EE5342

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EE5342 Semiconductor Device Modeling and
CharacterizationLecture 25 - Spring 2005

• Professor Ronald L. Carter
• ronc_at_uta.edu
• http//www.uta.edu/ronc/

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Fully biased n-MOScapacitor
VG
Channel if VG gt VT
VS
VD
EOx,xgt 0
e- e- e- e- e- e-
n
n
p-substrate
VsubVB
Acceptors
Depl Reg
y
0
L
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Fully biased MOScapacitor in inversion
VGgtVT
Channel
VSVC
VDVC
EOx,xgt 0
e- e- e- e- e- e-
n
n
p-substrate
VsubVB
Acceptors
Depl Reg
y
0
L
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Flat band with oxidecharge (approx. scale)
Al
SiO2
p-Si
lt--Vox--gt-
q(Vox)
Ec,Ox
q(ffp-cox)
Ex
q(fm-cox)
Eg,ox8eV
Ec
EFm
EFi
EFp
q(VFB)
Ev
VFB VG-VB, when Si bands are flat
Ev
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Flat-band parametersfor n-channel (p-subst)
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MOS energy bands atSi surface for n-channel
Fig 8.10
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Computing the D.R. W and Q at O.S.I.
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Qd,max and xd,max forbiased MOS capacitor
Fig 8.11
Qd,max/q (cm-2)
xd,max (microns)
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Fully biased n-channel VT calc
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Computing thethreshold voltage
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n-channel VT forVC VB 0
Fig 10.20
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Flat-band parametersfor p-channel (n-subst)
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Fully biased p-channel VT calc
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p-channel VT forVC VB 0
Fig 10.21
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Ion implantation
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Dotted box approx
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Mobilities
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Differential chargesfor low and high freq
high freq.
From Fig 10.27
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Ideal low-freqC-V relationship
Fig 10.25
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Comparison of lowand high freq C-V
Fig 10.28
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Effect of Qss onthe C-V relationship
Fig 10.29
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n-channel enhancementMOSFET in ohmic region
0lt VTlt VG
Channel
VS 0
0lt VDlt VDS,sat
EOx,xgt 0
e-e- e- e- e-
n
n
Depl Reg
p-substrate
Acceptors
VB lt 0
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Conductance ofinverted channel

• Qn - COx(VGC-VT)
• ns COx(VGC-VT)/q, ( inv elect/cm2)
• The conductivity sn (ns/t) q mn
• G sn(Wt/L) ns q mn (W/L) 1/R, so
• I V/R dV/dR, dR dL/(nsqmnW)

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Basic I-V relationfor MOS channel
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I-V relation for n-MOS (ohmic reg)
ohmic
ID
non-physical
ID,sat
saturated
VDS
VDS,sat
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Universal draincharacteristic
ID
VGSVT3V
9ID1
ohmic
saturated, VDSgtVGS-VT
VGSVT2V
4ID1
VGSVT1V
ID1
VDS
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Characterizing then-ch MOSFET
VD
ID
D
G
B
S
VGS
VT
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Low field ohmiccharacteristics
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MOSFET DeviceStructre Fig. 4-1, MA
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4-7a (AM)
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Figure 4-7b (AM)
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Figure 4-8a (AM)
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Figure 4-8b (AM)
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Body effect data
Fig 9.9
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References

• CARM Circuit Analysis Reference Manual,
  MicroSim Corporation, Irvine, CA, 1995.
• MA Semiconductor Device Modeling with SPICE,
  2nd ed., by Paolo Antognetti and Giuseppe
  Massobrio, McGraw-Hill, New York, 1993.
• MK Device Electronics for Integrated
  Circuits, 2nd ed., by Richard S. Muller and
  Theodore I. Kamins, John Wiley and Sons, New
  York, 1986.
• Semiconductor Physics and Devices, by Donald A.
  Neamen, Irwin, Chicago, 1997