Journal of the Korean Institute of Electrical and Electronic Material Engineers (한국전기전자재료학회논문지)

The Korean Institute of Electrical and Electronic Material Engineers (한국전기전자재료학회)
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Fabrication and Characteristics of ZnO TFTs for Flexible Display using Low Temp Process

Flexible Display용 Low Temp Process를 이용한 ZnO TFT의 제작 및 특성 평가

  • Received : 2009.08.12
  • Accepted : 2009.09.22
  • Published : 2009.10.01
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Abstract

Recently, transparent ZnO-based TFTs have attracted much attention for flexible displays because they can be fabricated on plastic substrates at low temperature. We report the fabrication and characteristics of ZnO TFTs having different channel thicknesses deposited at low temperature. The ZnO films were deposited as active channel layer on $Si_3N_4/Ti/SiO_2/p-Si$ substrates by RF magnetron sputtering at $100^{\circ}C$ without additional annealing. Also, the ZnO thin films deposited at oxygen partial pressures of 40%. ZnO TFTs using a bottom-gate configuration were investigated. The $Si_3N_4$ film was deposited as gate insulator by PE-CVD at $150^{\circ}C$. All Processes were processed below $150^{\circ}C$ which is optimal temperature for flexible display and were used dry etching method. The fabricated devices have different threshold slop, field effect mobility and subthreshold slop according to channel thickness. This characteristics are related with ZnO crystal properties analyzed with XRD and SPM. Electrical characteristics of 60 nm ZnO TFT (W/L = $20\;{\mu}m/20\;{\mu}m$) exhibited a field-effect mobility of $0.26\;cm^2/Vs$, a threshold voltage of 8.3 V, a subthreshold slop of 2.2 V/decade, and a $I_{ON/OFF}$ ratio of $7.5\times10^2$.

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References

  1. C. R. Gorla, N. W. Emanetoglu, S. Liang, W. E. Mayo, and H. Shen, "Structural, optical, and surface acoustic wave properties of epitaxial ZnO films", J. Appl. Phys., Vol. 85, No. 5, p. 2595, 1999. https://doi.org/10.1063/1.369577
  2. Bae H. S. and Yoon M. H., "Photodetecting properties of ZnO-based thin-film transistors", Appl. Phys. Lett., Vol. 83, No. 25, p. 5313, 2003. https://doi.org/10.1063/1.1633676
  3. R. L. Hoffman, B. J. Norris, and J. F. Wager, "ZnO-based transparent thin-film transistors", Appl. Phys. Lett., Vol. 82, No. 5, p. 735, 2003.
  4. B. Y. Oh, M. C. Jeong, M. H. Ham, and J. M. Myoung, "Effects of the channel thickness on the structural and electrical characteristics of room-temperature fabricated ZnO thinfilm transistors", Semicond. Sci. Technol., Vol. 22, p. 608, 2007. https://doi.org/10.1088/0268-1242/22/6/004
  5. Y. K. Moon, D. Y. Moon, S. Lee, S. H. Lee, and J. W. Park, "Effects of oxygen contents in the active channel layer on electrical characteristics of ZnO-based thin film transistors", J. Vac. Sci. Technol. B, Vol. 26, No. 4, p. 1472, 2008. https://doi.org/10.1116/1.2918329
  6. 조신호, “$O_{2}/Ar$ 혼합 유량비를 변수로 갖는 라디오파 마그네트론 스퍼터링으로 성장된 ZnO 박막의 특성”, 전기전자재료학회논문지, 20권, 11호, p. 932, 2007. https://doi.org/10.4313/JKEM.2007.20.11.932
  7. 김한기, 이지면, “산화아연 반도체의 광전소자 응용을 위한 오믹접합 기술 개발동향”, 전기전자재료, 21권, 2호, p. 15, 2008.
  8. S. R. Min, J. W. Lee, H. N. Cho, and C. W. Chung, “Etch characteristics of zinc oxide thin films in a $Cl_{2}/Ar$ plasma”, J. Korean Ind. Eng. Chem., Vol. 18, No. 1, p. 28, 2007.
  9. T. Hirao, M. Furuta, T. Hiramatsu, and M. Kakegawa, "Bottom-gate ZnO TFTs for AM-LCDs", IEEE Transactions on Electron Devices, Vol. 55, No. 11, p. 3139, 2008.
  10. S. Kishimoto, T. Yamamoto, Y. Nakagawa, K. Ikeda, H. Makino, and T. Yamada, "Dependence of electrical and structural properties on film thickness of undoped ZnO thin films prepared by plasma-assisted electron beam deposition", Superlattices and Microstructures, Vol. 39, p. 306, 2006. https://doi.org/10.1016/j.spmi.2005.08.069
  11. S. S. Lin and J. L. Huang, "Effect of thickness on the structural and optical properties of ZnO films by r.f. magnetron sputtering", Surface & Coatings Technology, Vol. 185, p. 222, 2004. https://doi.org/10.1016/j.surfcoat.2003.11.014