Dr Tony Williams – Gencoa Ltd, UK

Victor Bellido-Gonzalez, Dr Dermot Monaghan,

Dr Joseph Brindley, Robert Brown

SVC’2016, Indianapolis, IL, USA

L-8 (Wed 11th May 2016 @ 9:40am)

Linear Plasma Sources for Surface Modification and Deposition for Large Area Coating

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• Current source technology summary

• Five DC, AC & Hipims source examples for large areas

• The case for pre-treatment / deposition with self -regulating ‘smart’ operation

• Conclusions

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Linear Plasma Sources for Surface Modification and Deposition for Large

Area Coating – Dr Tony Williams – Gencoa Ltd

Plasma Pre-treatment & Deposition Products for Large Areas

Plasma Treatment Product Categories: Application / typical current uses

DC linear ion sources Low speed web & glass

DC magnetron based plasma treaters Low to High speed / power web

AC type dual electrode plasma sources Low to High speed / power web

AC type plasma CVD sources PECVD – deposition web or glass

Hipps+ positive beam ion etching Etching of metallic substrates

DC or pulsed DC ‘inverse sputter box’ Etching of metallic substrates

DC or AC hollow cathode Low to High speed / power web

Microwave & RF linear source technology PECVD – mainly solar cells – hard to scale / high cost

A wide variety of different source technologies exist depending upon need

Focus of this presentation

Plasma Treatment Sources

DC Linear ion sources

Linear ion sources are typically used to pre-treat before sputter coating

scalable robust devices based upon DC power

• Linear ion sources are a powerful means to improve coating adhesion and device performance - liberates moisture and burn-off hydrocarbons.

• The linear ions sources work at sputtering pressures and with low substrate speeds of <5m/min.

• Automatic gas feedback control via the DC power supply makes operation much more simple – self-regulated beams that adapts to chamber conditions.

Main advantage is easy scaling and simple

operation

Easy to scale - Internal mounting im4700 ‘worlds longest’ linear ion

source – 4.7m long beam length

NREL

Ion pre-treatment is a powerful means to improve

coating adhesion and device performance

Elcometer abrasion test (ISO 11998)

Sample without ion-beam pretreatment Sample treated by ion beam

• Abrasion resistance of coatings • Rubbing in wet conditions • Load: 100 gr. • No. Cycles: 500 • Comparative results of coating with and

without ion beam pre-treatment Results of single pass plasma pre-treat

Parallel on-axis in-lens secondary electron detection Sample with ion-beam pre-treatment

After the tempering process no visible defects were detected on the coating.

SEM analysis confirm the good state of the coating.

Sample not treated by ion beam

Samples without ion beam pretreatment show a hazy reflection.

Due to small bubbles (5 mm) in the coating.

Comparison of tempered glass with and without the use of a single pass

plasma pre-treat with linear ion source

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Example of practical uses for linear ion sources for surface

preparation - VISTA telescope - Parana

Credit: ESO Flame Nebula (VISTA image)

Parana – Chile VISTA Telescope

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VISTA Telescope mirror coater Ion Source IM1500 At VISTA with geometrical mask

Example of practical uses for linear ion sources for surface

preparation - VISTA telescope - Parana

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Large mirror ion etching – linear ion sources ideal as easy to scale and accurate

beam control – preventing mirror damage

Ion source

Large mirror coaters 2 -4.5m optics

Sputter source

Results Atomic Force Microscope – Surface Roughness

Untreated example ( from masked area of T-1K-R03X)

Zerodur λ/20

Highly Polished

(un-etched)

Results AFM 3D Mapping – 1h Treatment

T-1K-R01 T-1.5K-R02 T-2K-R03

The overall surface roughness doesn’t change substantially with the ion bombardment, however composite nanotopography is enhanced

Plus points Weakness

Highly scalable and controllable plasma beam

Low power levels – slow speeds only

DC power hence lower cost levels Less plasma excitation

High voltage beam – 500-1500 volt mean beam energies

Can damage sensitive structures – does not lead to increased roughness

Self-neutralized by electron tunnel effect – no charge build-up on insulating substrates

Low rate etching of the substrates – 1 Angstrom per pass for oxides, 40 Angstroms for polymers

Easy to implement and use – if gas has auto feedback control

Separate gas control leads to variable beam properties

Carbon anode and cathode prevents contamination

Source can etch rapidly if of a metallic nature and high power

Process Flexibilty – can be used for PECVD and PEALD

Very low rates, so only useful for R&D or ‘seed’ layers

Pros and cons of DC inverted magnetron

plasma sources

DC magnetron based plasmas for surface pre-treatment

Plasma Treatment Sources

A wide variety of internal and external DC magnetron based plasma treating designs

based upon process & system requirements

Plus points Weakness

Highly scalable and controllable plasma & can run at high substrate speeds and powers

DC or pulsed power hence relatively lower cost levels than RF and microwave

Less plasma excitation – voltages typically less than 500V

Self-neutralized plasma – no charge build-up on insulators

Can run in poisoned mode or ‘gettering’ mode

Need to ‘manage’ the power load to substrate type and atmosphere – needs feedback control

Pulsed DC required for ‘moisture’ rich atmospheres

Need to prevent arcing on the target by pulsing power modes

Single electrode Not suitable for very ‘reactive’ environments, eg PECVD

Pros and cons of DC based magnetron

plasma sources

AC type dual electrode plasma treaters (2kV) for surface pre-treatment

Magnetically enhanced AC type

higher voltage plasma

Magnetic packs angle adjustment for plasma – web interaction adjust

COMPACT AC powered magentically enhanced dual electrode operates with a

medium frequency generator

Very small sources possible – less than 60mm space required.

Water cooled dual electrodes

Pre-distributed gas injection

Pros and Cons of AC based magnetically enhanced

plasma sources

Plus Points Weakness

Switching high voltage AC plasma of high intensity

Could damage the substrate – adjust the magnetic angles to prevent damage

Self-neutralized switching plasma potential – no charge build-up on substrate or target – more robust in ‘dirty’ environments

Double electrode – switching from positive to negative so stable anode and cathode

Higher cost compared to single electrode DC

Highly scalable and controllable plasma & can run at high substrate speeds and powers

Higher cost compared to single electrode DC

Can run in poisoned mode or ‘gettering’ mode Need to ‘manage’ the power load to substrate type and atmosphere – needs feedback control

AC type dual electrode plasma treaters (2kV) for surface pre-

treatment for PACVD

Dual Electrode AC-MF – better for ‘chemical’ etching processes – high

plasma excitement

In dual AC-MF plasma discharges on each electrode the voltage alternates between cathode and anode potential providing an stable impedance for the plasma discharge

Pros and Cons of AC based magnetically enhanced

Chemical plasma sources

Plus Points Weakness

Two separate electrodes – easy to integrate and adapt to different process chambers by re-positioning

Fixed voltage once ‘setup’

Highly scalable and controllable plasma & can run at high substrate speeds and powers – gas pumping capacity dependant

The main challenge is the precursor gas delivery – into the plasma space and separate from the plasma source

Precursor delivery external to the sources and injected directly into the high intensity plasma zone – reduces electrode contamination & extends life

Need to guard against ‘sand’ like deposit in source – needs gas separation and easy to clean

Integrated Speedflo PEM control for automatic process control and gas delivery – option of in-vacuum or remote OPTIX plasma monitoring

Rates are mainly dependant upon vacuum pumping capacity

Hipps – ‘New’ High Impulse Positive pulses for rapid ion etching of

metallic substrates at earth potential

Hipv

Unique and patent pending use of a Hipps power mode with positive pulsing for

high rate etching of substrates

Hipv

‘cleaning’ box to collect sputtered

material to prevent system and substrate

contamination

• Power Supply: Hipps 6kW (500 Amp maximum, +1.4kV) – multiple power supplies for higher powers.

• Highly ionized argon and other background gases accelerated towards the metallic plates at upto 1.4 kV with 400A peak pulses – substrate at earth potential hence the substrate is effectively -1.4 kV relative to the plasma source. • The sources should be angled at upto 45 deg for maximum sputter efficiency and to allow better collection of sputtered material. • Rapid removal of surface oxides and contamination – high speed substrates • Stand alone source – easy system integration (customer to supply ‘cleaning’ box)

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Time (μs)

Unique and patent pending use of a Hipps power mode with positive

pulsing for high rate etching of substrates

‘positive’ pulse drives magnetically guided

ions at a high acceleration voltage towards an earthed substrate for rapid

etching

Hipv

Internal Ion Beams for cleaning tube internal diameters – not easy to

achieve by conventional means

Internal Ion Bombarder

+kV

DC discharge (no ion etching of internal wall) Hipv

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Copper inner wall

Positive etching plasma source - compact design

scalable design – multiple 6 kW PSU’s in parallel

• Compact design 166mm x 180mm and to any length (longer sources may require more power supplies connected in parallel) – new source development on-going

• Based upon high voltage / current positive pulse plasma cleaning / etching – subject to a Gencoa patent application • An alternative to inverted magnetron sputter etching for strip steel and metallic substrates

Von Ardenne

Hipv

Hipv

plasma sources

New alternative to inverted magnetron ‘sputter’ boxes

Positive pulse source Inverted ‘sputter’ box

Unique technology with highest plasma activation available – Hipps based

DC based

High voltage and currents best to sputter native surface oxides quickly

DC slower, pulsing need to prevent arcing

More compact - No need for magnetics behind the substrate – as in the case of ‘sputter boxes’

Require components both side of the substrate

Angled beam for maximum sputter efficiency – 45 deg ion bombardment angle results in max sputter yield

Normal magnetron type plasma

Easier cleaning and system maintenance – all debris is directed away from the source

Debris collects in the source and the substrate

Hipv

Conclusions

Choice of the correct plasma pre-treatment device depends upon process requirement

Best solution

Large scale optics and slow moving substrates Linear ion sources

High speed substrate pre-treatment DC magnetron or AC dual electrode

Reactive chemical etching / PACVD AC dual electrode / AC hollow cathode

Metallic strip / substrate cleaning Hipps positive pulse or inverted sputter box

Gencoa is actively combining technologies and developing ways to enhance thin film

devices – Thank you for your attention

Thank You

Please visit us at Booth 506 Gencoa