introduction to metal-oxide-semiconductor field effect transistors (mosfets) chapter 7, anderson and...
TRANSCRIPT
![Page 1: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/1.jpg)
Introduction toMetal-Oxide-
SemiconductorField Effect Transistors
(MOSFETs)
Chapter 7, Anderson and Anderson
![Page 2: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/2.jpg)
MOSFET• History• Structure• Future• Review• Threshold Voltage• I-V Characteristics• Modifications to I-V:
– Depletion layer correction (Sup. 3)– Mobility, Vsat– Short Channel Effects– Channel Length Modulation– Channel Quantum Effects
• MOSFET Scaling and Current Topics (Literature + Sup. 3)• Subthreshold Behavior• Damage and Temperature (Sup. 3)• Spice (Sup. 3)• HFET, MESFET, JFET, DRAM, CCD (Some in Sup. 3)
![Page 3: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/3.jpg)
MOSFET History (Very Short!)
• First Patents: – 1935
• Variable Capacitor Proposed: – 1959
• Silicon MOS: – 1960
• Clean PMOS, NMOS: – Late 1960s, big growth!
• CCDs: – 1970s, Bell Labs
• Switch to CMOS: – 1980s
![Page 4: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/4.jpg)
Structure: n-channel MOSFET(NMOS)
pn+n+
metal
LW
sourceS
gate: metal or heavily doped poly-Si G
drainD
bodyB
oxide
IG=0
ID=ISIS
x
y
(bulk or substrate)
![Page 5: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/5.jpg)
MOSFET Future (One Part of)
• International Technology Roadmap for Semiconductors, 2008 update.
• Look at size, manufacturing technique.
![Page 6: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/6.jpg)
![Page 7: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/7.jpg)
![Page 8: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/8.jpg)
From Intel
![Page 9: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/9.jpg)
Structure: n-channel MOSFET(NMOS)
pn+n+
metal
LW
sourceS
gate: metal or heavily doped poly-Si G
drainD
bodyB
oxide
IG=0
ID=ISIS
x
y
(bulk or substrate)
![Page 10: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/10.jpg)
![Page 11: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/11.jpg)
MOSFET ScalingECE G201
![Page 12: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/12.jpg)
Fin (30nm)
Gate
BOX
prevents “top” gate
![Page 13: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/13.jpg)
Circuit Symbol (NMOS)enhancement-type: no channel at zero gate voltage
G
D
S
B (IB=0, should be reverse biased)
ID= IS
IS
IG= 0
G-GateD-DrainS-SourceB-Substrate or Body
![Page 14: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/14.jpg)
![Page 15: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/15.jpg)
Structure: n-channel MOSFET(NMOS)
pn+n+
metal
LW
sourceS
gate: metal or heavily doped poly-Si G
drainD
bodyB
oxide
IG=0
ID=ISIS
x
y
(bulk or substrate)
![Page 16: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/16.jpg)
Energy bands
(“flat band” condition; not equilibrium) (equilibrium)
![Page 17: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/17.jpg)
Flatbands! For this choice of materials, VGS<0 n+pn+ structure ID ~ 0
pn+n+
n++
LW
sourceS
gateG
drainD
bodyB
oxide
+-
VD=Vs
![Page 18: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/18.jpg)
Flatbands < VGS < VT (Includes VGS=0 here). n+-depletion-n+ structure ID ~ 0
pn+n+
n++
LW
sourceS
gateG
drainD
bodyB
oxide
+-
+++
VD=Vs
![Page 19: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/19.jpg)
VGS > VT n+-n-n+ structure inversion
pn+n+
n++
LW
sourceS
gateG
drainD
bodyB
oxide
+-
+++++++++
- - - - -
VD=Vs
![Page 20: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/20.jpg)
VGS>VT
Channel Charge (Qch)
Qch
Depletion regioncharge (QB) is dueto uncovered acceptor ions
![Page 21: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/21.jpg)
pn+n+
n++
LW
Ec(y) with VDS=0
(x)
![Page 22: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/22.jpg)
Increasing VGS decreases EB
EB
y0 L
EF ~ EC
![Page 23: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/23.jpg)
Triode Region A voltage-controlled resistor @small VDS
G
pn+n+
metal
S DB
oxide
+-
+++
+++
- - - -
VGS1>Vt
pn+n+
metal
S DB
oxide
+-
+++
++++++
- - - - - -
VGS2>VGS1
pn+n+
metal
S DB
oxide
+-
+++
++++++
- - - - - - - - -
VGS3>VGS2+++
ID
VDS
0.1 v
increasingVGS
Increasing VGS puts more charge in the channel, allowing more drain current to flow
cut-off
![Page 24: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/24.jpg)
Saturation Regionoccurs at large VDS
pn+n+
metal
sourceS
gateG
drainD
bodyB
oxide
+-
+++++++++
VDS large
As the drain voltage increases, the difference in voltage between the drain and the gate becomes smaller. At some point, the difference is too small to maintain the channel near the drain pinch-off
![Page 25: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/25.jpg)
Saturation Regionoccurs at large VDS
pn+n+
metal
sourceS
gateG
drainD
bodyB
oxide
+-
+++++++++
VDS large
The saturation region is when the MOSFET experiences pinch-off.
Pinch-off occurs when VG - VD is less than VT.
![Page 26: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/26.jpg)
Saturation Regionoccurs at large VDS
pn+n+
metal
sourceS
gateG
drainD
bodyB
oxide
+-
+++++++++
VD>>Vs
VGS - VDS < VT or VGD <
VDS > VGS - VT
VT
![Page 27: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/27.jpg)
Saturation Regiononce pinch-off occurs, there is no further increase in
drain current
ID
VDS
0.1 v
increasingVGS
triode
saturation
VDS>VGS-VT
VDS<VGS-VT
![Page 28: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/28.jpg)
Band diagram of triode and saturation
![Page 29: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/29.jpg)
Simplified MOSFET I-V Equations
Cut-off: VGS< VT
ID = IS = 0
Triode: VGS>VT and VDS < VGS-VT
ID = kn’(W/L)[(VGS-VT)VDS - 1/2VDS
2]
Saturation: VGS>VT and VDS > VGS-VT
ID = 1/2kn’(W/L)(VGS-VT)2
where kn’= (electron mobility)x(gate capacitance)
= n(ox/tox) …electron velocity = nE
and VT depends on the doping concentration and gate material used (…more details later)
![Page 30: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/30.jpg)
Energy bands
(“flat band” condition; not equilibrium) (equilibrium)
![Page 31: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/31.jpg)
![Page 32: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/32.jpg)
VGS>VT
Channel Charge (Qch)
Qch
Depletion regioncharge (QB) is dueto uncovered acceptor ions
![Page 33: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/33.jpg)
![Page 34: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/34.jpg)
![Page 35: Introduction to Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) Chapter 7, Anderson and Anderson](https://reader033.vdocument.in/reader033/viewer/2022061415/56649e695503460f94b666fb/html5/thumbnails/35.jpg)
Threshold Voltage Definition
VGS = VT when the carrier concentration in the channel is equal to the carrier concentration in the bulk silicon.
Mathematically, this occurs when s=2f ,
where s is called the surface potential