A physically based base pushout model for submicrometer BJTs in the presence of velocity overshoot

By using a two-dimensional relaxation time approximation device simulator, base pushout phenomena for submicrometer bipolar junction transistors (BJTs) are analyzed. From the numerical analysis, it was clarified that, under the base pushout condition, the electron velocity exceeds the saturation velocity in most of the epi-collector region. Considering this velocity overshoot effect with two-dimensional carrier behavior, a base pushout model was developed. This model is applicable to the BJT equivalent circuit model. The model utility was verified for a 0.8 mu m emitter-width BIT, and excellent agreement with measured I-V characteristics was obtained over wide injection conditions. Scaling effects on the velocity overshoot are also calculated, based on the constant current scaling. It is shown that the base pushout is suppressed due to the increased velocity overshoot level as the device sizes are scaled down. >

[1]  H. Satake,et al.  Low-temperature (77 K) BJT model with temperature dependences on the injected condition and base resistance , 1990 .

[2]  D. Tremere,et al.  Current gain and cutoff frequency falloff at high currents , 1969 .

[3]  P. M. Solomon,et al.  Bipolar transistor design for optimized power-delay logic circuits , 1979 .

[4]  C. T. Kirk,et al.  A theory of transistor cutoff frequency (fT) falloff at high current densities , 1962, IRE Transactions on Electron Devices.

[5]  H. C. Poon,et al.  An integral charge control model of bipolar transistors , 1970, Bell Syst. Tech. J..

[6]  B. Hoefflinger,et al.  Optimization and scaling of CMOS-bipolar drivers for VLSI interconnects , 1986, IEEE Transactions on Electron Devices.

[7]  Ting-Wei Tang,et al.  Numerical modeling of hot carriers in submicrometer Silicon BJT's , 1987 .

[8]  J. R. Hauser,et al.  The effects of distributed base potential on emitter-current injection density and effective base resistance for stripe transistor geometries , 1964 .

[9]  H. N. Ghosh,et al.  A distributed model of the junction transistor and its application in the prediction of the emitter-base diode characteristic, base impedance, and pulse response of the device , 1965 .

[10]  F. A. Lindholm,et al.  High current regimes in transistor collector regions , 1973 .

[11]  Robert W. Dutton,et al.  Scaling rules for bipolar transistors in BiCMOS circuits , 1989, International Technical Digest on Electron Devices Meeting.

[12]  S. Laux,et al.  Monte Carlo simulation of non-equilibrium transport in ultra-thin base Si bipolar transistors , 1989, International Technical Digest on Electron Devices Meeting.

[13]  J.J. Liou,et al.  Base-collector junction capacitance of bipolar transistors operating at high current densities , 1987, IEEE Transactions on Electron Devices.

[14]  D.D. Tang,et al.  Method for determining the emitter and base series resistances of bipolar transistors , 1984, IEEE Transactions on Electron Devices.

[15]  H C De Graaff.  Compact bipolar transistor modelling , 1986 .

[16]  D. Tang,et al.  Bipolar circuit scaling , 1979, 1979 IEEE International Solid-State Circuits Conference. Digest of Technical Papers.

[17]  D. C. Agouridis,et al.  The cutoff frequency falloff in UHF transistors at high currents , 1966 .

[18]  G. P. Rosseel,et al.  Influence of device parameters on the switching speed of BiCMOS buffers , 1989 .

[19]  I. Getreu,et al.  Modeling the bipolar transistor , 1978 .