Creating self-healing moisture barriers by vacuum plasma

V. Bellido-Gonzalez, D. Monaghan, B. Daniel, J.Brindley, H. Li, I. Fernandez*, A. Wennberg*, F. Briones*

Gencoa, Liverpool, UK, *N4E, Madrid, Spain

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• Barrier layers & some applications • Dual rotatable cathodes for PVD & PAVCVD • Pulsed monomer injection cell • Sensors and process control • Multi-layer & single layer barriers of different types • Corrosion results • Conclusions

NREL

Structure of presentation

3

NREL

Encapsulation

Introduction

Low cost and high performance encapsulation

volume demand performance cost

Applications:

Electronic & Display: OLED, LCD, Electrophoretic Displays (e-paper), RFID tags,...

Energy: Solar Cells, Thin Film Li Batteries, Lighting, Mirrors concentrators

Food & Pharma packaging

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Barriers

Barrier levels for different applications

A typical plastic film has a permeability for water (WVTR) of 1~10 g/m2/day

•WVTR Needed for ~10 yr device lifetime:

•Organic LED 10-6 g/m2/day

•Solar Cells 10-4 g/m2/day

•LCD 10-3 g/m2/day

•Electroforetic displays (e-paper) 10-2 g/m2/day

•RFID tags 10-2 g/m2/day

Permeabilities and requirements for Oxygen are very similar

Robert Jan Visser, MIT·Stanford·UC Berkeley Nano Forum

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High performance super-barriers

Multilayer concept – first self-healing method

Atmosphere

Sensitive substrate

US 2003/203210 (A1) - “Barrier coatings and methods of making same” Priority 30th Apr 2002 WVTR & OTD barrier based on alternating polymer and Al2O3 applied to the OLED

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Organic Light Emission Diode (OLED) displays introduced by Samsung

Modern production of barriers for OLED is based upon at least a 3 layer systems based upon PACVD of silicon nitride and monomers. PACVD seems to be the method of choice, the ‘Vitex’ type layer although is effective is not widely used. PACVD seems to offer some advantage for barrier applications

7

Future demands for barrier layers - Thin film Power

Solid State Batteries

Substrate support/protection Encapsuation Anode Electrolyte Cathode Current collector Substrate support/protection

Oak Ridge Labs development Patent expiration 2014

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e-paper wearable electronics piezoelectric devices for harvesting energy from movement, self-charging.

Thin film Power

Solid State Batteries

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Perovskite (A)PbI3 Organic PV

Thin film PV cell

Encapsulation by barrier technology needed

Sources: APL Mater. 1, 042111 (2013) # Solliance

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NREL

HMDSO polymerisation vs SiOx formation

Process Basics – typical monomer used in vacuum plasma’s for barrier

The O2 or H2O levels control the HMDSO plasma reactions Plasma needs to be present to provide energy for the polymerisation / breakdown of the structure.

O2 defect or zero

SiOx

O2 excess O2 excess

SiOx

O2 excess

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• Gencoa DLIM Double Lower Impedance ‘linked’ magnetics for AC plasma generation from rotatable cathodes – PVD & PACVD method – more readily scalable than conventions large area PACVD source technology

• Self-cleaning aspect of rotatable electrode is important

Generating a uniform PACVD plasma over a large scale is challenging

Hybrid approach using PVD sources possible

Enhanced Plasma control by Double Low Impedance Magnetics - DLIM

Ideal for large are PACVD type process with AC power

DC

AC

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Rotatable magnetrons are flexible - switching the magnetic pack – DC, AC, RF/DC,

PECVD target diameter from 75 to 152mm ARC.

Gencoa Rotatable System a compact rotatable magnetron for targets

75, 90, 105, 152mm diameter targets

Designed to easily replace planar magnetrons

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GRS75500 in PACVD mode - Magnetic configuration weaker and power

supply higher AC voltage than typical for PVD

Samples

Monomer inj.

Monomer/ Gases

Different magnetic arrays are ideally taylored for specific purpose. In the image a PACVD array plasma glow is shown. This magnetic

array is different from a sputtering array.

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Feedback control & AC dual power

(with std Speedflo up to 8 gasses can be controlled)

Delivery of multiple gases is required with feedback control

Arg

on

Oxygen

HM

DS

O

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Arg

on

Oxygen

HM

DS

O

Speedflo-Mini™ feedback controller

Huettinger AC MF PSU

PEC pulse

Gencoa - N4E monomer pulsed injector

Gencoa and N4E have developed a unique pulsed effusion cell that can

deliver monomers or polymers into the plasma

Gencoa Pulsed Effusion Cells – PEC – corrosion free device for precision

delivery into vacuum of any organic material

A feedback control system can be added based upon Gencoa’s Speedflo for fast self regulation based upon measuring the flux levels in the chamber and feedback control of the valve frequency. Low temperature (LT) and high temperature (HT) versions available. Organics an use the PEC-LT version.

Pulsed Effusion Cells – PEC – A new generation of precision effusion cells for

today and tomorrows technology requirements

• Pulsing outlet valve for precision flow control • Rapid adjustment of vapour flow (fractions of a

second) • 3 different heat controlled zones – reservoir,

valve area, outlet area (cracker option) • Quartz based system to prevent corrosive attack • Optional direct or remote optical plasma sensing

and automatic feedback control of vapour flux

0 1 2 3 4 5 6 7 8 90

20

40

60

80

100

120

Se

flu

x (

A/s

ec

)

Pulsing frequency (Hz)

20ms

40ms

100ms

Aperture time

Time OFF

Flux ON Time ON

Flux OFF

Gencoa and their partner Nano4Energy have developed a unique type of Effusion Cell.

40% 60% 30% 65% SetPoint

Speedflo™ Process controller interface for PEC Pulsed Effusion Cell

Corrosion free effusion cells with feedback control for the precise delivery of such materials as Se, S and a wide range of organic and monomers vapours.

PACVD / PVD Hybrid process control is complex and needs good sensing

‘remote plasma sensing for vacuum processes ’

The method relies upon the generation of a remote plasma over a very wide pressure range on the chamber wall and spectral analysis of the plasma spectrum to yield information on the process that can be used for a variety of intelligent purposes. The concept is not new, but modern computing capacity allows power diagnostic abilities combined with self-actuation to control and correct process problems. This sensor can be used alone or in combination with process plasma sensors for enhanced control.

0

500

1000

1500

2000

2500

3000

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000

Vo

ltag

e (V

)

Pressure (mBar)

Voltage with pressure

Wider plasma generation range penning type gauge

AC DC

< 10E-5 10E-4 10E-3 10E-2 10E-1 1 10 100 1000

Edwards Penning

Gencoa “Super Penning” Gauge DC

Gencoa “Super Pening” Gauge AC

Pressure mBar

Plasma Generation Range

Potential further development

Plasma generation range

Analysis and control algorithms

Pressure RGA Process

troubleshooting Leak detection Process control

Vai – Vacuum Artificial Intelligence – intelligent use of spectral data to

automatically sense and control processes

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Reactive Sputtering is highly unstable, but advanced control makes widespread

production process in many sectors

Reactive gas input

To pumps

Layer creation

Sp

utter T

arg

et

Process Sensors

Process controller

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Gencoa vacuum process monitoring system and feedback controller

Flexible control of any vacuum deposition process

Controller

(Speedflo)

Actuator

(MFC,

PSU,

PEC)

Process

Reactive Sputtering

End-point detection

E-beam reactive gas

Drift elimination

Process diagnostics

Sensor (s)

(process P.E.M,

penning P.E.M, target

voltage, spectrometer,

Lambda etc)

Voltage Out Gas Flow

Plasma intensity etc

Voltage In – single

or multiple signals or

ratios

Demanded plasma

intensity etc

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Continuous DC with the highest deposition rate,

nearly doubling that for pulsed DC.

Ion source considerably reducing deposition rate,

due to very high ion energy

After deposition for 30 mins

CCD spectrometer as the sensor

Al Si O

Before HMDSO/O2 input

Al

Deposition with PEM control, looking at the process plasma

Multi-signal monitoring by spectrometer, Speedflo; Al signal suppressed during deposition

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Speedflo – multi-window monitoring and feedback control is needed to hold

the PACVD process in ‘balance’ and prevent ‘drift’

Effusion cell control and Si signal Al PEM control: O2 flow and Al signal

O signal and Ar flow

Speedflo example of PACVD plasma balancing O2 and Si composition - SiO2

layer from an HMDSO and O2 plasma

Speedflo is very effective in stabilizing CVD type plasma deposition to maintain composition and transparency Light

transmission at

550 nm: 97.5%

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PEM control level vs O signal

Coating depositions

Lower Al signal control from dual rotatable target

leading to higher O signal, useful to control

depositions with HMDSO input

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Signal stability during PACVD with Al GRS targets, O2 and HMDSO gases

PEM control - O2 flow and emission signals

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Speedflo is monitoring and controlling multiple elements of the process

via more than 1 sensor and more than 1 flow control output – multi-

channel simultaneous feedback control

Higher HMDSO input increases the Si in the plasma whilst decreasing the Al signal

Allowing compositional control of metal species

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Experimental; a wide range of layer types have been created to test the

effectiveness for barrier properties

Polymer

Aluminium Oxide

Aluminium

Glass Substrate

(A)

Al base layer is deposited in all cases to act as the ‘device’ and show corrosion during the tests

AlOx classic PVD layer

Plasma polymerisation single layer from precursor

Multilayer combination of above to create classic Vitex type layer as benchmark

SiAlOx PVD mainly type process – some CVD element

SiAlOx CVD mainly type process – still some smaller PVD element

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Example of multi-layer deposition process

0.5 0.5 0.5

O2 injection via feedback (Penning-PEM)

HMDSO injection with feedback (Penning-PEM) or without feedback

Time

3

Power kW

3 3 3

Adaptation between layers (shutters)

AlOx

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SEM cross section

Multilayer

Decreased effective diffusion path for molecules

Polymer

Polymer

Polymer

Polymer

AlOx

AlOx

AlOx

AlOx

AlOx

Active layer

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Example of other barrier multilayers combination 4 x (Butyl-Acrylate/AlOx)

Monomer injector

- ∆t = 1 ms

- Frequency: 0 – 100 Hz

- RT (3.3mmHg)

- 0.5kW AC

- 3bar Ar + monomer

AlOx

- 3kW AC

- 3bar Ar + O2

Shutter closed in between adjacent layers

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Cl2

Cl2

Cl2

Cl2

Cl2

Cl2

Cl2

Cl2

Cl2

Cl2

Cl2

Cl2

Cl2

Cl2

Cl2

Cl2

2Al + 3Cl2 2AlCl3

30 g NaCl

100 ml H2O

50 ml H2O2 30% v/v

200 ml HCl 1N

Permeable paper

(A)

(Aa) (Ap)

(Aap)

Corrosion test – accelerated ‘real-life’ testing

Barrier performance test newly developed for rapid assessment of barriers

Corrosion of Al layer will produce transparency similarly to the ‘Calcium’ test

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11/09/13 10:08

(A) (Aa) (Ap)

(Aap)

Corrosion test

Barrier performance test

Arrangement of samples at time=0

The test gives a powerful indication of barrier performance and provide and easy comparison of the merits of different layer types

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11/09/13 10:08

The test gives a powerful indication of barrier performance and provide and easy comparison of the merits of different layer types

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11/09/13 10:37

The test gives a powerful indication of barrier performance and provide and easy comparison of the merits of different layer types

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11/09/13 11:53

The test gives a powerful indication of barrier performance and provide and easy comparison of the merits of different layer types

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11/09/13 12:40

The test gives a powerful indication of barrier performance and provide and easy comparison of the merits of different layer types

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11/09/13 13:45

The test gives a powerful indication of barrier performance and provide and easy comparison of the merits of different layer types

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11/09/13 14:37

The test gives a powerful indication of barrier performance and provide and easy comparison of the merits of different layer types

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11/09/13 15:39

The test gives a powerful indication of barrier performance and provide and easy comparison of the merits of different layer types

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11/09/13 16:38

The test gives a powerful indication of barrier performance and provide and easy comparison of the merits of different layer types

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11/09/13 17:48

The test gives a powerful indication of barrier performance and provide and easy comparison of the merits of different layer types

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11/09/13 18:39

Al unprotected layer is starting to corrode as is the polymer layer

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11/09/13 21:07

Al unprotected layer is starting to corrode as is the polymer layer

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11/09/13 22:07

Al unprotected layer is starting to corrode as is the polymer layer

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11/09/13 22:12

Al unprotected layer is starting to corrode as is the polymer layer

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12/09/13 07:59

Al unprotected layer is starting to corrode as is the polymer layer

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12/09/13 08:24

Al unprotected layer is starting to corrode as is the polymer layer

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12/09/13 09:06

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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12/09/13 10:04

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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12/09/13 11:56

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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12/09/13 12:38

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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12/09/13 13:09

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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12/09/13 13:34

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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12/09/13 14:01

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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12/09/13 14:33

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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12/09/13 15:10

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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12/09/13 15:38

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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12/09/13 16:05

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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12/09/13 16:33

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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12/09/13 18:14

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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13/09/13 08:01

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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13/09/13 09:05

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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13/09/13 10:02

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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13/09/13 11:35

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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13/09/13 12:10

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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13/09/13 13:02

Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down

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13/09/13 13:52

Only the multilayer structure survives the test at this time internal

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A series of single layer AlOx and SiAlOx PVD/PACVD type layers deposited

to assess suitability as effective barrier layers

Light transmission without Al ‘device’ layer

Light transmission at 550nm:

94.7% for 30% Al PEM, 0.1mTorr HMDSO

97.9% for 20% Al PEM, 0.2mTorr HMDSO

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Corrosion performance of single layer pvd/pacvd type coatings with Al

‘device’ layer with different Al – Si compositions

Without encapsulation, Al coating corroded quickly

after 5hs; other three coatings remained intact

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After 22hs, Al coating corroded completely; AlOx and AlSiOx-1

corroded at many points; AlSiOx-2 started to corrode

AlSiOx-2 with the best performance but much worse than the

multi-layer performance

All these layer types are breaking down quickly in the acid vapour, these

single layer compositions do not provide barrier

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These single layer PVD/PACVD have a bias towards PVD ‘type’ films

Cross-sectional SEM images of SiAlOx layers

600nm thick 680nm thick

Coatings dense, but defects must be present that allow corrosive attack by acid vapour – not able to self-heal. Would need the

polymerisation multilayer type structure for good barrier performance.

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Next layers to be deposited have a more PACVD bias to process

Similar AlSiOx composition but with more CVD

• Layers created with more of PACVD element than PVD element look similar in X-section

• Very dense and featureless

• Also highly transparent

• But huge difference in the corrosion performance

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The AlSiOx single layer coating created with more PACVD element to the

process exhibit much better barrier performance

Single layer PACVD type material is as effective as the multi-

layer structure, has the same self-healing effect during

deposition – these single layers is now better than multi-layer

performance >3 months resistance to the acid vapour attack.

Start

Day 3 Day 12

Day 1

Day 17

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Conclusions

• Dual rotatable cathode AC discharge is a feasible technology for plasma polymerisation and PACVD with good potential for lower cost scale-up as PECVD source technology.

• With multi-level feedback control chemical species an be kept in balance in PACVD type discharge.

• PVD type single layer oxides of any composition need the addition of polymer layers to ‘heal’ the structure and provide good barrier protection.

• If the mode of deposition is pushed towards the PACVD type plasma, a single layer can be created which provides very good barrier performance.

• The PACVD layer must ‘self-heal’ during deposition and a PVD layer cannot do this to the same extent.

• The ‘self-healing’ effect needs to be explored more to highlight the mechanism - surface mobility of deposited species, composition, structure.

• A single layer PACVD type barrier would be a reduced cost simpler process than the currently available multi-layer solutions.

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Thanks & Open for Questions

THANK YOU

FOR YOUR ATTENTION

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