Temperature Sensitive Microelectromechanical Systems

1
Temperature Sensitive Micro-electro-mechanical
Systems

• Amy Kumpel
• Richard Lathrop
• John Slanina
• Haruna Tada
• Tufts University
• TAMPL REU 1999

2
Overview

• Background information of T-MEMS
• current project goals
• Experimental Setup
• recent modifications
• how it works
• Experimental Results
• imaging
• numerical model
• Conclusion and future work

3
An Introduction to T-MEMS

• Measurement and characterization
• mechanical properties of micro-scale devices
• thermal properties of device materials under high
  temperatures
• Application to rapid thermal processing (RTP)

4
Composition of T-MEMS

• Tri-layered cantilever beams
• 1.03 ?m SiO2, 0.54 mm poly-Si
• 0.19 ?m SiO2 (thin, protective coat)

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Composition of T-MEMS

• Tri-layered cantilever beams
• 1.03 ?m SiO2, 0.54 mm poly-Si
• 0.19 ?m SiO2 (thin, protective coat)

6
Fabrication Process

• Beams are processed at 840C
• initial experimental condition is room
  temperature
• Upward room temperature curvature
• due to differences in ?th of poly-Si and SiO2
  (beams bend downward when heated)
• Initial curvatures vary with material and/or
  deposition rate
• typical curvatures range from 5 to10 ?m for a
  100mm poly-Si beam

Poly-Si
SiO2
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Our Goals

• Modify the experimental setup to decrease system
  error
• Collect curvature data from poly-Si beams
• Determine Youngs Modulus, E(T), and the
  coefficient of thermal expansion, ?(T), of thin
  films (poly-Si, SiNx) at high temperatures
• Improve method for curve fitting and resolution
  analysis

8
Experimental Setup
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Modifications

• Fixed Mounting
• CCD camera, beam splitter, collimated light
  source
• Leveling
• all surfaces with mounting plates or rods
• the system is leveled to the Silicon wafer
  (sample)
• Alignment
• collimated light source to beam splitter
• CCD camera to beam splitter
• light source centered in the IMAQ image when
  aligned

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Experimental Setup with Modifications
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Experimental Procedure

• Center sample to CCD camera
• Heat T-MEMS (slowly) to 800C using W-halogen
  lamp then gradually cool to room temperature
• Save the beam image every 20-30 seconds during
  the run
• Set LabVIEW SCXI program to record temperature
  vs. time data

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Imaging Results
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Imaging Results
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Determining E(T) and ?(T)

• Two material properties approximate beam
  curvature for both Poly-Si and SiO2
• Youngs Modulus (E)
• Coefficient of Thermal Expansion (a)
• Estimate E(T) from previous publications
• Find a best fit ?(T) using a numerical model of
  the thin film poly-Si layer

15
Preliminary Results for a(T) of Poly-Si
Temperature (C)
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Conclusion

• Modified setup for increased accuracy
• Acquisition of data with new setup
• Used numerical method for determining the thermal
  properties

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Future Work

• Create x-y-z stage for easy movement of sample
• Take more data with new setup
• Modify numerical method for thermal properties

• Get more values for E(T) and ?(T)
• Modify LabVIEW programs
• Help Haruna with her thesis
• MACIS or MANTIS?

18
Any Questions
For Us?