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Semiconductor Device Modeling and Characterization EE5342, Lecture 20 -Sp 2002

Semiconductor Device Modeling and Characterization EE5342, Lecture 20 -Sp 2002. Professor Ronald L. Carter ronc@uta.edu http://www.uta.edu/ronc/. Equivalent circuit above OSI. Depl depth given by the maximum depl = x d,max = [2 e Si |2 f p |/(qN a )] 1/2

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Semiconductor Device Modeling and Characterization EE5342, Lecture 20 -Sp 2002

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  1. Semiconductor Device Modeling and CharacterizationEE5342, Lecture 20 -Sp 2002 Professor Ronald L. Carter ronc@uta.edu http://www.uta.edu/ronc/

  2. Equivalent circuitabove OSI • Depl depth given by the maximum depl = xd,max = [2eSi|2fp|/(qNa)]1/2 • Depl cap, C’d,min = eSi/xd,max • Oxide cap, C’Ox = eOx/xOx • Net C is the series comb C’Ox C’d,min

  3. MOS surface states**p- substr = n-channel

  4. n-substr accumulation (p-channel) Fig 10.7a*

  5. n-substrate depletion(p-channel) Fig 10.7b*

  6. n-substrate inversion(p-channel) Fig 10.7*

  7. Ideal 2-terminalMOS capacitor/diode conducting gate, area = LW Vgate=VG -xox SiO2 0 y 0 L silicon substrate tsub Vsub=VB x

  8. Band models (approx. scale) metal silicon dioxide p-type s/c Eo Eo qcox ~ 0.95 eV Eo qcSi= 4.0eV qfm= 4.28 eV for Al Ec qfs,p Eg,ox ~ 8 eV Ec EFm EFi EFp Ev Ev

  9. 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

  10. Values for gate workfunction, fm

  11. Values for fmswith metal gate

  12. Values for fmswith silicon gate

  13. Experimental valuesfor fms Fig 10.15*

  14. Calculation of thethreshold cond, VT

  15. Equations forVT calculation

  16. 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

  17. Effect of contacts,VS and VD

  18. Computing theD.R. width at O.S.I. Ex Emax x

  19. Computing thethreshold voltage

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

  21. 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

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

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

  24. Fully biased n-channel VT calc

  25. References * Semiconductor Physics & 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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