Takagi
Shinichi Takagi
1
Department of Electrical Engineering and Information Systems, The University of Tokyo
, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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a)
E-mail: kkato@mosfet.t.u-tokyo.ac.jp. Tel.: +81-3-5841-6733, Fax: +81-3-5841-0429
Appl. Phys. Lett. 112, 162105 (2018)
Article history
Received:
December 19 2017
Accepted:
April 03 2018
Citation
Kimihiko Kato, Hiroaki Matsui, Hitoshi Tabata, Mitsuru Takenaka, Shinichi Takagi; TiN/Al2O3/ZnO gate stack engineering for top-gate thin film transistors by combination of post oxidation and annealing. Appl. Phys. Lett. 16 April 2018; 112 (16): 162105. https://doi.org/10.1063/1.5020080
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