Effect of Two-Step Annealing on High Stability of a-IGZO Thin-Film Transistor

Peng, Cong; Yang, Shibo; Pan, Cheng-Chao; Li, Xifeng; Zhang, Jianhua

doi:10.1109/ted.2020.3017718

Cited by 51 publications

(24 citation statements)

References 38 publications

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“…Thus, the near E F defects strongly influence the electrical properties of the IGZO TFTs. Furthermore, the required annealing temperature to obtain good electrical properties and reliability for the IGZO TFTs is typically 300 °C [ 14 , 40 ].…”

Section: Resultsmentioning

confidence: 99%

Defect Passivation and Carrier Reduction Mechanisms in Hydrogen-Doped In-Ga-Zn-O (IGZO:H) Films upon Low-Temperature Annealing for Flexible Device Applications

2022

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Low-temperature activation of oxide semiconductor materials such as In-Ga-Zn-O (IGZO) is a key approach for their utilization in flexible devices. We previously reported that the activation temperature can be reduced to 150 °C by hydrogen-doped IGZO (IGZO:H), demonstrating a strong potential of this approach. In this paper, we investigated the mechanism for reducing the activation temperature of the IGZO:H films. In situ Hall measurements revealed that oxygen diffusion from annealing ambient into the conventional Ar/O2-sputtered IGZO film was observed at >240 °C. Moreover, the temperature at which the oxygen diffusion starts into the film significantly decreased to 100 °C for the IGZO:H film deposited at hydrogen gas flow ratio (R[H2]) of 8%. Hard X-ray photoelectron spectroscopy indicated that the near Fermi level (EF) defects in the IGZO:H film after the 150 °C annealing decreased in comparison to that in the conventional IGZO film after 300 °C annealing. The oxygen diffusion into the film during annealing plays an important role for reducing oxygen vacancies and subgap states especially for near EF. X-ray reflectometry analysis revealed that the film density of the IGZO:H decreased with an increase in R[H2] which would be the possible cause for facilitating the O diffusion at low temperature.

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Section: Resultsmentioning

confidence: 99%

Defect Passivation and Carrier Reduction Mechanisms in Hydrogen-Doped In-Ga-Zn-O (IGZO:H) Films upon Low-Temperature Annealing for Flexible Device Applications

2022

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“…Development of high-performance TFTs requires selection of an appropriate channel material, and amorphous oxide semiconductors have attracted attention for this purpose. In particular, amorphous oxide semiconductors have attracted attention as the channel material, the amorphous indium–gallium–zinc–oxide (a-IGZO), has been already used in mass production of oxide TFTs for display backplanes because of various advantages such as low off-current, high field-effect mobility (μ FET ), and optical transparency in the visible light region compared to amorphous silicon-based TFTs. − However, because high-end displays require higher aperture ratio and smaller pixel size, it is still necessary to improve the mobility of the a-IGZO TFTs, which is lower than low-temperature polycrystalline silicon TFTs. , Furthermore, the light stability of a-IGZO TFTs should be improved because the electrons are generated by ionization of oxygen vacancies (V o s) in the a-IGZO channel under light irradiation . However, if the V o concentration is excessively suppressed, the μ FET decreases as the electron concentration decreases. , Therefore, it is important to control the V o concentration in the a-IGZO channel to improve the μ FET and stability simultaneously. − …”

Section: Introductionmentioning

confidence: 99%

Vertically Graded Oxygen Deficiency for Improving Electrical Characteristics and Stability of Indium Gallium Zinc Oxide Thin-Film Transistors

Yoon

Kim

et al. 2021

ACS Appl. Mater. Interfaces

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We investigated a facile fabrication method, which is an insertion of a carrier-induced interlayer (CII) between the oxygenrich a-IGZO channel and the gate insulator to improve the electrical characteristics and stability of amorphous indium−gallium−zinc− oxide thin-film transistors (a-IGZO TFTs). The a-IGZO channel is deposited with additional oxygen gas flow during a-IGZO channel deposition to improve the stability of the a-IGZO TFTs. The CII is a less than 10 nm thick deposited thin film that acts to absorb the oxygen from the a-IGZO front channel through oxidation. Through oxidation of the CII, the oxygen concentration of the a-IGZO front channel is decreased compared to that of the oxygen-rich back channel, which forms a vertically graded oxygen deficiency (VGO) in the a-IGZO channel. Therefore, the electrical characteristics of the VGO TFTs are improved by increasing the carrier concentration of the front channel as the oxygen vacancy concentration in the front channel is increased through the oxidation of the CII. At the same time, the stability of the VGO TFTs is improved by maintaining a high oxygen concentration in the back channel even after oxidation of the CII. The field-effect mobility (μ FET ) of the VGO TFTs improved compared to that of the a-IGZO TFTs from 7.16 ± 0.6 to 12.0 ± 0.7 cm 2 /V•s. The threshold voltage (V th ) shifts under positive bias temperature stress and negative bias temperature illumination stress decreased from 6.00 to 2.95 V and −15.58 to −8.99 V, respectively.

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“…A series of Gaussian and Lorentzian peaks were fit to the data to deconvolute the peaks. The spectral deconvolutions include two peaks: the peak at ∼529.9 eV represents the metal oxygen (M-O) bonding and the peak at ∼531.3 eV is attributed to M-OH and other oxygen-related defects [20], [21]. To compare the different samples, the data were normalized and the relative areas of M-O and M-OH were extracted.…”

Section: A Izo Thin Film Characteristicsmentioning

confidence: 99%

Influence of Thermal Postdeposition on Trap States in Sol–Gel Indium–Zinc Oxide TFTs

Chatterjee

Weidling

Zhou

et al. 2022

IEEE Trans. Electron Devices

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In solution-processed oxide thin-film transistors, post-deposition thermal processing significantly changes the film's transport properties and is essential for high-performance devices. The mobility, bias stability and trapping-detrapping related hysteresis are improved with higher processing temperatures, which is generally attributed to decreased concentrations of localized states that act as electron traps. Fabricating and characterizing 29 devices, we provide further experimental evidence that post-deposition processing indeed leads to enhanced channel electron mobility in sol-gel indium zinc oxide TFTs, and, on the basis of a simple model, we extract physical parameters that yield a quantitative assessment of the changes in the densities and the properties of the localized trap states. The data is obtained for sol-gel indium zinc oxide thin films and TFTs subjected to thermal postdeposition processing from 300 to 500 0 C. The extracted parameters indicate that the trap state density in the bulk semiconductor and at the interface decrease by factors of 5 and 3, respectively. Furthermore, the localized states become shallower, and the band mobility increases with higher processing temperatures.

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Effect of Two-Step Annealing on High Stability of a-IGZO Thin-Film Transistor

Cited by 51 publications

References 38 publications

Defect Passivation and Carrier Reduction Mechanisms in Hydrogen-Doped In-Ga-Zn-O (IGZO:H) Films upon Low-Temperature Annealing for Flexible Device Applications

Defect Passivation and Carrier Reduction Mechanisms in Hydrogen-Doped In-Ga-Zn-O (IGZO:H) Films upon Low-Temperature Annealing for Flexible Device Applications

Vertically Graded Oxygen Deficiency for Improving Electrical Characteristics and Stability of Indium Gallium Zinc Oxide Thin-Film Transistors

Influence of Thermal Postdeposition on Trap States in Sol–Gel Indium–Zinc Oxide TFTs

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