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Temperature Sensitive Micro-electro-mechanical Systems (Part II)

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Trend: as time at 850 C increased, deflection becomes more negative. High Temperature Exposure. D. time (min) total time (min) deflection. m. m) curvature (1 ... – PowerPoint PPT presentation

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Title: Temperature Sensitive Micro-electro-mechanical Systems (Part II)


1
Temperature Sensitive Micro-electro-mechanical
Systems (Part II)
  • Amy Kumpel
  • Richard Lathrop
  • John Slanina
  • Haruna Tada
  • featuring MACIS
  • 16 July 1999
  • Tufts University
  • TAMPL REU

2
Overview
  • Brief review and progress report
  • Basic theory and setup
  • Imaging system, beam curvature
  • System Analysis
  • Incident light angle
  • High temperature exposure
  • E(T) and a(T) values
  • Conclusion and Future work

3
Brief Review of T-MEMS
  • Measurement and characterization
  • mechanical properties of micro-scale devices
  • thermal properties of device materials under high
    temperatures
  • Tri-layered Poly-Si and SiO2 cantilever beams

Determine Youngs Modulus, E(T), and the
coefficient of thermal expansion, ?(T), of thin
films (poly-Si, SiNx) at high temperatures
4
Recent Progress
  • More data (and more data) with current setup
  • Error Analysis
  • Modified the LabVIEW program for piecewise ?(T)
    analysis
  • Obtained additional values for ?(T) and E(T)
  • Assisted Haruna with her thesis

5
Setup MACIS
6
Theory Imaging System
Apparent Beam Length, Lbeam
7
Theory Beam Curvature
  • Nomenclature
  • radius of curvature, R
  • apparent length, Lbeam
  • tip deflection, h
  • half cone angle, q
  • arc angle of beam, f

changes with focusing
8
Analysis Tilt Angle (b)
C
  • Asymmetric data hints that the system is tilted
  • Angle b effects negative curvature values, but
    not positive
  • Adjust numerical program to compensate for b
  • Find b from experiments
  • Values 0.51.0

f
R
q
b
h
2q
q
Lbeam
9
Analysis High Temperature Exposure
  • Assumption beams experience fatigue when exposed
    to high temperatures
  • TMEMS heated to 850C for various amounts of
    time
  • Measured deflection after each run
  • Trend as time at 850C increased, deflection
    becomes more negative

10
High Temperature Exposure
D
time (min)
total time (min)
deflection
m
m)
curvature (1/
m
m)
(
0
0
0
0
5
5
-0.5
0.0001
10
15
-4
0.0008
15
30
-6
0.001202
20
50
-9.5
0.001906
11
Determining ?(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

12
Linear Approximation of aSi(T)
a300
  • Analyzed 5 different ranges of data
  • Averaged the aSi value for each range
  • Extrapolated to 50C and 300C

a50
100
0
200
300
temperature (C)
13
a(T) Values
Poly-Si
SiO2
14
Conclusions
  • The coefficient a was found for 50C to 1000C
    for both Poly-Si and SiO2
  • The experimental error in curvature was found
  • Angle b gives 3 for negative values
  • Variance in focusing gives 2 for all values

15
Future Work
  • Modify setup for Nitride beam analysis
  • Create x-y-z stage for easy movement of sample
  • Get more values for E(T) and ?(T) through more
    runs
  • Prepare for final presentation

16
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