Thermal Actuation, A Suitable Mechanism for High Frequency Electromechanical Resonators

120 Pages·2013·10.8 MB·English

Ultimate MEMS Sensors
(Resonant)

IEEE Sensors 2013 Tutorial Session 1: Novel Trends in
Sensing
Siavash Pourkamali

Department of Electrical Engineering
University of Texas at Dallas

November 3rd, 2013
1
What is a MEMS Resonator?
Scaling Guitar Strings
Guitar String
dB
-72
e
d -74
u Low Q
t
i
l
p -76
m
A
-78
. High Q
b
i
V
-80
5 5.02 5.04 5.06
110 Hz Freq.
Frequency (MHz)
Vibrating “A”
String (110 Hz)
Stiffness
Freq. Equation: 1st mode Out of plane
L = 100m, W = 20m Flexural vibration
1 k
f  r t = 9m, g = 0.5m
o
2 m
r
Guitar
Freq.
Mass
2
Piezoelectric MEMS Resonators
 Piezoelectric Actuation
Applied electrical field
Finite Element Modal Analysis of
a Piezo-Electric Resonator

Internal generation of

a mechanical force

Complex
Fabrication

AlN
B. Harrington, M. Shahmohammadi, and R. Abdolvand, “Toward Ultimate Performance in
GHz MEMS Resonators: Low Impedance and High Q,” IEEE MEMS 2010
3
Electrostatic MEMS Resonators
+ -
+ -
+ -
F F
+ -
+ -
+ -
d
V
 Actuation:  Read-out:
2 dC
V  A
0 i  V
F 
o
2 dt
2d
Pourkamali et al “Low-Impedance VHF and UHF Capacitive Silicon Bulk Acoustic
Wave Resonators-Part I: Concept, IEEE transaction on electron devices
4
Micro-Resonator Transduction
 Common Micro-Resonator Transduction
Mechanisms:

c
i
C
r
t
a
c
p
e
a
l
c e
i o
t
z
i
v e
e
i
P

Capacitive Silicon Bulk Acoustic 1GHz AlN on Silicon Piezoelectric
Wave Resonator1 Resonator2
1S. Pourkamali, Z Hao, and F Ayazi, VHF Single Crystal Silicon Capacitive Elliptic Bulk-Mode Disk Resonators—Part I:
Implementation and Characterization, JMEMS 2004.
2B. Harrington, M. Shahmohammadi, and R. Abdolvand, “Toward Ultimate Performance in GHz MEMS Resonators: Low
Impedance and High Q,” IEEE MEMS 2010
5
Thermal Actuation with
Piezo-Resistive Readout
 Thermal actuation:
L LT
L
 Piezoresistive Effect:
R  R
l l
F
6
Thermally Actuated Resonators
 Advantages
 Simplicity of fabrication
 Large actuation force
 Low operating voltage
 Robustness

 Disadvantage
 Power consumption
 Speed?
Usually known as slow actuators suitable for DC or very
low-frequency applications
7
Thermal Time Response
f = 6.5kHz
act
τ = 100µs → f = 10kHz
Thermal thermal
8
Thermal Time Response
f = 650kHz
act
τ = 100µs → f = 10kHz
Thermal thermal
9
Thermal Time Response
f = 65MHz
act
τ = 100µs → f = 10kHz
Thermal thermal
10