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Roll-to-Roll Manufacturing of Flexible Displays

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

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Roll-to-Roll Manufacturing of Flexible Displays

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  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 • 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 Newspapers 12 Commercial Packaging & other 47.7 print 7.35 Office 6.6 36m tons/yr Standard mail 5.8 Magazines 2.5 Millions of tons/year US Paper & board disposal, 2005 US EPA 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. A library in your hands Electronic Publishing is a Multi-$B Addressable Market • $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 50-100 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. OIL OIL OIL OIL OIL OIL OIL OIL OIL OIL OIL Paper Newspapers and the Environment OIL 1/5 ton per subscription per year *courtesy of Mike McCreary, E Ink

  8. 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 Economic Reasons to Move From Paper Newspapers Composite Newspaper Business Profile* 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 • 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

  11. Imprint Lithography is the Best Choice for R2R Patterning

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

  13. Iowa Thin Film Technologies is now PowerFilm Solar

  14. 1: coated substrate 2: coat with polymer 3: emboss 1μm 4: cure with UV 5: release 2 3 1 0 6: etch 20 m Basic Imprint Lithography Process Pixel speed depends linearly on mobility but inversely with the square of channel length ~40nm lines on 50μ polyimide Multilevel structures on flex at 5m/min 4 levels in 0.5 μ step heights

  15. SAIL: Self-Aligned Imprint Lithography 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 No misalignment because mask distorts with substrate Single mask used to pattern all the layers multiple times

  16. Disassemble array one layer at a time to expose structure. Begin by removing top metal Then remove semiconductor to expose gate dielectric Remove remaining polymer to expose completed backplane Next remove contact layer to expose channel semiconductor Etch polymer a second time to expose area covering TFT channel Etch through top metal and (optionally) other layers to form crossovers Etch the polymer down to expose the layers covering the gate lines Etch top metal and contact layer to define 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 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 Finally remove gate dielectric to expose gate lines that were isolated by the undercut SAIL backplane: patterning process flow

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

  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. W=100um Vsd=10.1V 1.E-05 1.E 1 1.E-06 1.E-07 W [μm] L [μm] 1.E 0 1.E-08 100.0 1.0 1.E-09 Isd/(W/L) (A) 100.0 2.0 Mobility [cm2/V/S] 100.0 5.0 1.E-10 1.E-1 100.0 10.0 1.E-11 100.0 20.0 1.E-12 100.0 50.0 1.E-2 100.0 100.0 1.E-13 1.E-14 -10 0 10 20 30 40 1.E-3 1.E 0 1.E 1 1.E 2 Vg(V) Channel Length [μm] 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 is shown as a function L in Figure 4.1.3.

  24. 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 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 Bridging caused by breakage of imprint stamp in narrow (~2u) regions Nonuniform imprinting results in premature mask erosion and feature loss

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

  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-08-2-0063 -- E Ink Corporation ASU Flexible Display Center

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