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Karen Kirkby, Justin Hamilton Surrey Ion Beam Centre, University of Surrey
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Transcript of Karen Kirkby, Justin Hamilton Surrey Ion Beam Centre, University of Surrey
PhD Presentation 20th December 2007
IAEA CRP Chiang Mai 2007
Karen Kirkby, Justin Hamilton
Surrey Ion Beam Centre, University of Surrey
The role of the Buried Oxide in SOI Structures Dopant Diffusion and Activation
PhD Presentation 20th December 2007
IAEA CRP Chiang Mai 2007
Thank you • PhD Students
– Justin Hamilton, Jim Sharp, Max Kah• Post Docs
– Andy Smith• Colleagues at Surrey
– Roger Webb, Russell Gwilliam, Brian Sealy, Nick Cowern (Newcastle)• IRC-irst, Trento
– Massimo Bersani and Damiano Giubertoni, Salvatore Gennaro• Bologna
– Andrea Parisini• Toulouse
– Fuccio Christiano• Applied Materials
– Erik Collart (UK)
PhD Presentation 20th December 2007
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ContentsContents• IntroductionIntroduction• Experimental DesignExperimental Design• Experimental ResultsExperimental Results
SOI Vs Bulk Si TempSOI Vs Bulk Si TempEffect of the buried interfaceEffect of the buried interfaceOptimisation & ModellingOptimisation & Modelling
• ConclusionsConclusions
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• Smaller• Faster• Cheaper
Miniaturisation: why?Miniaturisation: why?
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Transistor size , device per chip
Gordon Moore noticed in 1965: number of devices on a chip doubled every 18-24 months & predicted this trend would continue
Device down-scaling:Device down-scaling:
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Silicon-on-Insulator (SOI)Silicon-on-Insulator (SOI)
• Silicon wafer with a buried Oxide (BOX)
• Advantages of SOI over Bulk SiIncreased SpeedReduced Power ConsumptionIncreased radiation toleranceImmunity from latch-up
• Industry is moving towards SOI
BOXBOX
SiSi
BOXBOX
SiSi
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Down-scaling of MOS devices causes leakage current (short channel effects)
Down-scaling challenges:Down-scaling challenges:
• High activation level• Shallow penetration of dopants
S/D extension
Substrate
Lg
Xj
Ultra shallow source/drain extension regions require:
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Challenge for further down-scalingChallenge for further down-scaling
2005 ITRS requirements for p-type layers and future trends
• High activation level 800 ohms/sq• Shallow penetration of dopants 15nm
0300600900
120015001800
Junction depth @ 1E18cm-3 (nm)
RS (
ohm
s/sq
) Lg=28nmLg=20nm
Lg=14nm
0 128
Lg=10nm
A 50nm MOSFET in production from a 90nm process (courtesy
of Intel)
4
SOI
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Challenge for further down-scalingChallenge for further down-scaling
2006 ITRS requirements for p-type layers and future trends
• High activation level 1200 ohms /sq• Shallow penetration of dopants 8-10nm
A 50nm MOSFET in production from a 90nm process (courtesy
of Intel)
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Why pre-amorphisation?Avoids Boron channelling
Improves Boron activation
Solid Phase Epitaxy!
PAI & SPEPAI & SPE
No Channelling in a-Si
Depth (nm)
Con
cent
ratio
n (c
m-3
)
Channelling Tail in c-Si
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F. Cristiano et al, Mat. Sci. Eng. B, 114-115, p174 (2004)
A. Michel et al, Appl. Phys. Lett, 50, 7, p417 (1987)
Transient Enhanced Diffusion (TED)
Boron de-activation
Implant damage:Implant damage:• Implant B in c-Si
• Frenkel Pairs
• Plus One Model
(schematic representation)(schematic representation)
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depth
Amorphisation threshold
Amorphisation
(destruction of crystal structure)
I
V
Ge PAI
Net excess interstitials after local
recombination of I with V
No point defects survive
I
ImplantB
Pre-amorphisation & SPERPre-amorphisation & SPER
• Ge amorphises Si
• B implanted
• I & V recombine
• Net excess I
(schematic representation)(schematic representation)
(con
cent
ratio
n)
10 16
10 18
10 20
10 22
depth
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B initially shallow
and above solubility
SPEre-growth
Pre-amorphisation & SPERPre-amorphisation & SPER
• Ge amorphises Si
• B implanted
• I & V recombine
• Net excess I
• SPE re-growth
• EOR defect band
(schematic representation)(schematic representation)
(con
cent
ratio
n)
10 16
10 18
10 20
10 22
depth
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De-activation & diffusionDe-activation & diffusion
(schematic representation)(schematic representation)
(con
cent
ratio
n)
10 16
10 18
10 20
10 22
depth
BICs
• I flux toward surface
• BIC formation
• TED
• What happens in SOI material?
I flux
TED
BOX
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Experimental DesignExperimental Design
• PAI at a dose of 1x1015cm-2 Ge, with energies of 8keV & 20keV, bulk Si & SOI
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BO
X
20 keV GeB
55 nm38 nm
Surface
19 nm
8 keV Ge BO
XB
55 nm
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Experimental DesignExperimental Design• PAI at a dose of 1x1015cm-2 Ge, with
energies of 8keV & 20keV, bulk Si & SOI
• Implanted with 500eV Boron at dose of 2x1013cm-2, 2x1014cm-2 and 2x1015cm-2
• Re-growth study (570ºC for 30 – 150s), check for wafer re-crystallisation
• Activation & diffusion study, isochronal anneals (700ºC – 1000ºC for 60s)
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Experiment OneExperiment One
Do SOI and bulk Si samples experience a difference in temperature when
annealed together?
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• No effect of PAI energy on the re-growth rateNo effect of PAI energy on the re-growth rate
RBS – RBS – Re-growth RatesRe-growth Rates
• Re-growth rate increases with Boron doseRe-growth rate increases with Boron dose
Boron 8keV Ge Bulk 8keV Ge SOI 20keV Ge Bulk 20keV Ge SOI0 N/A N/A 0.27 0.26
2x1013cm-2 0.35 0.37 0.37 0.392x1014cm-2 0.4 0.42 0.4 0.442x1015cm-2 0.52 0.48 0.52 0.50
Re-growth Rate (nm/sec)
B dose incr.
• No real difference between Bulk Si and SOINo real difference between Bulk Si and SOI
Table of re-growth rate for increasing Boron doseTable of re-growth rate for increasing Boron dose
J.J. Hamilton, et al. Nucl. Instr. and J.J. Hamilton, et al. Nucl. Instr. and Meth. in Res. B 237, 107 (2005).Meth. in Res. B 237, 107 (2005).
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Experiment TwoExperiment Two
What are the electrical and structural differences between SOI and bulk Si?
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Hall MeasurementsHall MeasurementsBulk Si & SOI implanted with Boron at a dose 2x1015 cm-2 and
pre-amorphised with 8keV Ge – EOR at 20nm
Small difference between 8keV SOI Vs bulkSmall difference between 8keV SOI Vs bulk J.J. Hamilton, et al. Appl. Phys. J.J. Hamilton, et al. Appl. Phys. Lett. 89, 42111 (2006).Lett. 89, 42111 (2006).
700 750 800 850 900 950 10000
400
800
1200
1600
2000
2400S
heet
Res
ista
nce
(ohm
s/sq
.)
Temperature ºC
Bulk Si SOI
PhD Presentation 20th December 2007
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700 750 800 850 900 950 10000
300
600
900
1200
1500
1800S
heet
Res
ista
nce
(ohm
s/sq
.)
Temperature ºC
Bulk Si SOI
PAI & SPER Bulk Si Vs SOIPAI & SPER Bulk Si Vs SOIBulk Si & SOI implanted with Boron at a dose 2x1015 cm-2 and
pre-amorphised with 20keV Ge – EOR at 40nm
Less deactivation for 20keV SOI Vs bulkLess deactivation for 20keV SOI Vs bulk
~850ohm/sq.
~550ohm/sq.
35% reduction in ∆RsSOI than ∆RsSI
J.J. Hamilton, et al. Appl. Phys. J.J. Hamilton, et al. Appl. Phys. Lett. 89, 42111 (2006).Lett. 89, 42111 (2006).
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SIMS MeasurementsSIMS MeasurementsBulk Si & SOI implanted with Boron at a dose 2x1015 cm-2 and pre-amorphised with 8 & 20keV Ge + annealed at 800ºC for 60s
8keV 20keV
0 10 20 30 40 50 60 70 80
1E17
1E18
1E19
1E20
1E21
Ge 8 keV - bulk Ge 8 keV - SOI
11B
CO
NC
EN
TRA
TIO
N (a
t/cm
3 )
DEPTH (nm)
103
104
105
106
107
0 10 20 30 40 50 60 70 80
1E17
1E18
1E19
1E20
1E21
Ge 20 keV - bulk Ge 20 keV - SOI
11B
CO
NC
EN
TRA
TIO
N (a
t/cm
3 )
DEPTH (nm)
103
104
105
106
107
Higher level of out diffusion for 20keV SOI Vs bulk SiHigher level of out diffusion for 20keV SOI Vs bulk SiLess B trapping in 20keV SOI Vs bulk SiLess B trapping in 20keV SOI Vs bulk Si
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55nm
20keV20keV
40nm
CC DD
40nm
surface
800800ººC for 60s anneal for 8 & 20keV Ge in SOI & Bulk SiC for 60s anneal for 8 & 20keV Ge in SOI & Bulk Si
20nm55nm
Bulk SiBulk Si SOISOI
8keV8keV
AA BBBOXBOX
EOR defects EOR defects
20nm
BOXBOXEOR defectsEOR defects
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0 10 20 30 40 50 60 701E17
1E18
1E19
1E20
1E21
As-implanted 20 keV Ge Bulk Si 20 keV Ge SOI
11B
CO
NC
EN
TRA
TIO
N (a
t/cm
3 )
DEPTH (nm)
0 10 20 30 40 50 60 70
1E17
1E18
1E19
1E20
1E21
As-implanted 20 keV Ge Bulk Si 20 keV Ge SOI
11B
CO
NC
EN
TRA
TIO
N (a
t/cm
3 )
DEPTH (nm)
800ºC
SIMS MeasurementsSIMS MeasurementsBulk Si & SOI implanted with Boron at a dose 2x1015 cm-2 and
pre-amorphised with 20keV Ge + annealed for 60s at 800ºC & 850ºC
850ºC
Significant less B trapping in SOI Vs Bulk SiSignificant less B trapping in SOI Vs Bulk Si J.J. Hamilton, et al. Appl. Phys. J.J. Hamilton, et al. Appl. Phys. Lett. 89, 42111 (2006).Lett. 89, 42111 (2006).
PhD Presentation 20th December 2007
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Interstitia
l Flux
20keV Ge Bulk
20keV Ge SOI
BOX
Interstitial Flux
20keV Ge Bulk
20keV Ge SOI
BOX
De-activation & TED
Back interface sink for I Faster EOR dissolution
Physical MechanismPhysical Mechanism
(schematic representation)(schematic representation)
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Experiment ThreeExperiment Three
Optimisation of amorphisation
conditions in SOI
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Experimental DesignExperimental Design
• PAI at a dose of 1x1015cm-2 Ge, with energies of 8, 20, 24, 32 & 36keV, both Si & SOI
• Implanted with 500eV Boron at dose of 2x1015cm-2
• Isochronal annealing study (700ºC – 1000ºC for 60s)
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PAI dose of 1x1015cm-2 Ge, both Si & SOI+ 500eV Boron at dose of 2x1015cm-2Surface
20nm
8keV Ge
BO
X
55nm
B
40nm
20keV Ge
55nm
BO
XB
45nm
24keV Ge
BO
X
B
55nm
32keV Ge
55nm
BO
X
~55nm
B
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XTEM MeasurementsXTEM MeasurementsSOI and Bulk Si implanted with Boron at a dose 2x1015 cm-2 and pre-amorphised with 32keV Ge as-implanted + annealed at 700ºC for 60s
Re-growth has occurred, therefore has recrystallisedRe-growth has occurred, therefore has recrystallised
Defect trapping within the BOX interface in SOIDefect trapping within the BOX interface in SOI
EOR defects
SOI – as-implantedSOI – as-implanted SOI – annealedSOI – annealed Bulk Si – annealedBulk Si – annealed
~4nm~4nm
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0 10 20 30 40 50 60 701E17
1E18
1E19
1E20
1E21
1E22 Bulk Si SOI
B C
ON
CE
NTR
ATI
ON
(at/c
m3 )
DEPTH (nm)
SIMS MeasurementsSIMS Measurements
EOR defect band overlaps BOXEOR defect band overlaps BOX
Bulk Si & SOI implanted with Boron at a dose 2x1015 cm-2 and pre-amorphised with 32keV Ge, annealed at 850ºC for 60s
BO
X in
terfa
ce
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700 750 800 850 900 950 10000
400
800
1200
1600
2000
She
et R
esis
tanc
e (R
s)
Temperature (ºC)
8keV Ge 20keV Ge
700 750 800 850 900 950 10000
400
800
1200
1600
2000
She
et R
esis
tanc
e (R
s)
Temperature (ºC)
8keV Ge 20keV Ge 24keV Ge 32keV Ge
700 750 800 850 900 950 10000
400
800
1200
1600
2000
She
et R
esis
tanc
e (R
s)
Temperature (ºC)
8keV Ge 20keV Ge 24keV Ge
700 750 800 850 900 950 10000
400
800
1200
1600
2000
She
et R
esis
tanc
e (R
s)
Temperature (ºC)
8keV Ge
Van Der Pauw ResistivityVan Der Pauw ResistivitySOI implanted with Boron at a dose 2x1015 cm-2 and
pre-amorphised with 8, 20, 24 & 32keV Ge – EOR at 20, 40, 45 & ~55nm
Less than 80ohm/sq. RS peak deactivation for 32keV (from 700ºC to 850ºC)
29%
51% 57%
Minimal deactivation for Minimal deactivation for the 32keV PAIthe 32keV PAI
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0 10 20 30 40 501E17
1E18
1E19
1E20
1E21
1E22
As-implanted 8keV
B C
ON
CE
NTR
ATI
ON
(at/c
m3 )
DEPTH (nm)0 10 20 30 40 50
1E17
1E18
1E19
1E20
1E21
1E22
As-implanted 8keV 20keV
B C
ON
CE
NTR
ATI
ON
(at/c
m3 )
DEPTH (nm)0 10 20 30 40 50
1E17
1E18
1E19
1E20
1E21
1E22
As-implanted
B C
ON
CE
NTR
ATI
ON
(at/c
m3 )
DEPTH (nm)
SIMS MeasurementsSIMS MeasurementsSOI implanted with Boron at a dose 2x1015 cm-2 and
pre-amorphised with 8, 20 & 32keV Ge, annealed at 800ºC for 60s
0 10 20 30 40 501E17
1E18
1E19
1E20
1E21
1E22
As-implanted 8keV 20keV 32keV
B C
ON
CE
NTR
ATI
ON
(at/c
m3 )
DEPTH (nm)
32keV PAI shows highest level 32keV PAI shows highest level of activation, least TED and of activation, least TED and largest junction abruptnesslargest junction abruptness
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32keV Ge SOI
BOX
20keV Ge Bulk
20keV Ge SOI
BOX
Physical MechanismPhysical Mechanism
(schematic representation)(schematic representation)
De-activation & TED
Back interface sink for I Faster EOR dissolution
Interstitial Flux
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BOX InterfaceSurface
d
ModellingModelling
x d - x
Centroid
L1
1
L2
1
,1 Lx
CD EORII
2
,2 Lxd
CD EORII
2
21 Ld
LxdF
= fraction of interstitials Flowing towards the surface
PhD Presentation 20th December 2007
IAEA CRP Chiang Mai 2007J.J. Hamilton, et al. Appl. Phys. J.J. Hamilton, et al. Appl. Phys. Lett. 91, 92122 (2007).Lett. 91, 92122 (2007).
40 35 30 25 20 15 10 5 00
2x1013
4x1013
6x1013
8x1013
1x1014
L2 = / Nc
Dos
e of
exc
ess
Si i
nter
stiti
als
that
flow
to
war
ds th
e su
rface
(cm
-2)
Remaining crystal thickness after amorphization (nm)
40 35 30 25 20 15 10 5 00
2x1013
4x1013
6x1013
8x1013
1x1014
L2 = / Nc L
2 = 100
Dos
e of
exc
ess
Si i
nter
stiti
als
that
flow
to
war
ds th
e su
rface
(cm
-2)
Remaining crystal thickness after amorphization (nm)
40 35 30 25 20 15 10 5 00
2x1013
4x1013
6x1013
8x1013
1x1014
L2 = / Nc L
2 = 100
L2 = 30
Dos
e of
exc
ess
Si i
nter
stiti
als
that
flow
to
war
ds th
e su
rface
(cm
-2)
Remaining crystal thickness after amorphization (nm)
40 35 30 25 20 15 10 5 00
2x1013
4x1013
6x1013
8x1013
1x1014
L2 = / Nc L
2 = 100
L2 = 30
L2 = 10
Dos
e of
exc
ess
Si i
nter
stiti
als
that
flow
to
war
ds th
e su
rface
(cm
-2)
Remaining crystal thickness after amorphization (nm)
40 35 30 25 20 15 10 5 00
2x1013
4x1013
6x1013
8x1013
1x1014
L2 = / Nc
L2 = 100
L2 = 30
L2 = 10
L2 = 0
Dos
e of
exc
ess
Si i
nter
stiti
als
that
flow
to
war
ds th
e su
rface
(cm
-2)
Remaining crystal thickness after amorphization (nm)
40 35 30 25 20 15 10 5 00
2x1013
4x1013
6x1013
8x1013
1x1014
0.0
4.0x1013
8.0x1013
1.2x1014
1.6x1014
2.0x1014
L2 = / Nc
L2 = 100 L
2 = 30
L2 = 10 L
2 = 0
Dos
e of
exc
ess
Si i
nter
stiti
als
that
flow
to
war
ds th
e su
rface
(cm
-2)
Remaining crystal thickness after amorphization (nm)
Rel
ativ
e de
activ
ated
B d
ose
(cm
-2)
Deactivated B
ModellingModelling
PhD Presentation 20th December 2007
IAEA CRP Chiang Mai 2007
Challenge for further down-scalingChallenge for further down-scaling
2006 ITRS requirements for p-type layers and future trends
• High activation level 1200 ohms /sq• Shallow penetration of dopants 8-10nm
A 50nm MOSFET in production from a 90nm process (courtesy
of Intel)
• High activation level 1200 ohms /sq (800 ohms/sq)• Shallow penetration of dopants 8-10nm (20 nm)
PhD Presentation 20th December 2007
IAEA CRP Chiang Mai 2007
ConclusionsConclusions
Very promising for future USJ applications in SOIVery promising for future USJ applications in SOI
Negligible B de-activationNegligible B de-activationShallow, abrupt junctionShallow, abrupt junction
Two Mechanisms:Two Mechanisms:• BOX acts as a sink for interstitials, with near BOX acts as a sink for interstitials, with near
zero value for recombination lengthzero value for recombination length• EOR overlaps BOX, reducing initial I number to EOR overlaps BOX, reducing initial I number to
interact with Binteract with B
Very little c-Si is required to seed re-growthVery little c-Si is required to seed re-growth
SOI and Bulk Si experience same anneal temp.SOI and Bulk Si experience same anneal temp.
PhD Presentation 20th December 2007
IAEA CRP Chiang Mai 2007
Acknowledgements:Acknowledgements:E.J.H. Collart
Applied Materials
M. Bersani, D. Giubertoni and S. GennaroITC-irst
A. ParisiniCNR-IMM
B. ColombeauChartered Semiconductors
Justin HamiltonJ. A. Sharp, A. J. Smith, N. Bennett and M. Kah
University of Surrey
Nick CowernUniversity of Newcastle
PhD Presentation 20th December 2007
IAEA CRP Chiang Mai 2007
Any Questions?Any Questions?