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
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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)
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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
Any Questions
For Us?