surface preparation and wet cleaning for germanium surface · spcc2017 (surface preparation and...
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SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
1 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
Surface Preparation and Wet
Cleaning for Germanium Surface
J. Snow2*, M. Otsuji1, Y. Yoshida1, H. Takahashi1, F.Sebaai3, F. Holsteyns3, M. Sato1 and H. Shirakawa1
1 SCREEN Semiconductor Solutions Co., Ltd.
480-1 Takamiya-cho, Hikone, Shiga, 522-0292 Japan2 SCREEN SPE USA, LLC
820 Kifer Road, Suite B, Sunnyvale, CA 94086 USA3 IMEC vzw
Kapeldreef 75, B-3001 Leuven, Belgium
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
Outline
2 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
Introduction
– Key Cleaning Steps
– Challenges on Wet Cleaning of SiGe and Ge
Ge Surface Preparation
– PRE (Particle Removal Efficiency)
– MRE (Metal Removal Efficiency)
Material Removal Selective to SiGe/Ge
– Unreacted Ni Removal
Controlled SiGe/Ge Wet Etch
– SiGe Wet Etch Selective to Ge
Summary
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
3 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
Introduction
– Key Cleaning Steps
– Challenges on Wet Cleaning of SiGe and Ge
Ge Surface Preparation
– PRE (Particle Removal Efficiency)
– MRE (Metal Removal Efficiency)
Material Removal Selective to SiGe/Ge
– Unreacted Ni Removal
Controlled SiGe/Ge Wet Etch
– SiGe Wet Etch Selective to Ge
Summary
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
Assumed Logic Device Fabrication
4 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
Si Fin
SiGe Fin
SiGe GAA
10nm
7nm
5nm
Candidates
Structure becomes more complex while scaling down
New materials as SiGe, Ge and III-V will be introduced
< 3nm
Ref. imec
Candidates
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
Key Cleaning Steps on Ge
5 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
Material removal PR strip
Unreacted Ni removal
Controlled SiGe/Ge etch Controlled Ge-Fin Trimming
Selective SiGe etch for GAA
Surface preparation Post etch clean
Pre-epi clean
Ge
PR
PR strip
SiGe etch
Ge Ge nanowire
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
0
1
10
100
1000
110100100010000
Etc
h R
ate
[n
m/m
in]
SC1 conc. (NH4OH/H2O2/H2O=1/1/X)
SiGe/Ge loss in SC1
SiGe 45%
SiGe 55%
Ge 100%
Challenges on Wet Cleaning of SiGe/Ge
6 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
[M.Wada et al., Solid State Phenomena 187 (2012) 19]
Ge is easily dissolved in oxidizing solutions, i.e. SC1, DIO3
Ge loss management is mandatory
Diluted Concentrated
0
1
10
100
1000
0.1 1 10 100
Etc
h R
ate
[n
m/m
in]
DIO3 conc. [ppm]
SiGe/Ge loss in DIO3
SiGe 45%
SiGe 55%
Ge 100%
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
7 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
Introduction
– Key Cleaning Steps
– Challenges on Wet Cleaning of SiGe and Ge
Ge Surface Preparation
– PRE (Particle Removal Efficiency)
– MRE (Metal Removal Efficiency)
Material Removal Selective to SiGe/Ge
– Unreacted Ni Removal
Controlled SiGe/Ge Wet Etch
– Controlled Ge-Fin Trimming
– SiGe Wet Etch Selective to Ge
Summary
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
PRE on Ge with Conventional Chemistries
8 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
0
10
20
30
40
50
60
70
80
90
100
0.0 1.0 2.0 3.0 4.0 5.0 6.0
Ge loss [nm]
PR
E [%
]
UPW
dHCl
dNH4OH
DIO3/HCl DIO3
SC1 (1/1/5000)
Ge
SiGe
Surface lift-off by oxidizing chemistry is the dominant factor for
sufficient particle removal
> 3nm Ge etch for > 90% PRE with conventional chemistries
[H.Takahashi et al., ECS Transactions 2011 41(5), 163-170]
Applicable process:
Post gate etch clean
Particle: 30nm SiO2-Slurry
Measurement: SP2, Haze
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
0
10
20
30
40
50
60
70
80
90
100
0.0 0.5 1.0 1.5 2.0 2.5 3.0
PR
E [%
]
Ge loss [nm]
AOM (Ammonia/DIO3
Mixture) for Ge Clean
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AOM
(high NH4OH ratio)
AOM
(low NH4OH ratio)
High PRE with lower Ge loss is obtained by using a clean
with AOM, especially in high pH condition
[H.Takahashi et al., ECS Transactions 2011 41(5), 163-170]
DIO3
SC1
(200/1/20000)
Particle: 30nm SiO2-Slurry
Measurement: SP2, Haze
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
1.E+10
1.E+11
1.E+12
1.E+13
1.E+14
No clean HCl HF/HCl O3 O3/HCl
Met
al C
on
tam
inat
ion
[at
om
s/cm
2]
Mn
Co
Zn
Ti
Cr
Fe
Ni
HF/HCl performs best: Same trend observed for Si and Ge
surfaces, Native oxide removal by HF + Metal dissolution by HCl
MRE on Ge Surface
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Controlled contamination Spin dry Wet treatmentStored in FOUP
8 hours
Ge 500nm
or Bare-Si
TXRF
1.E+10
1.E+11
1.E+12
1.E+13
1.E+14
No clean HCl HF/HCl O3 O3/HCl
Met
al C
on
tam
inat
ion
[at
om
s/cm
2]
Mn
Co
Zn
Ti
Cr
Fe
Ni
Under detection limit Under detection limit
MRE on Bare-Si MRE on Ge
Metal solution
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
1.E+10
1.E+11
1.E+12
1.E+13
1.E+14
1 day 3 days 35 days 1 day 3 days 7 days 35 days
No clean HF/HCl
Met
al C
on
tam
inat
ion
[at
om
s/cm
2]
Mn
Co
Zn
Ti
Cr
Fe
Ni
Aging Effect on MRE on Ge Surface
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Controlled contamination Spin dry Wet treatmentStored in FOUP
X days
Ge 500nm
No aging effect on MRE with HF/HCl even after 1 month
Under detection limit
TXRFMetal solution
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
Summary for Surface Preparations on Ge
12 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
Recommended cleaning combination
– For particles: AOM (NH4OH/DIO3 mixture)
– For metals: HF/HCl mixture
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
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Introduction
– Key Cleaning Steps
– Challenges on Wet Cleaning of SiGe and Ge
Ge Surface Preparation
– PRE (Particle Removal Efficiency)
– MRE (Metal Removal Efficiency)
Material Removal Selective to SiGe/Ge
– Unreacted Ni Removal
Controlled SiGe/Ge Wet Etch
– SiGe Wet Etch Selective to Ge
Summary
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
Challenge & Approach for Galvanic Corrosion
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One example: Ge corrosion during wet Ni removal using dHCl
Ge NiGe
e-
GeO dissolves in
aqueous solution
Anode:
Ge + ½ O2 GeO + e-
Cathode:
H+ + e- H2
O2 + 2H2O + 4e- 4OH-
GeNiGe
Ge planar deviceGe-FinFET device
NiGe
Ge
FINSTI
Exposure of Ge & NiGe to the cleaning solution
during Ge integration
[F.Sebaai et al., Solid State Phenomena 219 (2014) 105-108]
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
10
100
1000
10000
20% 1% 10ppm
Ass
um
ed
DO
in li
qu
id o
n w
afe
r [p
pb
] Ambience-induced
Liquid-induced
Management of Low-O2
Processing
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8ppm
450ppb
25ppb
Ambient control allows to achieve low DO condition
(<25ppb) in process liquid on wafer
[Y.Yoshida et al., Solid State Phenomena 219 (2014) 85-88]
Chemistry
Ambient 20% 1% 10ppm
DO in liquid 170ppb 25ppb 25ppb
O2 dissolved
in liquid
O2 conc. in ambient:
X ppm
DO in liquid:
Y ppb
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
0
0.2
0.4
0.6
0.8
1
1.2
8ppm 450ppb 25ppb
NiG
e lo
ss [
a.u
.]
DO conc. in Liquid on wafer
Selective Ni Removal on Ge-FinFET
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DO 8ppm 450ppb 25ppb
SEM
image
VoidVoid No void
NiGe loss with HCl
Void occurrence can be suppressed by the control of the
oxygen concentration in liquid & ambient
[Y.Yoshida et al., Solid State Phenomena 219 (2014) 85-88]
Void occurrence reduced
Void occurrence dependency on DO in HCl
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
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Introduction
– Key Cleaning Steps
– Challenges on Wet Cleaning of SiGe and Ge
SiGe/Ge Surface Preparation
– PRE (Particle Removal Efficiency)
– MRE (Metal Removal Efficiency)
Material Removal Selective to SiGe/Ge
– Unreacted Ni Removal
Controlled SiGe/Ge etch
– SiGe Wet Etch Selective to Ge
Summary
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
SiGe Wet Etches Selective to Ge
18 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
SiGe etch
Ge Ge nanowire
HK/MG fill
GAA (Gate All Around)
Ge is too sensitive
Conventional chemistries
don’t work on this application
0
1
10
100
1000
110100100010000
Etc
h R
ate
[n
m/m
in]
SC1 conc. (NH4OH/H2O2/H2O=1/1/X)
SiGe 45%
SiGe 55%
Ge 100%
SiGe/Ge loss in SC1
More study is needed on this kind of applications
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
19 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
Introduction
– Key Cleaning Steps
– Challenges on Wet Cleaning of SiGe and Ge
SiGe/Ge Surface Preparations
– PRE (Particle Removal Efficiency)
– MRE (Metal Removal Efficiency)
Material Removals Selective to SiGe/Ge
– Unreacted Ni Removal
Controlled SiGe/Ge Wet Etch
– SiGe Wet Etch Selective to Ge
Summary
SPCC2017 (Surface Preparation and Cleaning Conference), Mar 29 2017
Summary
20 SE-76-4925-L1 SCREEN Semiconductor Solutions Co., Ltd.
SiGe/Ge Surface Preparation
☺ Particle removal on Ge surface
• AOM is recommended for particle removal steps
– 0.4 nm etch of Ge to achieve ~100% PRE
☺ Metal removal for overall cleaning applications:
• Sufficient removal confirmed by HF/HCl mixture cleaning
Material Removal Selective to SiGe/Ge
☺ Unreacted Ni removal
• Low-O2 is promising to full Ni remove without Ge corrosions
Controlled SiGe/Ge Wet Etch
SiGe wet etch selective to Ge
• Need more study