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Semiconductor Device Modeling and Characterization EE5342, Lecture 21 -Sp 2002

Semiconductor Device Modeling and Characterization EE5342, Lecture 21 -Sp 2002. Professor Ronald L. Carter ronc@uta.edu http://www.uta.edu/ronc/. Fully biased n-MOS capacitor. V G. Channel if V G > V T. V S. V D. E Ox,x > 0. e - e - e - e - e - e -. n+. n+. p-substrate.

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Semiconductor Device Modeling and Characterization EE5342, Lecture 21 -Sp 2002

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  1. Semiconductor Device Modeling and CharacterizationEE5342, Lecture 21 -Sp 2002 Professor Ronald L. Carter ronc@uta.edu http://www.uta.edu/ronc/

  2. Fully biased n-MOScapacitor VG Channel if VG > VT VS VD EOx,x> 0 e- e- e- e- e- e- n+ n+ p-substrate Vsub=VB Depl Reg Acceptors y 0 L

  3. Flat band with oxidecharge (approx. scale) Al SiO2 p-Si +<--Vox-->- q(Vox) Ec,Ox q(ffp-cox) Ex q(fm-cox) Eg,ox~8eV Ec EFm EFi EFp q(VFB) Ev VFB= VG-VB, when Si bands are flat Ev

  4. MOS energy bands atSi surface for n-channel Fig 8.10**

  5. Fully biased n-channel VT calc

  6. Q’d,max and xd,max forbiased MOS capacitor Fig 8.11** |Q’d,max|/q (cm-2) xd,max (microns)

  7. n-channel VT forVC = VB = 0 Fig 10.20*

  8. Flat-band parametersfor p-channel (n-subst)

  9. Fully biased p-channel VT calc

  10. p-channel VT forVC = VB = 0 Fig 10.21*

  11. Differential chargesfor low and high freq high freq. From Fig 10.27*

  12. Ideal low-freqC-V relationship Fig 10.25*

  13. Comparison of lowand high freq C-V Fig 10.28*

  14. Effect of Q’ss onthe C-V relationship Fig 10.29*

  15. Conductance ofinverted channel • Q’n = - C’Ox(VGC-VT) • n’s = C’Ox(VGC-VT)/q, (# inv elect/cm2) • The conductivity sn = (n’s/t) q mn • G = sn(Wt/L) = n’s q mn (W/L) = 1/R, so • I = V/R = dV/dR, dR = dL/(n’sqmnW)

  16. Basic I-V relationfor MOS channel

  17. n-channel enhancementMOSFET in ohmic region 0< VT< VG Channel VS = 0 0< VD< VDS,sat EOx,x> 0 e-e- e- e- e- n+ n+ Depl Reg p-substrate Acceptors VB < 0

  18. Conductance ofinverted channel • Q’n = - C’Ox(VGC-VT) • n’s = C’Ox(VGC-VT)/q, (# inv elect/cm2) • The conductivity sn = (n’s/t) q mn • G = sn(Wt/L) = n’s q mn (W/L) = 1/R, so • I = V/R = dV/dR, dR = dL/(n’sqmnW)

  19. I-V relation for n-MOS (ohmic reg) ohmic ID non-physical ID,sat saturated VDS VDS,sat

  20. Universal draincharacteristic ID VGS=VT+3V 9ID1 ohmic saturated, VDS>VGS-VT VGS=VT+2V 4ID1 VGS=VT+1V ID1 VDS

  21. Characterizing then-ch MOSFET VD ID D G B S VGS VT

  22. Low field ohmiccharacteristics

  23. MOSFET circuitparameters

  24. MOSFET circuitparameters (cont)

  25. Substrate bias effect on VT (body-effect)

  26. Body effect data Fig 9.9**

  27. 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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