Tài liệu The Devices ppt

© Digital Integrated Circuits
2nd
Devices
Digital Integrated
Digital Integrated
Circuits
Circuits
A Design Perspective
A Design Perspective
The Devices
The Devices
Jan M. Rabaey
Anantha Chandrakasan
Borivoje Nikolic
July 30, 2002
© Digital Integrated Circuits
2nd
Devices
Goal of this chapter
Goal 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
© Digital Integrated Circuits
2nd
Devices
The Diode
The Diode
n
p
p
n
B A
SiO
2
Al
A
B
Al
A
B
Cross-section of pn-junction in an IC process
One-dimensional
representation diode symbol
Mostly occurring as parasitic element in Digital ICs
© Digital Integrated Circuits
2nd
Devices

Depletion Region
Depletion Region
hole diffusion
electron diffusion
p n
hole drift
electron drift
Charge
Density
Distance
x+
-
Electrical
x
Field
x
Potential
V
ξ
ρ
W
2
-W
1
ψ
0
(a) Current flow.
(b) Charge density.
(c) Electric field.
(d) Electrostatic

potential.
© Digital Integrated Circuits
2nd
Devices
Diode Current
Diode Current
© Digital Integrated Circuits
2nd
Devices
Forward Bias
Forward Bias
x
p
n0
n
p0
-W
1
W
2
0
p
n
(W
2
)
n-region
p-region
L
p

diffusion
Typically avoided in Digital ICs
© Digital Integrated Circuits
2nd
Devices
Reverse Bias
Reverse Bias
x
p
n0
n
p0
-W
1
W
2
0
n-region
p-region
diffusion
The Dominant Operation Mode
© Digital Integrated Circuits
2nd
Devices
Models for Manual Analysis
Models for Manual Analysis
V
D
I
D

= I
S
(e
V
D
/
φ
T
– 1)
+
–
V
D
+
–
+
–
V
Don
I
D
(a) Ideal diode model (b) First-order diode model
© Digital Integrated Circuits
2nd
Devices
Junction Capacitance
Junction Capacitance
© Digital Integrated Circuits
2nd
Devices

Diffusion Capacitance
Diffusion Capacitance
© Digital Integrated Circuits
2nd
Devices
Secondary Effects
Secondary Effects
–25.0 –15.0 –5.0 5.0
V
D
(V)
–0.1
I
D
(A)
0.1
0
0
Avalanche Breakdown
© Digital Integrated Circuits
2nd
Devices
Diode Model
Diode Model
I
D
R
S
C
D

+
-
V
D
© Digital Integrated Circuits
2nd
Devices
SPICE Parameters
SPICE Parameters
© Digital Integrated Circuits
2nd
Devices
What is a Transistor?
What is a Transistor?
V
GS

≥

V
T
R
o n
S
D
A Switch!
|V
GS
|
An MOS Transistor

© Digital Integrated Circuits
2nd
Devices
The MOS Transistor
The MOS Transistor
Polysilicon
Aluminum
© Digital Integrated Circuits
2nd
Devices
MOS Transistors -
MOS Transistors -
Types and Symbols
Types and Symbols
D
S
G
D
S
G
G
S
D D
S
G
NMOS
Enhancement
NMOS
PMOS
Depletion

Enhancement
B
NMOS with
Bulk Contact
© Digital Integrated Circuits
2nd
Devices
Threshold Voltage: Concept
Threshold Voltage: Concept
n+n+
p-substrate
D
S
G
B
V
GS
+
-
Depletion
Region
n-channel
© Digital Integrated Circuits
2nd
Devices
The Threshold Voltage
The Threshold Voltage
© Digital Integrated Circuits
2nd
Devices

The Body Effect
The Body Effect
-2.5 -2 -1.5 -1 -0.5 0
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
0.9
V
BS
(V)
V
T
(V)
© Digital Integrated Circuits
2nd
Devices
Current-Voltage Relations
Current-Voltage Relations
A good ol’ transistor
A good ol’ transistor
Quadratic
Relationship
0 0.5 1 1.5 2 2.5

0
1
2
3
4
5
6
x 10
-4
V
DS
(V)
I
D
(A)
VGS= 2.5 V
VGS= 2.0 V
VGS= 1.5 V
VGS= 1.0 V
Resistive Saturation
V
DS
= V
GS
- V
T
© Digital Integrated Circuits
2nd
Devices
Transistor in Linear

Transistor in Linear
n
+
n
+
p-substrate
D
S
G
B
V
GS
x
L
V(x)
+–
V
DS
I
D
MOS transistor and its bias conditions
© Digital Integrated Circuits
2nd
Devices
Transistor in Saturation
Transistor in Saturation
n+n+
S
G
V

GS
D
V
DS
> V
GS
- V
T
V
GS
- V
T
+
-
Pinch-off
© Digital Integrated Circuits
2nd
Devices
Current-Voltage Relations
Current-Voltage Relations
Long-Channel Device
Long-Channel Device
© Digital Integrated Circuits
2nd
Devices
A model for manual analysis
A model for manual analysis
© Digital Integrated Circuits
2nd
Devices

Current-Voltage Relations
Current-Voltage Relations
The Deep-Submicron Era
The Deep-Submicron Era
Linear
Relationship
-4
V
DS
(V)
0 0.5 1 1.5 2 2.5
0
0.5
1
1.5
2
2.5
x 10
I
D
(A)
VGS= 2.5 V
VGS= 2.0 V
VGS= 1.5 V
VGS= 1.0 V
Early Saturation