1 Modeling of pulsed Laser Thermal Annealing for junction formation optimization and process control R. Negru, K. Huet, P. Ceccato, B. Godard EXCICO, 14 rue Alexandre, 92230 Genneviliers, France http://www.excico.com Excerpt from the Proceedings of the 2012 COMSOL Conference in Milan
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Confidential: modification, copy and distribution prohibited without prior written permission from Excico ® 1
Modeling of pulsed Laser Thermal Annealing for junction formation optimization and
process control
R. Negru, K. Huet, P. Ceccato, B. Godard
EXCICO, 14 rue Alexandre, 92230 Genneviliers, France
http://www.excico.com
Excerpt from the Proceedings of the 2012 COMSOL Conference in Milan
Confidential: modification, copy and distribution prohibited without prior written permission from Excico ® 2
OUTLINE
Laser Thermal Annealing technology
Experiments
Model
Phase-Field approach
Dopant diffusion and segregation
Results
Conclusions
COMSOL Conference Europe 2012 – Milan October 11th 2012
Confidential: modification, copy and distribution prohibited without prior written permission from Excico ® 3
OUTLINE
Laser Thermal Annealing technology
Experiments
Model
Phase-Field approach
Dopant diffusion and segregation
Results
Conclusions
COMSOL Conference Europe 2012 – Milan October 11th 2012
Confidential: modification, copy and distribution prohibited without prior written permission from Excico ® 4
Laser absorption
Melting and recrystallization
Low thermal budget process
High temperature localized in space and time
Shallow depth effect (<µm)
Ultrafast (<µs)
Pulsed excimer Laser Thermal Annealing (LTA)
COMSOL Conference Europe 2012 – Milan October 11th 2012
Technique for junction formation in process fabrication of semiconductor devices
Silicon
Laser shot
Confidential: modification, copy and distribution prohibited without prior written permission from Excico ® 5
Laser tool characteristics
High Energy Gas laser
XeCl excimer gas
UV 308nm wavelength
Pulsed
Challenge: process variability
Energy and pulse variations
COMSOL Conference Europe 2012 – Milan October 11th 2012
Confidential: modification, copy and distribution prohibited without prior written permission from Excico ® 6
Laser Thermal Annealing Process Parameters
Long pulse laser
Pulse Duration: ~150 ns
Uniform high Energy Density
Up to 3 J/cm2
Up to 2x2 cm2 area
COMSOL Conference Europe 2012 – Milan October 11th 2012
LTA Pulse
Uniform ED
Confidential: modification, copy and distribution prohibited without prior written permission from Excico ® 7
LTA process simulation
Linking tool parameters to process
Understanding process variability
Process variability and junction formation
Depend on
Laser Energy Density
Pulse shape
Other laser annealing process parameters
Melt Depth (ex-situ measurement)
Temperature (no direct measurement)
COMSOL Conference Europe 2012 – Milan October 11th 2012
Silicon
Dopants
Junction Depth
Laser shot
Silicon
Melting Temperature
Ambient Temperature
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LTA simulation: 2 steps
Laser parameters
Structure - Material properties - Geometric dimensions
Temperature profiles Melt dynamics
COMSOL Conference Europe 2012 – Milan October 11th 2012
Process Window determination to avoid damage
Temperature profiles &
Melt dynamics
- Dopant profiles Dopant distribution
Junction formation
Thermal step
Diffusion step
Confidential: modification, copy and distribution prohibited without prior written permission from Excico ® 9
OUTLINE
Laser Thermal Annealing technology
Experiments
Model
Phase-Field approach
Dopant diffusion and segregation
Results
Conclusions
COMSOL Conference Europe 2012 – Milan October 11th 2012
Confidential: modification, copy and distribution prohibited without prior written permission from Excico ® 10
1E+16
1E+17
1E+18
1E+19
1E+20
0 100 200 300 400
Co
nce
ntr
atio
n [
at/c
m3]
Depth [nm]
B30keV1e15 as-imp
1E+16
1E+17
1E+18
1E+19
1E+20
0 100 200 300 400
Co
nce
ntr
atio
n [
at/c
m3]
Depth [nm]
B30keV1e15 as-imp
SIMS ED2.2
SIMS ED2.4
SIMS ED2.8
SIMS ED3.2
Typical Boron profiles after LTA
Melt Depth estimation vs Energy Density Profiles not explained by simple diffusion (Fickian)
COMSOL Conference Europe 2012 – Milan October 11th 2012
Secondary Ion Mass Spectroscopy (SIMS) error: ±5% in depth and ±10 in concentration
1E+16
1E+17
1E+18
1E+19
1E+20
0 100 200 300 400
Co
nce
ntr
atio
n [
at/c
m3]
Depth [nm]
B30keV1e15 as-imp
SIMS ED2.4
1E+16
1E+17
1E+18
1E+19
1E+20
0 100 200 300 400
Co
nce
ntr
atio
n [
at/c
m3]
Depth [nm]
B30keV1e15 as-imp
SIMS ED2.2
SIMS ED2.4
SIMS ED2.8
SIMS ED3.2
Pile-up Depletion
1E+16
1E+17
1E+18
1E+19
1E+20
0 100 200 300 400
Co
nce
ntr
atio
n [
at/c
m3]
Depth [nm]
B30keV1e15 as-imp
SIMS ED2.4
SIMS ED2.8
1E+16
1E+17
1E+18
1E+19
1E+20
0 100 200 300 400
Co
nce
ntr
atio
n [
at/c
m3]
Depth [nm]
B30keV1e15 as-imp
SIMS ED2.2
SIMS ED2.4
SIMS ED2.8
SIMS ED3.2
MD estimation
Box-like profile
1E+16
1E+17
1E+18
1E+19
1E+20
0 100 200 300 400
Co
nce
ntr
atio
n [
at/c
m3]
Depth [nm]
B30keV1e15 as-imp
SIMS ED2.2
SIMS ED2.4
SIMS ED2.8
SIMS ED3.2
1E+16
1E+17
1E+18
1E+19
1E+20
0 100 200 300 400
Co
nce
ntr
atio
n [
at/c
m3]
Depth [nm]
B30keV1e15 as-imp
SIMS ED2.2
SIMS ED2.4
SIMS ED2.8
SIMS ED3.2
Confidential: modification, copy and distribution prohibited without prior written permission from Excico ® 11
OUTLINE
Laser Thermal Annealing technology
Experiments
Model
Phase-Field approach
Dopant diffusion and segregation
Results
Conclusions
COMSOL Conference Europe 2012 – Milan October 11th 2012
Confidential: modification, copy and distribution prohibited without prior written permission from Excico ® 12
Phase-Field model
Heat (T) and Phase () equations are connected by coupling terms
Formalism: -1 +1
Heat equation
Source equation
Phase change equation
Thermal and phase change simulation
[Karma and Rappel, PRE 1998] [La Magna et al., JAP 2004]
Pure liquid
Pure solid
x
n eRtPEDtxS )1()(),(
),(18
15
2)(
222 txSt
LTk
t
Tc
fus
p
Coupling with phase
22222 )1()()1(
M
fus
pTT
L
cW
t
Coupling with temperature
COMSOL Conference Europe 2012 – Milan October 11th 2012
Liquid
Solid
Laser shot
Silicon
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