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Ph.D. Presentation
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Ph.D. Presentation
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Ph.D. Presentation
Ph.D. Presentation
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Ph.D. Presentation
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Ph.D. Presentation

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My Ph.D. project was presented at the Technical University of Denmark the 16th of April 2010.

My Ph.D. project was presented at the Technical University of Denmark the 16th of April 2010.

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  • 1. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Piezoelectric MEMS Accelerometer - PiMEMS Christian Gammeltoft Hindrichsen Supervisor: Professor, Erik V. Thomsen
  • 2. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion
  • 3. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Piezoelectric Accelerometer What is piezoelectricity and how does an accelerometer work?
  • 4. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Piezoelectric effect http://electronicdesign.com/
  • 5. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Accelerometer operating in bending mode MEMS springs: Cantilever Piezoelectric V Plate acceleration F = m·a Mass Bridge Spring Fixed frame Membrane
  • 6. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Motivation Why use MEMS and what is state-of-the-art?
  • 7. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Applications 1 mm 100 μm 10 μm 1 μm 100 nm Bulk PZT Thick Film PZT Thin Film Nanotech
  • 8. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Accelerometer market Measurement and control Piezoelectric MEMS Capacitive Performance (bulk micromachined) MEMS Piezoelectric Movement monitoring and event detection MEMS Capacitive (surface micromachined) Special applications: Piezoresistive 1 10 100 1000 Optical Price [$] Servo
  • 9. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Smaller Lower fabrication costs Higher integration Comparable performance
  • 10. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion State-of-the-art Kunz et al. (2001) Yu et al. (2003) Resonance Voltage Charge Chip frequency sensitivity Sensitivity size [kHz] [mV/g] [pC/g] [mm] Yu et al. 22 0.47 0.19 4x4 Kunz et al. 0.5 - 22 7x7 Beeby et al. 7.6 - 16 12 x 12 Beeby et al. (2000)
  • 11. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Goal The Toolbox The MEMS Accelerometer Integrate PZT thick film and MEMS Design, model, fabricate, characterize an accelerometer: Design process flow • Resonance frequency > 20 kHz Optimize cleanroom processes • Chip size in the mm-range • Sensitivity as high as possible
  • 12. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Design What is special about this accelerometer?
  • 13. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Square Design Resonance Voltage Charge Chip frequency sensitivity Sensitivity size [kHz] [mV/g] [pC/g] [mm] 12.5 0.36 0.04 10 x 10 Hindrichsen et al., Analytical Model of a PZT Thick Film Triaxial Accelerometer for Optimum Design, IEEE Sensors Journal (2009) Hindrichsen et al., Triaxial MEMS Accelerometer with PZT Thick Film, Journal of Electroceramics (2010)
  • 14. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Circular Design Electrodes Dimensions: PZT Membrane radius: 1.8 mm Membrane Membrane Seismic mass: 6 mg Mass Silicon membrane: 20 μm z PZT thickness: 9 – 27 μm x x y x
  • 15. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Sensitivity-Resonance Balance Resonance frequency > 20 kHz Chip size in the mm-range Sensitivity as high as possible >1 mm 10 m m Membrane > 30 μm: thick film Membrane < 10 μm: thin film Hindrichsen et al., Advantages of PZT Thick Film for MEMS Sensors , Sensors and Actuators A (in review)
  • 16. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Proposal for Triaxial Design FEM model y z y x x
  • 17. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Fabrication How can we integrate PZT thick film and MEMS?
  • 18. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Oxidation Screen printing UV lithografy Plasma etch Metal evaporation Lou-Møller et al., Screen-printed piezoceramic thick films for miniturised devices, Journal of Electroceramics (2007)
  • 19. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Process Flow Silicon substrate PZT thick film Bottom electrode Silicon oxide Top electrode Fragile substrate High temperature sintering Diffusion barrier layer Adhesion Thin film electrodes Wafer scale production Reproducibility
  • 20. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Diffusion barrier layer (DBL) 31-mode PZT 33-mode DBL Si
  • 21. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Stylus Profiler Atomic Force Microscopy PZT Silicon Hindrichsen et al., Investigation of Top/Bottom Electrode and Diffusion Barrier Layer for PZT Thick Film MEMS Sensors , Ferroelectrics (2009)
  • 22. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Top electrode Lift-off process 20 μm thick photo resist No sonication
  • 23. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion 58 accelerometers 4 mask fabrication process Price estimation: 70 DKK per accelerometer Hindrichsen et al., Circular Piezoelectric Accelerometer for High Band Width Application, IEEE Sensor Conference (2009)
  • 24. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Packaging LTCC on front side Pyrex wafer on backside
  • 25. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Characterization How is the accelerometer performing?
  • 26. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Accelerometer Specifications Capacitance [pF] Couplings coefficient [%] Impedance analyzer Resonance frequency [kHz] Sensitivity [pC/g] Shaker setup Quality factor Range [g] PZT thickness: 9 μm – 27 μm Dielectric, mechanical & piezoelectric properties
  • 27. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Impedance Sweep (dielectric, mechanical, piezoelectric)
  • 28. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Impedance Sweep (dielectric, mechanical, piezoelectric)
  • 29. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Coupling Coefficient (dielectric, mechanical, piezoelectric)
  • 30. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Shaker Setup Charge Amplifier LabView Accelerometer Shaker Wave Generator
  • 31. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Frequency Sweep (mechanical) Quality factor: 150 - 250
  • 32. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Resonance Frequency (mechanical)
  • 33. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Charge Sensitivity (mechanical, piezoelectric)
  • 34. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Range and Linearity (dielectric, mechanical, piezoelectric)
  • 35. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Screen printed PZT on membranes with thicknesses down to 10 μm Designed process flow Diffusion barrier layer & thin film top electrode Detailed analytical and FEM model Square and circular design for triaxial sensing presented Accelerometers are fabricated with high yield Performance: Resonance Voltage Charge Capacitance frequency sensitivity Sensitivity [nF] [kHz] [mV/g] [pC/g] Yu et al. 22 0.47 0.19 2 Measured 25.8 0.28 0.46 1.6 Model 32.5 0.57 0.94 1.6
  • 36. Piezoelectric Accelerometer Motivation Design Fabrication Characterization Conclusion Thank you for your attention Acknowledgement Erik Thomsen, Thomas Pedersen, Christian Hansen, Jesper Olsen, Tobias, Jack Larsen, Johan Nagstrup, Ninia, Simon, Louise, Gustav, MEMS Applied Sensor Group, Rasmus Lou-Moller, Karsten Hansen, Ferroperm, Ole Hansen, Lars Kofoed , Danchip people, Kristian Hvass, Anne, ...

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