Carrier Generation Mechanism and Origin of Subgap States in Ar- and He-Plasma-Treated In–Ga–Zn–O Thin Films

Magari, Yusaku; Makino, Hisao; Furuta, Mamoru

doi:10.1149/2.0031709jss

Cited by 26 publications

(21 citation statements)

References 33 publications

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“…2h was averaged from 30 nanofibres selected from SEM images for each plasma treatment condition. The reduction in diameter is caused by the etching of the IGZO nanofibres by the additional Ar plasma, as Ar ions increase in the gas ratio of the Ar/O 2 mixed-plasma treatment 24,25 .…”

Section: Resultsmentioning

confidence: 99%

Performance improvement in electrospun InGaZnO nanofibres field-effect-transistors using low thermal budget microwave calcination and Ar/O2 mixed-plasma surface treatment

Cho

2020

Sci Rep

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In this study, we present a low thermal budget microwave annealing (MWA) method for calcination of electrospun In-Ga-ZnO (IGZO) nanofibres and demonstrate an improvement in the performance of IGZO nanofibre field-effect transistors (FETs) by Ar/O 2 mixed-plasma surface treatment. The IGZO nanofibres were fabricated by electrospinning method and calcined using MWA method. This process allowed for a significant reduction in the heat treatment temperature and time. Subsequently, plasma surface treatment using various ratios of Ar/O 2 gas mixtures was carried out. The surface morphology and chemical composition of MWA-calcined and plasma-treated IGZO nanofibres were studied by SEM and XPS analysis. In order to investigate the effects of MWA calcination combined with Ar/O 2 mixedplasma treatment on the electrical properties and the reliability of nanofibres-based transistors, IGZO nanofibres FETs were fabricated and applied to resistor-loaded inverters. Our results show that the O 2 plasma treatment significantly improves the performance of IGZO nanofibres FETs and the resistorloaded inverters based on IGZO nanofibres FETs, whereas Ar plasma treatment degrades the performance of these devices. The instability tests using positive bias temperature stress (PBTS) and negative bias temperature stress (NBTS) revealed that the O 2 plasma treatment contributed to the stability of IGZO nanofibres FETs. Our results suggest that the MWA calcination combined with the Ar/O 2 mixed-plasma surface treatment is a promising technique for the fabrication of high performance IGZO nanofibres FETs with low thermal budget processes. Recently, the application of amorphous oxide semiconductors (AOS) as backplanes for the thin film transistors (TFTs) of active matrix liquid crystal displays (AMLCDs) and active matrix organic light emitting diode displays (AMOLEDs) has been an actively researched topic owing to its advantages over the currently existing technology 1,2. Especially, amorphous indium gallium zinc oxide (a-IGZO) TFTs exhibit higher mobility than amorphous silicon (a-Si:H) TFTs, and they possess a superior uniformity compared with the polycrystalline silicon (poly-Si) TFTs because of their amorphous structure 3-5. In addition, a-IGZO has a wide band gap and high transmittance in the visible region, which makes it easy to access transparent optoelectronics 6,7. Despite these advantages, achieving a desired flexibility and stretchability in a-IGZO films still remains challenging. In addition, IGZO deposited by vacuum equipment, such as radio frequency (RF) magnetron sputtering, chemical vapor deposition (CVD) or atomic-layer-deposited (ALD), requires expensive equipment, and is disadvantageous for long process time and large area deposition. Recent intensive efforts have been focussed on the fabrication of IGZO nanofibres for their applications in the next-generation electronics, which are more flexible and stretchable 8-10. Electrospinning is one of the most commonly used manufacturing methods of nanofibres owing to its low manufac...

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Section: Resultsmentioning

confidence: 99%

Performance improvement in electrospun InGaZnO nanofibres field-effect-transistors using low thermal budget microwave calcination and Ar/O2 mixed-plasma surface treatment

Cho

2020

Sci Rep

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“…One of the major challenges in the fabrication of SA oxide TFTs is to form low-resistive S/D regions. Several methods have been proposed to reduce the resistance of the S/D regions using plasma treatment [7][8][9][10], aluminum reaction [11,12], ion implantation [13,14], or laser irradiation [15,16]. Among these, plasma treatment can be most readily inserted into the process flow for oxide TFTs.…”

Section: Introductionmentioning

confidence: 99%

Low-Resistive Source/Drain Formation Using Nitrogen Plasma Treatment in Self-Aligned In-Ga-Zn-Sn-O Thin-Film Transistors

Tsuji

Takei

Ochi

et al. 2022

IEEE J. Electron Devices Soc.

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In this work, we demonstrate the effectiveness of nitrogen plasma treatment on the formation of low-resistive source/drain (S/D) in self-aligned (SA) oxide thin-film transistors (TFTs) using a high-mobility oxide semiconductor (OS), In-Ga-Zn-Sn-O (IGZTO). The nitrogen plasma treatment was more effective at reducing the sheet resistance (Rsheet) of IGZTO films than the commonly used argon plasma treatment. Furthermore, Rsheet for nitrogen-plasma-treated IGZTO films remained low, even when the RF power and radiation time during the plasma treatment were increased when the minimum Rsheet was achieved. The same trends were also observed in OS films with different compositions, such as In-Ga-Zn-O and In-Sn-Zn-O. These results indicate that nitrogen plasma treatment is effective for achieving a reduction of Rsheet for various OS films with a wide process window regarding plasma processing parameters. The advantages could be attributed to the smaller sputtering effect on the OS films due to the lower mass of nitrogen ions than argon ions, which was verified by X-ray reflectivity and X-ray photoelectron spectroscopy analyses. For further validation, SA IGZTO TFTs with a channel length (L) of 3 to 100 m were fabricated with nitrogen or argon plasma treatment. The width-normalized parasitic SD resistance (RSDW) with the nitrogen plasma treatment was determined to be 11.3 •cm, which was ca. 40% lower than that with the argon plasma treatment. This improvement in RSDW resulted in higher mobility () in the nitrogen-plasma-treated SA IGZTO TFTs. A nitrogen-plasma-treated SA IGZTO TFT with L=10 m exhibited a high  of 27.2 cm 2 /Vs.

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“…Thin-film transistors (TFTs) based on oxide semiconductors (OSs) have attracted considerable attention for next generation flat-panel displays (FPDs) due to their advantages such as high field effect mobility (µ FE ), steep subthreshold swing, and low leakage current [1][2][3][4][5][6][7][8][9]. Although µ FE of the OS TFTs is more than an order of magnitude higher than that of hydrogenated amorphous silicon (a-Si:H) TFTs, further improvement of the µ FE has been required for OS TFTs to expand their applications [9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Quantum Confinement Effect in Amorphous In–Ga–Zn–O Heterojunction Channels for Thin-Film Transistors

et al. 2020

Self Cite

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Electrical and carrier transport properties in In-Ga-Zn-O thin-film transistors (IGZO TFTs) with a heterojunction channel were investigated. For the heterojunction IGZO channel, a high-In composition IGZO layer (IGZO-high-In) was deposited on a typical compositions IGZO layer (IGZO-111). From the optical properties and photoelectron yield spectroscopy measurements, the heterojunction channel was expected to have the type-II energy band diagram which possesses a conduction band offset (∆E c ) of~0.4 eV. A depth profile of background charge density indicated that a steep ∆E c is formed even in the amorphous IGZO heterojunction interface deposited by sputtering. A field effect mobility (µ FE ) of bottom gate structured IGZO TFTs with the heterojunction channel (hetero-IGZO TFTs) improved to~20 cm 2 V −1 s −1 , although a channel/gate insulator interface was formed by an IGZO−111 (µ FE =~12 cm 2 V −1 s −1 ). Device simulation analysis revealed that the improvement of µ FE in the hetero-IGZO TFTs was originated by a quantum confinement effect for electrons at the heterojunction interface owing to a formation of steep ∆E c . Thus, we believe that heterojunction IGZO channel is an effective method to improve electrical properties of the TFTs.

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Carrier Generation Mechanism and Origin of Subgap States in Ar- and He-Plasma-Treated In–Ga–Zn–O Thin Films

Cited by 26 publications

References 33 publications

Performance improvement in electrospun InGaZnO nanofibres field-effect-transistors using low thermal budget microwave calcination and Ar/O2 mixed-plasma surface treatment

Performance improvement in electrospun InGaZnO nanofibres field-effect-transistors using low thermal budget microwave calcination and Ar/O2 mixed-plasma surface treatment

Low-Resistive Source/Drain Formation Using Nitrogen Plasma Treatment in Self-Aligned In-Ga-Zn-Sn-O Thin-Film Transistors

Quantum Confinement Effect in Amorphous In–Ga–Zn–O Heterojunction Channels for Thin-Film Transistors

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