Cermet coating deposition by DC reactive co-sputtering process controlled by voltage

1. Cermet coating deposition by
DC reactive co-sputtering process
controlled by voltage
aintech@ain.es

2. Cermet coating deposition by DC
reactive
co-sputtering
process
controlled by voltage
Beatriz Navarcorena, Julián Rodrigo, Gonzalo G. Fuentes,
José A. García, Ramón Escobar, Carlos Prieto, José Angel
Sánchez, Eva Céspedes, J. M. Albella
IVC-19 2013 – September 9-13, Paris, FRANCE

3. Index
1
Objective
2
Introduction
3
Selective coating design
4
Deposition and characterization
5
Conclusions

4. Index
1
Objective
2
Introduction
3
Selective coating design
4
Deposition and characterization
5
Conclusions

5. Objective
To
develop
coating
a
solar
selective
for the parabolic trough solar
collectors that allows the operating temperature
of the transfer fluid to reach 600ºC, and to
develop an application method for them (PVD).

6. Index
1
Objective
2
Introduction
3
Selective coating design
4
Deposition and characterization
5
Conclusions

7. Introduction
Parabolic trough solar collector
Parabolic mirror
Absorber tube

8. Introduction
Key component: Absorber tube
AR-coated glass tube
(high solar transmittance)
Glass-to-metal seal
Selective absorber coating
(high solar absorptance and low
thermal emittance)
Vacuum Insulation
(minimized heat convection
losses)

9. Introduction
↑ Solar absorptance
1,44 µm
↓ Thermal emissivity

10. Index
1
Objective
2
Introduction
3
Selective coating design
4
Deposition and characterization
5
Conclusions

11. Selective coating design
Literature review
Anti-reflection coating
LMVF cermet absorbing layer
HMVF cermet absorbing layer
IR-reflective metal
Substrate

12. Selective coating design
Our stack
SiO2
SiO2:Mo (LMVF)
SiO2:Mo (HMVF)
IR-reflective metal (Ag)
Stainless steel

13. Selective coating design
Software simulations
To optimize the optical parameters
Dependence with the metal volume fraction
Dependence with the cermet thickness
SiO2 64 nm
LMVF-20% 70 nm
HMVF-40% 113 nm
Ag

14. Index
1
Objective
2
Introduction
3
Selective coating design
4
Deposition and characterization
5
Conclusions

15. Selective coating deposition
DC-Reactive Magnetron Sputtering
Elemental targets: Al, Ti, Si, etc.
Reactive gases: O2, N2, etc.
Inert gases: Ar, etc.
SiO2, Al2O3, Si3N2…
HYSTERESIS
EFFECT

16. Selective coating deposition
The hysteresis effect
Constant power
Metallic mode
Voltage
Reactive mode
Reactive gas flow rate

17. Selective coating deposition
The hysteresis effect
Control Methods
Increasing the pumping speed
Increasing the target-to–substrate distance
Obstructing reactive gas flow to the cathode
Pulsed reactive gas flow
Plasma emission monitoring
Voltage control
I.Safi “Recent aspects concerning DC reactive magnetron sputtering of thin films: a review” Surface and
Coatings Technology 127 (2000) 203-219

18. Selective coating deposition
The hysteresis effect
Stoichiometry
K.Koski et al. “Voltage controlled reactive sputerring process for aluminium oxide thin films” Thin Solid
Films 326 (1998) 189-193

19. Selective coating deposition
position
The hysteresis effect
Deposition rate
K.Koski et al. “Voltage controlled reactive sputerring process for aluminium oxide thin films” Thin Solid
Films 326 (1998) 189-193

20. Selective coating deposition
The hysteresis effect
Control method used
speedflo™ Mini is a multichannel closed-loop control
system
for
high
speed
adjustment of a reactive gas for
magnetron sputter processes.

21. Selective coating deposition
The hysteresis effect
SiO2
Power Si constant = 2000 W
loop point of maximal
deposition rate

22. Selective coating deposition
Characterization by FTIR: SiO2

23. Selective coating deposition
The hysteresis effect
SiO2:Mo
In co-Sputtering, the hysteresis loop of Si target
changes when the Mo target is on

24. Selective coating deposition
Silicon power
(W)
23
3000
60
4000
97
1000
2000
Deposition rate
(nm/min)
1000
1000
Molybdenum power
(W)
45
2000
62
3000
83
4000
111

25. Selective coating deposition
Characterization by ellipsometry
Si(1000W):Mo(4000W)

26. Selective coating deposition
Optical simulations with real optical values

27. Selective coating deposition
Silicon power
(W)
23
3000
60
4000
97
HMVF
1000
2000
Deposition rate
(nm/min)
1000
1000
Molybdenum power
(W)
45
LMVF
2000
62
3000
83
4000
111

28. Selective coating deposition
Layer
Material
MVF
Thickness (nm)
IR mirror
Ag
-
250
HMVF cermet
Mo/ SiO2
0.28
100
LMVF cermet
Mo/ SiO2
0.1
90
AR layer
SiO2
-
50

29. Optical characterization of the stack
FTIR dual MIR/NIR Spectrometer
Rango: NIR: 11000-3000 cm-1 (0.9 - 3.3 µm)
MIR: 4000-400 cm-1 (2.5 – 25 µm)
UV-Vis-NIR Spectrophotometer
Range: 200 nm – 3.3 mm

30. Optical characterization of the stack
Sample
Up-scaled
Temperature
λ2
∫λ
1
A(λ )
ε thn
0,804
0,047
0,804
0,076
0,804
0,111
650 °C
α sol
0,025
600 °C
∫
(θ , T ) = λ
0,804
500 °C
1
0,001
400 °C
∫λ [1 − R(λ ,θ )]A(λ )
=
0,804
300 °C
λ2
ε2
RT
λ2
α2
0,804
0,130
E (T , λ )[1 − RS (λ ,θ )]dλ
1
λ2
∫λ
1
E (T , λ )dλ

31. Index
1
Objective
2
Introduction
3
Selective coating design
4
Deposition and characterization
5
Conclusions

32. Conclusions
DC-reactive sputtering technique has important advantages for
depositing multipurpose oxide films controlled by voltage.
DC-reactive Magnetron process requires fast control methods in order
to obtain high deposition rates with the desired stoichiometry, and
with a low reactive gas flow rate.
High value CSP technology stack architecture can be achieved by cosputtering with a previous optical simulation.

33. Acknowledgments
The research leading to these results has
received funding from the European Community's
Seventh Framework Programme.
Thanks for your attention!