Oxygen Interstitial Creation in a-IGZO Thin-Film Transistors Under Positive Gate-Bias Stress

Effects of oxygen flow on positive bias temperature instability and hot carrier injection are investigated in Amorphous InGaZnO (IGZO) thin film transistors. The oxygen flow can suppress the oxygen vacancy density, but introduce shallow states near the conduction edges. The electron can tunnel into gate oxide via these shallow states. As a result, the IGZO channel with oxygen flow has more electrons trapped in the gate oxide than the channel without oxygen flow, leading to more positive V T shift after positive bias temperature instability. The IGZO without oxygen flow create oxygen vacancy (V O) in the channel. The hole generated by impact ionization during the hot electron injection can be trapped in V O to form V 2+ O. The V 2+ O leads to less positive V T shift for IGZO channel without oxygen flow than with the oxygen flow. Since the impact ionization occurs near the drain, the positive V T shift of the reverse measurement (V SD > 0) is smaller than the forward measurement (V DS > 0) after hot electron injection. INDEX TERMS Amorphous InGaZnO, thin film transistor, positive bias temperature instability, hot carrier injection, reliability, oxygen flow, ionized oxygen vacancies.

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“…flow [18]- [19]. The low-frequency noise (LFN) measurement for OF-IGZO and NOF-IGZO are shown in Fig.…”

Section: Figure 7 Normalized Noise Power Density Versus Frequency Fomentioning

confidence: 99%

Oxygen-related Reliability of Amorphous InGaZnO Thin Film Transistors

Yen

Tai

Liu

et al. 2020

IEEE J. Electron Devices Soc.

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“…In the case of change of subgap states in channel material, if the energy levels of changed subgap states are near the Fermi level for the gate voltage sweep range, electrons are captured by a newly‐created subgap state during gate voltage sweep; this phenomenon changes the shape of the I–V or C–V curve . Thus, a change in the shape of either curve after stress/recovery can be interpreted to mean that the number of subgap states has changed . For our PB‐stressed device, positive Δ V th and no gradual change of subthreshold slope SS in I–V curve occurred (Figure a, inset); this result indicates that PBS‐related degradation was mainly caused by electron trapping at the GI or at the interface between the channel and the GI.…”

Section: Resultsmentioning

confidence: 92%

“…This would be because the detectable range of I–V and C–V measurements for subgap states are different . Under PBS, the Fermi level is close to the conduction band, and formation energy of acceptor‐like states (usually oxygen interstitials or zinc vacancies in a‐IGZO) is lowered in the channel near the interface . Thus, a change in the shape of the C–V curve suggests that acceptor‐like states were also created in the channel near the interface during PBS …”

Section: Resultsmentioning

confidence: 99%

Relationship between Detrapping of Electrons and Negative Gate Bias during Recovery Process in a‐InGaZnO Thin Film Transistors

Kang

Lee

Kim

et al. 2019

Physica Status Solidi (a)

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The relationship between detrapping of electrons and negative gate bias in amorphous InGaZnO thin film transistors (a-IGZO TFTs) is investigated. In these devices, positive gate-bias stress (PBS) traps electrons at the gate insulator (GI) or at the interface between the channel and the GI, and creates acceptor-like states, which the authors speculate may be oxygen interstitials or zinc vacancies. In contrast, negative gate-bias stress (NBS) increases donor-like states, which are speculated as ionized oxygen vacancies, near the interface. When subsequent negative gate bias (SNB) is applied to a TFT after PBS, electrons are detrapped and donor-like states are increased simultaneously. Measurements with various SNB and PBS conditions suggests that SNB accelerates detrapping of electrons, and that those detrapped electrons interrupts the increase of donor-like states.

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“…As is well known in the display industry, the oxide TFTs generally have critical instability against prolonged bias stress, temperature, and light illumination, resulting in a threshold voltage shift due to the charge trapping in the GI or at the GI/channel interface, defect generation in the channel, and abnormal phenomena such as a transfer curve with a hump 34,36–38 . Since the Al-ITZO TFTs integrated in our FPS are subjected to row-by-row scanning at V G between −10 V and 20 V periodically, it is necessary to confirm the electrical stability performance of the oxide TFTs.…”

Section: Resultsmentioning

confidence: 99%

Highly Sensitive Active-Matrix Driven Self-Capacitive Fingerprint Sensor based on Oxide Thin Film Transistor

Jeon

Lee

et al. 2019

Sci Rep

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The fingerprint recognition has been widely used for biometrics in mobile devices. Existing fingerprint sensors have already been commercialized in the field of mobile devices using primarily Si-based technologies. Recently, mutual-capacitive fingerprint sensors have been developed to lower production costs and expand the range of application using thin-film technologies. However, since the mutual-capacitive method detects the change of mutual capacitance, it has high ratio of parasitic capacitance to ridge-to-valley capacitance, resulting in low sensitivity, compared to the self-capacitive method. In order to demonstrate the self-capacitive fingerprint sensor, a switching device such as a transistor should be integrated in each pixel, which reduces a complexity of electrode configuration and sensing circuits. The oxide thin-film transistor (TFT) can be a good candidate as a switching device for the self-capacitive fingerprint sensor. In this work, we report a systematic approach for self-capacitive fingerprint sensor integrating Al-InSnZnO TFTs with field-effect mobility higher than 30 cm 2 /Vs, which enable isolation between pixels, by employing industry-friendly process methods. The fingerprint sensors are designed to reduce parasitic resistance and capacitance in terms of the entire system. The excellent uniformity and low leakage current (<10 −12 ) of the oxide TFTs allow successful capture of a fingerprint image.

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Oxygen Interstitial Creation in a-IGZO Thin-Film Transistors Under Positive Gate-Bias Stress

Cited by 42 publications

References 31 publications

Oxygen-related Reliability of Amorphous InGaZnO Thin Film Transistors

Oxygen-related Reliability of Amorphous InGaZnO Thin Film Transistors

Relationship between Detrapping of Electrons and Negative Gate Bias during Recovery Process in a‐InGaZnO Thin Film Transistors

Highly Sensitive Active-Matrix Driven Self-Capacitive Fingerprint Sensor based on Oxide Thin Film Transistor

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