Positive Bias Instability of Bottom-Gate Zinc Oxide Thin-Film Transistors with a SiOx/SiNx-Stacked Gate Insulator
The positive bias instabilities of the zinc oxide thin-film transistors (ZnO TFTs) with a SiO x /SiN x -stacked gate insulator have been investigated. The film quality of a gate insulator of SiO x , which forms an interface with the ZnO channel, was varied by changing the gas mixture ratio of SiH 4...
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| Published in | Jpn J Appl Phys Vol. 50; no. 3; pp. 03CB09 - 03CB09-4 |
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| Main Authors | , , , , , , |
| Format | Journal Article |
| Language | English |
| Published |
The Japan Society of Applied Physics
25.03.2011
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| Online Access | Get full text |
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| Summary: | The positive bias instabilities of the zinc oxide thin-film transistors (ZnO TFTs) with a SiO x /SiN x -stacked gate insulator have been investigated. The film quality of a gate insulator of SiO x , which forms an interface with the ZnO channel, was varied by changing the gas mixture ratio of SiH 4 /N 2 O/N 2 during plasma-enhanced chemical vapor deposition. The positive bias stress endurance of ZnO TFT strongly depended on the deposition condition of the SiO x gate insulator. From the relaxations of the transfer curve shift after imposition of positive bias stress, transfer curves could not be recovered completely without any thermal annealing. A charge trapping in a gate insulator rather than that in bulk ZnO and its interface with a gate insulator is a dominant instability mechanism of ZnO TFTs under positive bias stress. |
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| Bibliography: | Schematic cross-sectional view of fabricated bottom-gate ZnO TFT. Transfer characteristics of ZnO TFTs with the gate insulators of GI A--C. Transfer characteristics were measured at drain voltages ($V_{\text{DS}}$) of 0.1 and 20.1 V. Changes in transfer characteristics of the ZnO TFTs with (a) GI-A, (b) GI-B, and (c) GI-C under positive gate bias stress of 20 V at 50 °C. Stress temperature dependence of $\Delta V_{\text{GS}}$ at $I_{\text{DS}}=1$ nA of the ZnO TFTs with (d) GI-A, (e) GI-B, and (f) GI-C at positive gate bias stress of 20 V. Changes in $\Delta V_{\text{GS}}$ at $I_{\text{DS}}=1$ nA of the ZnO TFTs with GI-A during and after positive (+20 V) and negative ($-20$ V) gate voltage stresses as a function of stress and recovery time. After positive and negative gate bias stresses for $10^{4}$ s, recovery of $\Delta V_{\text{GS}}$ at $I_{\text{DS}}=1$ nA was recorded until the recovery time of $4 \times 10^{4}$ s. |
| ISSN: | 0021-4922 1347-4065 |
| DOI: | 10.1143/JJAP.50.03CB09 |