1. Roll-to-Roll Manufacturing of Flexible Displays
Carl Taussig, Bob Cobene, Rich Elder, Warren Jackson, Mehrban Jam, Albert Jeans, Hao Luo, Ping Mei, Craig Perlov,
Hewlett-Packard Company, Palo Alto, CA
Frank Jeffrey, Marcia Almanza-Workman, Kelly Beacom, Steve Braymen, Bob Garcia, Jason Hauschildt, Han-Jun Kim, Ohseung Kwon, Don Larson,
Phicot Inc, Ames, IA

2. Outline Introduction Self-Aligned Imprint Lithography (SAIL)
Why we need paper-like displays
Self-Aligned Imprint Lithography (SAIL)
Benefits and challenges of roll-to-roll (R2R) manufacturing
SAIL basics
green manufacturing for green products
toolset for 1/3m wide line
world’s first R2R active matrix displays

3. Sustainability 1/3 waste is paper… of which 43% is print 36m tons/yr
Newspapers 12
Commercial
Packaging & other
print 7.35
And we waste more if we print.
Current and targetted printing markets generate millions of tons of waste in the US alone
landfill paper is a major greenhouse gas source, and
paper is one of the most water-intensive industries.
We must do better than this. Reflective color ePrint will be part of the solution.
Office 6.6
36m tons/yr
Standard mail 5.8
Millions of tons/year
US Paper & board disposal, 2005
US EPA
Magazines 2.5
Books 1.15
Directories 0.65

4. Macro-Trends Are Helping to Drive Electronic Paper
Mobile Internet
Clean Technology
Printed Electronics
Digital Media
*courtesy of Mike McCreary, E Ink

5. Electronic Publishing is a Multi-$B Addressable Market
A library in your hands
$100B- $300B annual publishing industry today, about the same as the whole current display industry*
Mobile electronic books have not previously succeeded because they lacked the attributes of paper: low cost, outdoor readability, light weight (low power), &mechanical toughness.
*courtesy of Mike McCreary, E Ink

6. Newspapers Need an Alternative to Paper
Paper newspaper subscriptions are dropping sharply
12 hour delay in receiving news
newest generations of people are on-line much more
increased sensitivity to ecology issues
Newspaper profitability is under pressure as a result
increasing energy costs
On-line subscriptions are growing but it takes on-line subscribers to make up for one lost paper subscription*
Digital distribution enables personalization
Geographic localization enhanced
Individually targeted content and advertising
A paper-like reader appliance is needed
Low cost, portable, daylight readable, mechanically tough
*courtesy of Mike McCreary, E Ink

7. Paper Newspapers and the Environment
OIL
OIL
OIL
OIL
OIL
OIL
OIL
OIL
OIL
½ ton of trees are required to produce the 1/5 ton of paper per subscription per year
Paper accounts for about 1/5 of the worldwide harvest of trees
very energy intensive process---plup and paper are the 5th largest industrial consumer of energy
more water to produce a ton of product than any other industry
accounts for 40% of our municipal waste (only ½ is paper packaging)
and paper use has grown 6X in the last 50 years and double in the last 30 years
Germany and Europe are leading efforts for recycled paper, US uses 1/3 of paper in the world
1/5 ton per subscription per year
OIL
*courtesy of Mike McCreary, E Ink

8. Economic Reasons to Move From Paper Newspapers
Newspapers could eliminate $27M (~38%) from its variable budget by moving away from printed newspapers
But it will be critical to keep subscriptions and advertising rates high with electronic newspapers
Composite Newspaper Business Profile*
revenue includes 15.8M paid circulation plus $3.9 online ad revenue
100,000 Circulation
$83.9M Revenue
$72.1M Total Cost
~10% Profit
*Published by Bill Richards (former NY Times and Washington Post reporter)
*courtesy of Mike McCreary, E Ink

9. Outline Introduction Self-Aligned Imprint Lithography (SAIL)
Why we need paper-like displays
Self-Aligned Imprint Lithography (SAIL)
Benefits and challenges of roll-to-roll (R2R) manufacturing
SAIL basics
green manufacturing for green products
toolset for 1/3m wide line
world’s first R2R active matrix displays

10. Challenges & Benefits of R2R Electronics Fabrication
Lower substrate cost
Lower process temperature
Steady state processing: high-throughput, high-yield
Defect repair
Lower cleanroom requirements
patterning
Cheaper equipment - better scaling?
Limited equipment available – no previous generation

11. Imprint Lithography is the Best Choice for R2R Patterning
Photolithography
Imprint lithography
Inkjet
Physical mask
Laser ablation
Throughput
Moderate: limited by step & repeat / stitching
High: > 5 meters/min
Low
Limited only by deposition
Resolution
Limited by substrate flatness ~10μ
100nm demonstrated
>10μ
10μ -100μ
~10μ
Alignment
Self alignment possible
External sensor required
poor
Issues
Scaling to large areas costly
New technology
Materials must be jettable
Cleaning, particles
Thermal effects, selectivity

12. Conventional Photo-Lith
a R2R Process for Manufacturing Active Matrix Backplanes Based on Plasma Processing and Self-Aligned Imprint Lithography
Vacuum deposition of metals, dielectrics, & semiconductors 5μ
Multiple mask levels imprinted as single 3D structure
Patterning completed w/ wet & dry processes
deposition
imprint
etch
Conventional Photo-Lith
SAIL
deposit
spin resist
align/expose
develop
strip/clean
etch
deposit
etch
imprint
mask

13. Iowa Thin Film Technologies is now PowerFilm Solar

14. Basic Imprint Lithography Process
1: coated substrate
1μm
Pixel speed depends linearly on mobility but inversely with the square of channel length
2: coat with polymer
3: emboss
~40nm lines on 50μ polyimide
4: cure with UV
20 m 1 2 3
5: release
Multilevel structures on flex at 5m/min
6: etch
4 levels in 0.5 μ step heights

15. SAIL: Self-Aligned Imprint Lithography
Photolithography
SAIL
Process induced distortion of 200ppm results in 20μ misalignment over 10cm
Multiple masking and alignment steps required
Different mask used to pattern each layer
SAIL encodes multiple patterns and alignments into thickness modulations of a monolithic masking structure
Single mask used to pattern all the layers multiple times
No misalignment because mask distorts with substrate

16. SAIL backplane: patterning process flow
Disassemble array one layer at a time to expose structure. Begin by removing top metal
Next remove contact layer to expose channel semiconductor
Finally remove gate dielectric to expose gate lines that were isolated by the undercut
Remove remaining polymer to expose completed backplane
Then remove semiconductor to expose gate dielectric
Etch top metal and contact layer to define TFT channel
Etch exposed stack all the way to the substrate undercutting the bottom metal in the thin regions to isolate the gate lines and the TFTs
Etch the polymer down to expose the layers covering the gate lines
Etch through top metal and (optionally) other layers to form crossovers
Etch polymer a second time to expose area covering TFT channel
Imprint mask on TFT stack consisting of
Top metal
Contact layer (optional)
Semiconductor
Dielectric
Bottom metal
Process produces complete backplane:
TFT
Pixel electrode
Data line
Crossover
Gate line

17. SAIL solves alignment problem & saves money
R2R SAIL
R2R photolith (AGI)
Multiple
photoresist applications
dominate photolithography
process materials costs
cost per ft2
Cost of Patterning
Backplane materials costs for R2R photolith & SAIL

18. Green manufacturing for a green product
Less is better: 50μm thick plastic vs. 0.7mm thick glass
Less process materials: removal of photolith reduces process consumables
Energy costs:
transients involved in batch consume energy; steady state is more efficient
Reduced clean room requirements:
Smaller equipment footprint

19. The web rolled on the core is its own clean room
HEPA filter
Ambient Process
Vacuum Process

20. Equipment footprint comparison between R2R and flat panel
Gen10 cluster tool
330mm imprint system

21. Patterning scaling: R2R imprinter compared to panel stepper
comparison made at equal throughput
Scaling similar for R2R and panel; cost much lower for R2R

22. PECVD Scaling: R2R photovoltaic compared to panel
comparison made at equal throughput
Again; scaling similar for R2R and panel; cost much lower for R2R

23. Performance of Full-SAIL a-Si TFTs
Full SAIL TFTs with thinner dielectrics have greatly improved performance
on-off ratio > 107
100μA on-current
mobility from linear portion of transfer curve as high as 0.8 cm2/V/S
near linear scaling of Ion vs 1/L to L~2μm
Channel Length [μm]
Mobility [cm2/V/S]
1.E 0
1.E-3
1.E-2
1.E-1
1.E 1
1.E 2
W=100um Vsd=10.1V
1.E-14
1.E-13
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
-10 10 20 30 40
Vg(V)
Isd/(W/L) (A)
W [μm] L [μm]
is shown as a function L in Figure

24. SAIL Backplane on flexible substrate
Initial display demonstrators
World’s first active matrix display made exclusively with R2R processes (including E Ink Front Plane)
SAIL Backplane on flexible substrate

25. Yield Improvements: Pareto process at work
Process Step
Severity
Thin film deposition
Shunt defects
1/mm2
Stress control
unstable
Particle generation
low
Imprinting
Master defects
Stamp defects
med
Imprint process
Etching
Endpoint control
Process design
Device test
Contact liquefaction
Probing errors/damage
Process flow
A bubble defect, voids are formed by insufficient volume of photopolymer to fill mold
pinhole defect in metal caused by etchant diffusing through pinhole in oxide
A crack defect typically results from imbalanced deposition stress
Tenting defect formed by particle between stamp and substrate at imprinting time or by void in stamp
Nonuniform imprinting results in premature mask erosion and feature loss
Bridging caused by breakage of imprint stamp in narrow (~2u) regions

26. 13” production solar cell deposition
R2R tool development
13” production solar cell deposition
13” wet etcher
13” imprinter
4” imprinter
10” drum PECVD
13” RIE
2005
2008
2007
2006
2009

27. Next steps towards commercialization
September 22, 2008 PowerFilm announced that it has taken a license to the SAIL technology
October 6th, 2008 PowerFilm announced it has won a $1.4M / year cooperative agreement from the U.S. Army for development of a 'self powered flexible display' . HP Labs and PowerFilm will collaborate on the contract.
PowerFilm Solar has created Phicot as a subsidiary to commercialize the technology

28. Acknowledgements
The authors gratefully acknowledge the support of their collaborators and sponsors --
FlexTech Alliance - contract RFP04-112F
ARL contract W911NF
E Ink Corporation
ASU Flexible Display Center