Encapsulation of Organic Photonic Elements Y. Leterrier Laboratoire de Technologie des Composites et Polymères (LTC) Ecole Polytechnique Fédérale de Lausanne (EFPL) CH-1015 Lausanne, Switzerland SwissLaser Net Workshop, Basel, June 25, 2008
Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
Polymers are (too) permeable 104 LDPE
102 101
Solar modules 100 10-1 10-2
PS
PP PC HDPE ABS Food products
3
2
OTR (100 um; cm /m /day/bar)
103
PET PA6 PVC PEN Cellulose EVOH (wet) PVDC PAN LCP EVOH (dry)
OLED displays
10-3 10-4 10-7
10-5
10-3
10-1
101
103
2
WVTR (100 um; g/m /day) Crank & Park, ‘Diffusion in polymers’ Academic Press (1968) Chatam, Surf. Coat. Technol. (1996) Pauly, in ‘Polymer Handbook’ Wiley (1999) Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
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High-Barrier Strategies Barrier Improvement Factor: BIF = Ps/P
nanolaminates Inorganic film (10-1000 nm)
Polymer substrate
BIF > 105
BIF ~ 100
Organic-inorganic hybrids
BIF ?
BIF ~ 1’000
Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
Nanosized inorganic coatings/polymer composites
h h c hs = + P Pc Ps
Coating permeability Pc, thickness hc Substrate permeability Ps, thickness hs 1000
OTR (cm3/day/m2/bar)
SiOx/PET films PET
100
Evaporation AlOx
10
Sputtering 1
Aluminized PET PECVD
0.1
0
100
200
300
400
500
Coating thickness (nm) Leterrier, Prog. Mater. Sci (2003) Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
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Defects in vapor-deposited inorganic films on polymers Critical coating thickness ranges between 8 and 15 nm
Defect dependent permeation
-15 Ep (PET)= 32.4±1.3 KJ/mole
-16 -17 -18 ln P
-19 -20
Ep (SiOx_PET)= 34.4 ± 2.1 KJ/mole
-21 -22 -23
SiOx/PET
-24 3.10 3.15 3.20 3.25 3.30 3.35 3.40 3.45 3.50 Temp (1/OK) x 103
Courtesy Tetra Pak
Roberts et al., J. Membrane Sci. (2002) Rochat, Leterrier, Månson, Fayet, Surf. Coat Technol. (2003, 2006) Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
100
400
80
1 µm
50 nm
300
60
200
40
10 nm
100
20
0
2
500
3
120
[cm /m /day/bar]
600
-1
Crack density [mm ]
10 nm SiOx on PET @ 10% strain
Oxygen transmission rate
Effect of coating defects on failure of barrier
0 0
0.02
0.04
0.06
0.08
0.1
Strain
Rochat, Leterrier et al., J. Appl. Phys. (2003) Singh, Leterrier, Månson, Fayet, Surf. Coat. Technol. (2007) Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
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High-Barrier Strategies Barrier Improvement Factor: BIF = Ps/P
nanolaminates Polymer substrate
Inorganic film (10-1000 nm)
BIF > 105
BIF ~ 100
Organic-inorganic hybrids
BIF ?
BIF ~ 1’000
Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
Why nanolaminate structures? Nanolaminates decouple defect structure
BIF > 105
WVTR (20°C) ~ 2·10-6 g/m2/day (Vitex Systems, CA)
Trophsa & Harvey, J. Phys. Chem. B (1997) Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
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Modeling of gas transport Barrier improvement obtained when adding a second inorganic layer
Trophsa & Harvey, J. Phys. Chem. B (1997) Schaepkens et al., J. Vac. Sci. Technol (2004) Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
Nanolaminate encapsulation
Producer
Encapsulation Structure
Number of layers
WVTR (g.m-2.day)
Crack Onset Strain (%)
Vitex (Barix)
[acrylate/Al2O3] n
10
~ 1 × 10-6
0.8
Philips (NONON)
[SiNx/SiOx] n
‘12’ + topcoat
3.6 × 10-6
1.0
GE (graded UHB)
[SiNx/SiOx] n
‘5’
8.6 × 10-6
-
Applied Materials
(SiN/lacquer)2
4
~ 1 × 10-5
1.0
Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
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High-Barrier Strategies Barrier Improvement Factor: BIF = Ps/P
nanolaminates Polymer substrate
Inorganic film (10-1000 nm)
BIF > 105
BIF ~ 100
Organic-inorganic hybrids
BIF ?
BIF ~ 1’000
Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
Why organic-inorganic hybrids? Organo-silanes reduce the severity of superficial defects (‘Griffith flaws’) R—Si—(OR’)3
Flaw
Physisorbed Chemisorbed layers Highly layers crosslinked region
Coating Substrate
Pluddemann, Silane Coupling Agents, Plenum Press (1990) Zinck et al., J. Mater. Sci. (1999). Haas et al., Surf. Coat. Technol. (1999) Bouchet et al., Surf. Coat Technol. (2005) Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
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Processing of organosilane-silica hybrids SiOx 12 nm PECVD from O2 diluted HMDSO on 12 µm thick PET web OTR ~ 2.1 cm3/m2/day/bar COS ~ 3.5%
NH2
Si(OC2H5)3
Gamma-aminopropyltriethoxysilane (γ-APS, Silquest A-1100TM)
1 - 20 %wt γ-APS/ethanol pH=11.4 and pH=8 (acetic acid)
Spin coating on SiOx/PET films 1000 rpm, 20 s
oligomerization: 12 h at 60°C 10 - 500 nm thick silane films Magni et al, J. Phys. D (2001) Bouchet, Leterrier et al., Surf. Coat. Technol. (2005, 2007) Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
Defect analysis in organosilane-silica hybrids Amino-silane treatment reduces the size and population of macro-defects SiOx/PET RIE 12 min. Average defect radius 720 nm
γ-APS/SiOx/PET RIE 12 min. Average defect radius 330 nm
Singh, Leterrier et al., Surf. Coat. Technol. (2007) Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
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Mechanical integrity of organosilane-silica hybrids
γ-APS/SiOx/PET
10 nm SiOx/PET reference
5 µm
0%
Crack onset strain 3.5%
0%
5 µm
10%
5 µm
12%
5 µm
20%
5 µm
Crack onset strain > 6%
Rochat et al. Thin Solid Films (2003) Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
Supertough high barrier encapsulation nanolaminates
Organic-inorganic hybrids
BIF > 105
COS ~ 5%
Supertough high barrier encapsulation
Stress state? Microcracking?
Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
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Origin of stress in polymer coatings
… Lack of dimensional stability … Void formation?
… Buckling and cracking
t
!(t) = 2 # G(t) 0
T
f "c "c dt + 2 # G($ s + )dT "t "T Tc
Cure Thermal stress (small for UVshrinkage curable polymers) stress Lange, Månson et al., Polymer (1995, 1997); Payne (1998) Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
Towards low stress encapsulation A low-stress material combines:
Tailored process temperature cycles ‘Low profile’ additives
reduced shrinkage ⇒ radiation curing retarded modulus build-up ⇒ hyperbranched polymers
Radiation curing … Hyperbranched polymers
Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
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Low Stress UV Curable Hyperbranched Polymer Nanocomposites
HBP + 5 vol% SiO2 Tg: 68°C
Tg: 126°C
Tg: 28°C 100 nm
HBP + 20 vol% SiO2
Photoinitiators: 1-Hydroxy-cyclohexyl-phenyl-ketone 1:1 blend of 1-Hydroxy-cyclohexylphenyl-ketone and benzophenone
100 nm
Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
Low Stress UV Curable Hyperbranched Polymer Nanocomposites
Microbattery, layer thickness 500 µm
SU8
Polyether HBP
FOM = (L x AR) / (Stress x Fab_Time) Resist
Layer thickness, L (µm)
Aspect ratio, AR
Residual stress (MPa)
Fabrication time (h)
FOM
Polyether HBP
850
7.7
2.4
0.5
5454
Polyester HBP
500
3.3
4.5
0.5
733
SU-8
250
11
25
3
37
Jin Y.-H., J. Micromech. Microeng., 17, 1147-1153 (2007). Schmidt et al., J. Micromech. Microeng. 18, 045022 (2008). Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
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High-Barrier Strategies Barrier Improvement Factor: BIF = Ps/P
nanolaminates Polymer substrate
Inorganic film (10-1000 nm)
BIF ~ 100 COS ~ 2%
BIF > 105 COS ~ 1%
Organic-inorganic hybrids BIF ~ 1000 COS ~ 5%
BIF ~ 1000 COS ~ 2%
Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
Acknowledgements • • • • • • • • • • • • •
F. Demarco, G. Rochat, B. Singh, J. Bouchet, J.-A. Månson, LTC-EPFL Dr. J. Andersons, Inst. Polymer Mechanics, Riga (LV) Dr. Y.-H. Jin, Pr. YH Cho, KAIST (KR) Dr. P. Bouten, Philips Research Laboratories (NL) Dr. N. Rutherford, Vitex Systems (USA) Dr. D. James, Dr. S. Lundmark, Perstorp SC (S) Dr. P. Fayet, Tetra Pak Suisse SA, Plasma Technology (CH) Centre Interfacultaire de Microscopie Electronique (CIME-EPFL) Centre de Micro-Nano-Technologies (CMI-EPFL) Swiss Commission for Technology and Innovation (CTI) and the Top Nano 21 Swiss initiative (TNS 5940.2) Swiss National Science Foundation (SNF 200020-111706) Swiss Federal Office for Education and Science (OFES - IST-2001-34215) FLEXIDIS (EU-IST 2004-4354)
THANK YOU!
Y. Leterrier - SwissLaser Net Workshop, Basel, June 25, 2008
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