125th Sept 2013
Roll-to-roll Vacuum Processing of Organic Electronics
Hazel AssenderDepartment of Materials
University of Oxford
DALMATIAN TECHNOLOGY
225th Sept 2013
Aim of the Research
- Flexible, polymer substrate (web)
- High speed (e.g. 1m/s web speed)
- R2R process
- Low cost materials
2
Possible application:
anticounterfeiting/product
tracking tags for packaging.
To demonstrate the ability to fabricate all-evaporated transistors in a
R2R web process environment exploiting the technology that is used
in the packaging industry.
325th Sept 2013 3
Issues to consider
5) Robustness of final devices
Gate Substrate
Source and Drain (Metal)
L W
Org. Semiconductor
Insulatore.g. 0.5m acrylic
e.g. 125m thick PEN
e.g. 90nm pentacene
1) Process parameters in R2R environment – building and testing transistors.
2) Circuit design tailored for the properties achievable with this manufacturing route
3) Materials (organic semiconductor and polymer gate insulator layer) developed for this manufacturing route
4) Patterning processes
425th Sept 2013
Substrate (e.g. PET)
Gate
Source and Drain (Metal)
4
Roll-to-roll devices
Polymer smoothing layer:
Flash evaporated monomers then cure
Gate:pattern metallization
Gate insulator layer:Flash evaporated monomers
then cure
Perhaps surface modification layer: Various options
Build complete device structure on the substrate
Insulator (e.g.
acrylic dielectric)
Possible interlayer
Possible surface modification
Molecular semiconductor: Evaporation
Source and Drain: pattern metallization
Encapsulation layer/gas barrier
Org. Semiconductor
WL
525th Sept 2013 5
Materials: pattern metallization
Evaporation zone 5 × 10-4 mbar
Winding zone
Unwind
Process Drum
Rewind
Anilox Roller and Oil Boiler Cliché Plate
PRINTING RESOLUTION
MD: 30-50 micron
TD: 30-50 micron
----
---S
ourc
e/D
rain
Ele
ctro
des-
-----
Magnification x 200
Magnification x 60
625th Sept 2013
• In-line process• High speed
Depositing the gate-insulator
Smooth Acrylic layer
VacuumHeat Tank 250 °C
i. Evaporate monomer (liquid)ii. Monomer condenses onto substrate (web) as a liquid (flat)iii. Polymerize (cure) in-situ to a solid
725th Sept 2013
Patterning the organic layers
Semiconductor:
High speed organic vapour jet printing.
We have demonstrated working devices made with OVJP.
Carrier gas in
Gas heating furnace
Semiconductor furnace
Nozzle
Gas out
Insulator:
Development of solventless printing (e.g. flexoprint and inkjet) of liquid monomer prior to e-beam or UV cure
SubstrateInk bath
Anilox roller
Printing plateDoctor blade
Cure
825th Sept 2013
Increase e-beam cure current
Make R2R process
-10
-8
-6
-4
-2
0-50 -40 -30 -20 -10 0
VD(V)I D
(nA
)
-10V-20V-24V-30V-40V-44V
VG
-50 -40 -30 -20 -10 0
-3
-2
-1
0
I D(µ
A)
VD(V)
-10V-20V-30V-40V-50V
Gate insulator deposition
8
First devices
Plasma cured, single pass
Anneal (150ºC 1hr)
-40 -30 -20 -10 0
-6
-4
-2
0
-10V-20V-30V-40V
I D(
A)VD(V)
E-beam cured + annealed
Ion/Ioff = 1.3x103
Vth = 15Vµ = 0.1cm2/Vs
-10
-5
0-40 -30 -20 -10 0
0V-10V-20V-30V-40V
I D(n
A)
VD(V)
VG
E-beam cured
925th Sept 2013
Modification of the insulator surface
Spin coat a thin (20-40nm) polymer layer:
1m0.01 0.1 1 10
0.01
0.1
PNPPSPVSPBMTPGDAPMMA
Mob
ility
(cm
2 /Vs)
Polar part surface energy (mN/m)
Ester:carbon ratio
1025th Sept 2013 10
Materials developments
DNTT, dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene, has better
environmental stability due to a reduced tendency to oxidize.
Synthetic route for DNTT:
DNTT synthesised and processed via A, literature route and B, an evolved method.
1125th Sept 2013
DNTT devicesVT (V) µ
(cm2 V-1 s-1) Ion/IoffS
(V/decade)
TPGDA / DNTT -4 0.12 105 1.8
TPGDA / Pentacene -12 0.04 103 8.0
TPGDA / PS / DNTT -1 0.95 ± 0.17 107 0.5
TPGDA / PS / Pentacene -10 0.57 ± 0.04 106 2.0
• Made with evaporated TPGDA/PS dielectric: 100%
-40 -20 0 20
1E-12
1E-10
1E-8
1E-6
1E-4
DNTT μ=1 cm2/VsPentacene μ=0.6 cm2/Vs
Vg(V)
I d(A
)
0.000
0.005
0.010
I d0.5 (
A0.
5 )
Yields, tested over batches of 96 transistors• Made with solution-cast PS dielectric: 66%
1225th Sept 2013
Modelling DNTT devicesParameter
Solution-deposited
PS insulator
Evaporated acrylic insulator
Evaporated acrylic insulator with PS buffer
Ambient Air Air Vacuum
W(m) 15900 3000 2400
L(m) 36 150 200
Ci (nF/cm2) 1.59 5.84 12.8
VT (V) -3.91 -4.78 -1.31
V0 (V) 1.45 3.12 0.31
VACC 1 1 1
ACC (cm2/Vs) 0.01 0.04 1.05
0.63 0.36 6x10-7
0.0124 0 0
MSAT 2.84 3.41 2.58
ASAT 0.20 1.42 1.41
I0 (fA) 30 30 30
0 (S) 7x10-14 1x10-20 1x10-13
RS (kΩ) 438 0 73.9
RD (kΩ) 337 0 86.6
-60
-40
-20
0
-40 -20 0VD(V)
I D(m
A) Vg=0V
-5V-10V-15V-20V-25V-30V
-10
-8
-6
-4
-30 -20 -10 0VG(V)
Log 1
0(I D
/A)
Vg=-0.5V-2.5V-4.0V
-30.0V
1325th Sept 2013
Invertor
-60-50-40-30-20-10
0
0 20 40 60
V ol
tage
(V)
Time (s)
V IN V OUT
-60
-50
-40
-30
-20
-10
0
-60 -10 40
V O
UT
(V)
V IN (V)
Drain -60 V Drain -40 VDrain -20 V
‐V
VIN
VOUT
Enhancement Load
Driver OTFT
Experimental Response Transfer Plot
1425th Sept 2013
NANDVIN 1 VIN 2 VOUT
0 0 10 1 11 0 11 1 0
‐60‐40‐200
0 4 8 12
V IN1 (V)
Time (s)
‐60‐40‐200
0 4 8 12
V IN2 (V)
Time (s)
‐60
‐40
‐20
0
0 4 8 12
V OUT(V)
Time (s)
Truth Table
Logic Circuits
NORVIN 1 VIN 2 VOUT
0 0 10 1 01 0 01 1 0
‐60‐40‐200
0 4 8 12
V IN1 (V)
Time (s)
‐60
‐10
0 4 8 12
V IN2 (V)
Time (s)
‐60
‐40
‐20
0
0 4 8 12
V OUT(V)
Time (s)
NAND NOR
Truth Table
1525th Sept 2013
Ring Oscillator
VDD (V) Frequency (kHz)Sim Expt
Amplitude(V)Sim Expt
-60 16.7 0.365 25.6 16.0
-40 5.1 0.137 8.3 7.0
-40-35-30-25-20-15-10-50
0 5 10 15 20
V O
UT
(V)
Time (ms)
VDD -60 VDD -40
1625th Sept 2013
Environmental testing
Dry vs. damp airIncrease in IoffMobility and VT unaffectedEffect of water recoverable
e.g. by exposing sample to vacuum.
Vacuum vs. dry airSmall VT shiftApparently stable performance over weeks if stored in dry conditions.
Lamination and in-line encapsulation (e.g. TPGDA followed by SiOx) tried• good working devices.
-40 -20 0 20
1E-10
1E-8
1E-6
1E-4Vac
Vg(V)
I d(A
)
Dry air
DNTT with acrylate/PS insulator
Dry air
-40 -20 0 20
1E-10
1E-8
1E-6
1E-4
RH 50%
Vg(V)I d(
A)
1725th Sept 2013
Mechanical testing
Polymer dielectric AlOx dielectric
1825th Sept 2013 18
Progress so far…..
1) Process parameters in R2R environment – building and testing transistors Plastic flexible substrates (125 µm thick PEN
substrate) Al gate electrode Improved in-line curing method (10 m/min
webspeed) Interface buffer layer (evaporated PS thin layer) Low hysteresis in devices and good stability Very high yield
1925th Sept 2013 19
Progress so far……2) Circuit design tailored for the properties achievable
with this manufacturing route Transistor characteristics modelled
3) Materials (semiconductor and gate insulator layer) developed for this manufacturing route New SC synthesised, more under development Tried new insulator materials
4) Robustness of final devices Strain to failure much greater than devices with ceramic insulators Device mobility stable on bending Devices can survive lamination
5) Patterning processes Favoured options for SC and insulator layers under development
2025th Sept 2013 20
Acknowledgements
BangorProf Martin TaylorMr Aled WilliamsMr Eifion Patchett
OxfordDr Gamal AbbasMr Ziqian DingDr Kanad Mallik
LeedsProf Long LinDr Weidong He
ManchesterProf Steve YeatesDr John Morrison