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FerroelectricpropertiesofHfO2anditsimplicationonhighlyscaledFerroelectricFieldEffectTransistors
DATASET·NOVEMBER2012
READS
35
15AUTHORS,INCLUDING:
EkaterinaYurchuk
Anvo-SystemsDresdenGmbH
30PUBLICATIONS111CITATIONS
SEEPROFILE
JonasSundqvist
LundUniversity
72PUBLICATIONS803CITATIONS
SEEPROFILE
Availablefrom:ThomasMikolajick
Retrievedon:04February2016
0 12,00 12,20
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Ferroelectric properties of HfO2 and its implication on highly scaled
Ferroelectric Field Effect Transistors
Ekaterina Yurchuk1, Johannes Müller2, Steve Knebel1, Raik Hoffmann2, Thomas Melde3, Stefan Müller1, Dominik Martin1, Stefan Slesazeck1, Jonas Sundqvist2, Roman Boschke3, Till Schlösser3, Ralf van Bentum3 , Martin Trentzsch3, Uwe Schröder1 and Thomas Mikolajick1
1 2 3
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Ferroelectric Field Effect Transistor
Metal-Gate
n+ n+ - - -
Ferroelectric
p-Substrate
- +
- + - +
Semiconductor
Idrain
Vgate
„0“ high Vth
„1“ low Vth
• Performance advantages:
• non-volatility
• non-destructive readout
• low power consumption
• reading and writing speed in
ns-time range
• low operation voltages
• high endurance
• Challenges:
• Compatibility with existing
CMOS process
• buffer layer between Si and
ferroelectric with high-k is
required
• scalibility below 20 nm
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0
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Ferroelectric Field Effect Transistor
Idrain
Vgate
„0“ high Vth
Metal-Gate
n+ n+ + + +
Ferroelectric
p-Substrate
- +
- +
- +
Semiconductor
• Performance advantages:
• non-volatility
• non-destructive readout
• low power consumption
• reading and writing speed in
ns-time range
• low operation voltages
• high endurance
• Challenges:
• Compatibility with existing
CMOS process
• buffer layer between Si and
ferroelectric with high-k is
required
• scalibility below 20 nm
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0
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4
Ferroelectric Field Effect Transistor
Metal-Gate
n+ n+ - - -
Ferroelectric
p-Substrate
- +
- +
- +
Semiconductor
Idrain
Vgate
„1“ low Vth
• Performance advantages:
• non-volatility
• non-destructive readout
• low power consumption
• reading and writing speed in
ns-time range
• low operation voltages
• high endurance
• Challenges:
• Compatibility with existing
CMOS process
• buffer layer between Si and
ferroelectric with high-k is
required
• scalibility below 20 nm
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0
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Ferroelectricity in HfO2
Orthorhombic phase
Tetragonal phase
Advantages of ferroelectric HfO2 over conventional ferroelectrics:
• fully compatible with the existing CMOS process
• low k-value (~20) (PZT and SBT: ~200-300)
• SiO2 can be used as buffer layer
• thin HfO2 films (10-30nm) can be used
• better scalibility due to more suitable aspect ratio
Monoclinic phase
P21/c
P42/nmc
Pbc21
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6
Ferroelectricity in HfO2
Orthorhombic phase
Tetragonal phase
Advantages of ferroelectric HfO2 over conventional ferroelectrics:
• fully compatible with the existing CMOS process
• low k-value (~20) (PZT and SBT: ~200-300)
• SiO2 can be used as buffer layer
• thin HfO2 films (10-30nm) can be used
• better scalibility due to more suitable aspect ratio
Monoclinic phase
P21/c
P42/nmc
Pbc21
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7
Ferroelectricity in HfO2
(220) o
(101) t
(111) m
(-111) m
(421) o
(133) o
(331) o
(022) o
cappedlog c
ounts
no cap
10 nm Si:HfO2
orthorhombic
monoclinic
tetragonal
2 Theta (degree)
20 40 60 80
• Crystallisation of Si:HfO2 under TiN Capping – ferroelectric behavior
• Piezoelectric behaviour – confirmation of the true ferroelectric properties
T.S. Böscke et al. Appl. Phys. Lett. 99, 102903 (2011)
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Effect of Si -Doping
• Doping of HfO2 with Si → Increase of crystallization temperature (TK)
• With increasing Si content → stabilization of the tetragonal phase in HfO2
100
200
300
400
500
600
700
10 20 30 40 50
SiO2
TiN
8.5 mol%
0 mol%
4.4 mol%
5.6 mol%
6.6 mol%
9 nm Si:HfO2
after 650oC Anneal
Sig
nal
[cou
nts
/sec
]
2Theta [degree]
m t m
m
m
t
TiN Si:HfO2
TiN Si-Substrate
0 2 4 6 8 10 12200
400
600
800
1000
amorphous mixture tetragonal/ monoclinic
monoclinic tetragonal
Tem
per
atu
re [
oC
]
SiO2 concentration [mol%]
Amorphous
M/T
T O
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0
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8,00
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9
-60
-40
-20
0
20
40
60
-3 0 3 -3 0 3 -3 0 3 -3 0 3 -3 0 3
SiO2
Ele
ctr
ic D
isp
lac
em
en
t [
C/c
m2
]
0 mol %
4.4 mol %
5.6 mol %
6.6 mol %
Electric Field [MV/cm]
8.5 mol %
1.5
2.0
2.5
3.0
3.5
4.0
4.5
-3 0 3 -3 0 3 -3 0 3 -3 0 3 -3 0 3
SiO2
Cap
ac
itan
ce
[F
/cm
2]
0 mo %
4,4 mol %
5,6 mol %
6,6 mol %
Electric Field [MV/cm]
8,5 mol %
• Increase of SiO2 concentration
→ Change in the electrical
properties :
paraelectric
↓
ferroelectric
↓
antiferroelectric
• The effect was confirmed
using both polarisation - and
capacitance -voltage
measurements
• Similar behavior for 9 nm
and 27 nm Si:HfO2 films
9 nm Si:HfO2 after 800oC Anneal
Effect of Si -Doping Pt
TiN
TiN
Si-substrate
Si:HfO2
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0
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10
-50
-25
0
25
50
-3 0 3 -3 0 3 -3 0 3 -3 0 3
after TiN
deposition
Ele
ctr
ic D
isp
lac
em
en
t [
C/c
m2
]
450C
650C
800C
1000C
1
2
3
4
5
6
7
-3 0 3 -3 0 3 -3 0 3 -3 0 3
after TiN
deposition
Ca
pacit
an
ce [
F/c
m2
]
450C
Electric Field [MV/cm]
650C
800C
1000C
Increasing film crystallinity with
annealing temperature
→ higher fraction of the ferroelectric
phase
→ rise in the remanent polarisation
9 nm Si:HfO2 with 4.4mol% SiO2
Effect of annealing temperature
500 600 700 800 900 10000
50
100
150
200
250
300
24.6 m
42.8 TiN
35.6 m
30.8 t
Re
man
en
t po
lariza
tion
[C
/cm
2]
17.6 m
Anneal T [oC]
-30
-20
-10
0
10
20
30
Inte
gra
l pea
k inte
nsity
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Effect of film thickness
0
5
10
15
20
25
400 500 600 700 800 900 10000.0
0.5
1.0
1.5
4.4 mol % SiO2
9 nm
27 nm
Rem
anen
t p
ola
riza
tio
n [
C/c
m2]
4.4 mol % SiO2
9 nm
27 nm
Co
erci
ve
fiel
d s
tren
gth
[M
V/c
m]
Anneal T [oC]
-3 0 3-50
-25
0
25
50
-3 0 3-50
-25
0
25
50
9 nm
Ele
ctri
c D
isp
lace
men
t [µ
C/c
m²]
Electric Field [MV/cm]
27 nm
Electric Field [MV/cm]
For thicker films:
• Pr reduction down to 2.5C/cm2
• Pr shows no dependence on the annealing
temperature
Coercive field strength shows no dependence on
the film thickness
Si:HfO2 with 4.4mol% SiO2 annealed at 1000oC
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• Decrease of TK with increasing film thickness
• Higher Si-Doping is needed to prevent crystallization of 27nm layers during
deposition of the top TiN electrode
• Monoclinic phase becomes more stable in thicker films
Effect of film thickness
0
100
200
300
400
500
25 30 35 40
SiO2 5.6 mol%
TiN
0 mol%
4.4 mol%
9nm Si:HfO2
after TiN deposition
Sig
nal
[cou
nts
/sec
]
2Theta [degree]
0
250
500
750
1000
1250
1500
25 30 35 40
SiO2 5.6 mol%
TiN
0 mol%
4.4 mol%
27 nm Si:HfO2
after TiN deposition
Sig
nal
[cou
nts
/sec
]2Theta [degree]
m m t
m m t
t
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6,40
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0
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6,40
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8,00
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13
-0.5 0.0 0.5 1.00
25
50
75
100
125
Idra
in [
A]
MW ~0,8V
-6 V
100 ns
+4.5 V
100 ns
Vgate [V]
Ferroelectric Field Effect Transistor
Poly-Si
Si-Substrate
SiO2 1.2 nm
Si:HfO2 9 nm
TiN 8 nm
• Memory window 800mV
• Program/erase performed with pulses: -6V 100ns and+4.5V 100ns
• 10 years retention is expected
Memory Window N-channel MFIS-FET W: 2m L:100nm
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Ferroelectric Field Effect Transistor
• Memory window 800mV
• Program/erase performed with pulses: -6V 100ns and+4.5V 100ns
• 10 years retention is expected
Memory Window
100
101
102
103
104
105
106
107
108
-0.5
0.0
0.5
1.0
10
day
s
Experimental data 25 oC
Extrapolation
10
yea
rs
programmed -6.0 V 100 ns
erased +4.5 V 100 ns
Thre
shold
volt
age
(V)
time (s)
Retention
-0.5 0.0 0.5 1.00
25
50
75
100
125
Idra
in [
A]
MW ~0,8V
-6 V
100 ns
+4.5 V
100 ns
Vgate [V]
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15
Conclusions
• Si-doped HfO2
• Increasing Si-content → increase of crystallyzation temperature ,
stabilization of tetragonal phase
• Ferroelectric behavior revealed at the phase transition between monoclinic and
tetragonal phases
• Increase of the remanent polarisation for higher annealing temperatures
due to higher film crystallinity
• 27 nm thick HfO2 films show reduced remanent polarisation and
a negligible change in the coercive field strength in comparison to 9 nm thick films
• Si:HfO2 based FeFET
• MFIS-FET with 100 nm channel length was fabricated
• memory window – 0.8V, switching time 100ns using +4.5V and -6V,
10 years data retention is expected
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16
Thank you for your attention!
Thanks to the FeFET – TEAM at:
This work was financially supported by
the free state of Saxony and the EFRE fund
(HEIKO project 100064806).
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MIM capacitors / Fabrication process
Deposition of TiN
bottom electrode
(CVD at 450oC)
Deposition of Si:HfO2
ALD (HfCl4 , SiCl4 ,H2O)
Deposition of TiN
top electrode
(CVD at 450oC)
Annealing in N2
Si-Substrate
Deposition of Pt-dots
+
Wet etch of TiN
TiN TiN Si:HfO2
TiN Si:HfO2
TiN
Pt
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Modeling (Thickness dependence)
0 2 4 6 8 10 120
1
2
3
4
5
0 5 10 15 20 25 300
1
2
3
4
5
Me
mo
ry W
indo
w [
V]
Remanent polarization [C/cm2]
Pr/Ps = 0.72
Ec=0.9 MV/cm
=25
fe-thickness 9 nm
1 nm SiO2
Me
mo
ry W
indo
w [
V]
Ferroelectric layer thickness [nm]
Pr=24 C/cm2
Ps=33 C/cm2
Ec=0.9 MV/cm
=25
1 nm SiO2
0 5 10 15 20 25 3070
75
80
85
90
95
100
Pr=24 C/cm2
Ps=33 C/cm2
Ec=0.9 MV/cm
=25
1 nm SiO2
Ed
ep /
Ec [
%]
Ferroelectric layer thickness [nm]
• For the remanent polarization > 3C/cm2 – marginal change of the memory window
• Increasing thickness of the ferroelectric layer
• larger memory window
• reduced depolarization field → better retention properties
Memory Window Depolarisation field at Vgate =0V
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19
Modeling (Thickness dependence)
0 2 4 6 8 10 12 14 160.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0Interface layer 1nm SiO
2
27 nm
9 nm
Me
mo
ry W
ind
ow
[V
]
Programming Voltage [V]
9 nm 27 nm0
50
100
Ede
po
lari
zation / E
c [%
] *
* for saturated memory window
-3 0 3-50
-25
0
25
50
-3 0 3-15
-10
-5
0
5
10
15Ec =0.9 MC/cm
Pr=24C/cm2
Ps=33 C/cm2
Pr/Ps=0,72
=25
9 nm
Ele
ctri
c D
ispla
cem
ent
[µC
/cm
²]
Electric Field [MV/cm]
27 nm
Electric Field [MV/cm]
Ec= 0.7 MV/cm
Pr =2.5 C/cm2
Ps=2.51 C/cm2
Pr/Ps=1
=25
Expected gain from implementation of
27 nm instead of 9nm thick Si:HfO2 :
• 2 times larger memory window
• better switching behavior
• lower depolarisation field →
better retention behavior
Experiment MIM 4,4 mol% SiO2 1000oC Anneal Simulation MFIS-FET
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20
Ferroelectric Field Effect Transistor
• Memory window 0.8V
• Program/erase performed with pulses : -6V 100ns and+4V 100ns
• 10 years retention is expected
Retention Temperature dependent
100
101
102
103
104
105
106
107
108
-0.5
0.0
0.5
1.0
10
day
s
Experimental data 25 oC
Experimental data 150 oC
Extrapolation
10
yea
rs
programmed -6.5 V 100 ns
erased +4.5 V 100 ns
T
hre
shold
volt
age
(V)
time (s)
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21
Phase transition
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22
• With increasing SiO2 content →
stabilization of the tetragonal phase
in HfO2
• Ferroelectric behavior is observed at
the phase transition from monoclinic to
tetragonal phase
Effect of Si -Doping 9 nm Hf1-xSixO2 after 800oC Anneal
10 20 30 40 50 60 70
TiN
8.5 mol% SiO2
6.6 mol%
5.6 mol%
4.4 mol%
0 mol%
Sig
na
l [c
ou
nts
/se
c]
orthorhombic Pbc2_1
tetragonal
2Theta (degree)
monoclinic
0 2 4 6 80
50
100
150
200
42.8 TiN
28.5 m
31.7 m
30.8 t/o
Inte
gra
l p
ea
k in
ten
sity
17.6 m/o
SiO2 content [mol %]
-20
-10
0
10
20
Re
ma
ne
nt p
ola
risa
tio
n [C
/cm
2]
