Journal of Electronic Materials

, Volume 28, Issue 12, pp 1452–1456

Optical characterization of hydrogenated amorphous silicon thin films deposited at high rate

  • S. H. Lin
  • Y. C. Chan
  • D. P. Webb
  • Y. W. Lam
Special Issue Paper

Abstract

The aim of this paper is to provide a better understanding of hydrogenated amorphous silicon thin films (a-Si:H) in relation to their optical properties: refractive index, optical gap, absorption coefficient, thickness and surface roughness. The transmission spectrum of the films, deposited with various rf discharge power densities by an optimized plasma enhanced chemical vapor deposition (PECVD) method, at a high rate (>10 Å/sec), was measured over a range in wavelength from 500 to 1100 nm. An approximate model is utilized to describe the surface roughness. In this model, the surface roughness is modeled as a mixed layer of 50 percent of a-Si:H and 50 percent of air and the optical constant of the rough layer is derived using the Bruggemann effective medium approximation (EMA). The gradient iteration method of numerical analysis is used to solve the nonlinear equations in the study. Our results show that the potential underestimation of refractive index and resulting overestimation of film thickness can be overcome by considering the reflection of the rough surface. The method is carried out on the transmission data and the influence of rf discharge power density on the properties of the film is discussed in detail.

Key words

Hydrogenated amorphous silicon thin film PECVD surface roughness absorption coefficient transmission EMA 

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References

  1. 1.
    J.A. Schmidt and F. A. Rubinelli, J. Appl. Phys. 83, 340 (1998).Google Scholar
  2. 2.
    M.H. Brodsky, M. Cardona, and J.J. Cuomo, Phys. Rev. B 16, 3556 (1997).CrossRefGoogle Scholar
  3. 3.
    E.C. Freeman and W. Paul, Phys. Rev. B 18, 4288 (1978).CrossRefGoogle Scholar
  4. 4.
    Alvin M. Goodman, Applied Optics 17, 2779 (1978).CrossRefGoogle Scholar
  5. 5.
    J.I. Szczyrbowski and A. Czapla, Thin Solid Films 46, 127 (1977).CrossRefGoogle Scholar
  6. 6.
    R. Swanepoel, J. Phys. E: Sci. Instrum. 16, 1214 (1983).CrossRefGoogle Scholar
  7. 7.
    R. Swanepoel, J. Phys. E: Sci. Instrum. 17, 896 (1984).CrossRefGoogle Scholar
  8. 8.
    W. Hu, Florence Y.M. Chan, D.P. Webb, Y.C. Chan, and Y.W. Lam, J. Electron. Mater. 25, 1837 (1996).Google Scholar
  9. 9.
    K. Mui and F.W. Smith, Phys. Rev. B 38, 10623 (1998).CrossRefGoogle Scholar
  10. 10.
    D.E. Aspnes and J.B. Theeten, Phys. Rev. B 20, 815 (1979).CrossRefGoogle Scholar
  11. 11.
    J. Tauc, Optical Properties of Solids, ed. F. Abeles (Amsterdam, The Netherlands: North-Holland Publishers, 1970).Google Scholar
  12. 12.
    Xuanyin Lin, Kuixun Lin, Yunpeng Yu, Y.W. Lam, Y.C. Chan, S.H. Lin, and Y.M. Chan, IEEE First WCPEC (New York: IEEE, 1994), p. 638.Google Scholar
  13. 13.
    X. Lin, H. Wang, K. Lin, Y.P. Yu, and S.L. Fu, Thin Solid Films 237, 310 (1994).CrossRefGoogle Scholar
  14. 14.
    Florence Y.M. Chan, Y.W. Lam, Y.C. Chan, S.H. Lin, W.S. Lau, and S.J. Chau, MRS Symp. A, Proc., Spring Meeting (Pittsburgh, PA: MRS, 1996).Google Scholar
  15. 15.
    S.H. Lin, Y.C. Chan, D.P. Webb, and Y.W. Lam, IUMRS-ICAM. Symp. M (Beijing, China, June 1999).Google Scholar

Copyright information

© TMS-The Minerals, Metals and Materials Society 1999

Authors and Affiliations

  • S. H. Lin
    • 1
  • Y. C. Chan
    • 1
  • D. P. Webb
    • 1
  • Y. W. Lam
    • 1
  1. 1.Department of Electronic EngineeringCity University of Hong KongHong Kong

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