Discrete Semiconductor Devices and Circuits_17_Bipolar Junction Transistors in Active Mode
Semiconductor Devices 2 Field-Effect Transistors L R · PDF fileField-Effect Transistors ch L...
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Semiconductor Devices 2 www.tu-ilmenau.de Page 1 JFET MOSFET Field-Effect Transistors ch L R A Channel resistance: Area Conductivity
Transcript of Semiconductor Devices 2 Field-Effect Transistors L R · PDF fileField-Effect Transistors ch L...
Semiconductor Devices 2
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JFET MOSFET
Field-Effect Transistors
ch
LR
AChannel resistance:
Area Conductivity
Semiconductor Devices 2
MOSFET
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Semiconductor Devices 2
Band Diagram
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Depletion
Inversion
p-type substrate n-type substrate
Semiconductor Devices 2
Poisson Equation (1D)
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2
2
0 0
ed ( ) ( )e x p e x p
d V V
i A
s s T T i
n Ny y
y n
1 / 2
( ) 2 c o s h c o s h2
s b s bT A
s s b
D ì T T T i
V NE s ig n
L V V V n
0
2 e
s T
D i
i
VL
n
Intrinsic Debye Length:
s in h2
bA
i T
N
n V
or with
Semiconductor Devices 2
Surface Field
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s (V)
Semiconductor Devices 2
Surface Field
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Semiconductor Devices 2
Surface Field and total space-charge density
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-0.6 -0.4 -0.2 0.0 0.2 0.4 0.610
2
103
104
105
106
107
Es (
V / c
m )
s (V)
N A (cm
-3)
1018
1017
1016
1015
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.610
-10
10-9
10-8
10-7
10-6
10-5
Qto
t ( A
s / c
m2)
s (V)
NA (cm
-3)
1018
1017
1016
1015
accumulation
Es< 0
depletion
Es> 0
inversion
Es> 0"
0to t s sQ E
Semiconductor Devices 2
Approximation
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Depletion:
1 / 2 1 / 2
0
2 e( )
bT A A
b
D i T i s
V N NE
L V n
Accumulation:
1 / 2
( ) e x p 1bT
D T
VE
L V
Inversion:
1 / 2
2( ) e x p 1
b bT
D T T
VE
L V V
0
2 e
s T
D
A
VL
N
near flat band: ( ) s ig n
2
s bT
s b
TD
VE
VL
Semiconductor Devices 2
Second Integration
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Depletion:
Accumulation:
Inversion:
fü r u n d 0d ep s b
l L y
2
0
e
2
A
b
s
Ny L
max. depletion length:
0
ed
d
A
s
Ny L
y
02 | 2 |
e
s b
d ep
A
lN
ch Dy L
8ln
2
bD
ch
Tb
T
Ly
V
V
Semiconductor Devices 2
Differential Capacitance
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-0.6 -0.4 -0.2 0.0 0.2 0.4 0.610
3
104
105
106
107
Es
Cs
s (V)
|Es| (
V / c
m )
NA=10
16 cm
-3
10-8
10-7
10-6
10-5
10-4
C" s (
F / c
m2 )
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.610
-8
10-7
10-6
10-5
10-4
N A (cm
-3)
1018
1017
1016
1015
s (V)
"
"
0
d d ( )
d d ( )
to t s s
s s
s s s
Q EC
E
Semiconductor Devices 2
Differential Capacitance
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Capacitance at flat-band condition: " 0
0
d
d 2
s s
F B s
s D
EC
L
minimum capacitance for
" 0
m in 0
d
d
s s
s
s d ep
EC
l
1 / 2
0
2 eA
s s b
s
NE
s b
Depletion:
1 / 2
0
d e
d 2
s A
S s s b
E N
Semiconductor Devices 2
Band Diagram
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FM
Fs
ci
eVFB
EG
EV
EC
EVac
EF
EC
Semiconductor Devices 2
Potential Balance
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'
G S F B G S o x s bV V V V
without IF states:o x o x o x
V E d o x o x s s
E E
'
1 / 2
s ig n 2 c o s h c o s h2
G S s bo x o x o x
S
s s o x
s b s bT A
s b
D T T T i
VEE
d
V N
L V V V n
Semiconductor Devices 2
Graphical Method
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Semiconductor Devices 2
Graphical Method
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Semiconductor Devices 2
Numerical Solution
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-4 -2 0 2 4-0.8
-0.4
0.0
0.4
0.8
s (
V)
VGS
(V)
NA (cm
-3)
1016
1017
1018
dox
=10nm
Semiconductor Devices 2
Numerical Solution
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-4 -2 0 2 4-0.8
-0.4
0.0
0.4
0.8
-b
s (
V)
VGS
(V)
dox
(nm)
10
50
NA=10
16cm
-3
b
Semiconductor Devices 2
Approximation
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Accumulation:
1 / 2
'e x p 1
T s o x b s
G S s b
o x D T
V dV
L V
2'
ln 1G S
s b T
p
VV
V
Inversion:
1 / 2
' 2e x p 1
T s o x b s b
G S s b
o x D T T
V dV
L V V
2'
2 2ln 1
b G S b
s T b
T p
VV
V V
1 / 2
'
0
e x p 1
p
T s o x b s
G S s b
o x D T
V
V dV
L V
1 / 2
'
2
2e x p 1
b
T s o x b s b
G S s b
o x D T T
V dV
L V V
Semiconductor Devices 2
Approximation
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Depletion:
1 / 2
1 / 20'
"
0
2 e2 eA sA s bs o x
G S s b s b
o x s o x
NNdV
C
2 2
' '
2 4s b G S G S
a aV a V
1 / 2
1 / 20'
"
0
2 e2 eA sA s bs o x
G S s b s b
o x s o x
a
NNdV
C
Semiconductor Devices 2
Comparison
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-4 -2 0 2 4-0.8
-0.4
0.0
0.4
0.8
NA=10
16cm
-3
dox
=10nm
s (
V)
VGS
(V)
numerisch
Näherung
Semiconductor Devices 2
Ideal MIS Structure
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Band diagram
Charge distribution
Semiconductor Devices 2
MIS Capacitance
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-4 -2 0 2 40.0
0.2
0.4
0.6
0.8
1.0
C'' M
OS / C
'' ox
V 'GS
/ V
dox
(nm)
10
50
NA=10
16cm
-3
-4 -2 0 2 40.0
0.2
0.4
0.6
0.8
1.0
dx=10nm
C'' M
OS / C
'' ox
V 'GS
/ V
NA (cm
-3)
1016
1017
1018
Semiconductor Devices 2
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Semiconductor Devices 2
MIS Capacitance
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Semiconductor Devices 2
MIS Capacitance at f=6kHz
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Semiconductor Devices 2
MIS Capacitance
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Semiconductor Devices 2
MIS Capacitance at f=1MHz
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Semiconductor Devices 2
MIS Capacitance of a p-type SC
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VFB=0
a) low frequency
b) intermadiate frequency
c) high frequency
d) high frequency (deep depl.)
Semiconductor Devices 2
Real MOS Structure
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Semiconductor Devices 2
Influence of fixed IF Charges
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p-type SC
n-type SC
Semiconductor Devices 2
Oxid trapped charge
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Band diagram
Charge distribution
Semiconductor Devices 2
IF Traps
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Distribution functions (occupancy):
1( )
1 e x pk
d o n tD
F tD
d
f EE E
gT
1( )
11 e x p
k
a c c tA
tA F
a
f EE E
g T
donor traps
acceptor traps
Semiconductor Devices 2
Inluence of IF Traps
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Semiconductor Devices 2
MIS Capacitance
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Semiconductor Devices 2
MOSFET
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n+ n+
p-Si
S DG
y
x
0
( , ) fü r 0
( , ) d
i
D G S D S S B
y
D n
I f V V V
I w J x y y
''
0
d de ( , ) d ( )
d d
iy
F n F n
D n nI w n x y y w Q x
x x
''
0
C h a rg e : ( ) e ( , ) d
iy
Q x n x y y
Semiconductor Devices 2
Band diagram and Charge distribution in Inversion
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Equilibrium Nonequilibrium near drain
Semiconductor Devices 2
Charge per unit area
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Assumptions: GCA (gradual channel approximation)
ldep independent on x
'' ''( ) ( )
o x G S th F nQ x C V V x
'' ''
''
e( ) (0 ) ( )
A d ep
o x G S F B s b F n
o x
N lQ x C V V x
C
(0 ) ( ) 2s b s G S b
V
'' ''
''
e( ) ( 2 ) ( )
A d ep
o x G S F B b F n
o x
N lQ x C V V x
C
Semiconductor Devices 2
Simple Shockley Equation
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2
''
2
''
( ) ,2
( ) ,
2
D S
o x G S th D S D S G S th
D
G S th
o x D S G S th
VwC V V V V V V
LI
V VwC V V V
L
' 2
2
' ''
1
1 ,( ) u n d =
20 ,
D
D
D
D S
D S G S thG S th
G S tho x
D S G S th
I I
VV V VV Vw
V VI CL
V V V
Semiconductor Devices 2
Mobility vs Transverse Field
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Semiconductor Devices 2
Influence of the lateral Field
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| | | |( )v E µ E | | 1 /
| |
( )
1 ( / )n
n
sa t
µµ E
E E
Semiconductor Devices 2
Influence of the lateral Field
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Semiconductor Devices 2
Current Equations
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''
0 0 0
d d ( ) dD S D S
L V VD
D F n o x G S e ff F n F n
sa t
II x w µ C V x
E
'' 2( )
( )2
G S o x sa t D S
D G S th D S
sa t D S
µ V w C E VI V V V
L E V
2 ( )1 1
G S th
D S a t sa t
sa t
V VV E L
E L
Saturation Voltage:
'' d( )
d1 d1
d
F n
D o x G S e ff F n
F n
sa t
µI w C V x
x
E x
Semiconductor Devices 2
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µ=const.
µ=f(E||)
Semiconductor Devices 2
Increase of the depletion region
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linearer region
onset of saturation
saturation region
Semiconductor Devices 2
Inversion Charge
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0
''
2 2e2
e
s b S BA
th F B b
o x A
VNV V
C N
0'' ''
''
2 2 ( )e( ) 2 ( )
e
s b S B F nA
o x G S F B b F n
o x A
V xNQ x C V V x
C N
Threshold Voltage
Semiconductor Devices 2
Drain Current
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'' 0
'' 2
2 e2( 2 )
2 3
D S A s
D o x G S F B b D S
o x
V NwI C V V V
L C
2 / 3 2 / 3
( 2 ) ( 2 )b S B D S b S B
V V V
'' 2
0
'' 2
0
e 22 1 1 ( )
e
A s o x
P G S F B b G S F B S B
o x A s
N CV V V V V V
C N
Pinch-off voltage
Semiconductor Devices 2
S/D Contact Resistance
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' ' ( )
G S G S D S D S D S D S DV V I R V V I R R
Semiconductor Devices 2
S/D Contact Resistance
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2
''
''
2
2
D S
o x G S e ff D S
D
D S
o x S D G S e ff
Vw µ C V V
IV
L w µ C R V
' 'A s s u m p tio n : I
G S G S D G S e ff D SV V K V V
''
''
o x G S e ff D S
D
o x S D G S e ff
w µ C V VI
L w µ C R V
Semiconductor Devices 2
Subthreshold Region
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2
2 0e
e x p 1 e x p2 ( )
A s i s b D S
D T
s b A T T
N n VwI V
L N V V
Diffusion
Drift
Semiconductor Devices 2
Influence of Temperature
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Subthreshold Swing Vth and µ
Semiconductor Devices 2
Short-Channel Effects
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Long channel Short channel
Semiconductor Devices 2
Narrow-Channel Effects
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LOCOS STI
(local oxidation of silicon) (shallow-trench-isolated)
Semiconductor Devices 2
Short-Channel Effects (Charge Sharing)
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VDS > 0 VDS = 0
Semiconductor Devices 2
Short-Channel Effects
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''
e 2 21 1 1 1
2
A B j s d
th
o x j j
N d r y yV
C L r r
0 02 ( ) 2 ( )
u n d e e
s D s s D s D S
s d
A A
V V Vy y
N N
Semiconductor Devices 2
Narrow-Channel Effects
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LOCOS STI
''
e2 1
2
A B B
th F B b
o x
N d dV V
C w
''
22
B
th F B b
o x F
QV V
C w L C
02 2
lns F o x
F
o x
L dC
d
Semiconductor Devices 2
Short-Channel Effects
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Transfer Characteristics Vth
Semiconductor Devices 2
Short-Channel Effects
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NA=1015cm-3 NA=1014cm-3
Semiconductor Devices 2
Drain-induced barrier lowering (DIBL)
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Semiconductor Devices 2
Punch-Through-Effect
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Surface-Puch-Through Bulk-Puch-Through
Semiconductor Devices 2
Current Components under high fields
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Semiconductor Devices 2
Drain current, gate current and substrate current
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lightly doped drain(LDD)
n+/n ≈ 10…100
Semiconductor Devices 2
Scaling
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Semiconductor Devices 2
Capacitances
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Semiconductor Devices 2
Intrinsic Capacitances
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3 3 2
2 2
( ) ( )2 2 1
3 ( ) ( ) 3 1
G S th G D th
G o x o x
G S th G D th
V V V VQ C C
V V V V
2
, ,
2 1 2
3 (1 )G D B
G
g s o x
S V V V
QC C
V
2
2
, ,
2 2
3 (1 )G S B
G
g d o x
D V V V
QC C
V
0 ( 1) :2
02 3
( 0 ) :D S D S D sa t
o x
g s g d g s o x g dV
CC C CV CV C
Semiconductor Devices 2
Intrinsic Capacitances
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Cox=32pF, Uth=1.2V
0 1 2 30.0
0.5
1.0
1.5
2.0
2.5
CG
X (
pF
)
VDS
(V)
VGS
(V)
2
2.5
3
Cgd
Cgs
3 2 1 00.0
0.5
1.0
1.5
2.0
2.5
CG
X (
pF
)V
GS (V)
VDS
(V)
0.5
1
1.5
Cgd
Cgs
Semiconductor Devices 2
Small-signal equivalent circuit
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Semiconductor Devices 2
Cutoff Frequency ft
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S
G
DS‘ D‘RS RD
D S
T 2
o L is G S th2 ( ) 1 2 ( )
µVf
wL L L µ C R V V
L
D G S th
fü r : S D
R R R
R I V V
0.01 0.1 1 1010
6
108
1010
1012
1014
channel lenght (µm)
cuto
ff fre
quency (
Hz)
Lpar
(µm) R()
0 0
10 0
10 100
10 500
VGS-Vth=3V; VDS=1V; dox=10nm
Semiconductor Devices 2
CMOS
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VDD
S
S
D
DVin
Vout
p-Kanal
n-Kanal
Vin
Vout
VDD
VDD
Semiconductor Devices 2
BiCMOS
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Semiconductor Devices 2
CMOS
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T1 T2
vertical T2: n+(source) p(well) n(substrate)
lateral T1: p(well) n(substrat) p+(source)
Semiconductor Devices 2
CMOS-SOI-Technology
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Semiconductor Devices 2
MOSFET
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n+ n+
p-Si
S DG
B
G
Bulk SOI
n+ n+
p-Si
S D
p-Si
floatend B
"
0
''e
to t s s
B A d ep
Q E
Q N l
''
0
e
sb
B A d ep
E
Q N l
ssb
bs
dGOX
dBOX
dSi
"
0( )
to t s s sbQ E E
Thick layer thin layer
''
0
e
sb
B A S i
E
Q N d
Semiconductor Devices 2
SOI
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ldep f ldep b ldep f
ldep b
Thick layer thin layer
neutral
region
Semiconductor Devices 2
SOI
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1 / 2
2 2 2
2( ) 2 c o s h c o s h s in h
b s G B b G B b s b b G BT
b s b s b
D T T T T
V V VVE s ig n
L V V V V
1 / 22
2 1( ) 2 c o s h c o s h s in h
sb s sb s bT
s s sb sb
D T T T T
VE s ig n E
L V V V V
o x o x b s sb
sb b s B O X
s s B O X
E E Ed
m in
m in
m in m in
d ds ig n ( ) m it ( ) 0
( ) ( )
sb
s
S i sd E
E E
Semiconductor Devices 2
SOI
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Potential balance:
1G S F B f G O X s sb S B G O X s bV V V V V
1S B b sbV
2G B F B b B O X b s b S BV V V V
Semiconductor Devices 2
SOI
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Semiconductor Devices 2
a-Si-TFT
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Semiconductor Devices 2
a-Si-TFT
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Semiconductor Devices 2
a-Si-TFT
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Semiconductor Devices 2
a-Si-TFT
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Semiconductor Devices 2
3D-MOSFET
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Semiconductor Devices 2
Power MOSFETs
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VMOS UMOS
Semiconductor Devices 2
DMOS
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Vertical DMOS LDMOS
Semiconductor Devices 2
Memory Devices
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Semiconductor Devices 2
RAM
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SRAM DRAM
Semiconductor Devices 2
Nonvolatile Memory Devices
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Semiconductor Devices 2
Floating-Gate Transistor
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Semiconductor Devices 2
FLOTOX-Transistor
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Tunneling for both programming and erasing
Semiconductor Devices 2
Charge-Coupled Device (CCD)
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Surface-channel buried-channel
Semiconductor Devices 2
CCD
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Semiconductor Devices 2
CCD charge transfer
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3-Phase Gate voltage
2-Phase staged oxid
Semiconductor Devices 2
CCD
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Semiconductor Devices 2
CMOS Active Pixel Sensor
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Semiconductor Devices 2
JFET MESFET
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3 / 2 3 / 2022
e ( ) ( )3 e
s
D D D S D G S D S D G S
D
wI N aV V V V V V
L N
Semiconductor Devices 2
MESFET
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Small-signal equivaent circuit Small-signal elements and structure
Semiconductor Devices 2
MESFET Structures
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Semiconductor Devices 2
MODFET
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Structure Band gap
Semiconductor Devices 2
MODFET
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Semiconductor Devices 2
MODFET
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