ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS...
Transcript of ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS...
![Page 1: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/1.jpg)
ECE-305: Fall 2017
MOS Capacitors and Transistors
Professor Peter BermelElectrical and Computer Engineering
Purdue University, West Lafayette, IN [email protected]
Pierret, Semiconductor Device Fundamentals (SDF)Chapters 15+16 (pp. 525-530, 563-599)
11/2/2017 Bermel ECE 305 F17 1
![Page 2: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/2.jpg)
MOS capacitor
2
VG
p-Si
‘metal’/heavily doped
polysilicon
SiO2
tox » 1- 2 nm
Bermel ECE 305 F17
1) Gate voltage2) Example problem3) MOS capacitors4) MOS field-effect transistors
11/2/2017
![Page 3: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/3.jpg)
gate voltage and surface potential
33
EC
EV
Ei
EF
Si
metal
DVS
DVOX
EFM
¢VG = DVOX +fS
0 < fS < 2fF
¢VG = ?
Gate voltage is surface potential + oxide voltage drop
11/2/2017 Bermel ECE 305 F17
DVox = xoE ox
![Page 4: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/4.jpg)
band banding in p-type MOS
4Fig. 16.6, Semiconductor Device Fundamentals, R.F. Pierret
Flat band Accumulation Depletion Inversion
¢VG = 0 ¢VG < 0 0 < ¢VG <VT ¢VG > ¢VT
fS = 0 fS < 0 0 <fS < 2fF fS > 2fF
11/2/2017 Bermel ECE 305 F17
![Page 5: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/5.jpg)
5
E x( )
x
P
E S =qNA
k Se0
W
1
2E SW = fS
E S
W
W =2k Se0fS
qNA
cm
E S =2qNAfS
k se0
V/cm
QB = - 2qk se0NAfS C/cm2
QB = -qNAW fS( )C/cm2
0 <fS < 2fF
¢VG = -QB fS( )Cox
+fS
MOS electrostatics: depletion(results from last time)
Bermel ECE 305 F1711/2/2017
![Page 6: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/6.jpg)
MOS electrostatics: inversion
6
EC
EV
Ei
EF
Si
f x( ) f 0( )
x
fF
fS » 2fF fF
WT
WT =2KSe0
qNA
2fF
é
ëê
ù
ûú
1/2 Maximum depletion region depth
11/2/2017 Bermel ECE 305 F17
![Page 7: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/7.jpg)
delta-depletion approximation
7
r
x
metal
-xo
WT
r = -qNA
QB = -qNAWT
Qn
WT =2k Se0 2fF
qNA
11/2/2017 Bermel ECE 305 F17
![Page 8: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/8.jpg)
delta-depletion approximation
8
E x( )
x
P
W
E S
E 0+( ) = - QB
KSe0
E 0( ) = -QS
KSe0
Bermel ECE 305 F1711/2/2017
![Page 9: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/9.jpg)
MOS electrostatics: inversion
9
EC
EV
Ei
EF
Si
f x( ) f 0( )
x
fF
fS » 2fF
fF
WT
WT =2KSe0
qNA
2fF
é
ëê
ù
ûú
1/2
¢VG = -QB 2fF( ) +Qn
Cox
+ 2fF
¢VT = -QB 2fF( )
Cox
+ 2fF
Qn = -Cox ¢VG - ¢VT( )
¢VG = -QS
Cox
+ 2fF
Bermel ECE 305 F1711/2/2017
![Page 10: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/10.jpg)
MOS capacitor
10
VG
p-Si
‘metal’/heavily doped
polysilicon
SiO2
tox » 1- 2 nm
Bermel ECE 305 F17
1) Gate voltage2) Example problem3) MOS capacitors4) MOS field-effect transistors
11/2/2017
![Page 11: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/11.jpg)
11
example
source drain
SiO
2
silicon
S G D
Assume n+ poly Si gate1018 channel dopingtox = 1.5 nm
What is VT?e-field in oxide at VG = 1V?
Bermel ECE 305 F1711/2/2017
![Page 12: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/12.jpg)
12
example (cont.)
¢VG = -QS fS( )Cox
+fS
¢VT = -QB 2fF( )
Cox
+ 2fF
VT = fms -QB 2fF( )
Cox
+ 2fF
fF =kBT
qln
NA
ni
æ
èçö
ø÷
Cox = KOe0 xo
QB = - 2qk se0NA 2fF
QB = -qNAW 2fF( )
fms = -kBT
qln
NAND
ni2
æ
èçö
ø÷
fF = 0.48 V
Cox = 2.36 ´10-6 F/cm2
QB = -5.71´10-7 C/cm2
fms = -1.06 VVT = 0.14 V
Bermel ECE 305 F1711/2/2017
![Page 13: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/13.jpg)
13
example (cont)
Qn = -Cox VG -VT( )
E OX = -QS
k oxe0
= -Qn +QB 2fB( )
k oxe0
Qn = -2.06 ´10-6 C/cm2
E OX = 7.3´106 V/cm
Qn
q= -1.3´1013 C/cm2
Bermel ECE 305 F1711/2/2017
![Page 14: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/14.jpg)
MOS capacitor
14
VG
p-Si
‘metal’/heavily doped
polysilicon
SiO2
tox » 1- 2 nm
Bermel ECE 305 F17
1) Gate voltage2) Example problem3) MOS capacitors4) MOS field-effect transistors
11/2/2017
![Page 15: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/15.jpg)
MOS capacitor
15
p-Si
vS sinwt
+VG
+
-
-
VG + vS sinwt
~
11/2/2017 Bermel ECE 305 F17
![Page 16: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/16.jpg)
MOS capacitor in depletion
16
VG
p-Si
W fS( ) W VG( )
11/2/2017 Bermel ECE 305 F17
![Page 17: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/17.jpg)
17
MOS capacitor in depletion
xo
W fS( )
KO
KS
C = ?
Gate
Undepleted P-type semiconductor
11/2/2017 Bermel ECE 305 F17
![Page 18: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/18.jpg)
18
a simpler problem
xo
W fS( )
KO
KSCS =
KSe0
W fS( )
Cox =KOe0
xo
1
C=
1
Cox
+1
CS
C =CSCox
CS + Cox
C =Cox
1+ Cox CS
C =Cox
1+KOW fS( )
KSxo
11/2/2017 Bermel ECE 305 F17
![Page 19: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/19.jpg)
result
xo
W fS( )
k ox
k Si
C =Cox
1+KOW fS( )
KSxo
VG
Cox
CS
fS
11/2/2017 Bermel ECE 305 F17 19
![Page 20: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/20.jpg)
20
s.s. gate capacitance vs. d.c. gate bias
C
VG¢
C =Cox
1+KOW fS( )
KSxo
accumulationdepletion
inversion
VT¢
flat band
Cox
11/2/2017 Bermel ECE 305 F17
![Page 21: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/21.jpg)
21
s.s. gate capacitance vs. d.c. gate bias
C
VG¢
C =Cox
1+KOW fS( )
KSxo
accumulation
depletion
inversion
VT¢
flat band
Cox
11/2/2017 Bermel ECE 305 F17
![Page 22: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/22.jpg)
22
capacitance vs. gate voltage
C
VG¢
accumulationdepletion
inversion
VT¢
flat band
Cox
11/2/2017 Bermel ECE 305 F17
C =Cox
1+KOW fS( )
KSxo
![Page 23: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/23.jpg)
23
high frequency vs. low frequency
C
VG¢
accumulationdepletion
inversion
VT¢
flat band
Cox
high frequency
low frequency
11/2/2017 Bermel ECE 305 F17
C =Cox
1+KOW fS( )
KSxo
![Page 24: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/24.jpg)
24
high frequency vs. low frequency
C
VG¢VT
¢
Cox
high frequency
low frequency
11/2/2017 Bermel ECE 305 F17
![Page 25: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/25.jpg)
25
high frequency vs. low frequency
p-Si
n+-Si n+-Si
MOS capacitor
11/2/2017 Bermel ECE 305 F17
![Page 26: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/26.jpg)
MOS capacitor
26
VG
p-Si
‘metal’/heavily doped
polysilicon
SiO2
tox » 1- 2 nm
Bermel ECE 305 F17
1) Gate voltage2) Example problem3) MOS capacitors4) MOS field-effect transistors
11/2/2017
![Page 27: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/27.jpg)
side and top views of a MOSFET
Bermel ECE 305 F17
p-type silicon
S Dn-Si
VGVS = 0 VD
n-Si
SiO2
side view
L
top view
LW
source draingate
Metal Oxide Semiconductor Field Effect Transistor
27
![Page 28: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/28.jpg)
transistors
Bermel ECE 305 F1711/2/2017 28
![Page 29: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/29.jpg)
transistor as a “black box”
control
terminal 1
terminal 2
I1
There are many kinds of transistors:
MOSFETSOI MOSFETSB FETFinFETMODFET (HEMT)bipolar transistorJFETheterojunction bipolar transistorBTBT FETSpinFET…
black box
Bermel ECE 305 F17
terminal 4
11/2/2017 29
![Page 30: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/30.jpg)
the bulk MOSFET
source drain
SiO
2
silicon
S G D
(Texas Instruments, ~ 2000)
Bermel ECE 305 F17
B
Source Drain
Gate
ID
Body
circuit symbol
3011/2/2017
![Page 31: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/31.jpg)
the MOSFET as a 2-port device
Source
Drain
Gate
current vs. voltage (IV)characteristics
MOSFET circuit symbol
ID VG ,VS ,VD( )
ID
S
D
G
ID
VGS
VDS
common source
input
output
ID VGS( ) at a fixed VDS
ID VDS( ) at a fixed VGS
transfer
output 31
![Page 32: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/32.jpg)
IV characteristics: resistor
R
I
V
I I = V R
more resistance
less resistance
V
+
-
Ohm’s LawI = V R
Bermel ECE 305 F17 3211/2/2017
![Page 33: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/33.jpg)
IV characteristics: ideal current source
VI0
V
I
I = I0+
-
I
I = I0
Bermel ECE 305 F1711/2/2017 33
![Page 34: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/34.jpg)
IV characteristics: transistors
VDS
S
D
G
ID
n-channel enhancement mode MOSFET
ID
VGS1
gate voltage controlled resistor“linear region”
gate voltage controlled current source
“saturation region”34
![Page 35: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/35.jpg)
IV characteristics: real current sources
V
I
I0
VI0
+
-
R0
I
I = I0 +V R0
Bermel ECE 305 F1711/2/2017 35
![Page 36: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/36.jpg)
IV characteristics: transistors
VDS
S
D
G
ID
n-channel enhancement mode MOSFET
ID
VGS1
Bermel ECE 305 F1711/2/2017 36
![Page 37: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/37.jpg)
MIOSFET IV: output characteristics
VDS
S
D
G
ID
n-channel enhancement mode MOSFET
ID
“saturation region”“linear region”
VGS
“subthreshold region”
Bermel ECE 305 F1711/2/2017 37
![Page 38: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/38.jpg)
output vs. transfer characteristics
VDS
ID
S
D
G
output characteristics
VGS
ID
VDS2 >VDS1
VDS1
VT
“threshold voltage”
Ilow VDS
high VDS
transfer characteristics
“saturation voltage”
VDSAT
Bermel ECE 305 F17 38
![Page 39: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/39.jpg)
applications of MOSFETs
symbol
D
SG
switch amplifier
input signal
output signal
S
D
G
S
D
G
Bermel ECE 305 F1711/2/2017 39
![Page 40: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/40.jpg)
n-channel vs. p-channel MOSFET
VD > 0VS = 0
p-type silicon
S Dn-Si n-Si“channel”
side view
L
VG >VT
n-MOSFET
IDID
VG <VT
Bermel ECE 305 F17
VD < 0VS = 0
n-type silicon
S Dp-Si p-Si
side view
L
p-MOSFET
“channel”
11/2/2017 40
![Page 41: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/41.jpg)
MOSFET device metrics
VDS
ID
mA mm( )
VDD
on-current (mA/μm)
ID VGS = VDS = VDD( )
transconductance
gm ºDID
DVGS VDS
mS mm( )
on-resistance
RON W- mm( )output resistance:
rd W- mm( )
VGS
Bermel ECE 305 F1711/2/2017 41
![Page 42: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/42.jpg)
MOSFET device metrics (ii)
VGS
ID
mA mm( )
VDD
transfer characteristics:
VDS = 0.05 V
VDS = VDD
VTSAT VTLIN
threshold voltage
off-current
ION
11/2/2017 42
![Page 43: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/43.jpg)
MOSFET device metrics (iii)
VGS
log10 ID
mA mm( )
VDD
transfer characteristics:
ION
VDS = 0.05 V
VDS = VDD
subthreshold swing:
mV decade( )
DIBL (drain-induced barrier lowering)
mV V( )off-current
VT
Bermel ECE 305 F1711/2/2017 43
![Page 44: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/44.jpg)
summary
Given the measured characteristics of a MOSFET, you should be able to determine:
Bermel ECE 305 F17
1. on-current: ION
2. off-current: IOFF
3. subthreshold swing, S4. drain induced barrier lowering: DIBL5. threshold voltage: VT (lin) and VT (sat)6. on resistance: RON
7. drain saturation voltage: VDSAT
8. output resistance: ro
9. transconductance: gm
Our goal is to understand these device metrics.
11/2/2017 44
![Page 45: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/45.jpg)
Example: 32 nm N-MOS technology
Bermel ECE 305 F1711/2/201745
![Page 46: ECE-305: Fall 2017 MOS Capacitors and Transistors/uploads/15_MOS... · ECE-305: Fall 2017 MOS Capacitors and Transistors Professor Peter Bermel Electrical and Computer Engineering](https://reader036.fdocuments.in/reader036/viewer/2022062508/604d3cf9c9f4fe68fb35b3b9/html5/thumbnails/46.jpg)
conclusions
Can calculate the charge distribution, surface potentials, and gate voltage ranges for each MOS regime
Can then calculate capacitance as a function of frequency and gate voltage
The MOS capacitor is the foundation for MOS field effect transistors, characterized by many device metrics
Next time, we will use band structures to estimate the device metrics for MOSFETs
11/2/2017 Bermel ECE 305 F17 46