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Transcript of EE141 © Digital Integrated Circuits 2nd Devices 1 Digital Integrated Circuits A Design Perspective...
![Page 1: EE141 © Digital Integrated Circuits 2nd Devices 1 Digital Integrated Circuits A Design Perspective The Devices Jan M. Rabaey Anantha Chandrakasan Borivoje.](https://reader035.fdocuments.us/reader035/viewer/2022062422/56649f115503460f94c23b51/html5/thumbnails/1.jpg)
EE1411
© Digital Integrated Circuits2nd Devices
Digital Integrated Digital Integrated CircuitsCircuitsA Design PerspectiveA Design Perspective
The DevicesThe Devices
Jan M. RabaeyAnantha ChandrakasanBorivoje Nikolic
July 30, 2002
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EE1412
© Digital Integrated Circuits2nd Devices
Goal of this chapterGoal of this chapter
Present intuitive understanding of device operation
Introduction of basic device equations Introduction of models for manual
analysis Introduction of models for SPICE
simulation Analysis of secondary and deep-sub-
micron effects Future trends
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EE1413
© Digital Integrated Circuits2nd Devices
The DiodeThe Diode
n
p
p
n
B A SiO2Al
A
B
Al
A
B
Cross-section of pn-junction in an IC process
One-dimensionalrepresentation diode symbol
Mostly occurring as parasitic element in Digital ICs
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EE1414
© Digital Integrated Circuits2nd Devices
Depletion RegionDepletion Regionhole diffusion
electron diffusion
p n
hole driftelectron drift
ChargeDensity
Distancex+
-
ElectricalxField
x
PotentialV
W2-W1
(a) Current flow.
(b) Charge density.
(c) Electric field.
(d) Electrostaticpotential.
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EE1415
© Digital Integrated Circuits2nd Devices
Diode CurrentDiode Current
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EE1416
© Digital Integrated Circuits2nd Devices
Forward BiasForward Bias
x
pn0
np0
-W1 W20p n
(W2)
n-regionp-region
Lp
diffusion
Typically avoided in Digital ICs
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EE1417
© Digital Integrated Circuits2nd Devices
Reverse BiasReverse Bias
x
pn0
np0
-W1 W20n-regionp-region
diffusion
The Dominant Operation Mode
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EE1418
© Digital Integrated Circuits2nd Devices
Models for Manual AnalysisModels for Manual Analysis
VD
ID = IS(eVD/T – 1)+
–
VD
+
–
+
–VDon
ID
(a) Ideal diode model (b) First-order diode model
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EE1419
© Digital Integrated Circuits2nd Devices
Junction CapacitanceJunction Capacitance
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EE14110
© Digital Integrated Circuits2nd Devices
What is a Transistor?What is a Transistor?
VGS VT
RonS D
A Switch!
|VGS|
An MOS Transistor
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EE14111
© Digital Integrated Circuits2nd Devices
The MOS TransistorThe MOS Transistor
Polysilicon Aluminum
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EE14112
© Digital Integrated Circuits2nd Devices
MOS Transistors -MOS Transistors -Types and SymbolsTypes and Symbols
D
S
G
D
S
G
G
S
D D
S
G
NMOS Enhancement NMOS
PMOS
Depletion
Enhancement
B
NMOS withBulk Contact
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EE14113
© Digital Integrated Circuits2nd Devices
Threshold Voltage: ConceptThreshold Voltage: Concept
n+n+
p-substrate
DSG
B
VGS
+
-
Depletion
Region
n-channel
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EE14114
© Digital Integrated Circuits2nd Devices
The Threshold VoltageThe Threshold Voltage
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EE14115
© Digital Integrated Circuits2nd Devices
The Body EffectThe Body Effect
-2.5 -2 -1.5 -1 -0.5 00.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
0.9
VBS
(V)
VT (
V)
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EE14116
© Digital Integrated Circuits2nd Devices
Transistor in LinearTransistor in Linear
n+n+
p-substrate
D
SG
B
VGS
xL
V(x) +–
VDS
ID
MOS transistor and its bias conditions
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EE14117
© Digital Integrated Circuits2nd Devices
Transistor in SaturationTransistor in Saturation
n+n+
S
G
VGS
D
VDS > VGS - VT
VGS - VT+-
Pinch-off
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EE14118
© Digital Integrated Circuits2nd Devices
A model for manual analysisA model for manual analysis
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EE14119
© Digital Integrated Circuits2nd Devices
Current-Voltage RelationsCurrent-Voltage RelationsA good ol’ transistorA good ol’ transistor
QuadraticRelationship
0 0.5 1 1.5 2 2.50
1
2
3
4
5
6x 10
-4
VDS (V)
I D (
A)
VGS= 2.5 V
VGS= 2.0 V
VGS= 1.5 V
VGS= 1.0 V
Resistive Saturation
VDS = VGS - VT
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EE14120
© Digital Integrated Circuits2nd Devices
Process DataProcess Data
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EE14121
© Digital Integrated Circuits2nd Devices
Current-Voltage RelationsCurrent-Voltage RelationsThe Deep-Submicron EraThe Deep-Submicron Era
LinearRelationship
-4
VDS (V)0 0.5 1 1.5 2 2.5
0
0.5
1
1.5
2
2.5x 10
I D (
A)
VGS= 2.5 V
VGS= 2.0 V
VGS= 1.5 V
VGS= 1.0 V
Early Saturation
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EE14122
© Digital Integrated Circuits2nd Devices
Velocity SaturationVelocity Saturation
(V/µm)c = 1.5
n
(m/s
)
sat = 105
Constant mobility (slope = µ)
Constant velocity
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EE14123
© Digital Integrated Circuits2nd Devices
Velocity Saturation (Computation)Velocity Saturation (Computation)
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EE14124
© Digital Integrated Circuits2nd Devices
PerspectivePerspective
IDLong-channel device
Short-channel device
VDSVDSAT VGS - VT
VGS = VDD
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EE14125
© Digital Integrated Circuits2nd Devices
IIDD versus V versus VDSDS
-4
VDS (V)0 0.5 1 1.5 2 2.5
0
0.5
1
1.5
2
2.5x 10
I D (
A)
VGS= 2.5 V
VGS= 2.0 V
VGS= 1.5 V
VGS= 1.0 V
0 0.5 1 1.5 2 2.50
1
2
3
4
5
6x 10
-4
VDS (V)
I D (
A)
VGS= 2.5 V
VGS= 2.0 V
VGS= 1.5 V
VGS= 1.0 V
ResistiveSaturation
VDS = VGS - VT
Long Channel Short Channel
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EE14126
© Digital Integrated Circuits2nd Devices
A unified modelA unified modelfor manual analysisfor manual analysis
S D
G
B
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EE14127
© Digital Integrated Circuits2nd Devices
Transistor Model Transistor Model for Manual Analysisfor Manual Analysis
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EE14128
© Digital Integrated Circuits2nd Devices
The Sub-Micron MOS TransistorThe Sub-Micron MOS Transistor
Threshold Variations Subthreshold Conduction Parasitic Resistances
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EE14129
© Digital Integrated Circuits2nd Devices
Threshold VariationsThreshold Variations
VT
L
Long-channel threshold Low VDS threshold
Threshold as a function of the length (for low VDS)
Drain-induced barrier lowering (for low L)
VDS
VT
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EE14130
© Digital Integrated Circuits2nd Devices
The MOS TransistorThe MOS Transistor
Polysilicon Aluminum
![Page 31: EE141 © Digital Integrated Circuits 2nd Devices 1 Digital Integrated Circuits A Design Perspective The Devices Jan M. Rabaey Anantha Chandrakasan Borivoje.](https://reader035.fdocuments.us/reader035/viewer/2022062422/56649f115503460f94c23b51/html5/thumbnails/31.jpg)
EE14131
© Digital Integrated Circuits2nd Devices
MOSFET Capacitance ModelMOSFET Capacitance Model
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EE14132
© Digital Integrated Circuits2nd Devices
MOSFET Gate CapacitanceMOSFET Gate Capacitance
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EE14133
© Digital Integrated Circuits2nd Devices
MOSFET DB and SB CapacitanceMOSFET DB and SB Capacitance
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EE14134
© Digital Integrated Circuits2nd Devices
Junction CapacitanceJunction Capacitance
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EE14135
© Digital Integrated Circuits2nd Devices
More Process DataMore Process Data
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EE14136
© Digital Integrated Circuits2nd Devices
Problems (2)Problems (2)
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EE14137
© Digital Integrated Circuits2nd Devices
Problems (3)Problems (3)
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EE14138
© Digital Integrated Circuits2nd Devices
Problems (8)Problems (8)
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EE14139
© Digital Integrated Circuits2nd Devices
Problems (17)Problems (17)
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EE14140
© Digital Integrated Circuits2nd Devices
Latch-upLatch-up