Abnormal Hump Effect Induced by Hydrogen Diffusion During Self-Heating Stress in Top-Gate Amorphous InGaZnO TFTs

Chen, Hong-Chih; Chen, Jianjie; Tu, Yu‐Fa; Zhou, Kuan‐Ju; Kuo, Chang-Hung; Su, Wan-Ching; Hung, Yang‐Hao; Shih, Yu‐Shan; Huang, Hui‐Chun; Tsai, Tsung‐Ming; Huang, Jen‐Wei; Lai, Wei-Chih; Chang, Ting‐Chang

doi:10.1109/ted.2020.2994539

Cited by 18 publications

(8 citation statements)

References 29 publications

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“…When the sufficient hydrogen in a-IGZO acts as shallow donors, it can raise the Fermi level (E F ) of a-IGZO [29], [30]. There are more carriers in a-IGZO:H, lowering the effective barrier height in the conduction path [29], [31]. Thus, hydrogen can make the conductive n + a-IGZO as the S/D contact regions (Fig.…”

Section: Resultsmentioning

confidence: 99%

Mobility Enhancement and Abnormal Humps in Top-Gate Self-Aligned Double-Layer Amorphous InGaZnO TFTs

Lee

Chiu

et al. 2022

IEEE J. Electron Devices Soc.

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The mobility enhancement and the positive bias stress of top-gate self-aligned TFTs using the a-IGZO channel with a front barrier are investigated. The a-IGZO front barrier can keep electrons in the a-IGZO channel away from the top-gate oxide to significantly enhance the electron mobility at the top gate operation. The parasitic channel induces a hump in the transfer characteristics. The positive bias stress shifts the hump to the negative voltage abnormally. The H 2 O in the polymer film on array layer is responsible for the abnormal shift. The H 2 O diffuses into the top-gate insulator and is electrolyzed to create H + , which forms a parasitic channel with a negative shift of threshold voltage, leading to the abnormal hump. The abnormal humps are increasingly significant with the increasing channel width and the decreasing channel length. The channel width dependence on positive bias stress is due to the inverse narrow width effect caused by the fringe electric field. The channel length dependence on positive bias stress is due to the H + diffusion toward the center of the parasitic channel from both the source and drain sides.INDEX TERMS Positive bias stress (PBS), a-IGZO, hump, polymer film on array (PFA).

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Section: Resultsmentioning

confidence: 99%

Mobility Enhancement and Abnormal Humps in Top-Gate Self-Aligned Double-Layer Amorphous InGaZnO TFTs

Lee

Chiu

et al. 2022

IEEE J. Electron Devices Soc.

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“…Hydrogen greatly influences the IGZO sub‐gap state by generating defects principally at shallow donor levels. [ 24,49,65 ] It forms hydroxide bond (OH) and could be ionized to H + and generates a free electron. During the fabrication process, hydrogen is not intentionally incorporated, but inevitably inter‐diffused into the IGZO.…”

Section: Resultsmentioning

confidence: 99%

Suppressing Undesired Channel Length‐Dependent Electrical Characteristics of Fully Integrated InGaZnO Thin‐Film Transistors via Defect Control Layer

Kim

Yang²,

Han³

et al. 2022

Adv Elect Materials

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InZnO have been used to replace conventional Si-based TFTs because of their superior electrical properties, transparency, and large-area applicability. [1][2][3][4] With above promising competitivities, oxide semiconductor technologies have been commercialized in active matrix flat-panel displays. [5,6] Recently, such semiconductors have found many applications beyond display backplanes, for example, as versatile sensors (e.g., detecting distance, pressure, and light), artificial neuromorphic computing, memory devices, and in healthcare systems. [7][8][9][10][11][12][13] Interestingly, Tan et al. exhibited imitating biological synaptic behaviors and implementing image detection by using IGZO based sensory device as an artificial photonic synapse with electric potential modulation. [7] Despite the mass production in display industry, a gap remains between emerging oxide TFTs and conventional Si-based TFTs in terms of field effect mobility (µ FE ), stability, and process immunity; such issues still limit widespread commercialization of oxide TFTs. [14,15] To expand oxide TFT technology for broader applications in displays, a short-channel capability is in high demand; this property can boost the driving current, increase integration density, reduce the dead area, and enhance productivity. Besides, it is necessary to enable low leakage current in the scaled device. Hua et al. demonstrated steep switching behavior accompanied with negligible leakage using 2D transition metal dichalcogenides of molybdenum disulfide (MoS 2 ), and Shukla et al. reported comparable device characteristics using hybrid phase transition of vanadium dioxide (VO 2 ). [16,17] Similarly, IGZO TFTs represents negligible leakage current (<1 pA), favorable for low power consumption. [3,14] To retain the advantages of a low leakage current in the short channel, the threshold voltage (V th ) must be carefully controlled, so operation in the enhancement mode is preferred. [18,19] However, the well-known short-channel effects ("hot carrier", drain-induced barrier lowering [DIBL], and reduced channel resistance) render the electrical characteristics inconsistent when the channel length (L CH ) is shortened. [20][21][22] Typically, the L CH value of oxide TFTs reported to date is about a few Demand for increased scalability of oxide thin-film transistors (TFTs) continues to rise, along with the need for ever-higher integration densities and driving currents. However, the undesirable channel length (L CH )-dependency renders short channels difficult. To overcome such behavior in back-channel etched devices, back-channel interface engineering using commercially favorable silicon oxide (SiO x ) and the effects thereof on the electrical characteristics of fully integrated TFTs are investigated. Process-dependent investigation reveals that a sequential formation of double-layered SiO x with a defect control layer (DCL) effectively alleviates back-channel damage. The proposed method imparts advanced functionality to conventional materials of SiO x . The DCL p...

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“…This is a general behavior for coplanar a‐IGZO TFTs with SiO 2 passivation. [ 15,16,31,32 ] Chen et al reported that hydrogen diffuses into the intrinsic a‐IGZO for the coplanar oxide TFTs. [ 15,31 ] Therefore, the TFT becomes more depletion mode by decreasing L .…”

Section: Resultsmentioning

confidence: 99%

“…[ 15,16,31,32 ] Chen et al reported that hydrogen diffuses into the intrinsic a‐IGZO for the coplanar oxide TFTs. [ 15,31 ] Therefore, the TFT becomes more depletion mode by decreasing L . [ 13–15 ] Therefore, the TFT has a large negative shift of V th from −0.6 V ( L = 10 μm) to −11.4 V ( L = 1.5 μm), as shown in Figure 2a.…”

Section: Resultsmentioning

confidence: 99%

Improvement of Thermal and Environmental Stabilities of Short Channel Coplanar Amorphous InGaZnO Thin‐Film Transistors by Introducing Amorphous ZrAlO_x Interlayer

Lee

Islam

et al. 2021

Adv Eng Mater

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The short channel coplanar amorphous indium gallium zinc oxide (a‐IGZO) thin‐film transistor (TFT) is reported by introducing a ZrAlO x (ZAO) interlayer deposited by spray pyrolysis at the substrate temperature of 350 °C. The atomic ratio (at. %) of In:Ga:Zn:O is 1:2.5:1.2:5.2 in the a‐IGZO film deposited by sputtering. The a‐IGZO TFT with ZAO layer with 0.87 μm channel length exhibits the field‐effect mobility of 6.44 cm2 V−1 s−1, the threshold voltage of −2.16 V, and on/off current ratio of 7.6 × 107. It is found from the X‐ray photoelectron spectroscopy depth profile and high‐resolution transmission electron microscope analysis that some Zr atoms diffuse into the a‐IGZO underlayer. The formation of ZrO bonds on a‐IGZO surface region reduces the carrier concentration in the a‐IGZO TFT offset region, between source/drain contact and the channel, and blocks the carrier diffusion into the channel. This reduces the field‐effect mobility of 10 μm channel length TFT from 21.86 to 14.01 cm2 V−1 s−1, but the ZAO layer protects the a‐IGZO from the diffusion of H2O and O2. As a result, 0.87 μm TFT shows high on/off current ratio and stable under 85 °C and 85% relative humidity test for 2 days.

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Abnormal Hump Effect Induced by Hydrogen Diffusion During Self-Heating Stress in Top-Gate Amorphous InGaZnO TFTs

Cited by 18 publications

References 29 publications

Mobility Enhancement and Abnormal Humps in Top-Gate Self-Aligned Double-Layer Amorphous InGaZnO TFTs

Mobility Enhancement and Abnormal Humps in Top-Gate Self-Aligned Double-Layer Amorphous InGaZnO TFTs

Suppressing Undesired Channel Length‐Dependent Electrical Characteristics of Fully Integrated InGaZnO Thin‐Film Transistors via Defect Control Layer

Improvement of Thermal and Environmental Stabilities of Short Channel Coplanar Amorphous InGaZnO Thin‐Film Transistors by Introducing Amorphous ZrAlO_x Interlayer

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Abnormal Hump Effect Induced by Hydrogen Diffusion During Self-Heating Stress in Top-Gate Amorphous InGaZnO TFTs

Cited by 18 publications

References 29 publications

Mobility Enhancement and Abnormal Humps in Top-Gate Self-Aligned Double-Layer Amorphous InGaZnO TFTs

Mobility Enhancement and Abnormal Humps in Top-Gate Self-Aligned Double-Layer Amorphous InGaZnO TFTs

Suppressing Undesired Channel Length‐Dependent Electrical Characteristics of Fully Integrated InGaZnO Thin‐Film Transistors via Defect Control Layer

Improvement of Thermal and Environmental Stabilities of Short Channel Coplanar Amorphous InGaZnO Thin‐Film Transistors by Introducing Amorphous ZrAlOx Interlayer

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Product

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Improvement of Thermal and Environmental Stabilities of Short Channel Coplanar Amorphous InGaZnO Thin‐Film Transistors by Introducing Amorphous ZrAlO_x Interlayer