Upload
others
View
6
Download
0
Embed Size (px)
Citation preview
MiNDs (Micro/Nano Devices and Systems) Laboratory mems.utdallas.edu
UTD MEMS/NEMS Research Lab.
Metallic Nano Electro Mechanically Actuated Gripper and Tunable
Nano Photonic DeviceJeong-Bong (J-B.) Lee
Department of Electrical EngineeringThe University of Texas at DallasThe University of Texas at Dallas
Richardson, Texas
MiNDs (Micro/Nano Devices and Systems) Laboratory mems.utdallas.edu
Objectivesg Nanoelectromechanical systems (NEMS)
– Possible to realize smaller mechanical, biological and chemical systems
g Nano grippers– Actuators for nano manipulation devices/systems– Relatively large displacement with low actuation
voltagesg 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
g 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.
g 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
500 nm width/spacing and 500 nm thick gold comb-drive~400 nm width ~2 µm thick
SU-8 test structures
g E-beam lithography– Positive PR (e.g., PMMA)
• Ideal for lift off.
– Negative PR (SU-8, UVN-30)• Very small exposure dose
(~1 µC/cm2), a factor 100 times smaller dose (exp. time)!
MiNDs (Micro/Nano Devices and Systems) Laboratory mems.utdallas.edu
Sub- µm Thermal Actuatorg Process
– Electron beam exposure for PMMA– Electroplate nickel ~1 hr for 1 µm– Removal of PMMA by oxygen RIE
g Sub-micron thermal actuator– Reproducible displacement results
• Type “A”: 370 nm by 146 mV
3:1 aspect ratio 1 µm thick PMMA mold
Hot arm w = 350 nmLHOT=38 µm
MiNDs (Micro/Nano Devices and Systems) Laboratory mems.utdallas.edu
Sub- µm Gripper45um
θ
1.5um
14.25 um4.75 um4.5 um
14.25 um
5 um
Line: 350 nmSpacing: 1150 nm
LFlex
LCold
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 5 10 15 20 25 30
Current [mA]
Dis
plac
emen
t [um
]
MiNDs (Micro/Nano Devices and Systems) Laboratory mems.utdallas.edu
NEMS-Enabled Tunable Photonic Crystalg 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.
g 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%).g 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
Mechanically Controlled Photonic Crystal (McPC)
MiNDs (Micro/Nano Devices and Systems) Laboratory mems.utdallas.edu
Mechanically Controlled Photonic Crystalg McPC structure is
– Composed of Si rods embedded in flexible polymer such as Polyimide
– Mechanical tuning by stretching/releasing McPC with NEMS/MEMS actuators
g 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
Unstretched McPC
10% Stretched McPCθi = 12o
ωa/2πc = 0.39
Si
Polyimide
Stretchingalong Γ-K direction
Γ-M direction
Incidentbeam
Refractedbeam
θi
θr
Stretchingalong Γ-K direction
Γ-M direction
Incidentbeam
Refractedbeam
θi
θr
-80
-60
-40
-20
0
20
0 5 10 15 20 25 30
Incident Angle (degree)
Ref
ract
ion
Ang
le (d
egre
e)
No Elongation
5% Elongationalong -KΓ
10% Elongationalong -KΓ
g Tuning of more than 70o with small mechanical stress (~10%)
g Switching between positive & negative refraction regimes
MiNDs (Micro/Nano Devices and Systems) Laboratory mems.utdallas.edu
Tunable Negative Index Lensg 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
point source point image
Can also maintain identical focusing characteristics over wide frequencyRange with ∆ω/ωο up to 30%.Can adjust focal length
MiNDs (Micro/Nano Devices and Systems) Laboratory mems.utdallas.edu
McPC Structures
Si Pillar Matrix EmbeddedIn Polyimide Film
Air Suspended McPC Membrane withSi Ridge Waveguide for In-Coupling Magnified View of Joint Region
McPC
Si WG
Si Deflection Block
McPCSi Support
Sub-µm Comb Drive ActuatorNegative Refraction Observed in McPC
Si input waveguideinclined 6o fromHorizontal (λ = 1.54 µm)
light coupling outto free space: no refraction
light coupling into McPC: negative refraction
MiNDs (Micro/Nano Devices and Systems) Laboratory mems.utdallas.edu
Tunable McPC Applications
Operating Frequency Feature size Fabrication Visible & Near-IR 200 ~ 500 nm e-beam lithography, reactive ion etch (RIE) Mid & Far-IR 0.5 ~ 10 µm UV lithography, RIE Terahertz 10 ~ 50 µm UV lithography, Si Deep RIE
g 3D FPCs– Multispectral sensing and detection over
extremely wide range of frequency.
g Wide range beam steering device– Electronically tunable giant negative
refraction in 2D slab PCg 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.
Unstretched FPC
5% stretched FPC
MiNDs (Micro/Nano Devices and Systems) Laboratory mems.utdallas.edu
Acknowledgments
g Funding– National Science Foundation CAREER AWARD– National Science Foundation Nanoscale Exploratory
Research Program– NIST ATP Program
g Contributions – UTD MiNDs former/current Lab members
• J-S. Lee, M. Tinker, D. Park, A. Nallani,
g Material donation, characterization supports– Zyvex, TePla America, MicroChem
g Other supports– UTD Clean room staffs