1. Professor Ronald L. Carter ronc@uta.edu http://www.uta.edu/ronc/
Semiconductor Device Modeling and Characterization EE5342, Lecture 23 -Sp 2002
Professor Ronald L. Carter
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2. Extracting RB and RE from fg data
iB = (IS/BF)exp[(vBE,X - iB(RB+RE) - iCRE)/NF•Vt] + negligible terms.
iB/iB = 1 = (iB/NF•Vt) (vBE,X/iB - (RB+RE) - REiC/iB)
NF•Vt/iB = vBE,X/iB -(RB+RE) -REiC/iB
y=vBE,X/iB-NF•Vt/iB=REiC/iB+(RB+RE)
plot y vs. iC/iB, slope=RE, int.= RB+RE
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3. Extraction of RE and RB from fg data
The figure shows
[vBE,X/iB-NF•Vt/iB] versus iC/iB
From the slope, we have RE = 32 ohms.
The intercept (RE = RB) is 77 ohms so RB = 45 ohm.
Data generated from RB = 100 and RE = 1
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4. Extracting RB and RE from rg data
iB = (IS/BR)exp[(vBC,X - iB(RB+RC) - iERC)/NR•Vt] + negligible terms.
iB/iB = 1 = (iB/NR•Vt) (vBC,X/iB - (RB+RC) - RCiE/iB)
NR•Vt/iB = vBC,X/iB -(RB+RC) -RCiE/iB
y=vBC,X/iB-NR•Vt/iB=RCiE/iB+(RB+RC)
plot y vs. iE/iB, slope=RC, int.= RB+RC
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5. MOSFET equivalent circuit elements
Fig 10.51*
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6. MOS small-signal equivalent circuit
Fig 10.52*
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7. MOS channel- length modulation
Fig 11.5*
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8. Analysis of channel length modulation
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9. Channel length mod- ulated drain char
Fig 11.6*
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10. Fully biased n- channel VT calc
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11. Q’d,max and xd,max for biased MOS capacitor
Fig 8.11**
|Q’d,max|/q (cm-2)
xd,max (microns)
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15. Values for fms with silicon gate
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16. I-V relation for n-MOS ohmic ID non-physical ID,sat saturated VDS,sat
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17. Analysis of channel length modulation
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18. Associating the output conductanceID
ID,sat
VDS,sat
VDS
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19. n-channel enhancement MOSFET in ohmic region
0< VT< VG
e- channel ele + implant ion
Channel
VS = 0
0< VD< VDS,sat
EOx,x> 0 n+
e-e- e- e- e- n+
Depl Reg
p-substrate
Acceptors
VB < 0
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20. Ion implantation
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21. “Dotted box” approx
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23. Mobilities
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24. Fully biased n- channel VT calc
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25. Subthreshold conduction
Below O.S.I., when the total band-bending < 2|fp|, the weakly inverted channel conducts by diffusion like a BJT.
Since VGS>VDS, and below OSI, then Na>nS >nD, and electr diffuse S --> D
Electron concentration at Source
Concentration gradient
driving diffusion
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26. Subthreshold current data
Figure 10.1**
Figure 11.4*
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27. Mobility variation due to Edepl
Figures 11.7,8,9*
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28. Velocity saturation effects
Figure 11.10*
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29. References
*Semiconductor Physics and Devices, by Donald A. Neamen, Irwin, Chicago, 1997.
**Device Electronics for Integrated Circuits, 2nd ed., by Richard S. Muller and Theodore I. Kamins, John Wiley and Sons, New York, 1986
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