Effect of SiO&lt;sub&gt;2&lt;/sub&gt; and SiO&lt;sub&gt;2&lt;/sub&gt;/SiN&lt;sub&gt;&lt;italic&gt;x&lt;/italic&gt;&lt;/sub&gt; Passivation on the Stability of Amorphous Indium-Gallium Zinc-Oxide Thin-Film Transistors Under High Humidity

Chowdhury, Delwar Hossain; Mativenga, Mallory; Um, Jae Gwang; Mruthyunjaya, Ravi K.; Heiler, Gregory; Tredwell, T.J.; Jang, Jin

doi:10.1109/ted.2015.2392763

Cited by 74 publications

(59 citation statements)

References 26 publications

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“…On the contrary, the wet sample exhibits different behavior. It has been known that water acts as donor-like states in the a-IGZO active layer for a small amount of exposure to water [14]. In this case, an assumption for the role of the water is that there is no chemical reaction between water and the a-IGZO active layer.…”

Section: Resultsmentioning

confidence: 99%

“…It is necessary to investigate the effect of the long-period exposure to ambient water on the active layer, because the stability also critically depends on the exposure time of the ambient. In addition, the ambient effect should be studied for a very long time over several years under moderate-humidity conditions, which is the typical TFT operation condition in practical applications [14]. However, it is impossible to perform the humidity stability experiments such a long time in a research level.…”

Section: Introductionmentioning

confidence: 99%

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Electrical Stability of Solution-Processed a-IGZO TFTs Exposed to High-Humidity Ambient for Long Periods

Lee

Jeong

2019

IEEE J. Electron Devices Soc.

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The variations in the electrical and mechanical properties of solution-processed amorphous indium-gallium-zinc-oxide thin-film transistors exposed to high-humidity ambient conditions for long periods were analyzed. When the TFT was exposed to high-humidity conditions, field-effect mobility severely decreased, while ON/OFF current ratio improved and subthreshold slope value remained nearly constant, which is different from that exposed to low-humidity condition. We found that the H 2 O molecules induce mechanical peeling of the active layer such that they act as acceptor-like deep states, which is very different from the prior results under low humidity condition. The variations in electrical characteristics were systematically analyzed using a technology-CAD simulation before and after exposure to highhumidity conditions. INDEX TERMS a-IGZO, thin film transistor, humidity, stability, ambient.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electrical Stability of Solution-Processed a-IGZO TFTs Exposed to High-Humidity Ambient for Long Periods

Lee

Jeong

2019

IEEE J. Electron Devices Soc.

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“…As previously reported, adsorption of H 2 O molecules in the ambient (relative humidity larger than 40%) causes significant negative threshold voltage (V th ) shifts in unpassivated oxide-based TFTs. [18][19] In this study, the experiment was performed in air with relative humidity of 60%. To discuss more insight into the interaction of O 2 molecules and avoid H 2 O adsorption on ZTO films at the initial state of TFT devices, all devices were put into a vacuum chamber (3 × 10 −5 torr) for 6 hour and then dry O 2 gas was vented into the chamber until the chamber pressure reached 760 torr.…”

Section: Resultsmentioning

confidence: 99%

“…This observation clearly indicates that adsorption of oxygen will not affect the ZTO TFT performance; nevertheless, as reported in the literature, water molecules in air (60% relative humidity) adsorbed on ZTO surface act as electron donors and consequently increase electron carriers in ZTO channel layers. 19,[28][29] On the other hand, the V th and I D-off of 5 nm-thick ZTO TFT do not change apparently despite in air, dry O 2 or vacuum. All three devices are not passivated on the back surface.…”

Section: -24mentioning

confidence: 99%

Ambient Constancy of Passivation-Free Ultra-Thin Zinc Tin Oxide Thin Film Transistor

Liu

Chen

Jeng

2015

ECS Solid State Letters

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An ultra-thin (5 nm-thick), unpassivated zinc tin oxide (ZTO) thin-film transistor TFT, fabricated with solution process, exhibits a good field-effect mobility (13 ∼ 14 cm 2 /Vs), small subthreshold swing (∼0.30 V/dec.) and high on/off current ratio (∼10 8 ). The field-effect mobility can be further enhanced by increasing the ZTO thickness to 12 nm and 22 nm. Furthermore, I D -V G characteristics of the 5 nm-thick ZTO TFT remain unaffected, regardless of working in air (60% relative humidity), vacuum or dry O 2 atmosphere. The dissimilar TFT characteristics are discussed in terms of oxygen deficiency content, as well as the Fermi level position (E F to E C ) for ZTO of various thicknesses to explain the moisture immunity of the 5 nm-thick solution-processed ZTO TFT. © The Author Zinc oxide-based thin film transistors (TFTs) have been applied in a wide range of electronic circuits, such as flat-panel displays, light emitting diodes and charge trapping non-volatile memory.1-2 Among them, zinc tin oxide (ZTO) TFT that is indium-and gallium-free has gained an advantage because of the low-cost competition.3-5 In addition, the solution process has attracted much attention for TFT fabrication since it enables process simplification and high throughput even for large-area displays, thereby providing a reduction in manufacturing costs for flat-panel displays.6 Furthermore, the stability and reliability of TFTs has been intensively studied in recent years, which are one of the most important issues for their practical application. 7-8Thus, our previous study had investigated transistor characteristics and bias stability with and without light illumination for solution processed ultra-thin ZTO TFTs without passivation.9 However, for unpassivated devices, the back surface of metal oxides are sensitive to the ambiance (oxygen, water and/or dipole molecules), which may be the dominant factors affecting the threshold voltage (V th ).10-12 The comparison of back and front channel conduction in ZnO-based TFT, using ionic liquid and SiO 2 dielectrics, respectively, has also been reported. 13 On the other hand, the effect of active layer thickness on the electrical performance of oxide TFTs has been investigated for oxide TFTs, [14][15][16] including solution processed ZTO. 17 However, not much attention has been paid on the characteristics of TFTs with ultrathin active oxide films (less than 10 nm). In addition, oxygen vacancy content in ZTO may be thickness dependent and will influence the ambient effect as well. In this work, we report the ZTO thickness dependence of oxygen deficiency content and its impact on electrical characteristics with different ambiances for solution processed ZTO TFTs. The relationship between oxygen deficiency content and adsorption of water molecules by comparing the TFT performance in air (relative humidity of 60%), vacuum (3 × 10 −5 torr) and dry O 2 (760 torr) atmosphere for varying ZTO thickness are investigated in detail. ExperimentalThe bottom-gate, top contact ZTO TFTs were fabricated on ptype ...

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“…For type A sample, once the passivation is done, it can be hardly affected by the moisture in the ambient. Since the SiN x passivation layer is a good barrier to block water vapor [21], [22], even with a thermal annealing, the residual H 2 O molecules still cannot escape from the device. While for type B sample without a SiN x passivation, the residual H 2 O molecules could be removed during the annealing process.…”

Section: A Unified Degradation Model Of Nbs and Nbis A Nbsmentioning

confidence: 99%

A Unified Degradation Model of a-InGaZnO TFTs Under Negative Gate Bias With or Without an Illumination

Wang

Zhang

et al. 2019

IEEE J. Electron Devices Soc.

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Degradation behaviors of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) under negative bias stress (NBS) and negative bias illumination stress (NBIS) are investigated systematically. In some cases, a two-stage degradation behavior of a-IGZO TFTs is observed under both NBS and NBIS, which begins with a small positive shift of threshold voltage (V th), and is followed by a large negative V th shift. There is an intrinsic correlation between the degradations of NBS and NBIS. Quantitatively, both stress gate biases (V G) and temperature dependencies of V th of the two degradations are found to be the same and the recovery processes are also very similar. A unified model of NBS and NBIS is proposed to consistently explain the degradation behaviors of a-IGZO TFTs and their correlation. INDEX TERMS a-InGaZnO, thin-film transistors (TFTs), degradation, light illumination, gate bias stress.

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Effect of SiO<sub>2</sub> and SiO<sub>2</sub>/SiN<sub><italic>x</italic></sub> Passivation on the Stability of Amorphous Indium-Gallium Zinc-Oxide Thin-Film Transistors Under High Humidity

Cited by 74 publications

References 26 publications

Electrical Stability of Solution-Processed a-IGZO TFTs Exposed to High-Humidity Ambient for Long Periods

Electrical Stability of Solution-Processed a-IGZO TFTs Exposed to High-Humidity Ambient for Long Periods

Ambient Constancy of Passivation-Free Ultra-Thin Zinc Tin Oxide Thin Film Transistor

A Unified Degradation Model of a-InGaZnO TFTs Under Negative Gate Bias With or Without an Illumination

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