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Metrology of Defect Annealing in Advanced USJ Formation Processes
P. J. Timans1, Y. Z. Hu1, Y. Lee1, J. Gelpey1, S. McCoy1,W. Lerch1, S. Paul1, D. Bolze2 and H. Kheyrandish3
1 Mattson Technology2 IHP, Frankfurt (Oder), Germany3 CSMA Ltd., U. K.
Metrology of Defect Annealing in Advanced USJ Formation Processes
P. J. Timans1, Y. Z. Hu1, Y. Lee1, J. Gelpey1, S. McCoy1,W. Lerch1, S. Paul1, D. Bolze2 and H. Kheyrandish3
1 Mattson Technology2 IHP, Frankfurt (Oder), Germany3 CSMA Ltd., U. K.
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Outline
Introduction— Trade-offs in annealing — Metrology challenges
Diffusion & Electrical ActivationDamage annealing— Reflectance Spectra— Junction Leakage (RsL)— Photoluminescence— Thermal Wave
Paths forward for advanced junction engineeringConclusions
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Advanced USJ Requirements
C.-H. Jan et al., IEDM 2005, p.65Minimize Dopant Diffusion Maximize electrical activation“Enough” defect annealing— Junction leakage:
Becoming significant for low power CMOS
— High channel/halo doping greatly increases leakage
Need to optimize all 3 “dimensions”Damage metrology:— Traditional - TEM, devices— Non-Contact:
ReflectanceRsL – RS & Junction LeakagePhotoluminescenceThermal Wave
Rapid Process Optimization
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Trends in Millisecond Annealing
Currently, millisecond anneal is being combined with spike annealing— Polysilicon gate activation— Gate overlap— Implant damage recovery
As technology progresses, the desire is to lower the thermal budget further— Reduce dopant diffusion— Metal gate / high-K integration— Strain engineering integration
Reduce peak T of spike anneal or migrate to millisecond anneal only?— Residual defect concerns
Damage engineering - implant & anneal
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Experiment
PAI: 1015 Ge/cm2 @ 30 keV
Halo: 4x1013 As/cm2 @ 40 keV
B: 1015 B/cm2 @ 500 eV
Anneal
PAIPAI
Anneal
B Implant
PAI
Halo
10-15 Ωcm n-type (100), 200 mm Si
Pre-anneal: 1050°C, 10 s, 10% O2
Anneals:•SPE: 650°C, 5 s•Spike: 1050°C•fRTP: Various conditions
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Millisecond Annealing with Flash-Assisted RTPTM
Flash-Assisted RTPTM
(fRTPTM ):—150 K/s ramp to Ti
—Pulsed surface heating
—MilliosTM tool provides real-time T measurement on front & back of wafer
600700800900
10001100120013001400
4.5 5.0 5.5 6.0
Temperature (°C)
Time (s)
600700
800900
1000
11001200
1300
4.835 4.840 4.845 4.850 4.855
Top TempBot Temp
Time (s)
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Outline
IntroductionDiffusion & Electrical ActivationDamage annealingPaths forward for advanced junction engineeringConclusions
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Diffusion Behaviour in c-Si Wafers
Minimal diffusion with fRTP, except for highest teff
Concentration-enhanced diffusion ⇒ More abrupt junctions
1018
1019
1020
1021
0 5 10 15 20 25 30 35
As ImplantedfRTP: 700°C/1250°CfRTP: 700°C/1300°CfRTP: 750°C/1300°CfRTP: 2x 750°C/1300°CfRTP: 750°C/1350°CSpike: 1050°C
Con
cent
ratio
n (c
m-3
)
Depth (nm)
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Halo Doping and Pre-Annealing Effects (c-Si Case)
Halo suppresses B ion channelling, but introduces TEDPre-annealing halo ⇒ Behaviour similar to c-Si caseExpect high junction leakage with halo
— Junctions at ~15-30 nm depth, doping > 6x1018/cm3
— High doping concentration: ⇒ Narrow depletion region (~ 15 nm)— Residual damage from PAI and halo implants
1018
1019
1020
1021
0 10 20 30 40 50 60
H: As-Implanted (B)AH: As-Implanted (B)H: Spike (B)AH: Spike (B)H: fRTP 700/1300°C (B)AH: fRTP 700/1300°C (B)Halo-SRIM (As)Halo with Diffusion (As)
Con
cent
ratio
n (c
m-3
)
Depth (nm)
a-Si/c-Si PAI
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fRTP: Improved Activation & Reduced Diffusion
fRTP gives a major improvement over spike anneal in RS/XJtrade-off for both c-Si & PAINo benefit evident for use of PAI over c-Si
200
250
300
350
400
450
500
550
600
10 15 20 25 30 35 40
c-Si, fRTPc-Si, SpikePAI, fRTPPAI, SpikePAI, SPE
4PP
-Hg
Prob
e R
S (Ω
/sq.
)
XJ (7x1018 cm-3) (nm)
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Outline
IntroductionDiffusion & Electrical ActivationDamage annealing— Reflectance Spectra— Junction Leakage (RsL)— Photoluminescence— Thermal Wave
Paths forward for advanced junction engineeringConclusions
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Reflection Spectra Reveal Implant Damage
Peaks at 3.4 and 4.6 eV reflect “long range” crystalline order— Disrupted by implant damage
Oscillations < 3 eV ⇒ amorphous layer— ~ 50 nm thick for PAI; ~ 30 nm for halo (heavy damage layer)
0.3
0.4
0.5
0.6
0.7
1.5 2 2.5 3 3.5 4 4.5 5 5.5
c-Sic-Si + BPAI + BHalo + Bc-Si + B(Spike Anneal)
Ref
lect
ance
Energy (eV)
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Evolution of Reflectance Peaks with Annealing
Behaviour at peaks is sensitive to annealing, especially 3.4 eV peakAt 3.4 eV light penetrates ~10 nm⇒ Probes heavily B-doped region
More sophisticated analysis should be possible
0.45
0.50
0.55
0.60
0.65
0.70
0.75
3.0 3.5 4.0 4.5 5.0
c-SiAs ImplantedSpike750°C/1300°C
Ref
lect
ance
Energy (eV)
c-Si + B Implant
0.45
0.50
0.55
0.60
0.65
0.70
0.75
3.0 3.5 4.0 4.5 5.0
c-SiAs ImplantedSpike750°C/1300°CSPE
Ref
lect
ance
Energy (eV)
PAI + B Implant
0.45
0.50
0.55
0.60
0.65
0.70
0.75
3.0 3.5 4.0 4.5 5.0
c-SiAs ImplantedSpike750°C/1300°C
Ref
lect
ance
Energy (eV)
c-Si + Halo + B Implant
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Junction
Depletion
Substrate
Spreading
Modulated LED Beam
Vin Vout
Recombination
Junction
Depletion
Substrate
Spreading
Modulated LED Beam
Vin Vout
Recombination
RsLTM: Non-Contact Sheet Resistance & Leakage
1. Modulated light source creates free carriers in junction & substrate.
2. Carrier drift & leakage monitored by dual-probe measurement of junction photo-voltage (JPV).
3. Carrier spreading analysis gives sheet resistance, RS.
4. Frequency dependence of JPV gives recombination leakage current, JL.
RsL probe(Frontier Semiconductor)
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Junction Leakage Reveals Dominant Role of Halo
Halo doping greatly increases leakage (narrow depletion region)— Pre-annealing halo damage reduces JL, esp. in c-Si
For PAI, 1300°C fRTP significantly reduces JL from SPE level
0.1
1
10
100
1000
10000
c-S
i
c-S
i,H
c-S
i,AH
PAI
PA
I,H
PA
I,AH
Wafer Type
J L (u
A/c
m2 ) SPE
SpikefRTP, 700°C/1250°CfRTP, 750°C/1300°C
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Photoluminescence for Damage Characterization
Room temperature photoluminescence measurements were performed using a system from Accent (Now Nanometrics)The PL signal is very sensitive to defects that alter electron-hole recombination behaviour
A. Buczkowski, ECS Trans. 11(3) p.109 (2007)
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Photoluminescence Shows Damage Annealing Trends
For c-Si, halo damage effect and annealing trend are evidentWith PAI, halo condition makes little difference1300°C fRTP ⇒ Damage levels ≅ spike annealing result
1
10
100
1000
10000
c-S
i
c-S
i,H
c-S
i,AH
PA
I
PA
I,H
PA
I,AH
Wafer Type
Def
ect L
evel
(Arb
. Uni
ts)
As implantedSPESpikefRTP, 700°C/1250°CfRTP, 750°C/1300°C
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Thermal Wave Characterization
Thermal wave measurements were performed using a TP630XP system from KLA-TencorThe TW signal can be affected by both defects and by doping distributions
S. Cherekdjian et al., ECS PV 2002-11, (2002) p.339
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Thermal Wave Results Reveal Doping & Damage Phenomena
TW Signals initially reduce with annealingHalo implant has large effect on final signal values— But, pre-annealing has relatively little effect
Results suggest that doping plays a key part in the TW signal
101
102
103
c-Si
c-Si,H
c-Si,AH
TW S
igna
l (Ar
b. U
nits
)
fRTP
SPE:
650
°C
Spik
e: 1
050°
C
700/
1250
°C
700/
1300
°C
750/
1300
°C
2x 7
50/1
300°
C
750/
1350
°C
Non
e 101
102
103
PAI
PAI,H
PAI,AH
TW S
igna
l (Ar
b. U
nits
)fRTP
SPE:
650
°C
Spi
ke: 1
050°
C
700/
1250
°C
700/
1300
°C
750/
1300
°C
2x 7
50/1
300°
C
750/
1350
°C
Non
e
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Outline
IntroductionDiffusion & Electrical ActivationDamage annealingPaths forward for advanced junction engineeringConclusions
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Minimizing Halo Doping is Essential for Leakage Control
Millisecond Annealing enables shallower junctions and hence improved short-channel effect control— Halo dose can be
reducedReduced BTBTReduced damage from halo
T. Hoffmann et al., IIT 2008 Conference, Monterey, 2008
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Damage/Activation/Diffusion Engineering Requires Innovation in BOTH Implantation and Annealing
Selection of implant approach has major effect on residual damage:— PAI & dopants: Mass, dose, energy, dose rate, temperature— Co-implants: Diffusion & activation control— Novel implant schemes: Molecular implants, plasma doping, GCIB
1.00E-08
1.00E-07
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
B B+PAI BF2 BF2 + PAI B18 B18 + PAI
RsL
Lea
kage
Cur
rent
(A/c
m2)
Spike 1000Spike 1080Flash 1300Laser 1300SPE 650 B18H22 implant
shows greatly reduced RsLleakage current(SemEquip data)
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Boron Doping Profile: Carborane Implant and MSA
1 E + 1 5
1 E + 1 6
1 E + 1 7
1 E + 1 8
1 E + 1 9
1 E + 2 0
1 E + 2 1
1 E + 2 2
0 1 0 2 0 3 0 4 0 5 0D e p t h ( n m )
B C
ON
CE
NT
RA
TIO
N (
at
A s -Im p l a n t e d X j: 8 . 9 n m
A b r u p t n e s s : 0 .9 3 n m /d e c a d e
R s : 9 5 8 .7 o h m s / s qX j : 1 0 . 5 n m @ 5 E 1 8
SIMS profile of flash annealed carboraneimplant. Note superior Xj/Rsand junction abruptness
J. Gelpey et al., Ultra-Shallow Junction Formation using Flash Annealing and Advanced Doping Techniques, IWJT-2008.
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Damage and Activation Improvements with High Temperature Preheat in Millisecond Anneal
Improved activation and greatly reduced junction leakage demonstrated by using flash-lamp annealing with higher pre-heat temperature & B18H22 implant
K. Yako et al.(NEC)
16th IEEE International Conference on Advanced Thermal Processing of Semiconductors -RTP2008
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Novel metrology techniques ⇒ very rapid assessment of defect phenomena & optimization of implant & annealing choices
Conclusions
The halo implant is dominant in determining junction leakage:Dose and halo implant damage are criticalPre-annealing halo damage reduced leakage
Annealing approaches offer trade-offs :Spike anneals remove defects, but introduce excessive diffusionSPE gave good activation with very little diffusion, but junctions show severe leakageMillisecond annealing with fRTP showed improved activation with minimal diffusion, as well as improved defect annealing
The next steps in USJ technology require advances in both implantation and annealing— Novel implantation methods can help overcome the damage
annealing challenge
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Acknowledgements
H. Phan, G. Stuart & D. Camm - Mattson Technology
M. Current, T. Nguyen, J. Halim and V. Faifer - Frontier Semiconductor
A. Buczkowski, Z. Li and T. Walker - Accent (now Nanometrics)
J. Chen, T. Dimitrova, W. Liu, N. Jaeger and D. Dimitrov - Four Dimensions
S. Prussin & J. Reyes - UCLA
M. Bakshi, D. Shaughnessy and A. Salnik - KLA-Tencor
L. Romano and K. Jones - University of Florida
A. Kontos, L. Godet, C. Hatem, G. Papasouliotis, J. Scheuer - Varian Semiconductor Equipment Associates
K. Sekar, W. Krull, T. Horsky, D. Jacobson - SemEquip