• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1455-1458
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• 2008

Amorphous silicon (a-Si:H) thin-film transistors (TFTs) are fabricated on flexible organic polymer foil substrates. As-fabricated performance, electrical bias-stability at elevated temperatures, electrical response under mechanical flexing, and prolonged mechanical stability of the TFTs are studied. TFTs made on plastic at ultra low process temperatures of $150^{\circ}C$ show initial electrical performance like TFTs made on glass but large gate-bias stress instability. An abnormal saturation of the instability against operation temperature is observed.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.256-256
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• 2012

Oxide semiconductors such as zinc tin oxide (ZTO) or indium gallium zinc oxide (IGZO) have attracted a lot of research interest owing to their high potential for application as thin film transistors (TFTs) [1,2]. However, the instability of oxide TFTs remains as an obstacle to overcome for practical applications to electronic devices. Several studies have reported that the electrical characteristics of ZnO-based transistors are very sensitive to oxygen, hydrogen, and water [3,4,5]. To improve the reliability issue for the amorphous InGaZnO (a-IGZO) thin-film transistor, back channel passivation layer is essential for the long term bias stability. In this study, we investigated the instability of amorphous indium-gallium-zinc-oxide (IGZO) thin film transistors (TFTs) by the back channel contaminations. The effect of back channel contaminations (humidity or oxygen) on oxide transistor is of importance because it might affect the transistor performance. To remove this environmental condition, we performed vacuum seasoning before the deposition of hybrid passivation layer and acquired improved stability. It was found that vacuum seasoning can remove the back channel contamination if a-IGZO film. Therefore, to achieve highly stable oxide TFTs we suggest that adsorbed chemical gas molecules have to be eliminated from the back-channel prior to forming the passivation layers.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.164.2-164.2
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• 2014

In order to combine advantages of ZnO thin film transistors (TFTs) with a high on-off ratio and graphene TFTs with extremely high carrier mobility, we present a facile methodology for fabricating ZnO thin film/graphene hybrid two-dimensional TFTs. Hybrid TFTs exhibited ambipolar behavior, an outstanding electron mobility of $329.7{\pm}16.9cm^2/V{\cdot}s$, and a high on-off ratio of $10^5$. The ambipolar behavior of the ZnO/graphene hybrid TFT with high electron mobility could be due to the superimposed density of states involving the donor states in the bandgap of ZnO thin films and the linear dispersion of monolayer graphene. We further established an applicable circuit model for understanding the improvement in carrier mobility of ZnO/graphene hybrid TFTs.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.546-549
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• 2009

In this paper, we investigated the effects of different source/drain (S/D) electrode materials in thin film transistors (TFTs) based on indium-gallium-zinc oxide (IGZO) semiconductor. A transfer length and effective resistances between S/D electrodes and amorphous IGZO thin-film transistors were examined. Intrinsic TFT parameters were extracted by the transmission line method (TLM) using a series of TFTs with different channel lengths measured at a low drain voltage. The TFTs fabricated with Cu S/D electrodes showed the lowest contact resistance and transfer length indicating good ohmic characteristics, and good transfer characteristics with a field-effect mobility (${\mu}_{FE}$) of 10.0 $cm^2$/Vs.

• Journal of Sensor Science and Technology
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• v.28 no.5
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• pp.329-333
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• 2019

Solution-processed oxide thin-film transistors (TFTs) have garnered great attention, owing to their many advantages, such as low-cost, large area available for fabrication, mechanical flexibility, and optical transparency. Negative bias stress (NBS)-induced instability of sol-gel IGZO TFTs is one of the biggest concerns arising in practical applications. Thus, understanding the bias stress effect on the electrical properties of sol-gel IGZO TFTs and proposing an effective recovery method for negative bias stressed TFTs is required. In this study, we investigated the variation of transfer characteristics and the corresponding electrical parameters of sol-gel IGZO TFTs caused by NBS and positive bias recovery (PBR). Furthermore, we proposed an effective PBR method for the recovery of negative bias stressed sol-gel IGZO TFTs. The threshold voltage and field-effect mobility were affected by NBS and PBR, while current on/off ratio and sub-threshold swing were not significantly affected. The transfer characteristic of negative bias stressed IGZO TFTs increased in the positive direction after applying PBR with a negative drain voltage, compared to PBR with a positive drain voltage or a drain voltage of 0 V. These results are expected to contribute to the reduction of recovery time of negative bias stressed sol-gel IGZO TFTs.

• ETRI Journal
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• v.34 no.6
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• pp.966-969
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• 2012

From a practical viewpoint, the topic of electrical stability in oxide thin-film transistors (TFTs) has attracted strong interest from researchers. Positive bias stress and constant current stress tests on indium-gallium-zinc-oxide (IGZO)-TFTs have revealed that an IGZO-TFT with a larger Ga portion has stronger stability, which is closely related with the strong binding of O atoms, as determined from an X-ray photoelectron spectroscopy analysis.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2353-2358
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• 2017

A femtosecond laser pre-annealing process based on indium zinc oxide (IZO) thin-film transistors (TFTs) is fabricated. We demonstrate a stable pre-annealing process to analyze surface structure change of thin films, and we maintain electrical stability and improve electrical performance. Furthermore, dynamic electrical characteristics of the IZO TFTs were investigated. Femtosecond laser pre-annealing process-based IZO TFTs exhibit a field-effect mobility of $3.75cm^2/Vs$, an $I_{on}/I_{off}$ ratio of $1.77{\times}10^5$, a threshold voltage of 1.13 V, and a subthreshold swing of 1.21 V/dec. And the IZO-based inverter shows a fast switching behavior response. From this study, IZO TFTs from using the femtosecond laser annealing technique were found to strongly affect the electrical performance and charge transport dynamics in electronic devices.

• Korean Journal of Materials Research
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• v.5 no.2
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• pp.203-207
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• 1995

Polysilicon this film transistors (poly-Si TFTs) with different channel dimensions were fabricated on low-temperature crystalized amorphous silicon films and on as-deposited polysilicon films. The electrical characteristics of these TFTs were characterized and compared. The performance of the TFTs fabricated on the solid-phase crystalized amophous silicon films ws showon to be superior to that of the TFTs fabricated on the as-deposited polysilicon films. It was found that the performance of poly-Si TFTs depends strongly on the material characteristics of the polysilicon films used as the active layers, but only weakly on the channel dimensions.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.534-536
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• 2009

We have fabricated solution-processed zinc-tin oxide thin film transistors (TFTs) and simple circuits on glass substrates. We report a solutionprocessed zinc-tin oxide TFTs on silicon wafer with mobility greater than 9 $cm^2/V{\cdot}s$ (W/L = 100/5 ${\mu}m$) and threshold voltage variation of less than 1 V after bias-stressing. Also, we fabricated solution-processed zinc-tin oxide circuits including inverters and 7-stage ring oscillators fabricated on glass substrates using the developed zinc-tin oxide TFTs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.9
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• pp.566-571
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• 2017

A soft baking process was used to enhance the electrical characteristics of solution-processed indium-zincoxide (IZO) thin-film transistors (TFTs). We demonstrate a stable soft baking process using a hot plate in air to maintain the electrical stability and improve the electrical performance of IZO TFTs. These oxide transistors exhibited good electrical performance; a field-effect mobility of $7.9cm^2/Vs$, threshold voltage of 1.4 V, sub-threshold slope of 0.5 V/dec, and a current on/off ratio of $2.9{\times}10^7$ were measured. To investigate the static response of our solutionprocessed IZO TFTs, simple resistor load type inverters were fabricated by connecting a resistor (5 or $10M{\Omega}$). Our IZO TFTs, which were manufactured using the soft baking process at a baking temperature of $120^{\circ}C$, performed well at the operating voltage, and are therefore a good candidate for use in advanced logic circuits and transparent display backplanes.