Download - Process of magnetron sputtering
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 1/21
Process of magnetron sputtering
Laurent Marota, Grégory De Temmermana b; Andrey Litnovskyb, Grégory Covarelc and Peter Oelhafena
Rhodium coated mirrors deposited
by magnetron sputtering for first mirror
a Institute of Physics, University of Basel, Switzerlandb now: Center for Energy Research, University of California at San Diego, USAc Institut für Plasmaphysik, Ass. EURATOM, TEC, Forschungszentrum Jülich, Germanyd Mechanical Laboratory, University of Haute-Alsace, France
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 2/21
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SS
W
MoRh
Cu
Ref
lect
ivit
y (%
)Wavelength (nm)
Motivation
1Handbook of optical constants of solids, ed. E.D. Palik, Acad. Press, 1985 and 1991
Calculated with (n, k) from [1]
Rhodium is a very attractive
option for first mirror material:
Good reflectivity
High melting point (1966 °C)
Low sputtering yield (high Z)
High price of the raw material calls for developing thin film technology
Existing studies made with electro-deposition or magnetron
(Reference: G Maddaluno 11th ITPA, N.V Klassen 10th ITPA)
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 3/21
Routine process:
Total time deposition: 25 hours
Total Rh thickness deposited:
35 microns
Rhodium layeron copper
[2] Characterization of magnetron sputtered rhodium films for reflective coatings , L. Marot et al, submitted to Surface Coating Technology
Process of magnetron sputtering
Vacuum deposition technique
Typical deposition conditions:
Pressure: 0.6 Pa - argon gas DC power, 25 W (U = -225 V / I = 0.11 A ) Deposition rate: 0.6 nm / s Deposition on silicon and metallic
substrates
Investigated conditions:
Pressure, Power applied to the target,
Deposition temperature [2]
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 4/21
No impurities (carbon, oxygen, argon) were detected by in-situ XPS on the surface after deposition
Homogeneous rhodium film with dense columnar structure (up to 2.4 m thick)
SEM cross section observation of rhodium film deposited on Si at RT
SEM cross section observation of rhodium film deposited on Si at 350 °C
Characterization of the layer / 1
1.2 m 1.8 m
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 5/21
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1.5
2.0
Mo before deposition Ra = 4 nm
Rh after deposition on Mo Ra = 4.2 nm
Dif
fuse
ref
lect
ivit
y (%
)
Wavelength (nm)
Ra = 4.2 nm / Before deposition 4 nm
Crystallite size = 10 nm
SEM observation of a rhodium layer (1,5 m) on molybdenum
Characterization of the layer / 2
Diffuse reflectivity measured before and after deposition
No polishing after deposition
Low roughness after deposition
Film roughness depends on the initial substrate
roughness
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 6/21
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Sp
ec
ula
r re
fle
cti
vit
y (
%)
Wavelength (nm)
Deposition RT Deposition 170°C Deposition 350°C
Characterization of the layer / 3
RSpecular = RTotal - RDiffuse
Specular reflectivity measured on Rh layer deposited on stainless steel at different temperatures
Film roughness depends on the deposition temperature
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0.9
1.0
1.1
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1.3
1.4
1.5
350 °C
170 °C
RT
Roughness
Afte
r D
eposi
tion
Roughness
Befo
re D
eposi
tion
Temperature (°C)
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 7/21
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84.6°70.1°
47.9°
41.2°
Rh(311)Rh(220)Rh(200)
Rh(111)
Rel
ativ
e In
ten
sity
2 (degrees)
X-ray diffraction measurements:
Polycrystalline, no specific texture, no specific orientation for the grains
Grain size around 10 nm (Calculated by
Scherrer formula)
Characterization of the layer / 4
X-ray diffraction pattern of deposited rhodium film
Nanohardness (3 mN) measurements:
The hardness of a rhodium layer (1.7 m thick)
is 9.2 GPa, in comparison to 1.2 GPa for the
annealed bulk rhodium
Influence of the hardness for
erosion?
Rel
ativ
e In
tens
ity
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 8/21
Layer deposited on metallic substrate (Mo, Cu, stainless steel) for layer thickness > 1 m
Total reflectivity measured on Rh layer deposited on metallic substrates
No influence of the
substrates on the
optical properties
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To
tal r
efle
cti
vity
(%
)
Wavelength (nm)
Rhodium reference [1] Rh on Stainless Steel Rh on Copper Rh on Molybdenum
Influence of the substrate on the optical properties
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 9/21
Stainless Steel 273 30 < 2
Critical Load (N)
1.5
8.8
8.3Stainless Steel 273 350
Stainless Steel 273 170 9.5
Molybdenum 261 30
Copper 122 30
SubstrateHardness Vickers
Hv 0.1Temperature of deposition (°C)
Scratch test measurements: load from 0 to 20 N at a rate of 10 N·min-1)
Influence of the substrates for the adhesion of the coating
Main part of a scratch track of rhodium film sample deposited at 170°C on stainless steel
The adhesion
properties increase
with the substrate
hardness
First crack
1.7 N 4 N
First breakthrough
Lc = 9.5N
First pad adhering Worn out30 m
19.5 N
Scratch direction
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 10/21
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Total reflectivity
Lambda = 660 nm
s p
Ref
lect
ivit
y (%
)
Angle of incidence (°)
Reflectivity at 40, 50, 60, 70 and 80° for s and p polarizations at 660 nm of rhodium layer
For some laser diagnostics (LIDAR, MSE) the polarisation of the linearly polarised laser radiation is relevant
Measurement of polarization reflectivity by ellipsometry
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 11/21
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Rhodium reference Rh (1000nm) on Stainless Steel Same layer after 10 times annealing Rh (1250nm) on Molybdenum Same layer after 10 times annealing
To
tal r
efle
ctiv
ity
(%)
Wavelength (nm)
Annealing cycles: 10 times @ 5h at 200 °C in air
Effect of annealing cycles on the mirror reflectivity
The optical
observations did not
reveal any
modification or
delamination of the
layer
Total reflectivity of Rh layer before and after annealing cycles
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 12/21
Laboratory experiments for erosion by deuterium ions of rhodium mirrors [4]
Deuterium RF plasma with a graphite hollow cathode
Bias on sample: - 300 V to
control impinging ions energy
Pressure: 6 Pa
Time of plasma: 13 h
Fluence: 2×1020 ions/cm2
Laboratory experiments for erosion / 1
[4] Same process described by G. De Temmerman et al, 10th ITPA
Setup for D2 plasma sputtering, for rhodium deposition and in situ XPS
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 13/21
Post Cleaning D2 RF Plasma
-100 V / 30 min / 300 °C
Laboratory experiments for erosion / 2
Total reflectivity measured on Rh layer (1.8 m) deposited on Mo
Reflectivity after D2 sputtering
Weight measurements
allow the determination
of the eroded tickness:
375 nm eroded
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tal r
efle
ctiv
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(%)
Wavelength (nm)
Rhodium layer (1.8 m) on Mo Same layer after Deuterium Plasma
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To
tal r
efle
ctiv
ity
(%)
Wavelength (nm)
Rhodium layer (1.8 m) on Mo Same layer after Deuterium Plasma Post Cleaning after Deuterium Plasma
Carbon on the surface (measured by XPS)
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 14/21
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Rh after deposition on Mo Ra = 4.2nm Rh after D2 Plasma Ra = 2.8 nm Rh after Post D2 Cleaning Ra = 5.6 nm
Dif
fuse
ref
lect
ivit
y (%
)
Wavelength (nm)
Ra = 4.2 nm
Ra = 2.8 nm
Ra = 5.6 nm
Diffuse reflectivity measured before, after D2 sputtering and after post cleaning
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Rh after deposition on Mo Ra = 4.2nm Rh after D2 Plasma Ra = 2.8 nm Rh after Post D2 Claning Ra = 5.6 nm
Dif
fuse
ref
lect
ivit
y (%
)
Wavelength (nm)
Laboratory experiments for erosion / 3
No significant change of roughness after erosion
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 15/21
Laboratory experiments for erosion / 4
Total reflectivity measured on Rh layer deposited on Stainless Steel and Copper
Same experiment on 2 layers (> 1 m) deposited on Stainless Steel and Copper
After erosion by
deuterium ions the
reflectivity is constant
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To
tal r
efle
ctiv
ity
(%)
Wavelength (nm)
Rh on SS Rh on SS After D2 Plasma
Rh on Cu Rh on Cu After D2 Plasma
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tal r
efle
ctiv
ity
(%)
Wavelength (nm)
Rh on SS Rh on SS After D2 Plasma Rh on SS After Cleaning Rh on Cu Rh on Cu After D2 Plasma Rh on Cu After Cleaning
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 16/21
TEXTOR, Jülich, Germany
• 19 shots, ~ 210 plasma seconds
• Mirror temperature 300 – 500 °C
• D+ energy: ~ 250 - 300 eV
• Fluence = 2x1020 ions/cm2
Mirrors exposed in the Scrape-Off layer plasma of TEXTORRh Uni.
Basel Rh [5] SC Mo
[5] G Maddaluno 11th ITPA
Exposure of Rh mirrors under erosion conditions in TEXTOR
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 17/21
No significant change of the XRD measurements
=> No crystallographic change (temperature exposure 300 – 500
°C)
=> No delamination
XRD measurements before and after exposure
Exposure of Rh mirrors under erosion conditions in TEXTOR
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Before Exposure After Exposure
Rh(311)Rh(220)Rh(200)
Rh(111)
Rel
ativ
e In
tens
ity
2 (degrees)
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 18/21
Total reflectivity measured before and after exposure
Reflectivity of mirrors exposed in the Scrape-Off layer plasma of TEXTOR
Eroded thickness for rhodium: 440 nm
SIMS / XPS after exposure: Mo and/or MoCand MoO ( 5 - 8 %)and Amorphous Carbon
Rh Basel
Exposure of Rh mirrors under erosion conditions in TEXTOR
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 19/21
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ecu
lar
refl
ecti
vity
(%
)
Wavelength (nm)
Rh Basel Before Exposure Ra = 6.3 nmRh Basel After Exposure Ra = 8.9 nm
Possibility of mirror
cleaning
Same Post Cleaning experiment with : D2 RF plasma -100 V / 45 min / 250 °C
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Rh Basel Before Exposure Ra = 6.3 nm Rh Basel After Exposure Ra = 8.9 nm Post Cleaning D2 Plasma Ra = 6.5 nm
250 °C / -100 V / 45 min
Dif
fuse
ref
lect
ivit
y (%
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Wavelength (nm)
Exposure of Rh mirrors under erosion conditions in TEXTOR
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Dif
fuse
ref
lec
tivi
ty (
%)
Wavelength (nm)
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3.5
Dif
fuse
ref
lect
ivit
y (%
)
Wavelength (nm)
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D
iffu
se r
efle
ctiv
ity
(%)
Wavelength (nm)
Rh Basel Before Exposure Ra = 6.3 nmRh Basel After Exposure Ra = 8.9 nmPost Cleaning D2 Plasma Ra = 6.5 nm
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 20/21
No impurities were detected by XPS on the surface after deposition
Homogeneous rhodium film with dense columnar structure ( up to 2.4 m thick) with small grain size (~10 nm)
Low roughness after Rh deposition (depending on the substrates)
No effect of annealing treatment in air on the reflectivity(10 times @ 5h at 200 °C in air)
Good adhesion of coating on hard substrate (measured by scratch test)
Rh-coating has survived the exposure in erosion-dominated conditions in laboratory experiment and in TEXTOR
Conclusion
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 21/21
On going
Erosion test for high D+ energy :500 - 600 eV (Karkov Institute, V. Voitsenya)
Measurement of the sputtering yield of rhodium film (to compare with that of bulk Rh)
Effect of baking cycles (400 °C) in vacuum
Thank you for your attention
Questions ?
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 22/21
Process of magnetron sputtering
Laurent Marota, Grégory De Temmermana b; Andrey Litnovskyb, Grégory Covarelc and Peter Oelhafena
Rhodium coated mirrors deposited
by magnetron sputtering for first mirror
a Institute of Physics, University of Basel, Switzerlandb now: Center for Energy Research, University of California at San Diego, USAc Institut für Plasmaphysik, Ass. EURATOM, TEC, Forschungszentrum Jülich, Germanyd Mechanical Laboratory, University of Haute-Alsace, France
L. Marot - ITPA 12 meeting, Princeton March 28, 2007 n° 23/21
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Rh Basel Before Exposure Rh Basel After Exposure SC Mo Before Exposure SC Mo After Exposure Rh ENEA After Exposure
T
ota
l ref
lect
ivit
y (%
)
Wavelength (nm)Total reflectivity measured before and after exposure
Mirrors exposed in the Scrape-Off layer plasma of TEXTOR
Exposure of Rh mirrors under erosion conditions in TEXTOR