Hot Carrier Degradation of Gain in Bipolar Transistors


In this paper hot carrier related aging of n-p-n bipolar transistors is investigated experimentally and theoretically to bring physical insight into the bipolar transistor hFE (common emitter current gain) degradation. Electrical stress experiments are performed on transistors with different base doping profiles at varying temperatures. Detailed process simulations are performed to determine the doping profiles of the base-emitter junction. Monte Carlo transport simulations are then performed at different temperatures and bias conditions to determine the electron and hole distribution functions in the baseemitter junction. AT&T’s 0.8 μ.m BICMOS technology is used to fabricate the experimental bipolar transistor structures. For this non-self aligned technology we attribute hFE degradation to the presence of hot holes and secondary electrons which are generated by hot hole impact ionization. This feed-back due to impact ionization has a dominant effect on the high energy tails of the distribution of both holes and electrons even when the overall current multiplication is low. Simple hot electron energy transport models do not contain the complexity to properly describe ionization feedback and carrier heating, and are therefore inadequate. An exponential dependence of the transistor lifetime on BVEBO is deduced for constant voltage stress (Vstress < BVEBO) conditions, confirming the importance of secondaries in the process of degradation.

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  1. 1

    D.R. Collins, Appl. Phys. Lett., 13, 264 (1968).

    Article  Google Scholar 

  2. 2

    D.R. Collins, IEEE Trans. Electron Devices, 16, 403 (1969).

    Article  Google Scholar 

  3. 3

    B.A. McDonald, IEEE Trans. Electron Devices, 17, 871 (1970).

    Article  Google Scholar 

  4. 4

    S.P. Joshi, R. Lahri, and C. Lage, IEDM Tech. Digest, 182 (1987).

    Google Scholar 

  5. 5

    D.D. Tang and E. Hackbarth, IEEE Trans. Electron Devices, 35, 2101 (1988).

    Article  Google Scholar 

  6. 6

    J.D. Burnett and C. Hu, IEEE Trans. Electron Devices, 35, 2238 (1988).

    Article  Google Scholar 

  7. 7

    D. Burnett and C. Hu, Proc. IEEE International Reliability Symposium, 164 (1990).

    Google Scholar 

  8. 8

    C.J. Huang, T.A. Grotjohn, D.K. Reinhard, and C.J. Sun, IEEE Proc. Bipolar Circuits and Technology Meeting, 134, (1992).

    Google Scholar 

  9. 9

    D. Burnett, T. Horiuchi, and C. Hu, IEDM Tech. Digest, 181 (1990).

    Google Scholar 

  10. 10

    M.S. Tyagi, Solid State Electron., 11, 99 (1968).

    Article  Google Scholar 

  11. 11

    I. Getreu, Modeling the Bipolar Transistor, Beaverton, Oregon : Tektronics Inc., 1976.

    Google Scholar 

  12. 12

    J.D. Burnett and C. Hu, IEEE Trans. Electron Devices, 37, 1171 (1990).

    Article  Google Scholar 

  13. 13

    M. Cohen, T. K. Bergstresser, Phys. Rev, 141, 789 (1965).

    Article  Google Scholar 

  14. 14

    H. Shichijo, J. Y. Tang, J. Bude, D. Yoder, in Monte Carlo device simulation: full band and beyond, pp. 285–307, edited by K. Hess, Kluwer Academic Publishers, Boston, 1991.

    Google Scholar 

  15. 15

    J. Bude, G. J. Iafrate, K. Hess, Phys. Rev. B, 45, 10958, (1992).

    CAS  Article  Google Scholar 

  16. 16

    J. Bude, K. Hess, J. Appl. Phys. 72, 3554 (1992).

    CAS  Article  Google Scholar 

  17. 17

    P. Habas, A. Lugbauer, S. Selberherr, in Workshop on Numerical Modeling of Process and Devices for Integrated Circuits: NUPAD IV edited by M. Law, A. Strojwas, 135 (1992).

  18. 18

    S. M. Sze, Physics of Semiconductor Devices, p. 15, John Wiley & Sons, New York, 1981.

    Google Scholar 

  19. 19

    E. O. Kane, “Zener tunneling in semiconductors,” Journal Phys. Chem. Solids, 12,181 (1959).

    Article  Google Scholar 

  20. 20

    G. A. M. Hurkx, “On the modeling of tunneling currents in reverse-biased P-N junctions,” Solid-State Electron., 32, 665 (1989).

    Google Scholar 

  21. 21

    I.C. Kizilyalli and J.D. Bude, IEEE Trans. Electron Devices, 41,1083 (1994).

    Article  Google Scholar 

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Kizilyalli, I.C., Bude, J.D. Hot Carrier Degradation of Gain in Bipolar Transistors. MRS Online Proceedings Library 391, 11 (1995).

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