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Micromachined Infrared Sensor Arrays on Flexible Polyimide Substrates

Micromachined Infrared Sensor Arrays on Flexible Polyimide Substrates

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Micromachined Infrared Sensor Arrays on Flexible Polyimide Substrates

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  1. Micromachined Infrared Sensor Arrays on Flexible Polyimide Substrates Aamer Mahmood, Shadi Dayeh, Donald P. Butler, and Zeynep Çelik-Butler Dept. of Electrical Engineering, University of Texas at Arlington Arlington, TX USA

  2. Outline • Why flexible substrates. • Microbolometers on flexible substrates. • Fabrication • Results • Conclusions.

  3. Advantages of Flexible Substrates • Conform to underlying object. • Batch fabrication potential for low cost. • Enable applications on complex geometries. • Multilayer construction. • Integrated electronics in the future (TFTs). • Large area electronics, reel-to-reel processing. • TFT’s, OLE Displays, flexible keyboards, etc. have been demonstrated.

  4. Some Examples of Flexible Microsensors Si islands containing micromachined pressure sensors and circuitry joined by a polyimide membrane:Y. Xu, Y.-C. Tai, A. Huang, and C.-M. Ho, “IC-Integrated flexible shear-stress sensor skin”, Solid State Sensor, Actuator and Microsystems Workshop, Hilton Head Island, South Carolina, June 2-6, 2002. Bolometers Directly on Kapton and Spin-on Polyimide 1x10 array made of 60x60 mm2 microbolometers Responsivity 103-104 V/W Detectivity 106-107 cmHz1/2/W A. Yaradanakul, Z. Celik-Butler, and D.P. Butler, IEEE Trans. on Electron Devices 49, 930 (2002).

  5. Microbolometer FabricationTrench Geometry YBCO Au Ti Ti Si3N4 PI2610 Al SrTiO3 Si3N4 PI5878 Si

  6. Microbolometer FabricationMesa Geometry 60x60 μm 2 after ashing sacrificial layer 40x40 μm 2 after ashing sacrificial layer YBCO PI2737 Au Ti Al SrTiO3 Si3N4 PI5878 Si

  7. Micromachined Infrared Microsensors on a Flexible Substrate A picture showing a part of our flexible skin and its silicon carrier. The flexible skin contains 384 infrared microsensors. A picture showing a two die flexible skin applied to the little finger.

  8. SEM Micrographs of 40x40 μm2 Microbolometers 1x10 array of infrared microbolometers (40x40 mm2) 3 micromachined infrared microbolometers (40x40 mm2) Coated with 40-nm-thick Au to eliminated charging

  9. I-V Characteristics DD7,10 (Mesa Geometry)

  10. W Temperature Coefficient of Resistance (TCR) 1b4 Trench Geometry

  11. Responsivity/Detectivity 1b4 (Trench Geometry)

  12. Responsivity/Detectivity DD15 (Mesa Geometry)

  13. Area scans of bolometersDevice 1b4 (Trench Geometry)

  14. Area scans of bolometersDevice DD15 (Mesa Geometry)

  15. Future Work • Encapsulate microbolometers in a vacuum cavity on the no strain plane with polyimide superstrate. • Integrate flow sensors and pressure/strain sensors to form a “sensitive skin”.

  16. Conclusions • Can fabricate micromachined infrared sensors on flexible polyimide substrates with performance similar to those fabricated directly on rigid Si substrates. • Can bend flexible substrate containing microbolometers over a 1.5 mm radius of curvature without any apparent damage. • Successful fabrication requires an emphasis on low temperature processing. • Future work involves vacuum packaging the microbolometers with a superstrate. Acknowledgement This work is based in part upon work supported by the NSF under grant ECS-0245612.