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Title: Nano-crystallization in ZnO-doped In{sub 2}O{sub 3} thin films via excimer laser annealing for thin-film transistors

Abstract

In a previous work, we reported the high field effect mobility of ZnO-doped In{sub 2}O{sub 3} (IZO) thin film transistors (TFTs) irradiated by excimer laser annealing (ELA) [M. Fujii et al., Appl. Phys. Lett. 102, 122107 (2013)]. However, a deeper understanding of the effect of ELA on the IZO film characteristics based on crystallinity, carrier concentrations, and optical properties is needed to control localized carrier concentrations for fabricating self-aligned structures in the same oxide film and to adequately explain the physical characteristics. In the case of as-deposited IZO film used as the channel, a high carrier concentration due to a high density of oxygen vacancies was observed; such a film does not show the required TFT characteristics but can act as a conductive film. We achieved a decrease in the carrier concentration of IZO films by crystallization using ELA. This means that ELA can form localized conductive or semi-conductive areas on the IZO film. We confirmed that the reason for the carrier concentration decrease was the decrease of oxygen-deficient regions and film crystallization. The annealed IZO films showed nano-crystalline phase, and the temperature at the substrate was substantially less than the temperature limit for flexible films such as plastic, whichmore » is 50°C. This paves the way for the formation of self-aligned structures and separately formed conductive and semi-conductive regions in the same oxide film.« less

Authors:
; ; ;  [1]; ; ;  [2]; ; ;  [3]
  1. Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan)
  2. Delft University of Technology, Feldmannweg 17, P.O. Box 5053, 2600 GB Delft (Netherlands)
  3. Idemitsu Kosan Co., Ltd., 1280 Kami-izumi, Sodegaura, Chiba, 299-0293 (Japan)
Publication Date:
OSTI Identifier:
22611555
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Advances; Journal Volume: 6; Journal Issue: 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; CARRIERS; CONCENTRATION RATIO; CRYSTALLIZATION; DENSITY; DOPED MATERIALS; EXCIMER LASERS; INDIUM OXIDES; IRRADIATION; MOBILITY; NANOSTRUCTURES; OPTICAL PROPERTIES; OXYGEN; PLASTICS; SUBSTRATES; THIN FILMS; TRANSISTORS; ZINC OXIDES

Citation Formats

Fujii, Mami N., E-mail: f-mami@ms.naist.jp, Ishikawa, Yasuaki, Bermundo, Juan Paolo Soria, Uraoka, Yukiharu, Ishihara, Ryoichi, Cingel, Johan van der, Mofrad, Mohammad R. T., Kawashima, Emi, Tomai, Shigekazu, and Yano, Koki. Nano-crystallization in ZnO-doped In{sub 2}O{sub 3} thin films via excimer laser annealing for thin-film transistors. United States: N. p., 2016. Web. doi:10.1063/1.4954666.
Fujii, Mami N., E-mail: f-mami@ms.naist.jp, Ishikawa, Yasuaki, Bermundo, Juan Paolo Soria, Uraoka, Yukiharu, Ishihara, Ryoichi, Cingel, Johan van der, Mofrad, Mohammad R. T., Kawashima, Emi, Tomai, Shigekazu, & Yano, Koki. Nano-crystallization in ZnO-doped In{sub 2}O{sub 3} thin films via excimer laser annealing for thin-film transistors. United States. doi:10.1063/1.4954666.
Fujii, Mami N., E-mail: f-mami@ms.naist.jp, Ishikawa, Yasuaki, Bermundo, Juan Paolo Soria, Uraoka, Yukiharu, Ishihara, Ryoichi, Cingel, Johan van der, Mofrad, Mohammad R. T., Kawashima, Emi, Tomai, Shigekazu, and Yano, Koki. 2016. "Nano-crystallization in ZnO-doped In{sub 2}O{sub 3} thin films via excimer laser annealing for thin-film transistors". United States. doi:10.1063/1.4954666.
@article{osti_22611555,
title = {Nano-crystallization in ZnO-doped In{sub 2}O{sub 3} thin films via excimer laser annealing for thin-film transistors},
author = {Fujii, Mami N., E-mail: f-mami@ms.naist.jp and Ishikawa, Yasuaki and Bermundo, Juan Paolo Soria and Uraoka, Yukiharu and Ishihara, Ryoichi and Cingel, Johan van der and Mofrad, Mohammad R. T. and Kawashima, Emi and Tomai, Shigekazu and Yano, Koki},
abstractNote = {In a previous work, we reported the high field effect mobility of ZnO-doped In{sub 2}O{sub 3} (IZO) thin film transistors (TFTs) irradiated by excimer laser annealing (ELA) [M. Fujii et al., Appl. Phys. Lett. 102, 122107 (2013)]. However, a deeper understanding of the effect of ELA on the IZO film characteristics based on crystallinity, carrier concentrations, and optical properties is needed to control localized carrier concentrations for fabricating self-aligned structures in the same oxide film and to adequately explain the physical characteristics. In the case of as-deposited IZO film used as the channel, a high carrier concentration due to a high density of oxygen vacancies was observed; such a film does not show the required TFT characteristics but can act as a conductive film. We achieved a decrease in the carrier concentration of IZO films by crystallization using ELA. This means that ELA can form localized conductive or semi-conductive areas on the IZO film. We confirmed that the reason for the carrier concentration decrease was the decrease of oxygen-deficient regions and film crystallization. The annealed IZO films showed nano-crystalline phase, and the temperature at the substrate was substantially less than the temperature limit for flexible films such as plastic, which is 50°C. This paves the way for the formation of self-aligned structures and separately formed conductive and semi-conductive regions in the same oxide film.},
doi = {10.1063/1.4954666},
journal = {AIP Advances},
number = 6,
volume = 6,
place = {United States},
year = 2016,
month = 6
}
  • A high-performance polysilicon thin-film transistor (TFT) fabricated using XeCl excimer laser crystallization of pre-patterned amorphous Si films is presented. The enhanced TFT performance over previous reported results is attributed to pre-patterning before laser crystallization leading to enhanced lateral grain growth. Device performance has been systematically investigated as a function of the laser energy density, the repetition rate, and the number of laser shots. Under the optimal laser energy density, poly-Si TFT`s fabricated using a simple low-temperature ({le} 600 C) process have field-effect mobilities of 91 cm{sup 2}/V{center_dot}s (electrons) and 55 cm{sup 2}/V{center_dot}s (holes), and ON/OFF current ratios over 10{sup 7}more » at V{sub DS} = 10 V. The excellent overall TFT performance is achieved without substrate heating during laser crystallization and without hydrogenation. The results also show that poly-Si TFT performance is not sensitive to the laser repetition rate and the number of laser shots above 10.« less
  • High-performance polysilicon thin-film transistors (TFT`s) are fabricated using an excimer laser to recrystallize the undoped channel and dope the source-drain regions. Using a technique the authors call grain engineering they are able to control grain microstructure using laser parameters. Resulting polysilicon films are obtained with average grain sizes of {approximately}4--9 {micro}m in sub-100 nm thick polysilicon films without substrate heating during the laser recrystallization process. Using a simple four-mask self-aligned aluminum top-gate structure, they fabricate TFT`s in these films. By combining the grain-engineered channel polysilicon regions with laser-doped source-drain regions, TFT`s are fabricated with electron mobilities up to 260 cm{supmore » 2}/Vs and on/off current ratios greater than 10{sup 7} To their knowledge, these devices represent the highest performance laser-processed TFT`s reported to date fabricated without substrate heating or hydrogenation.« less
  • A KrF excimer laser with 30 ns pulse duration is used for crystallization of a-GaAs grown on silicon substrate using molecular beam epitaxy technique. The effect of laser energy density and film thickness on grain morphology has been studied. Scanning electron microscopy and high-resolution electron backscatter diffraction have been used to study the texture and microstructure evolution during the crystallization of initially amorphous GaAs thin films. The integrated information on grain size distribution, preferred orientation, and nature of grain boundaries provides useful information to postulate the mechanism of grain growth and the likely role of different contributing parameters in themore » evolution of final texture under the highly transient processing conditions prevailing during the short laser irradiation. The texture ranges from weak <111> fiber texture to strong <100> texture depending on film thickness and laser influence. The grain structure and texture development are discussed based on the three melting regimes: (1) partial meting regime; (2) complete melting regime; and (3) near-complete melting regime.« less
  • In this paper, we observed and characterized changes in the microstructure and texture during recrystallization and grain growth in polycrystalline GaAs thin films using multiple pulses crystallization by a KrF excimer laser. Films of various thicknesses were studied to assess film thickness and laser energy density effects. In the low temperature domain corresponding to the partial melting regime, normal grain growth was observed. In the superlateral grain growth regime the increase in grain size was notable with grain sizes much greater than the film thickness. A bimodal grain size distribution emerged implying the onset of secondary grain growth. The changemore » in grain size distribution, texture, and grain boundary texture were analyzed using scanning electron microscopy and electron backscatter diffraction. It was found that grain growth is accompanied by a strengthening in (001) texture, indicating that the grain growth phenomenon is strain energy driven. The experimental results are explained with theory of secondary grain growth in thin films.« less
  • No abstract prepared.