Review of Present Reliability Challenges in Amorphous In-Ga-Zn-O Thin Film Transistors

Hsieh, Tien-Yu; Chang, Ting‐Chang; Chen, Te-Chih; Tsai, Ming-Yen

doi:10.1149/2.013409jss

Cited by 45 publications

(26 citation statements)

References 32 publications

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“…This device performs a good mobility of 13∼14 cm 2 /Vs, as well as a small subthreshold swing (∼0.30 V/dec.) and high on/off current ratio (∼10 8 ), regardless of working in vacuum, dry O 2 or moisture-contained air (60% relative humidity) ambiance. The superb ambient stability degrades if the ZTO thickness increases.…”

Section: Discussionmentioning

confidence: 99%

“…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][8] Thus, 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 ).…”

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confidence: 99%

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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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Section: Discussionmentioning

confidence: 99%

mentioning

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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“…Many metal‐oxide‐based materials have been used, such as ZnO, ZnMgO, ZnSnO, and InMgO, which directly serve as the active channel in the TFT structure for their clear response to UV light illumination . In industry, the metal oxide composition material InGaZnO 4 (IGZO) was originally proposed for display applications . Due to its high transparency, uniformity, and mobility, IGZO has significant attention for various applications and their related TFT reliability issues .…”

Section: Comparisons Of the Features Of Many Other Uv Sensing Devicesmentioning

confidence: 99%

A Dual‐Gate InGaZnO₄‐Based Thin‐Film Transistor for High‐Sensitivity UV Detection

Chen

Tsao

Chien

et al. 2019

Adv Materials Technologies

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produces some real risks, including wrinkles, pigmented flat spots known as liver spots, and even skin cancer. [1][2][3][4] These are mostly attributed to the effects of UV light, a shorter wavelength than the visual spectrum. Therefore, over the past decades, developments in UV sensors have received significant attention for their potential positive effects on human health.When considering the performance of many different UV sensors, required features include high sensitivity, stability, and linearity. Most importantly, a compact design compatible with current device fabrication process is key for low-cost production. [5,6] Previous studies mostly focused on a two terminal photodiode device based on wide bandgap (WBG) semiconductor materials such as TiO 2 , SiC, and ZnO materials. [7][8][9] Later, some III-V compounds, such as gallium nitride (GaN), also received attention as UV photodetector materials. [10,11] Some metal-semiconductor-metal (MSM) structures have also been proposed to simplify device fabrication processes. [7][8][9][10][11][12] Although such WBG-based UV sensors have the advantages of a simple structure and high intrinsic visible-blindness; numinous drawbacks such as poor crystal quality or high activation energy of dopants have slowed developments. In addition, UV-sensing devices have received significant recent attention for applications in areas such as human health, fire detection, and optical communication.One key factor for product commercialization is determining the optimal materials that allow for integration of excellent UV-sensing properties with compatibility with industrial fabrication processes. However, current UV sensors often fail to achieve this due to either mismatched materials or a device that must be excessively large in order to produce enough photocurrent for UV detection. The UV-light-sensing properties of an amorphous InGaZnO 4 (IGZO) thin-film transistor with a dual-gate structure and relatively small device size (width/length = 50 μm/10 μm) that achieves high sensitivity through a threshold-voltage-(V th )-adjustment method is proposed. Comparing the drain currents under UV exposure to those under darkened conditions indicates that the ratio between the photoinduced and dark current reaches 10 6 . Furthermore, the UV sensitivity of the dual-gate transistors can be adjusted by varying the bottom gate voltage, with each pixel of the sensor then being read out separately via scan line pulses. This allows the dual-gate a-IGZO transistor to be used for high-performance UV sensing while being effectively integrated in display applications. SensorsAlmost all living things on Earth rely on the sun for nutrition and survival, whether directly or indirectly. The sun provides radiant heat, and gives energy to plants for the photosynthesis process, thus providing basic needs and food for creatures and humans. However, exposure to the sun for human beings also

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“…Amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs) have attracted much attention for active matrix liquid crystal display (AMLCD) and active matrix organic light emitting diode (AMOLED) applications due to their high electron mobility, high transparency to visible light and low-temperature process [1][2][3]. Among a variety of amorphous oxide semiconductors, a-IGZO TFTs are thought to be the most promising device for practical applications.…”

Section: Introductionmentioning

confidence: 99%

51.3: A Mobility Enhancing Method Adopting A Multi‐Active Layer Structure in Thin Film Transistors

Tsai

Chang

Chu

et al. 2015

Symp Digest of Tech Papers

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This letter demonstrates a mobility enhancing method using a multi-active layer structure in oxide TFTs. The active layers are deposited in sequence according to their different conductivities, which can be performed with different materials or different process conditions. The multi-active layer comprises bottom, middle, and top layers, forming a carrier-confinement structure. The middle layer has a higher carrier concentration, while bottom and top layers have lower ones. In this way, the main channel current flows through the middle layer, and this avoidance of the gate insulator/active layer and active layer/passivation interface leads to higher mobility. In this work, the multi-layer oxide TFTs shows better mobility of 46.5 cm2/Vs when compared to any single layer.

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Review of Present Reliability Challenges in Amorphous In-Ga-Zn-O Thin Film Transistors

Cited by 45 publications

References 32 publications

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

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

A Dual‐Gate InGaZnO₄‐Based Thin‐Film Transistor for High‐Sensitivity UV Detection

51.3: A Mobility Enhancing Method Adopting A Multi‐Active Layer Structure in Thin Film Transistors

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Review of Present Reliability Challenges in Amorphous In-Ga-Zn-O Thin Film Transistors

Cited by 45 publications

References 32 publications

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

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

A Dual‐Gate InGaZnO4‐Based Thin‐Film Transistor for High‐Sensitivity UV Detection

51.3: A Mobility Enhancing Method Adopting A Multi‐Active Layer Structure in Thin Film Transistors

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A Dual‐Gate InGaZnO₄‐Based Thin‐Film Transistor for High‐Sensitivity UV Detection