Plastic Logic at the 12th Microelectronics Academy

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Plastic Logic's Director of Process Engineering, Dr. Octavio Trovarelli gave an introduction to OTFTs and Plastic Logic's flexible display technology at the 12th Microelectronics Academy in Dresden.

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Plastic Logic at the 12th Microelectronics Academy

  1. 1. Organic Electronics –Introduction to OTFT & Plastic Logic’sFlexible Display TechnologyDr. Octavio Trovarelli | 12th Dresden Microelectronics Academy | September 7, 2012
  2. 2. Introduction to Organic Electronics Outline ● Organic Electronics – Key Milestones ● Principles of organic semiconductors and materials ● OTFT and properties ● Plastic Logic - Introduction ● Challenges in Establishing Volume Manufacturing ● Technical achievements and potential applications 12th Dresden Microelectronics Academy September 7, 2012 2
  3. 3. Organic Electronics – Some Key Milestones● First organic TFT demonstrated (1986): low mobility <10-4 cm2/Vs● First demonstration of clean field-effect mobilities within an order of magnitude to that of a-Si: pentacene (1995), poly-3- hexylthiophene (1997)Current status:● Mobilities of 0.1 – 1 cm2/Vs achievable now in a range of solution PARC processed OSCs (p-type & n-type)● Reliability comparable to a-Si (p-type)Demonstrators / Applications:● First demonstration of integration of OTFT backplane with e-paper (Lucent / E-Ink 1998) PolyIC● Demonstration of 13.56 MHz (non-standard) RFID tag (Philips, PolyIC 2007)● QQVGA of flexible OLED display driven by OTFT backplane (Sony 2007)● 2007: Announcements by Polymer Vision and Plastic Logic to commercialise OTFT technology in e-paper displays Sony 12th Dresden Microelectronics Academy September 7, 2012 3
  4. 4. Why Organic Electronics?Some advantages● Organic transistors can be manufactured at relative low-T compared to single-crystalline Si (>800°C) or a-Si:H (>200°C), and● On flexible plastic substrates (and even paper) on large scales!● Enabling novel products foldable, bendable, rollable, thin, ultra-light, robust…Comparison to conventional Si-based electronics● Basic operation of OTFTs and MOSFET have similarities and differences (see next pages)● Materials, device structures and performance are very different● Plastic circuits not expected to replace silicon but… … one should instead look for new and emerging applications where inorganic transistors cannot be used due to their mechanical properties or cost. 12th Dresden Microelectronics Academy September 7, 2012 4
  5. 5. Organic Material Characteristics ● Organic Semiconductors: formed by conjugated organic materials – alternating single and double bonds between covalently bound C- atoms ● Delocalised π-electrons provide both conduction and valence bands Example: Benzene poly (p-phenylene) t0 t1 + - - + Energy + - + - - - + + - + 4 t1 LUMO π* “conduction” band 2 t0 π “valence” band + + - 4 t1 - HOMO + Density of States H. SirringhausUnique attributes of organic semiconductors: ● Science: Low-dimensional, molecular semiconductors with strong electron – ion and electron - electron interactions ● Technology: Compatible with solution-processing and direct-write printing; low-T processing 12th Dresden Microelectronics Academy September 7, 2012 5
  6. 6. Examples of “p-type” Organic Semiconductors µ = 1-5 cm2/Vs µ = 0.1 cm2/Vs µ = 15-20 cm2/Vs µ = 0.6 cm2/Vs H. Sirringhaus 12th Dresden Microelectronics Academy September 7, 2012 6
  7. 7. Low-Temperature Solution Processing Challenges: ● Control of molecular self-assembly from solution ● Understanding of defects ● Effect of dynamic disorder on electronic properties S. Tretiak, LANL 12th Dresden Microelectronics Academy September 7, 2012 7
  8. 8. Organic Thin Film Transistors● Organic Transistors are Field-Effect-Transistors (FET)● Typical Structures: H. Klauk 12th Dresden Microelectronics Academy September 7, 2012 8
  9. 9. Organic Thin Film Transistors Typical material● Typical contacting for p-type OTFT: thicknesses: ~0.1µm ~1µm● Example of typical I-V characteristic curves of Pentacene-based p-type OTFT: H. Klauk 12th Dresden Microelectronics Academy September 7, 2012 9
  10. 10. Transport in Organic Semiconductors Polycrystalline PentaceneFactors influencing mobility in organic semiconductors: ● Overlapping degree of conjugated π-systems ● Chemical purity ● Neighbour molecules ● Degree of molecular order (crystallinity) ● Energy density and distribution of localized statesTypical values of mobilities of organic materials (RT): 10-5 – 10 cm2/VsComparison: channel carrier mobilities in FETPolycrystalline a-Si:H Poly-Si Crystalline Si Pentacene ~500 cm2/Vs (e-)0.1 – 1 cm2/Vs ~0.5 cm2/Vs >50 cm2/Vs ~200 cm2/Vs (h+) H. Klauk 12th Dresden Microelectronics Academy September 7, 2012 10
  11. 11. Mobility & Transistor Performance limitations Logic PolyIC OLED displays Sony A. Salleo Flexible E-paper displays Vsd I sd = W ⋅ µFET ⋅ Ci ⋅ (Vg − VT ) ⋅ LMaterial challenges: Plastic Logic ● High mobility ● Purity, stability in air, not toxic, solution processing ● Cost effective, high-volume availability, manufacturability ● Reliability: stable I_sat, V_th during product life-time 12th Dresden Microelectronics Academy September 7, 2012 11
  12. 12. OTFT – Basic Differences to MOSFET● OTFT: “intrinsic” semiconductor in the channel and in the S / D contact region● OTFTs operate in accumulation and not in inversion mode● No selective doping no p-n junctions as in Si-MOSFETs● “Shottky”-type barriers existing at the contacts: Example of p-type OTFT: barrier (ϕm >> EA) blocks e- injection from D contact to LUMO H. Klauk 12th Dresden Microelectronics Academy September 7, 2012 12
  13. 13. OTFT – Work Function Matching● In general, HOMO-LUMO energy difference is large only one carrier type can be efficiently injected / extracted● Difficulty of CMOS technology with organic materials H. Klauk p-type n-type Copper-Phthalocyanin F16CuPc (CuPc) Work function of Pentacene some metals (eV) Au 5.1 – 5.47 Pd 5.22 – 5.6 X = 3eV IP = 4.9eV Ca 2.87 X = 2.7eV X = 4.5eV IP = 4.8eV IP = 6.3eV 12th Dresden Microelectronics Academy September 7, 2012 13
  14. 14. Origins of Plastic LogicCambridge became a scientific epicentre for the field of plastic electronics:A research group of top scientists headed by Prof. Sir Richard Friend and Prof. HenningSirringhaus has a track record of world-leading innovations: ● Discovery of polymer electroluminescence in 1989 ● Discovery of polymer electroluminescence in 1989 ● First polymer FET (1988) ● First integration of polymer FET with polymer LED (1998) ● First polymer FET with mobility of 0.1 cm2/Vs (1999) ● Inkjet printing process for polymer FETs (2000) ● First n-type polymer FET (organic CMOS) (2005) ● First ambipolar light emitting transistor (2006) ● First ambipolar polymer FET with mobility > 2 cm2/Vs (2011) 12th Dresden Microelectronics Academy September 7, 2012 14
  15. 15. The Company Plastic Logic 12th Dresden Microelectronics Academy September 7, 2012 15
  16. 16. Plastic Electronics Technology● Uses plastic instead of traditional silicon semiconductor and glass● Fully industrialized flexible displays based on organic electronics● Enables a revolutionary design and form-factor Shatterproof, Thin, Large and Light Display 12th Dresden Microelectronics Academy September 7, 2012 16
  17. 17. Display Development History (Plastic Logic) 2002: 4x4 TFT 2003: 80x60 50 PPI 2004: 80x60 50PPI 2005: 80x60 100PPI Array2008: 1280x960 150PPI 2006: 800x600 100PPI 2005: 80x60 300PPI 2005: 80x60 10PPI 2011: 1920x1440 225PPI 2011: 75PPI Colour 2012: 75PPI Video (b/w & colour) 12th Dresden Microelectronics Academy September 7, 2012 17
  18. 18. Plastic Logic - Company History Technology Development10+ transistors 100+ transistors 1.2 M transistors Colour EPD 2.8 M transistors Research, Process Development and Manufacturing Cambridge Technology Dresden display factory Cambridge University Center translating research First plastic electronics Research in organic electronics into products factory in the world 12th Dresden Microelectronics Academy September 7, 2012 18
  19. 19. Backplane: OTFT, Pixel and Matrix Array Pixel Design Pixel Design (top-down view) (cross-section) Display Pixel Array (top-down view) Example: S2G2, S4G4, S4G3 pixels addressed 12th Dresden Microelectronics Academy September 7, 2012 19
  20. 20. Front plane: Electrophoretic Display Media ™ Principles of Operation ● Oppositely charged reflective submicron pigments are encapsulated in a clear liquid ● Particles move in opposite directions in an electric field ● Partial capsule imaging is possible enabling high resolution capability ● Bi-stable, turn the power off – the image stays! 12th Dresden Microelectronics Academy September 7, 2012 20
  21. 21. Establishing Volume Manufacturing 12th Dresden Microelectronics Academy September 7, 2012 21
  22. 22. Dresden – Center for Organic Electronics see also: http://www.oes-net.de/en/home.html 12th Dresden Microelectronics Academy September 7, 2012 22
  23. 23. Plastic Logic Dresden FAB – Timeline – Major Milestones● Groundbreaking May 2007● Fab and Office Buildings Completed January 2008● Clean Room Validation / handover April 2008● Equipment Move-in, Installation and Start April 2008 to August 2008● Process Installation and Development September 2008 to December 2009● Production ramp in 2010 12th Dresden Microelectronics Academy September 7, 2012 23
  24. 24. R&D and Production Set-Up Technology Transfer Cambridge R&D Prototype Line (14”) Cambridge R&D Prototype Line ● Proof of concepts ● Highly configurable process ● New designs in < 1 month ● 1” Chips to A4 displays ● R&D Engineers 12th Dresden Microelectronics Academy September 7, 2012 24
  25. 25. R&D and Production Set-Up Technology Transfer Dresden Factory (Gen 3.5) Dresden Gen. 3.5 Pilot and Production Facility ● Fully automated backplane manufacturing ● Qualified volume process ● Equipment development with suppliers ● Process and Test development ● Large scale reliability work ● Technology transfer ● Thousands of displays/week 12th Dresden Microelectronics Academy September 7, 2012 25
  26. 26. Competence in Organic and Printed Electronics Manufacturing of OTFTs ● World’s largest flexible OE display (10.7”) ● High density (1.2 m OTFTs per display) ● Large area (Gen 3.5 | 780 x 650 mm | ~11 m OTFTs per glass plate) ● Full scale (24/7) Development of OTFTs ● Process and stack development for the manufacture of flexible displays ● Material development with suppliers ● Strong IP position ● Unique tool development with suppliers Broad network ● Wide portfolio of co-operations with suppliers, universities and institutes 12th Dresden Microelectronics Academy September 7, 2012 26
  27. 27. Organic Electronic Volume Production Set-Up: ChallengesAdaptation of equipment from the pilot-line set up in Cambridge● From Lab to standard production equipment for flat panel Gen 3.5● Industrialization of new specified and developed equipment prototypesVerification of process specification for stable volume production● Size of the backplane differs by factor 10! impact on processesTest of new materials in volume production● Specifications to be developed● Selection and qualification of suppliersInstallation of production control and test concept● Test structures to be developed● Failure analysis to be developedIdentification of yield- and defects- key driversTraining, know how for a new team● with experience in silicon and volume production for new equipment, materials and process flows 12th Dresden Microelectronics Academy September 7, 2012 27
  28. 28. Process Differences have Consequences for Equipment The key differentiators of our technology for organic and flexible electronics are: ● Solution processing ● Direct-write fabrication techniques to avoid mask-alignment ● Combination of wet coating and dry patterning ● Low process temperatures to permit use of cheap flexible substrates Our key focus areas for equipment and process know how are: ● Printing, spraying and other deposition of organic and inorganic materials ● Cleaning and conditioning of the layers ● Laser processing for printable electronics We focus on the manufacturability of these processes such as: ● Reproducibility ● Homogeneity 12th Dresden Microelectronics Academy September 7, 2012 28
  29. 29. Equipment / Process Differences+ 400nm Layer thickness [nm] Equipment / process 1 Equipment / process 2- 400nm 12th Dresden Microelectronics Academy September 7, 2012 29
  30. 30. Process Learning & Development Printing process Year 1Thickness mean Year 2 Thickness mean Deposition process Year 1Thickness mean Year 2 Thickness mean 12th Dresden Microelectronics Academy September 7, 2012 30
  31. 31. OTFT On-Resistance Improvement Reduction of OTFT On-Resistance by factor of 5 over a year ● Always using the same materials and processes ● „Just“ optimising processing and handling conditionsOTFT Ron – Relative to current target 12th Dresden Microelectronics Academy September 7, 2012 31
  32. 32. Yield Enhancement Including Defect Density Improvement● Defect density analysis throughout all process steps● Factory and equipment design analysis● Optical inspectionswith defect analysis Very small Embedded Embedded Surface embedded particles residues particles 12th Dresden Microelectronics Academy September 7, 2012 32
  33. 33. Material Analysis and in-situ MeasurementsNew organic materials are normally still analyzed separately in a laboratoryProduction requires analysis of: ● Complex samples with layer stacks ● Thickness analysis of layers with similar composition or behaviour ● In-situ measurements in the production flow ● Local material analysis in µm areas Layer stacksState of the art Failure Analysis techniques for Si had to be developed again 12th Dresden Microelectronics Academy September 7, 2012 33
  34. 34. Display Testing and ReliabilityTest development for transistor and display parameters ● Definition of test specifications ● Electrical and Optical tests for production ● Test methods for OTFT and other characterisation structuresTesting includes handling and alignment of flexible displaysReliability test development for quality and lifetime behavior ● Accelerated test under different environmental conditions for lifetime projections ● Based on existing models for Si-based integrated circuits ● Parameters adapted to organic materials in terms of temperature sensitivities and reaction to cycling 12th Dresden Microelectronics Academy September 7, 2012 34
  35. 35. Reliability Testing Name Test PurposeThermo cycling TST Mechanical robustness & CTE mismatchHigh Temperature Storage HTS Storage of transport conditionsAdvance Humidity Storage AHS Stability against moisture ingressLow Temperature Storage LTS Storage of transport conditionsReal World Usage RWU Display use in non accelerated modeAdvance Humidity Operation AHO Accelerated operation at high humidityLow Temperature Operation LTO Accelerated operation at low temperatureAmbient Operation AO Accelerated operation at ambient conditionsSolar storage SOR Solar robustnessAltitude test ALT Pressure sensitivity 12th Dresden Microelectronics Academy September 7, 2012 35
  36. 36. Reliability Problems During the Development Phase Defects-driven fails Line outs during operation Equipment / Process-driven failsDelamination during climatic tests Dead pixels during operational stress Inhomogeneity during operational stress 12th Dresden Microelectronics Academy September 7, 2012 36
  37. 37. Display Qualification Achieved in 2011 12th Dresden Microelectronics Academy September 7, 2012 37
  38. 38. Technical Achievements 12th Dresden Microelectronics Academy September 7, 2012 38
  39. 39. Flexible, robust, thin, lightweight and daylight readable OTFT-based displays Transmissive display Ultrathin display Lightweight 12th Dresden Microelectronics Academy September 7, 2012 39
  40. 40. Plastic Logic’s Technology in Action ● Flexible Colour Plastic e-paper Display (LINK) ● Incredibly Robust Display: The Stomp Test! (LINK) ● Displays can be literally “cut” in half and they still work! (LINK) ● Demonstrator: Video-Rate Animation (LINK)… and many more at: http://www.youtube.com/plasticlogic 12th Dresden Microelectronics Academy September 7, 2012 40
  41. 41. 41World Class Leading Investors & Support Additionally, we also acknowledge financial support from the German “Federal Ministry of Education and Research“, grant number 13N10225. 12th Dresden Microelectronics Academy September 7, 2012 41
  42. 42. Thank You! Contact: Octavio.Trovarelli@plasticlogic.com www.plasticlogic.com Further enquires: info@plasticlogic.comFollow Plastic Logic!:Especial thanks to Henning Sirringhaus and Hagen Klauk for some of the illustrations used in this presentation 12th Dresden Microelectronics Academy September 7, 2012 42

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