Digital Integrated Circuits A Design Perspective

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Digital Integrated CircuitsA Design Perspective
Jan M. Rabaey Anantha Chandrakasan Borivoje
Nikolic
The Devices
July 30, 2002
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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

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The Diode
Mostly occurring as parasitic element in Digital
ICs
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Depletion Region
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Diode Current
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Forward Bias
Typically avoided in Digital ICs
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Reverse Bias
The Dominant Operation Mode
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Models for Manual Analysis
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Junction Capacitance
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What is a Transistor?
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The MOS Transistor
Polysilicon
Aluminum
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MOS Transistors -Types and Symbols
D
D
G
G
S
S
Depletion
NMOS
Enhancement
NMOS
D
D
G
G
B
S
S
NMOS with
PMOS
Enhancement
Bulk Contact
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Threshold Voltage Concept
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The Threshold Voltage
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The Body Effect
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Transistor in Linear
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Transistor in Saturation
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A model for manual analysis
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Current-Voltage RelationsA good ol transistor
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Process Data
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Current-Voltage RelationsThe Deep-Submicron Era
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Velocity Saturation
Constant velocity
Constant mobility (slope µ)
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Velocity Saturation (Computation)
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Perspective
I
D
Long-channel device
V
V
GS
DD
Short-channel device
V
V
V
- V
DSAT
DS
GS
T
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ID versus VDS
Long Channel
Short Channel
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A unified modelfor manual analysis
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Transistor Model for Manual Analysis
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The Sub-Micron MOS Transistor

• Threshold Variations
• Subthreshold Conduction
• Parasitic Resistances

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Threshold Variations
Low
V

threshold
Long-channel threshold
DS
VDS
L
Threshold as a function of
Drain-induced barrier lowering
the length (for low
V
)
(for low
L
)
DS
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The MOS Transistor
Polysilicon
Aluminum
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MOSFET Capacitance Model
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MOSFET Gate Capacitance
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MOSFET DB and SB Capacitance
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Junction Capacitance
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More Process Data
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Problems (2)
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Problems (3)
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Problems (8)
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Problems (17)
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Latch-up