Upload
others
View
3
Download
0
Embed Size (px)
Citation preview
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
2
• 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
4
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
5
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
6
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
8
e-paper wearable electronics piezoelectric devices for harvesting energy from movement, self-charging.
Thin film Power
Solid State Batteries
9
Perovskite (A)PbI3 Organic PV
Thin film PV cell
Encapsulation by barrier technology needed
Sources: APL Mater. 1, 042111 (2013) # Solliance
10
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
11
• 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
13
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
15
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.
16
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
17
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
25
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
26
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
27
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
28
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%
30
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
31
Signal stability during PACVD with Al GRS targets, O2 and HMDSO gases
PEM control - O2 flow and emission signals
32
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
33
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
34
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
35
SEM cross section
Multilayer
Decreased effective diffusion path for molecules
Polymer
Polymer
Polymer
Polymer
AlOx
AlOx
AlOx
AlOx
AlOx
Active layer
36
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
37
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
38
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
39
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
40
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
41
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
42
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
43
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
44
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
45
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
46
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
47
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
48
11/09/13 18:39
Al unprotected layer is starting to corrode as is the polymer layer
49
11/09/13 21:07
Al unprotected layer is starting to corrode as is the polymer layer
50
11/09/13 22:07
Al unprotected layer is starting to corrode as is the polymer layer
51
11/09/13 22:12
Al unprotected layer is starting to corrode as is the polymer layer
52
12/09/13 07:59
Al unprotected layer is starting to corrode as is the polymer layer
53
12/09/13 08:24
Al unprotected layer is starting to corrode as is the polymer layer
54
12/09/13 09:06
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
55
12/09/13 10:04
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
56
12/09/13 11:56
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
57
12/09/13 12:38
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
58
12/09/13 13:09
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
59
12/09/13 13:34
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
60
12/09/13 14:01
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
61
12/09/13 14:33
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
62
12/09/13 15:10
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
63
12/09/13 15:38
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
64
12/09/13 16:05
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
65
12/09/13 16:33
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
66
12/09/13 18:14
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
67
13/09/13 08:01
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
68
13/09/13 09:05
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
69
13/09/13 10:02
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
70
13/09/13 11:35
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
71
13/09/13 12:10
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
72
13/09/13 13:02
Al layer completely removed polymer layer large areas removed, AlOx layer starting to break down
73
13/09/13 13:52
Only the multilayer structure survives the test at this time internal
74
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
75
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
76
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
77
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.
78
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
79
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
80
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.
81
Thanks & Open for Questions
THANK YOU
FOR YOUR ATTENTION
www.gencoa.com