Chapter 2MOS Transistors

2.2 STRUCTURE AND OPERATION OF THE MOS TRANSISTOR

2.2 Structure and Operation of the MOS Transistor

2.2 Structure and Operation of the MOS Transistor

2.2 Structure and Operation of the MOS Transistor

2.3 THRESHOLD VOLTAGE OF THE MOS TRANSISTOR

2.3 Threshold Voltage of the MOS Transistor

Intrinsic carrier concentration :

Mass action law :

Difference between intrinsic and actual Fermi level :

p-type material case :

Gate oxide capacitance :

2.3 Threshold Voltage of the MOS Transistor

(2.1)

(2.2)

(2.3a)

(2.3b)

(2.4)

(2.5)

2.3 Threshold Voltage of the MOS Transistor

2.3 Threshold Voltage of the MOS Transistor

2.3 Threshold Voltage of the MOS Transistor

2.3 MOS Structure2.3.4 The Depletion Approximation

2.3 MOS Structure2.3.4 The Depletion Approximation

2.47

2.71

2.72

2.73

2.74

2.75

2.76

2.77

2.78

2.79

2.80

2.81

2.82

2.83

2.3 MOS Structure2.3.4 The Depletion Approximation

2.84

2.85

2.86

2.87

2.88

2.89

2.90

2.3 MOS Structure2.3.4 The Depletion Approximation

2.3 MOS Structure2.3.4 The Depletion Approximation

2.91

2.92

2.93

2.94

Change of Quasi-Fermi Potentials across the Space-Charge Region

17

18

Modern VLSI Devices

19

Modern VLSI Devices

20

21

22

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24

25

26

27

28

29

Silicon-gate device work function difference :

Flat-band condition :

Depletion layer(p-type) thickness :

Bulk charge :

(Inversion)

(Body bias)

2.3 Threshold Voltage of the MOS Transistor

(2.6)

(2.7)

(2.8)

(2.9a)

(2.9b)

Threshold voltage :

Body-effect coefficient(body factor)Flat-band condition :

2.3 Threshold Voltage of the MOS Transistor

(2.10)

(2.11)

(2.12)

2.4 Effect of Gate-Body Voltage on Surface Condition

2.4.26

2.3 Threshold Voltage of the MOS Transistor

2.4 FIRST-ORDER CURRENT-VOLTAGE CHARACTERISTICS

2.4 First-Order Current-Voltage Characteristics

Charge area density at the point y :

Drain-source current :

(Carrier velocity : )

2.4 First-Order Current-Voltage Characteristics

(2.13)

(2.14)

(2.15)

Process transconductance parameter :

Drain-source current :

(Device transconductance parameter : )

2.4 First-Order Current-Voltage Characteristics

(2.16)

(2.17a)

(2.17b)

2.4 First-Order Current-Voltage Characteristics

Saturation voltage :

Drain-source current (saturation) :

(Shortening the electrically effective value of L)

2.4 First-Order Current-Voltage Characteristics

(2.18)

(2.19)

(2.20)

2.4 First-Order Current-Voltage Characteristics

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2.5 DERIVATION OF VELOCITY-SATURATED CURRENT EQUATION

2.5.1 Effect of High Fields

2.5.1 Effect of High Fields

(2.21)

2.5.1 Effect of High Fields

Critical field values :

Carrier velocity :

Consider boundary condition :

(2.22)

(2.23a)

(2.23b)

(2.24)

2.5.1 Effect of High Fields

Linear region operation

2.5.2 Current Equations for Velocity-Saturated Devices

(2.25)

Saturation region operation

Limiting cases : ( )

( )

(2.26)(2.27)

(2.28)

(2.29)

2.5.2 Current Equations for Velocity-Saturated Devices

2.5.2 Current Equations for Velocity-Saturated Devices

5.2 Carrier Velocity Saturation

5.2.16

5.2.17

Copyright © 2004 The McGraw-Hill Companies, Inc. All rights reserved.

1X devices

2.5.2 Current Equations for Velocity-Saturated Devices

Equations for deep submicron devices

Saturation region

Channel length modulation

Linear region

2.5.2 Current Equations for Velocity-Saturated Devices

2.6 ALPHA-POWER LAW MODEL

2.6 Alpha-Power Law Model

(2.30a)

(2.30b)

(2.31)

2.6 Alpha-Power Law Model

2.7 SUBTHRESHOLD CONDUCTION

2.7 Subthreshold Conduction

2.5.1 Effect of High Fields

Current equation:

Slope factor :

2.7 Subthreshold Conduction

(2.32)

(2.33)

Copyright © 2004 The McGraw-Hill Companies, Inc. All rights reserved.

Copyright © 2004 The McGraw-Hill Companies, Inc. All rights reserved.

Copyright © 2004 The McGraw-Hill Companies, Inc. All rights reserved.

Copyright © 2004 The McGraw-Hill Companies, Inc. All rights reserved.

2.8 CAPACITANCES OF THE MOS TRANSISTOR

2.8 Capacitances of the MOS Transistor

2.8.1 Thin-Oxide Capacitance

Total capacitance of the thin-oxide :

Examples : i) technology, oxide thickness

ii) process, with

(2.34)

2.8.1 Thin-Oxide Capacitance

7.3 A MEDIUM-FREQUENCY SMALL-SIGNAL MODEL FOR THE INTRINSIC PART

7.3 A Medium-Frequency Small-Signal Model for the Intrinsic Part

7.3.1

7.3.2

7.3 A Medium-Frequency Small-Signal Model for the Intrinsic Part

7.3.37.3.4

7.3.5

7.3 A Medium-Frequency Small-Signal Model for the Intrinsic Part

8.2 A Complete Quasi-Static Model for the Intrinsic Part

8.2.1 Complete Description of Intrinsic Capacitance Effects 8.2.3

8.2.4

8.2.5

8.2.6

8.2.7

8.2.8

8.2 A Complete Quasi-Static Model for the Intrinsic Part

8.2.1 Complete Description of Intrinsic Capacitance Effects

8.2.9

8.2.10

8.2.11

8.2.12

8.2 A Complete Quasi-Static Model for the Intrinsic Part

8.2.2 Small-Signal Equivalent Circuit Topologies

8.2 A Complete Quasi-Static Model for the Intrinsic Part

8.2.2 Small-Signal Equivalent Circuit Topologies

8.2.17

8.2.18

8.2.19a

8.2.19b

8.2.19c

8.2.20

8.2 A Complete Quasi-Static Model for the Intrinsic Part

8.2.2 Small-Signal Equivalent Circuit Topologies

7.3 A Medium-Frequency Small-Signal Model for the Intrinsic Part

7.3.6

7.3 A Medium-Frequency Small-Signal Model for the Intrinsic Part

7.3.7

7.3.8

7.3.9

7.3.10

7.3 A Medium-Frequency Small-Signal Model for the Intrinsic Part

7.3.11

7.3.12

7.3.13

7.3.14

7.3.15

7.3.16

7.3.17

7.3.18

7.3 A Medium-Frequency Small-Signal Model for the Intrinsic Part

7.3.19

7.3.20

7.3 A Medium-Frequency Small-Signal Model for the Intrinsic Part

• Nonsaturation with VDS = 0 (=1)

• Saturation (=0)

7.3.21

7.3.22

7.3.23, 24

7.3.25

7.3.26

7.3.27

7.3.28

7.3.29

7.3 A Medium-Frequency Small-Signal Model for the Intrinsic Part

7.3 A Medium-Frequency Small-Signal Model for the Intrinsic Part

ClickIntrinsic+Extrinsic (7.4)

2.8.1 Thin-Oxide Capacitance

Current-voltage characteristic :

Built-in junction potential :

2.8.2 pn Junction Capacitance

(2.35)(2.36)

(2.37)

2.8.2 pn Junction Capacitance

Junction capacitance :

Zero-bias junction capacitance :

For of the NMOS device :

2.8.2 pn Junction Capacitance

(2.38)

(2.39)

(2.40)

2.8.2 pn Junction Capacitance

Total junction capacitance :

Simplification :

( , )

2.8.2 pn Junction Capacitance

(2.41)

(2.42)

Equivalent voltage-independent capacitance

2.8.2 pn Junction Capacitance

2.8.2 pn Junction Capacitance

(2.43)

(2.44)

(2.45)

2.8.3 Overlap Capacitance

(2.46)

(2.47)

2.8.3 Overlap Capacitance

2.9 SUMMARY

2.9 Summary

2.9 Summary

2.9 Summary

2.9 Summary

2.9 Summary

2.9 Summary

2.9 Summary