Design for Printability From Device to Circuit for Flexible Electronics Tsung-Ching (Jim) Huang Tim Cheng February 10th 2007

2 Outline Introduction Introduction Motivation – Why design with flexible electronics Motivation – Why design with flexible electronics Limitation – What difference from Si MOFET circuit design Limitation – What difference from Si MOFET circuit design  A-Si:H TFT  Organic TFT Robust Circuit Design for Flexible Electronics Robust Circuit Design for Flexible Electronics A-Si:H TFT A-Si:H TFT  Robust building blocks Organic TFT Organic TFT  Cell library design  Printable circuit layout

3 Why Design with Flexible Electronics Poly IC Polymer Vision Plastic LogicASU U. Tokyo

4 What Differences from Si MOFET Circuit Design Si MOFET A-Si:H TFT Organic TFT Process Temperature 1000 °C 200 °C < 100 °C ProcessTechnology Photolithography multi-layers w/via Photolithography Multi-layer w/via Roll-to-Roll & Ink-Jet w/o via Design Rule <= 90 nm 20 μm 50 μm SubstrateWaferGlass/Plastic Plastic/Metal Foil Device Type N-type & P-type N-typeP-type Mobility 1500 cm 2 /Vs 1 cm 2 /Vs 0.5 cm 2 /Vs Cost/AreaHighMediumLow LifetimeYearsMonthsDays

5 Outline Introduction Introduction Motivation – Why design with flexible electronics Motivation – Why design with flexible electronics Limitation – What difference from Si MOFET circuit design Limitation – What difference from Si MOFET circuit design  A-Si:H TFT  Organic TFT Robust Circuit Design for Flexible Electronics Robust Circuit Design for Flexible Electronics A-Si:H TFT A-Si:H TFT  Robust building blocks Organic TFT Organic TFT  Cell library design  Printable circuit layout

6 Pseudo-Complementary A-Si:H TFT Inverter

7 A-Si:H TFT Inverter Transfer Function ModelVDDVGGVSSN-TFT RPI (W50L5) 18 V V C-TFT RPI (W50L5) 18 V 21 V -2 V -2 V

8 Signal strength after propagation will diminish due to insufficient noise margin Insufficient for circuit design with a certain degree of complexity Output Reponses of N-TFT Inverter Chain

9 Output Reponses of C-TFT Inverter Chain Signal strength after propagation remains at the same level as input signal Sufficient for circuit design of higher complexity

10 Immunity to Threshold Voltage Variation V TH V TH ’ VGGVDDVSS 1.1 V 5.5 V 21 V 18 V -2 V

11 Compensation to Threshold Voltage Variation V TH V TH ’ VGGVDDVSS 1.1 V 5.5 V 29 V 18 V -2 V

12 Outline Introduction Introduction Motivation – Why design with flexible electronics Motivation – Why design with flexible electronics Limitation – What difference from Si MOFET circuit design Limitation – What difference from Si MOFET circuit design  A-Si:H TFT  Organic TFT Robust Circuit Design for Flexible Electronics Robust Circuit Design for Flexible Electronics A-Si:H TFT A-Si:H TFT  Robust building blocks Organic TFT Organic TFT  Cell library design  Printable circuit layout

13 ~ k Ω ~ pF Ref: M. Fadlallah et al, Plastic Logic, J. Applied Physics 2006 Published OTFT Model Top Gate Bottom Contact

14 Printed Passive Component Ref: D. Radinger et al, J. Electron Device ‘04 Physical dimension for high-impedance resistance: 1KΩ  2mm x 1mm (190ºC, 1-layer) 50 μm drop size Resistance Capacitance Ink-jetted resistance normally can have much higher value than standard clean-room process High impedance resistance can be beneficial in implementing pseudo-complementary design

15 Pseudo-Complementary OTFT Inverter Ratio-less LogicModelVDDVSSVGGR AMI 0.6 μm 3.3 V 0 V -1 V 1 k Ω PMOS together with necessary series resistance is used for OTFT equivalent model

16 Inverter Layout 1 Unit = 50 μm 32 Units 46 Units

17 Output Response to Threshold Voltage Variation PC-OTFT exhibits robustness again V TH variation due to electrical or chemical degradation

18 Output Response of Inverter Chain Signal propagation will not diminish in PC-OTFT inverter design because of ratio-less design After 10-stage signal propagation, ordinary OTFT inverter can not generate the same signal strength

19 2-Input NAND Layout 85 Units79 Units

20 3-Input NAND Layout 115 Units 90 Units

21 2-Input NOR Layout 79 Units61 Units

22 PC-OTFT D Flip-Flop Output Response D-FF composed of PC-OTFT NAND gates exhibits good noise-margin in output response

23 2-Bit ROM Layout 89 Units 79 Units Ex1. Input [ ]  Output [ ] Ex2. Input [ ]  Output [ ]

24 Summary Flexible electronics technology is now emerging and more commercial applications will become available Flexible electronics technology is now emerging and more commercial applications will become available Low-cost, bendable, thin-film, and light-weight properties are highly desirable in consumer electronics Low-cost, bendable, thin-film, and light-weight properties are highly desirable in consumer electronics Circuit reliability and lifetime remain to be the biggest challenges to make wide use and market penetration Circuit reliability and lifetime remain to be the biggest challenges to make wide use and market penetration Novel circuit building blocks and printable layout are demonstrated to extend circuit lifetime Novel circuit building blocks and printable layout are demonstrated to extend circuit lifetime Significant innovations in material/device/design/testing area are still required Significant innovations in material/device/design/testing area are still required

25 Q & A Thank you for your attention !!