UTD MEMS/NEMS Research Lab.
Metallic Nano Electro
Mechanically Actuated
Gripper and Tunable
Nano Photonic Device
Jeong-Bong (J-B.) Lee
Department of Electrical Engineering
The University of Texas at Dallas
Richardson, Texas
MiNDs (Micro/Nano Devices and Systems) Laboratory
mems.utdallas.edu
Objectives
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Nanoelectromechanical systems (NEMS)
– Possible to realize smaller mechanical, biological
and chemical systems
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Nano grippers
– Actuators for nano manipulation devices/systems
– Relatively large displacement with low actuation
voltages
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Tunable Nano Photonic Devices
– New functionalities unachievable with passive nano
photonic devices.
– Real-time, on-demand control can greatly enhance
the functionality of photonic devices and systems.
MiNDs (Micro/Nano Devices and Systems) Laboratory
mems.utdallas.edu
UTD’s Nano Tech Related Facilities
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UTD Clean Room
– 5,866 sq. ft. class 1,000 and 100
– Equipped with various processing and metrology
equipment including evaporators, sputters, RIE,
PECVD, LPCVD, mask aligners, e-beam lithography
system, SEM, AFM, ellipsometer, Flexus, etc.
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UTD’s Nano Research Facilities
– Dual beam FIB, XPS, TEM, Field Emission SEM w/
E0beam Lithography System, Ultra High Vacuum
Wafer Bonding System, Diamond coating CVD
system
MiNDs (Micro/Nano Devices and Systems) Laboratory
mems.utdallas.edu
Sub-µm Metallic Structures
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E-beam lithography
– Positive PR (e.g., PMMA)
•
Ideal for lift off.
– Negative PR (SU-8, UVN30)
•
Very small exposure dose
(~1 µC/cm2), a factor 100
times smaller dose (exp.
time)!
500 nm width/spacing and 500 nm thick gold comb-drive
MiNDs (Micro/Nano Devices and Systems) Laboratory
~400 nm width ~2 µm thick
SU-8 test structures
mems.utdallas.edu
Sub- µm Thermal Actuator
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Process
– Electron beam exposure for PMMA
– Electroplate nickel ~1 hr for 1 µm
– Removal of PMMA by oxygen RIE
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3:1 aspect
ratio 1
µm thick
PMMA
mold
Sub-micron thermal actuator
– Reproducible displacement results
• Type “A”: 370 nm by 146 mV
Hot arm w = 350 nm
LHOT=38 µm
MiNDs (Micro/Nano Devices and Systems) Laboratory
mems.utdallas.edu
Sub- µm Gripper
45um
1.5um
Line: 350 nm
Spacing
: 1150 nm
14.25 um
θ
4.5 um4.75 um 14.25 um
LFlex
5 um
LCold
1.6
Displacement [um]
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
5
10
15
20
25
30
Current [mA]
MiNDs (Micro/Nano Devices and Systems) Laboratory
mems.utdallas.edu
NEMS-Enabled Tunable Photonic Crystal
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What is photonic crystal?
– Dielectric materials with a periodically varying index of refraction
– Photons behaves similar to electrons in a semiconductor crystal; their behavior
can be described by a photonic band structure
– Ability to control/manipulate the flow of electromagnetic waves.
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Tunable Photonic Crystal: conventional approaches
– Tuning by electro-optic materials (e.g. liquid crystal)
– Tunability is very limited due to small attainable changes in
refractive index (∆n/n < 15%).
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Our approach
– A radically different approach - Mechanical tuning
– Photonic bands are extremely sensitive to physical changes
in the photonic crystal structure.
– Wide tunability by mechanical force
Æ Mechanically Controlled Photonic Crystal (McPC)
MiNDs (Micro/Nano Devices and Systems) Laboratory
mems.utdallas.edu
Mechanically Controlled Photonic Crystal
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McPC structure is
– Composed of Si rods embedded in flexible polymer such as
Polyimide
– Mechanical tuning by stretching/releasing McPC with
NEMS/MEMS actuators
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The new material structure is compatible with the
conventional semiconductor technology
– In terms of both fabrication process and materials
MiNDs (Micro/Nano Devices and Systems) Laboratory
mems.utdallas.edu
Widely Tunable Beam Steering Device
Γ-M direction
Stretching
along
Γ-K direction
Refracted
beam
θr
10% Elongation
along Γ-K
Refraction Angle (degree)
20
Incident
beam θi
Unstretched McPC
Si
Polyimide
0
5% Elongation
along Γ-K
-20
-40
10% Stretched McPC
No Elongation
-60
-80
0
5
10
15
20
25
30
θi = 12o
ωa/2πc = 0.39
Incident Angle (degree)
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g
Tuning of more than 70o with small mechanical stress
(~10%)
Switching between positive & negative refraction regimes
MiNDs (Micro/Nano Devices and Systems) Laboratory
mems.utdallas.edu
Tunable Negative Index Lens
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Sub-wavelength resolution, tunability allows
– changing focal lengths for adjustable working distance and
– dynamically selecting the desired wavelength or scanning
over a range of frequencies.
point source
point image
Can adjust focal length
MiNDs (Micro/Nano Devices and Systems) Laboratory
point source
point image
Can also maintain identical focusing
characteristics over wide frequency
Range with ∆ω/ωο up to 30%.
mems.utdallas.edu
McPC Structures
Si Pillar Matrix Embedded
In Polyimide Film
Air Suspended McPC Membrane with
Si Ridge Waveguide for In-Coupling
Magnified View of Joint Region
Si Deflection Block
McPC
McPC
Si WG
Si Support
Negative Refraction Observed in McPC
Si input waveguide
light coupling out
o
inclined 6 from
to free space
Horizontal (λ = 1.54 µm) : no refraction
light coupling in
to McPC
: negative refraction
MiNDs (Micro/Nano Devices and Systems) Laboratory
Sub-µm Comb Drive Actuator
mems.utdallas.edu
Tunable McPC Applications
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3D FPCs
– Multispectral sensing and detection over
extremely wide range of frequency.
Operating Frequency
Visible & Near-IR
Mid & Far-IR
Terahertz
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Feature size
Fabrication
200 ~ 500 nm e-beam lithography, reactive ion etch (RIE)
0.5 ~ 10 µm UV lithography, RIE
10 ~ 50 µm UV lithography, Si Deep RIE
Wide range beam steering device
Unstretched FPC
– Electronically tunable giant negative
refraction in 2D slab PC
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Tunable sub-wavelength focusing lens
– NIM can enable sub-wavelength focusing
– But the focusing property is strongly
wavelength-dependent.
– Tunability allows dynamically selecting the
desired wavelength or scanning over a
range of frequencies.
5% stretched FPC
MiNDs (Micro/Nano Devices and Systems) Laboratory
mems.utdallas.edu
Acknowledgments
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Funding
– National Science Foundation CAREER AWARD
– National Science Foundation Nanoscale Exploratory
Research Program
– NIST ATP Program
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Contributions
– UTD MiNDs former/current Lab members
•
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J-S. Lee, M. Tinker, D. Park, A. Nallani,
Material donation, characterization supports
– Zyvex, TePla America, MicroChem
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Other supports
– UTD Clean room staffs
MiNDs (Micro/Nano Devices and Systems) Laboratory
mems.utdallas.edu