High Mobility ZnO thin film transistors using the novel deposition of high-k dielectrics

Abstract

In order to investigate the performance of ZnO-based thin film transistors (ZnO-TFTs), we fabricate devices using amorphous hafnium dioxide (HfO2) high-k dielectrics. Sputtered ZnO was used as the active channel layer, and aluminium source/drain electrodes were deposited by thermal evaporation, and the HfO2 high-k dielectrics are deposited by metal-organic chemical vapour deposition (MOCVD). The ZnO-TFTs with high-k HfO2 gate insulators exhibit good performance metrics and effective channel mobility which is appreciably higher in comparison to SiO2-based ZnO TFTs fabricated under similar conditions. The average channel mobility, turn-on voltage, on-off current ratio and subthreshold swing of the high-k TFTs are 31.2 cm2V-1s-1, -4.7 V, ~103, and 2.4 V/dec respectively. We compared the characteristics of a typical device consisting of HfO2 to those of a device consisting of thermally grown SiO2 to examine their potential for use as high-k dielectrics in future TFT devices.

This is a preview of subscription content, access via your institution.

References

  1. 1.

    A.R. Moore, Electron and hole drift mobility in amorphous silicon . Applied Physics Letters, 1976. 31(11): p. 761–4.

    Google Scholar 

  2. 2.

    H. Gleskova and S. Wagner, Electron mobility in amorphous silicon thin-film transistors under compressive strain . Applied Physics Letters, 2001. 79(20): p. 3347–9.

    CAS  Article  Google Scholar 

  3. 3.

    T. Yi, et al, Study of light induced instability in intrinsic hydrogenated amorphous silicon films by the photomixing technique . Applied Physics Letters, 1996. 68(5): p. 640–2.

    Article  Google Scholar 

  4. 4.

    E.N. Voronkov Current instability in a-Si:H solar cells after their exposure to light. 2001. Russia: MAIK Nauka.

    Google Scholar 

  5. 5.

    D. Ngwashi, R.B. Cross, and S. Paul . Electrically Air-stable ZnO Thin Film Produced by Reactive RF Magnetron Sputtering for Thin Film Transistors Applications . in Mat. Res. Soc. 2009. 1201: p. 153–158

    Article  Google Scholar 

  6. 6.

    T. Hirao, et al, Bottom-gate zinc oxide thin-film transistors (ZnO TFTs) for AM-LCDs . IEEE Transactions on Electron Devices, 2008. 55(11): p. 3136–3142.

    CAS  Article  Google Scholar 

  7. 7.

    T. Hirao, et al Distinguished paper: High mobility top-gate Zinc Oxide Thin-Film Transistors (ZnO-TFTs) for active-matrix liquid crystal displays. 2006. San Francisco, CA, United states: Society for Information Display.

    Google Scholar 

  8. 8.

    P.F. Carcia, et al, Transparent ZnO thin-film transistor fabricated by rf magnetron sputtering . Applied Physics Letters, 2003. 82(7): p. 1117–1119.

    CAS  Article  Google Scholar 

  9. 9.

    J. Nishii, et al, High mobility thin film transistors with transparent ZnO channels . Japanese Journal of Applied Physics, Part 2 (Letters), 2003. 42(4A): p. 347–9.

    Article  Google Scholar 

  10. 10.

    F.M. Hossain, et al, Modeling and simulation of polycrystalline ZnO thin-film transistors . Journal of Applied Physics, 2003. 94(12): p. 7768–77.

    CAS  Article  Google Scholar 

  11. 11.

    A.P. Milanov, et al, Lanthanide oxide thin films by metalorganic chemical vapor deposition employing volatile guanidinate precursors . Chemistry of Materials, 2009. 21(22): p. 5443–5455.

    CAS  Article  Google Scholar 

  12. 12.

    K. Remashan, et al, Impact of hydrogenation of ZnO TFTs by plasma-deposited silicon nitride gate dielectric . IEEE Transactions on Electron Devices, 2008. 55(10): p. 2736–43.

    CAS  Article  Google Scholar 

  13. 13.

    Y. Taur and T.H. Ning, Fundamentals of Modern VLSI Devices. 1998: Cambridge University Press. p. 128.

    Google Scholar 

  14. 14.

    Y.R. Park, J. Kim, and Y.S. Kim, Effect of hydrogen doping in ZnO thin films by pulsed DC magnetron sputtering . Applied Surface Science, 2009. 255(22): p. 9010–9014.

    CAS  Article  Google Scholar 

  15. 15.

    G.A. Shi, et al, “Hidden hydrogen” in as-grown ZnO . Applied Physics Letters, 2004. 85(23): p. 5601–3.

    CAS  Article  Google Scholar 

Download references

Author information

Affiliations

Authors

Corresponding author

Correspondence to K. D. Ngwashi.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Ngwashi, K.D., Cross, B.M.R., Paul, S. et al. High Mobility ZnO thin film transistors using the novel deposition of high-k dielectrics. MRS Online Proceedings Library 1315, 618 (2011). https://doi.org/10.1557/opl.2011.721

Download citation