Ivc 2013-1

Cermet coating deposition byDC reactive co-sputtering process

controlled by voltage

aintech@ain.es

Cermet coating deposition by DCreactive co-sputtering processcontrolled by voltage

Beatriz Navarcorena, Julián Rodrigo, Gonzalo G. Fuentes,José A. García, Ramón Escobar, Carlos Prieto, José AngelSánchez, Eva Céspedes, J. M. Albella

IVC-19 2013 – September 9-13, Paris, FRANCE

1

Introduction2

Selective coating design3

Objective

Index

Selective coating design3

Deposition and characterization4

Conclusions5

1

Introduction2

Selective coating design3

Objective

Index

Selective coating design3

Deposition and characterization4

Conclusions5

� To develop a solar selectivecoating for the parabolic trough solar

collectors that allows the operating temperature

Objective

collectors that allows the operating temperatureof the transfer fluid to reach 600ºC, and todevelop an application method for them (PVD).

1

Introduction2

Selective coating design3

Objective

Index

Selective coating design3

Deposition and characterization4

Conclusions5

Parabolic trough solar collectorParabolic trough solar collector

Introduction

Parabolic mirrorParabolic mirror Absorber tubeAbsorber tube

Key component: Absorber tubeKey component: Absorber tube

Introduction

AR-coated glass tube(high solar transmittance)

AR-coated glass tube(high solar transmittance)

Selective absorber coating(high solar absorptance and low

thermal emittance)

Selective absorber coating(high solar absorptance and low

thermal emittance)

Vacuum Insulation(minimized heat convection

losses)

Vacuum Insulation(minimized heat convection

losses)

Glass-to-metal sealGlass-to-metal seal

Introduction

↑ Solar absorptance ↓ Thermal emissivity

1,44 µm

1

Introduction2

Selective coating design3

Objective

Index

Selective coating design3

Deposition and characterization4

Conclusions5

LMVF cermet absorbing layer

Anti-reflection coating

Literature reviewLiterature review

Selective coating design

Substrate

IR-reflective metal

LMVF cermet absorbing layer

HMVF cermet absorbing layer

SiO2:Mo (LMVF)

SiO2

Our stackOur stack

Selective coating design

Stainless steel

IR-reflective metal (Ag)

SiO2:Mo (LMVF)

SiO2:Mo (HMVF)

Software simulationsSoftware simulations

� Dependence with the metal volume fraction� Dependence with the metal volume fraction

To optimize the optical parametersTo optimize the optical parameters

Selective coating design

� Dependence with the cermet thickness� Dependence with the cermet thickness

SiO2 64 nm

LMVF-20% 70 nm

HMVF-40% 113 nm

Ag

1

Introduction2

Selective coating design3

Objective

Index

Selective coating design3

Deposition and characterization4

Conclusions5

Selective coating deposition

Elemental targets: Al, Ti, Si, etc.

Reactive gases: O2, N2, etc.

DC-Reactive Magnetron SputteringDC-Reactive Magnetron Sputtering

Inert gases: Ar, etc.

HYSTERESIS EFFECT

SiO2, Al2O3, Si3N2…

Selective coating deposition

The hysteresis effectThe hysteresis effect

Metallic mode

Constant power

Voltage

Reactive gas flow rate

Reactive mode

Selective coating deposition

Increasing the pumping speed

Increasing the target-to–substrate distance

Control Methods

The hysteresis effectThe hysteresis effect

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 andCoatings Technology 127 (2000) 203-219

The hysteresis effectThe hysteresis effect

Selective coating deposition

Stoichiometry

K.Koski et al. “Voltage controlled reactive sputerring process for aluminium oxide thin films” Thin SolidFilms 326 (1998) 189-193

The hysteresis effectThe hysteresis effect

Selective coating depositionposition

Deposition rate

K.Koski et al. “Voltage controlled reactive sputerring process for aluminium oxide thin films” Thin SolidFilms 326 (1998) 189-193

Selective coating deposition

Control method used

speedflo™ Mini is a multi-

The hysteresis effectThe hysteresis effect

speedflo™ Mini is a multi-channel closed-loop controlsystem for high speedadjustment of a reactive gas formagnetron sputter processes.

Selective coating deposition

The hysteresis effectThe hysteresis effect loop point of maximal deposition rate

SiO2

Power Si constant = 2000 W

Selective coating deposition

Characterization by FTIR: SiO2Characterization by FTIR: SiO2

Selective coating deposition

The hysteresis effectThe hysteresis effect

SiO2:Mo

In co-Sputtering, the hysteresis loop of Si targetchanges when the Mo target is on

Selective coating deposition

Silicon power

(W)

Molybdenum power

(W)

Deposition rate

(nm/min)

1000

1000 23

3000 60

4000 97

2000

1000 45

2000 62

3000 83

4000 111

Selective coating deposition

Characterization by ellipsometryCharacterization by ellipsometry

Si(1000W):Mo(4000W)

Selective coating deposition

Optical simulations with real optical valuesOptical simulations with real optical values

Selective coating deposition

Silicon power

(W)

Molybdenum power

(W)

Deposition rate

(nm/min)

1000

1000 23

3000 60

4000 97

2000

1000 45

2000 62

3000 83

4000 111

HMVF

LMVF

Selective coating deposition

Layer Material MVF Thickness (nm)

IR mirror Ag - 250IR mirror Ag - 250

HMVF cermet Mo/ SiO2 0.28 100

LMVF cermet Mo/ SiO2 0.1 90

AR layer SiO2 - 50

Optical characterization of the stack

UV-Vis-NIR Spectrophotometer

Range: 200 nm – 3.3 mm

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)

Optical characterization of the stack

Sample Up-scaled

Temperature αααα2 εεεε2

RT 0,804 0,001

300 °°°°C 0,804 0,025

400 °°°°C 0,804 0,047

500 °°°°C 0,804 0,076

600 °°°°C 0,804 0,111

650 °°°°C 0,804 0,130

[ ]

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λ

λ

λ

λ

λ

λθλα

A

AR

sol( )

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∫

∫ −=

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λ

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dTE

dRTET

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thn

1

Introduction2

Selective coating design3

Objective

Index

Selective coating design3

Deposition and characterization4

Conclusions5

Conclusions

DC-reactive sputtering technique has important advantages fordepositing multipurpose oxide films controlled by voltage.

DC-reactive Magnetron process requires fast control methods in orderDC-reactive Magnetron process requires fast control methods in orderto obtain high deposition rates with the desired stoichiometry, andwith a low reactive gas flow rate.

High value CSP technology stack architecture can be achieved by co-sputtering with a previous optical simulation.

Acknowledgments

The research leading to these results hasreceived funding from the European Community'sSeventh Framework Programme.

Thanks for your attention!