Transcript Titre de la Communication

Ulis 2003
4th European Workshop on
ULtimate Integration of Silicon
Theoretical investigation of hole
phonon-velocity in strained Si
inversion layer
F. Payet(1,2), N. Cavassilas(1), J.L. Autran(1)
(1) Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
(2) STMicroelectronics
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Outline
 Strained Silicon
 Deformed Si lattice
 Strain contribution on the valence band
 Strain consequences on transport properties
 Strained Silicon inversion layer
 Strained Si MOSFET
 Tensile strain and quantization effects
 Transport results
 Conclusion
STMicroelectronics
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
The System Strained Si on SiGe
[001]
a//(x)
a//(x)
a^(x)
strained Si
[010]
aSiGe(x)
Si1-xGe x
aSiGe(x)
[100]
aSiGe(x)
Two strain contributions:
Hydrostatic
Uniaxial → lower lattice symmetry
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
Tensile Strain Contribution on Band Structure
4 2
4
4 2
EG
2
LH HH
SO
EG
LH HH
LH
HH
SO
SO
Cubic
silicon
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Hydrostatic
strain
Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
Uniaxial
strain
Tensile Strain Contribution on Band Structure
Band Structure
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
Strain Contribution on the Valence Band
0.2
0.0
Si bulk
Si/Si0.5Ge0.5
phonon
-0.1
HH
0.1
LH
-0.2
-0.3
SO
Energy (eV)
Energy (eV)
LH
E(LH-HH)
0.0
-0.1
HH
-0.2
-0.4
SO
-0.3
-0.5

[100]

[100]
[110]
[110]
Si/SiGe
Unstrained Si
[100]
[110]
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[010]
LH Band
[100]
Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
[110]
[010]
HH Band
Strain Consequences on Transport Properties
< 1 % in HH
≈ 86 % in HH
F= 30 kV/cm
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
Strain Consequences on Transport Properties
HH Band
LH Band
Distribution Functions
ky
ky
F
kx
kx
F = 50 kV/cm
8
6
Hole drift velocity (10 cm/s)
10
6
4
2
0
0.0
0.5
1.0
1.5
2.0
2.5
Time (ps)
Hole Drift Velocity
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
3.0
F
Strain Consequences on Transport Properties
HH Band
LH Band
Distribution Functions
ky
ky
F
kx
kx
F = 50 kV/cm
8
6
Hole drift velocity (10 cm/s)
10
6
4
2
0
0.0
0.5
1.0
1.5
2.0
2.5
Time (ps)
Hole Drift Velocity
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
3.0
F
Strain Consequences on Transport Properties
HH Band
LH Band
Distribution Functions
ky
ky
F
kx
kx
F = 50 kV/cm
8
6
Hole drift velocity (10 cm/s)
10
6
4
2
0
0.0
0.5
1.0
1.5
2.0
2.5
Time (ps)
Hole Drift Velocity
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
3.0
F
Strain Consequences on Transport Properties
HH Band
LH Band
Distribution Functions
ky
ky
F
kx
kx
F = 50 kV/cm
8
6
Hole drift velocity (10 cm/s)
10
6
4
2
0
0.0
0.5
1.0
1.5
2.0
2.5
Time (ps)
Hole Drift Velocity
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
3.0
F
Strain Consequences on Transport Properties
HH Band
LH Band
Distribution Functions
ky
ky
F
kx
kx
F = 50 kV/cm
8
6
Hole drift velocity (10 cm/s)
10
6
4
2
0
0.0
0.5
1.0
1.5
2.0
2.5
Time (ps)
Hole Drift Velocity
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
3.0
F
Strain Consequences on Transport Properties
HH Band
LH Band
Distribution Functions
ky
ky
F
kx
kx
F = 50 kV/cm
8
6
Hole drift velocity (10 cm/s)
10
6
4
2
0
0.0
0.5
1.0
1.5
2.0
2.5
Time (ps)
Hole Drift Velocity
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
3.0
F
Strain Consequences on Transport Properties
HH Band
LH Band
Distribution Functions
ky
ky
F
kx
kx
F = 50 kV/cm
8
6
Hole drift velocity (10 cm/s)
10
6
4
2
0
0.0
0.5
1.0
1.5
2.0
2.5
Time (ps)
Hole Drift Velocity
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
3.0
F
Strain Consequences on Transport Properties
HH Band
LH Band
Distribution Functions
ky
ky
F
kx
kx
F = 50 kV/cm
8
6
Hole drift velocity (10 cm/s)
10
6
4
2
0
0.0
0.5
1.0
1.5
2.0
2.5
Time (ps)
Hole Drift Velocity
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
3.0
F
Strain Consequences on Transport Properties
HH Band
LH Band
Distribution Functions
ky
ky
F
kx
kx
F = 50 kV/cm
8
6
Hole drift velocity (10 cm/s)
10
6
4
2
0
0.0
0.5
1.0
1.5
2.0
2.5
Time (ps)
Hole Drift Velocity
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
3.0
F
Strained Si MOSFET
Relaxed
Relaxed SiGe
SiGe
CB
CB
LH
LH sub-Band
sub-Band
HH
HH sub-Band
sub-Band
VB
VB
Energy
Energy Levels
Levels Non
Non Localised
Localised in
in
the
the Strained
Strained Si
Si Channel
Channel
Depth
Depth (m)
(m)
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
Hole Density (u.a.)
Energy (eV)
Strained Si
Si
ox
ox Strained
Tensile Strain and Quantization Effects
1 > 2
LH
HH
HH
LH
Si bulk
1
Strained Si
(tensile)
2
(LH)1
(HH)1
(LH)2
(HH)2
Quantization in
inversion layer
Strain and Confinement in [001] direction
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
Transport Results: Strain effects
Tsi = 10 nm
F = 50 kV/cm
Hole Velocity versus Time
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
Transport Results: Quantization Effects
Hole Velocity versus Electric Field
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
Transport Results
Enhancement factor
3.5
3.0
Low field mobility
2.5
2.0
1.5
1.0
0.0
0.1
0.2
0.3
0.4
0.5
SiGe alloy composition
Hole Mobility Enhancement versus Strain
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr
Conclusion
 Strain-induced effects increase hole transport
performances in silicon.
 Quantization in MOSFET inversion layer tends to
decrease the splitting between LH and HH band.
 Holes must be localized in the strained channel.
 As a consequence, device structure should be
carefully optimized:
 tsi ≥ 10nm
[Ge] ≥ 30%
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Laboratoire Matériaux et Microélectronique de Provence
UMR CNRS 6137 - Marseille/Toulon (France) - www.l2mp.fr