Organic electronics: Photolithography or...
Transcript of Organic electronics: Photolithography or...
Giles LloydFlex Europe Conference, 25th October 2016
ORGANIC ELECTRONICS: PHOTOLITHOGRAPHY OR PRINTING
Organic Electronics: Photoligthography or Printing? Lithography
Enabling flexible TFT sheet-fed
production using traditional mask-based microfabrication techniques
Layers patterned with light for high
resolution displays
Enabling flexible electronics from the roll
Printing
Ultimate approach to cost effective
manufacture of large & small area electronics
Organic TFT made
in-house with Merck OTFT and photo-resist materials
Organic TFT Stack
Source: FlexEnable.com
Fastest integration route to
market enabling display makers to ‘fill’ existing LCD lines with minimal investment
Layers patterned additively - no
subtractive etching, photolithography, or vacuum processing steps required
3
Dielectric 2
Dielectric 1
OSC
Substrate
Source Drain
Gate
Planarisation
Passivation
Organic Electronics: Printing or Photolith? ¦ Flex Conference, 25th October 2016
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Organic Semiconductors
-30 -20 -10 0 101E-12
1E-11
1E-10
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
VD -5V, -60V
Linear
Saturated
Gate voltage [V]
Dra
in c
urr
ent [A
]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Mobili
ty [cm
2/V
s]
Merck Performance Materials polymer semiconductors deliver performance combined withsolution processability
-30 -20 -10 0 101E-12
1E-11
1E-10
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4D
rain
curr
ent [A
]
Gate voltage [V]
VD -5V, -60V
Linear
Saturated0.0
0.5
1.0
1.5
2.0
Mobili
ty [cm
2/V
s]
SP400 SP500
lisicon® SP400
Mobility 0.5 – 1 cm2/Vs
lisicon® SP500
Mobility > 2 cm2/Vs
PHOTOLITHOGRAPHY
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The Whole Package
Dielectric 2
Dielectric 1
OSC
Substrate
Source Drain
Gate
Planarisation
All the organic actives and passives plus support materials
Passivation/Interlayer
SubstrateGlass, PEN, PET etc.
lisicon® P-series PlanarisationStable surface for uniform semiconductor coating.
ElectrodesGold, Silver
lisicon® SP-series Polymer SemiconductorsPerformance better than amorphous silicon
lisicon® D-series Low-k dielectricsClean, low-k interface and good solvent resistance
lisicon® AP-series cross-linked dielectricsRobust surface for gate-metal processing
lisicon® P-series passivation/interlayerLow-k for low capacitive coupling
Merck Performance Materials FPD PhotoresistStandard positive tone resist, optimised strippers
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Collaboration Makes Us Stronger
Hsinchu, Taiwan
PhotoresistMaterials
<600 PPI <600~750PPI >750PPI
High Resolution FPD Photoresist
Conventional PR2 µm CD
Performance Materials High Contrast PR1.5 µm CD
Performance Materials Chemically Amplified PR1 µm CD
Chilworth, UK
OTFT Chemistry, Formulation & Printing
High Performance OTFT
In development
OTFT for Printing OTFT for Photolithography
Fully Printed OTFTstack
Photopatterned OTFT stack
+ =
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D-series dielectric and Patterning
Dielectric 1
FPDPR
FPDPR PR
300 nm layer of dielectric 1
>1 um layer of FPD photoresist
50 mJ/cm2 UV
(aligner or stepper)
TMAH develop
O2 RIE etch Strip with DMSO
(or alternative)
g/h-line UV
Developed for photolithography applications
• Dielectric constant of 2.0
• Low solvent permeability* protects the OSC interface
• Compatible with full photolithography process:
*Solvent permeability
Permeability reduced by a factor of 4 compared to previous generation dielectric(measured using PGMEA)
Patterned OSC/Dielectric 1
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AP-series Dielectric
500 nm layer of dielectric 2
~200 mJ/cm2 UV
(aligner or stepper)
i-line or g/h-line
Develop with PGMEA
~1 J/cm2 “hard” cure
Deposit gate
(evaporation or sputtering)
Dielectric 2
g/h-line UV
UV Cross-linkable 2nd layer dielectric
• Dielectric constant of 2.5
• Resistant to metal sputtering and etching (including film edges)
• Formulated for use in i-line exposure tools (g/h-line under development) 10 um via-holes patterned in dielectric 2
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Patterned OTFT Device Data
Un-patterned TFT (as-spun)Drain currentGate Current
Un-patterned TFT (as-spun)Drain currentGate Current
SP400
-60 -40 -20 0 20
10-13
10-12
10-11
10-10
10-9
10-8
10-7
10-6
10-5
Curr
ent
[A]
Gate Voltage [V]
SP500Un-patterned TFTs exhibit a significant parasitic current
• Attributed to bulk conductivity through the semiconductor layer
-60 -40 -20 0 20
10-13
10-12
10-11
10-10
10-9
10-8
10-7
10-6
10-5
Curr
ent
[A]
Gate Voltage [V]
Patterning gives significant benefits to OTFT performance
• Significant reduction in parasitic current
• Order-of-magnitude reduction in off-current
The full stack and process is transferrable to SP500
• The same benefits are seen
• Identical materials and process
• On/off ratio > 107 can be achieved
Reducedleakage
Reducedleakage
PRINTING
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Performance, stability and stack robustness:
Chemistry of the active components
Solvents providing homogeneous structures
Good interfacial properties (electrical + mechanical)
Safety / environmental friendliness:
Engineered solubility profile of the solid components
Non-toxic and non-flammable solvents can be used
Formulations compliant with industrial-scale manufacturing lines
Processability
Simple and stable processing, R2R compatible (no surface treatments such as Vac. Plasma or Corona)
Focus on high resolution: limited and controlable ink spreading with negligible edge effects
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Printing - Major goals
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lisicon®SP400 – OTFT stack development
lisicon® SP400- Printable (e.g. Gravure and Flexo)- Performance close to amorphous silicon- Stable and uniform
lisicon® M001- Provides low contact resistance- Printable (Ink-jet, spray, syringe
dispensing…)
lisicon® D320- Low-k- Printable, (e.g. Gravure and Screen)- Optimised for high performance and stability
lisicon® AP048- Printable (e.g. Gravure)- UV curable – high chemical resistance- Good wetting properties
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Dielectric 2
Dielectric 1
OSC
Substrate
Source Drain
Gate
Note:- Source/drain contacts are Ag and printed by Flexo. Ag gate contact screen printed.
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Formulation development concept – Gravure printingOE: Photolithography or Printing?
Layer thickness requirements
Feature quality and resolution
Form
ula
tion
develo
pm
ent
Pri
nting p
rocess
develo
pm
ent
ViscositySolid
content
Cell sizeEngraving
type
Optimisation of printing parameters
D320
SP400
AP048
Profiles of Gravure printed SP400 and dielectrics takenthroughinterferometric confocal microscope
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SP400 printing process
Gravure printing using mechanically engraved cells
Uniform thickness of the printed features in 30 - 150nm range
SP400 surface roughness <5nm – similar to planarised PEN
Example of a Gravure printed feature of SP400(30nm thick and 100µm wide) on Q65 HA takenthrough interferometric confocal microscope
300µm
30nm thick
150nm thick
Gravure printed SP400 on a flexo printed Source/Drain electrode structuretaken through optical microscope
SP400 features in a range of 30 – 150nm thicknessGravure printed using different rasters
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SP400 Printing at VTT
Printed at…
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Dielectrics: D320 and AP048 - printing
120
-200
100
µm 750 800
100µm
400nm
0 500µm
0 µm 100 400
nm
Gravure printed D320 line with engraving cell image (middle) and profile taken by using mechanical profilometer (Dektak)
Gravure printing, mechanically engraved cells (GRT GmbH & Co. KG)
Uniform thickness profiles, variations <7% of the total thickness
Thicknesses achievable for D320: 100 – 520nm
Gravure printed AP048and profile taken through confocal microscopy with engraving cell image
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The final stack – electrical performance
Good transfer characteristic achieved for all the channel lengths from 30 to 130µm
Leakage currents <10pA
No hysteresis was observed
-40 -30 -20 -10 0 1010
-13
10-12
10-11
10-10
10-9
10-8
10-7
10-6
10-5
Dra
in C
urr
ent
[A]
Gate Voltage [V]
VD = -1 V
VD = -3 V
VD = -30 V
Typical transfer characteristic from 55 x 1000µm (L x W) printed OTFT
100µm
Optical microscope image of 55 x 1000µm (L x W) printed S/Delectrode structureused for the OTFT stackgiving transfer curves as shown on the right
Full printed OTFT devices
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ATLASS EU-Funded Project
Both OSC & passives patterned through additive manufacturing
Merck co-ordinates
EU-funded project exploring new applications for (printed) active-matrix backplanes
Merck interlayer (S2S)
Merck dielectric (R2R)
Fully-printedOTFT Stack
*Advanced high-resolution printing of organic Transistors for Large-Area Smart Surfaces. 14 EU partners.
*
Pressure sensor for crash testing
Temperature sensor (NFC)
Intelligent label (NFC)
Sensing skin for robotics
Non-industrial pilot lines
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Different display medias (electrophoretic, LCD, OLED) have been demonstrated using OTFT backplanes
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OTFTs in real Flexible Display applications
OTFTs for EPD OTFTs for LCD OTFTs for OLED
Flexible electrophoretic display OTFT integrated with liquid crystal frontplane
OTFT-driven OLED display prototype
Source:
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Digital transport signage Digital fashion
Flexible Display – Example use cases!
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The final remarks
Organic Electronics: Photolithography or Printing...?
Material and formulation development demonstrated for both traditional photolithography and printing processes
Future production processes can use either or a combination of both!
In the near term, photolithography processes expected to dominate and allow utilization of existing infrastructure whilst the technology matures
In the long term, printing opens up new possibilities for production at ultra high volume, for example, continuous processes such as Roll to Roll!
Either! Both!or
R&D Director
PM-A, New Platforms
Southampton, UK
DR MARK JAMESSenior Manager, Marketing and Project Management
PM-A, New Platforms.
Southampton, UK
DR GILES LLOYD
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