Theory of Defects in the MOS System

  • Arthur H. Edwards

Abstract

Without doubt, the single most important technology for electronic device fabrication relies on the metal-oxide-silicon (MOS) system. In recent years III-V semiconductors have promised great increases in device speed and, because they are direct-gap materials, have been very important in electro-optical applications (i. e. light emitting diodes). However, these semiconductors have very complicated surfaces with high densities of surface-states and, hence, very low surface electron densities. While bare silicon surfaces also have low electron densities due to surface-states, most of these states can be eliminated by growing a thermal oxide. For other semiconductors, no such passivating process exists, so that, for instance, inversion devices such as enhancement-mode MOSFET’s (field effect transistors) are practical only in silicon. It is not surprising, then, that the MOS system has been studied intensely over the past thirty years. One of the most important areas of investigation has been the study of point defects. Defects in the oxide lead to shifts in threshold voltage in MOSFET’s [1]. Also, the residual unpassivated defects at the Si/SiO2 interface are responsible for decreased surface mobility, and for “soft” threshold characteristics. We should note that while some defects are inherent, i. e. arise from differences in the thermal expansion coefficients of silicon and silicon dioxide, and from lattice-network mismatch, most exist due to ionizing radiation or hot-electron injection. They can be created during fabrication (during X-ray lithography, or during the various plasma-assisted etching steps), or they can be a result of exposure to a space environment where even a modest flux of gamma rays can cause dramatic changes in device characteristics [2].

Keywords

Silicon Atom Hyperfine Interaction Dangling Bond Unpaired Spin Hyperfine Tensor 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. 1.
    For a thorough though somewhat dated review of charge trapping in the MOS system, see E. H. Nicollian and J. R. Brews, MOS ( Metal Oxide Semiconductor) Physics and Technology, John Wiley and Sons (New York, 1982 ) Chapter 11.Google Scholar
  2. 2.
    P. Winokur at The Natural Space Radiation and VLSI Technology Conference, Houston, Tx., 1986 (in press).Google Scholar
  3. 3.
    By intrinsic we mean those defects that involve only the elements silicon, oxygen and hydrogen. While an ideal MOS structure can be built of only oxygen and silicon, hydrogen is always present, and is so fundamentally important, that we include it in our study.Google Scholar
  4. 4.
    For reviews of intrinsic defects in a-Si02, see D. L. Griscom in: The Physics of SiO and its interfaces, ed. S. T. Pantelides (Pergamon, New York, 1978) p 232;W. B. Fowler in: Structure and Bonding in Noncrystalline Solids, eds. G. E. Walrafen and A. G. Revesz (Plenum, New York, 1986) p157; A. H. Edwards in: Defects in Glasses, eds. F. L. Galeener, D. L. Griscom and M. J. Weber (MRS, Pittsburgh, 1986) p. 3.Google Scholar
  5. 5.
    For extended discussions of the dangling silicon orbital defect at the 111 Si/Si02 interface see A. H. Edwards, Phys. Rev. B Pt. II 36; A. H. Edwards in The Physics and Technology of a-Si02 (in press).Google Scholar
  6. 6.
    D. L. Griscom and D. B. Brown, this proceedings.Google Scholar
  7. 7.
    K. L. Brower, this proceedings.Google Scholar
  8. 8.
    A. H. Edwards and W. B. Fowler in: Structure and Bonding in Noncrystalline Solids, eds. G. E. Walrafen and A. G. Revesz (Plenum, 1986) p. 139; A. H. Edwards and G. Germann, Nucl. Inst. and Meth. in Phys. Res. (in press).Google Scholar
  9. 9.
    D. L Griscom, Phys. Rev. B 22, 4192 (1980).Google Scholar
  10. 10.
    J. Isoya, J. Weil, and L.Halliburton, J. Chem. Phys. 74, 5436 (1981).Google Scholar
  11. 11.
    J. K. Rudra, W. B. Fowler, and F. J. Feigl, Phys. Rev. Lett. 55 (1985) 2614.Google Scholar
  12. 12.
    M. G. Jani, R. B. Bossoli, and L. E. Halliburton, Phys. Rev. B 27 (1983) 2285.Google Scholar
  13. 13.
    R. H. Silsbee, J. Appl Phys. 32 (1961) 1459.Google Scholar
  14. 14.
    It is interesting to compare these results with the hyperfine data for the E4’ center (ref. 10). At low temperatures, the spin is localized predominantly on the long-bond side of the vacancy in contradistinction to the E1’ center. In this case Isoya et aI. observed three weak hyperfine interactions. At higher temperatures, when the spin is delocalized onto both silicon atoms neighboring the vacancy, they observe five weak hyperfine interactions. Again, Si3 in Fig. 2 is oriented so that there is strong cancellation of the defect wave-function at its nucleus.Google Scholar
  15. 15.
    J. K. Rudra and W. B. Fowler, Phvs. Rev, B15 Dt. II 35, 8223 (1987).Google Scholar
  16. 16.
    F. J. Feigl, W. B. Fowler, and K. L. Yip, Sol. State Commun. 14, 225 (1974).CrossRefGoogle Scholar
  17. 17.
    K. L. Yip and W. B. Fowler, Phys. Rev. B 11 (1975) 2327.Google Scholar
  18. 18.
    A. H. Edwards and W. B. Fowler, J. Phys. Chem. Solids 46, 841 (1985).CrossRefGoogle Scholar
  19. 19.
    The dependence on initial Si-Si separation is easy to explain using eq. (1). As this distance increases, the excitation energy decreases, while the force and coupling constants remain roughly unchanged.Google Scholar
  20. 20.
    F. Schirmer in The Physics of MOS Insulators, eds. G. Lucovsky, S. T. Pantelides and F. L. Galeener ( Pergamon, New York, 1980 ) p. 102.Google Scholar
  21. 21.
    Y. Bar-Yam and S. T. Pantelides (unpublished).Google Scholar
  22. 22.
    D. C. Allan and M. P. Teter, Still. Am. Phys. Soc. 33, 438 (1988).Google Scholar
  23. 23.
    D. L. Griscom, Phys. Rev B 22, 4192 (1980).CrossRefGoogle Scholar
  24. 24.
    D. L. Griscom, E. J. Friebele, and G. H. Sigel Jr., Solid State Comm. 15, 479 (1974).CrossRefGoogle Scholar
  25. 25.
    J. Vitko, J. Appl. Phys. 49 5530 (1978).CrossRefGoogle Scholar
  26. 26.
    T-E Tsai and D. L. Griscom J. Non-Cryst. Solids 91, 170 (1987).CrossRefGoogle Scholar
  27. 27.
    M. Stapelbroek, D. L. Griscom, E. J. Friebele, and G. H. Sigel, Jr., J. Non-Cryst. Solids. 32, 313 (1979).CrossRefGoogle Scholar
  28. 28.
    E. J. Friebele, D. L. Griscom, M. Stapelbroek, and R. A. Weeks, Phys. Rev. Lett. 42, 1346 (1979).CrossRefGoogle Scholar
  29. 29.
    D. L. Griscom and E. J. Friebele, Phys. Rev. B24, 4896 (1981).CrossRefGoogle Scholar
  30. 30.
    E. H. Poindexter and P. J. Caplan, J. Appl. Phys. (in press).Google Scholar
  31. 31.
    W. Carlos, Appl. Phys. Lett. 49, 1767 (1986).Google Scholar
  32. 32.
    B. B. Triplett, T. Takahashi, and T. Sugano, Appl. Phys. Lett 50 1663 (1987).CrossRefGoogle Scholar
  33. 33.
    H. S. Witham and P. M. Lenahan, Appl. Phys. Lett. 51, 1007 (1987).CrossRefGoogle Scholar
  34. 34.
    E. H. Poindexter, E. R.Ahlstrom, and P. J. Caplan in The Physics of Si02 and its Interfaces, ed. S. T. Pantelides ( Pergamon, N. Y., 1978 ), p. 227.Google Scholar
  35. 35.
    K. L. Brower, Appl. Phys. Lett. 43, 1111 (1983).Google Scholar
  36. 36.
    E. H. Poindexter, G. J. Gerardi, M.-E. Rueckel, P. J. Caplan, N. M. Johnson, and D. K. Biegelsen, J. Appl. Phvs. 56, 2844 (1984).CrossRefGoogle Scholar
  37. 37.
    Lenahan and Dressendorfer, J. Appl. Phys. 55, 3495 (1984).Google Scholar
  38. 38.
    M. Cook and C. T. White, Phys. Rev Lett. 59, 1741 (1987).CrossRefGoogle Scholar
  39. 39.
    A. H. Edwards, Phys. Rev. B15 pt. II 36, 9638 (1987).Google Scholar
  40. 40.
    A. Redondo, W. Goddard, and T. McGill, J. Vac. Sci. Technol. 21, 649 (1982).CrossRefGoogle Scholar
  41. 41.
    A. Redondo, W. Goddard, T. McGill, and T. Surratt, Solid State Comm. 20, 733 (1976).CrossRefGoogle Scholar
  42. 42.
    Y. Bar-Yam and J. Joannopoulos, Phys. Rev. Lett. 56, 2203 (1986).CrossRefGoogle Scholar
  43. 43.
    E. H. Poindexter, P. J. Caplan, B. E. Deal, and R. R. Razouk, J. Appl. Phys 52, 879 (1981).CrossRefGoogle Scholar
  44. 44.
    G. J. Gerardi, E. H. Poindexter, P. H. Caplan, and N. M. Johnson, Appl. Phys. Lett. 49, 348 (1986).CrossRefGoogle Scholar
  45. 45.
    K. L. Brower, Z. fur Physik. Chem. 151 S, 177 (1987).Google Scholar
  46. 46.
    J. S. Binkley, M. Frisch, K. Raghavachari, D. DeFrees, H. B. Schegel, R. Whitside, E. Fluder, R. Seeger, D. J. Fox, M. Head-Gordon, and S. Topiol, GAUSSIAN-82 Release C, Carnegie Mellon University.Google Scholar
  47. 47.
    P. J. Bishof, J. Am. Chem. Soc. 98 (1976) 6844.CrossRefGoogle Scholar
  48. 48.
    R. C. Bingham, M. J. S. Dewar, and D. H. Lo, J. Am. Chem. Soc. 97, 1285 (1975).CrossRefGoogle Scholar
  49. 49.
    As in ref. 39, the HOMO can be defined as the defect state because most (in this case 0.51 e)of the wave-function amplitude is on the defect atom.Google Scholar
  50. 50.
    A. Carrico, R. Elliott, and R. Barrio, Phys. Rev. B 34, 872 (1986).CrossRefGoogle Scholar
  51. 51.
    S. T. Pantelides and M. Long in The Physics of Si02 and its Interfaces, ed. S. T. Pantelides ( Pergamon, New York, 1978 ) p. 339.Google Scholar
  52. 52.
    C. T. White (private communication).Google Scholar
  53. 53.
    D. K. Biegelsen and M. Stutzmann, Phys. Rev. B15 33, 3006 1986.Google Scholar
  54. 54.
    M. Cook in Physics and Technology of a-Si02, eds. R. Devine and J. Arndt (in press).Google Scholar

Copyright information

© Springer Science+Business Media New York 1988

Authors and Affiliations

  • Arthur H. Edwards
    • 1
  1. 1.U.S. Army E.T. and D. LaboratoryFt. MonmouthUSA

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