MEMS-BASED
MEMS BASED FLUID FLOW
      SENSOR




           by Jean P. Cortes
                   P
Outline

  Senior Design
  S i D i #1
     Objective
     Applications
     Design
          Flow
          Pressure/Vacuu...
Senior design #1
Design and evaluate a MEMS sensor with
capabilities in measuring parameters, such as:


   • Pressure/vac...
Applications
   Aerospace,
   Aerospace velocity measurements
  Medical, respirators for pre-matured born, &
diagnostics o...
Current technology: Bulky instruments




 Flow meter that uses a mechanical principle.   Bourdon Gage that uses a mechani...
Hotwire principle: Low-power Micro-scale capability


                                             B)
A)

     Flow




  ...
Example of MAF in a car




 Rw= Rref [1 + TCR (Tw-Tref)]




      Schematic representation of the Hotwire anemometry.
Pressure measurement
                                              R= impingement Rate




                               ...
Design - flow (1)




                                        250 μm
3.5 mm




                      the three resistor f...
Design – pressure (1)
                              Small heater




8mm




                                  1.5 mm


  ...
Fabrication of Al-based sensor

    Wafer
    Wf                         Cleaning the processed samples




 Piranha clean...
Fabrication of Ni/Cr based sensor


   Glass




   Ni/Cr
 deposition




 PR, UV-light,
     UV light,
  developing




 ...
Fabrication summary
                                          Hot Wire Principle


                   Flow                ...
Testing



                                            Vacuum Chamber and probes.




“Special” probe station with sensor ...
Results

                                                                                                Resistance vs. Pr...
Cost
                        Total Cost for making HOT MEMS
                                              HOT-MEMS


     ...
Conclusion

 A hot wire based flow and pressure sensor was designed
   hot-wire
and fabricated
 A single element hotwire w...
Acknowledgements

  D Mh
  Dr. Mohamed-Ali H
            d Ali Hasan ( d i   )
                        (advisor)
  Dr. Asg...
THAT’S ALL FOLKS!
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Senior Design#2 Cortes

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Senior Design#2 Cortes

  1. 1. MEMS-BASED MEMS BASED FLUID FLOW SENSOR by Jean P. Cortes P
  2. 2. Outline Senior Design S i D i #1 Objective Applications Design Flow Pressure/Vacuum Senior Design #2 Fabrication approaches Testing Pressure/Vacuum sensor Micro gears. gears Summary
  3. 3. Senior design #1 Design and evaluate a MEMS sensor with capabilities in measuring parameters, such as: • Pressure/vacuum • Fluid Flow rates • Velocity/direction based on thermal convection.
  4. 4. Applications Aerospace, Aerospace velocity measurements Medical, respirators for pre-matured born, & diagnostics of asthmatic attacks Automotive industry, Education, Education related experiments Semiconductor industry, Control of home environment environment,
  5. 5. Current technology: Bulky instruments Flow meter that uses a mechanical principle. Bourdon Gage that uses a mechanical principle.
  6. 6. Hotwire principle: Low-power Micro-scale capability B) A) Flow HEATER Rw= Rref [1 + TCR (Tw-Tref)] A) Hotwire: flow rate depends on the loss of heat at the heater B) H t i anemometry: fl Hotwire t flow rates and di t d direction can b measured. ti be d For flow measurement one or three elements can be used.
  7. 7. Example of MAF in a car Rw= Rref [1 + TCR (Tw-Tref)] Schematic representation of the Hotwire anemometry.
  8. 8. Pressure measurement R= impingement Rate P Vacuum Chamber Heater Pumping Gas Molecules Schematic representation of the application to measure pressure. For pressure measurement one element is needed.
  9. 9. Design - flow (1) 250 μm 3.5 mm the three resistor for flow measurement.
  10. 10. Design – pressure (1) Small heater 8mm 1.5 mm Large heater 1.5 mm Fast response Miniture Economical Low power consumption less thermal mass More accurate 2 mm
  11. 11. Fabrication of Al-based sensor Wafer Wf Cleaning the processed samples Piranha cleaning Pi hl i and Oxidation Al- deposition Spin Coater used for PR PR, UV-light, developing PR strip Al- Al etching
  12. 12. Fabrication of Ni/Cr based sensor Glass Ni/Cr deposition PR, UV-light, UV light, developing Nichrome PR strip etching
  13. 13. Fabrication summary Hot Wire Principle Flow Pressure Magnitude Direction Vacuum Nichrome Al Nichrome RAl_large = 15 Ω RNiCr = 53 kΩ RNiCr small heater = 7.8 kΩ large NiCr_small_heater RAl_small = 18 Ω RNiCr_small_detectors = 80 Ω RNiCr_small = 7 kΩ RAl_large_2 = 55 Ω RNiCr_large_heater = 3 kΩ RNiCr large detectors = 50 Ω NiCr_large_detectors t = 500 Å of thickness on glass TCR = 120 ppm/oC This t affects TCR!
  14. 14. Testing Vacuum Chamber and probes. “Special” probe station with sensor on it Dr. Hashmi on the probe station Vacuum Chamber and probes.
  15. 15. Results Resistance vs. Pressure Resistance vs Pressure 0.135 80.0 0.134 75.0 70.0 0.133 Resistan (Ohm) Resistance… Resistance… Resistance (Ohm) 65.0 0.132 nce 60.0 0.131 ( 55.0 0.130 50.0 0.129 45.0 0.128 R 40.0 0.127 20 70 120 170 220 0 0.02 0.04 0.06 0.08 0.1 Pressure (mTorr) Pressure (mTorr) Al-small sensor: P goes down R goes up
  16. 16. Cost Total Cost for making HOT MEMS HOT-MEMS Total Tooling Total Labor Manufacturing Operation Cost cost Cost/Wafer cost Cleaning $21.00 $2.50 $23.50 $0.94 Oxidation $23.00 $2.50 $25.50 $0.51 Metal Deposition $260.00 $2.50 $262.50 $17.50 Mask creation $35.00 $50.00 $85.00 $3.74 Photolithography $25.80 $5.00 $30.80 $30.80 Metal Etch $4.20 $2.50 $6.70 $6.70 Dicing $10.50 $5.00 $15.60 $15.50 Total $369.50 $70.00 $439.60 *$75.69 1800 devices…….so the final price is ~ $ 0.045 • 6‘’ wafer
  17. 17. Conclusion A hot wire based flow and pressure sensor was designed hot-wire and fabricated A single element hotwire was used for pressure measurement A three component: hotwire + 2 sensors was used for flow measurement Two style of sensors were fabricated: Large and small Two materials system were used: Al and NiCr Testing showed considerable change in resistance with change in pressure
  18. 18. Acknowledgements D Mh Dr. Mohamed-Ali H d Ali Hasan ( d i ) (advisor) Dr. Asghar Hashmi Mr. John Hudak Tanya Dias y Dr. Terry Xu
  19. 19. THAT’S ALL FOLKS!

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