Transcript Temperature Sensitve Micro-electro

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
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
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 Young’s Modulus, E(T), and
the coefficient of thermal expansion,
a(T), of thin films (poly-Si, SiNx) at high
temperatures
Recent Progress
• More data (and more data) with current setup
• Error Analysis
• Modified the LabVIEW program for piecewise
a(T) analysis
• Obtained additional values for a(T) and E(T)
• Assisted Haruna with her thesis
Setup: MACIS
CCD camera
beam splitter
collimated
light source
quartz plate
Al reflector
thermocouple
Si wafer
W-halogen lamp
and housing
quartz rod
sample
Theory: Imaging System
reflection from curved beam
I.
Apparent Beam Length, Lbeam
substrate
beam
II.
image of beam on camera
Theory: Beam Curvature
C
• Nomenclature
f
– radius of curvature, R
R
– apparent length, *Lbeam
q
– tip deflection, h
h
2q
A
– arc angle of beam, f
q
B
Lbeam
– half cone angle, q
*changes with focusing
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
f
R
q
b
h
2q
• Values: 0.5°~1.0°
Lbeam
q
Analysis: High Temperature
Exposure
• Assumption: beams experience fatigue
when exposed to high temperatures
• TMEMS heated to ~850°C for various
amounts of time
• Measured deflection after each run
• 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/m m)
0
5
10
15
20
0
5
15
30
50
0
-0.5
-4
-6
-9.5
0
0.0001
0.0008
0.001202
0.001906
Determining a(T)
• Two material properties approximate beam
curvature for both Poly-Si and SiO2
– Young’s Modulus (E)
– Coefficient of Thermal Expansion (a)
• Estimate E(T) from previous publications
• Find a best fit a(T) using a numerical model
Linear Approximation of aSi(T)
a
300
• Analyzed 5 different
ranges of data
• Averaged the aSi
value for each range
• Extrapolated to
50°C and 300°C
a
50
0
100
200
temperature (°C)
300
a(T) Values
7.00E-06
6.00E-06
5.38E-06
5.00E-06
Alpha (1/°C)
6.13E-06
Poly-Si
4.00E-06
3.00E-06
2.54E-06
2.00E-06
SiO2
1.00E-06
1.83E-06
5.00E-07
0.00E+00
0
200
400
600
Temperature (°C)
800
1000
1200
Conclusions
• The coefficient a was found for 50°C to
1000°C 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
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 a(T) through
more runs
• Prepare for final
presentation
Any Questions
For Us?