Post on 21-May-2018
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MEMS Sensors and Bioimaging
Dr. Huikai Xie
Biophotonics & Microsystems Laboratory
Interdisciplinary Microsystems Group
Department of Electrical and Computer Engineering
University of Florida
January 5, 2005
Outline
Introduction: What’s MEMS?
MEMS Research at UF
Integrated Inertial Sensors
Micromirrors
MEMS-Based Optical Imaging
What Is MEMS?
Micro Electro Mechanical SystemsOr Microengineering or Microsystem Technology (MST) (Europe)Or Micromachining (Japan)
Making miniature sensors and actuatorsInvolving almost every discipline Leveraging the existing IC technology Enabling technology for many emerging markets
What Is MEMS? – Application Areas
BiosensorsBiomedical imagingLab-on-chip Micro-pumps, …
Chemical sensorsMicro fluidicsMass spectroscopy…
Inertial sensorsGas sensorsPressure, liquid level, …
MicromirrorsAll-optical switchesMicrophonesMicrospeakers…
Ink-jet nozzles,Displays,Data storage,…
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What Is MEMS? -- Renowned Examples
Micromirror arrays for compact projectorsAccelerometers for automotive airbagsMicromirrors for optical switchingRF MEMS switchesMany others
Texas Instruments’Digital Micromirror Device
Analog Devices’Accelerometer
Lucent Technology’s2D micromirror for optical switch
Raytheon RF MEMS capacitive switch
Interdisciplinary Microsystems Group (IMG)
Five faculty membersMechanical and Aerospace Engineering
• Mark Sheplak• Lou Cattafesta• Hugh Fan
Electrical and Computer Engineering• Toshi Nishida• Huikai Xie
MEMS Research at UF
MEMS Research at UF – Research Areas
• Acoustic MEMS– Devices for fundamental acoustic measurements, arrays, proximity, etc.
• MEMS Shear-Stress Sensors– Thermal and floating-element (optical & piezoresistive) devices
• Flow Control– Development of sensors, actuators, & real-time flow control algorithms
• BioMEMS– Microfluidics, biosensors, lab-on-a-chip devices, etc.
• CMOS MEMS– Development of MEMS sensors with integrated CMOS circuits
• Meso-Scale Energy Reclamation and Control– Piezoelectric-based reclamation/control; energy harvesting
• Optical MEMS (MOEMS)– Micromirrors, microlenses, microgratings– MEMS-based Optical Imaging
Dr. Xie’s MEMS Group
• The mission of BML is to develop portable/disposable biophotonicmicrosystems and wearable microsensors with improved performance, functionality and affordability to allow more people and people with disabilities to obtain better medical care and have better quality of life.
• The research approach is monolithic integration of multiple sensors/actuators, single-crystal silicon microstructures and electronics for high performance, small size, low cost and low power.
• Current research activities:– CMOS-compatible microfabrication technology development– Integrated inertial sensors; Interface circuits design; High-Q resonators– Optical MEMS: micromirrors, microlenses– MEMS-based optical imaging
• Current Sponsors:– National Science Foundation– Semiconductor Research Corporation– Florida Photonics Center of Excellence
Biophotonics & Microsystems Laboratory (BML)
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Research Projects
CMOS-MEMS Process
Integrated inertial sensors
Interface circuits design
High-Q resonators
Optical MEMS: micromirrors, microlenses
MEMS-based optical imaging
Biophotonics & Microsystems Laboratory (BML)
CMOS-MEMS Process
metal-1metal-2metal-3
(a) Backside etch
CMOS-region
Single-crystal Si (SCS) membrane
poly-Si
oxide
(b) Oxide etch
STS: 12-sec etching130-sccm SF6, 13-sccm O2, 23 mT, 600 W coil power, 12 W platen power;8-sec passivation85-sccm C4F8, 12 mT, 600 W coil power, 0 platen power.
PlasmaTherm-790: 22.5-sccm CHF3, 16-sccm O2, 100 W, 125 mT for 125 minutes and then 100 mT for 10 minutes.
CMOS-MEMS Process (cont’d)
(c) Deep Si etchCMOS layer
STS: same as Step (a).
Flat structure
(d) Si undercutSCS layer (20~100µm)
Thin-film structure
STS: 130-sccm SF6, 13-sccm O2, 23 mT, 600 W coil power, and 0 platen power.
(a)
(b)
Research Projects
CMOS-MEMS Process
Integrated Inertial Sensors
Interface circuits design
High-Q resonators
Optical MEMS: micromirrors, microlenses
MEMS-based optical imaging
Biophotonics & Microsystems Laboratory (BML)
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Top view
anchor
Self-test actuator
sense combfingers
proof mass
self-test actuator
z-spring
Z-axis CMOS-MEMS Accelerometer
Size: 0.5mm x 0.6mmResonance: 3.9 kHzSensitivity: 2.6 mV/g(calculated 4.0 mv/g)Range: > 10 gLinearity: 0.5% (F.S.) Noise floor: 1 mg/Hz1/2
(Brownian 2.5 µg/Hz1/2)
y
x
z
H. Xie, et al., J. MEMS, 2002
CMOS-MEMS Gyroscope
Electrical isolation of bulk silicon
Drive in xCoriolis acceleration sense in z
y-axis rotation detection
X-drive spring
proof mass
z-spring
X-drive comb fingers
Z-sense fingers
y
xz
Ωy
Coriolis acceleration:
xyz Va ×Ω⋅= 2
H. Xie, G. Fedder, IEEE Sensors Journal, 2003
Top viewanchor
X- sense combfingers
X/Y-spring
Z-spring
Triaxial CMOS-MEMS Accelerometer
y
xz
Y- sense combfingersZ- sense comb
fingers
H. Qu, H. Xie, IEEE Sensors Conference, 2004
Low-Power Low-Noise Interface Circuits Architecture
Low Noise• Noise Matching• High chopping
frequency (2 MHz)
Low Power• 2-stage, open-loop• Stage-1 optimized for noise• Staeg-2 optimized for signal
swing and linearity
DC biasing
Vm+
Vm-
Stage-1
Sensor offsetcancellation
DC offset cancellation
modulationDemod.
CL
Vout+
Vout-
φ
Cbp
vos1
vos2
Aaux
Stage-2
×1
×1
D. Fang, H. Xie, IASTED International Conference on Circuits, Signals and Systems, 2004
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Applications of MEMS Inertial Sensors
• Low cost – Automobiles, computer games, motion detection
• Small size -- Camcorders, nano-satellites, health monitoring
• Integrated Inertial Measurement Unit (IMU) system
Traditional applications of inertial sensors
MEMS inertial sensors
Emerging applications
Research Projects
CMOS-MEMS Process
Integrated inertial sensors
Interface circuits design
High-Q MEMS Resonator for Trapezoidal Waveform Generator for Adiabatic Circuits
Optical MEMSMicromirrors
Microlenses
MEMS-based optical imaging
Trapezoidal Waveform Generation
x
yStator
Rotor
2d
2dd
h yCd
ε=
y1
C
yy1
11
h yCd
ε=
y2
y2
C1
0
v
Not considering fringing effect
SEM Picture of The Resonator
Sensing combsActuation combs
Resonator beam
Isolation beam
M. He, M. Frank, H. Xie, SPIE International Symposium on Nano- and Micro- Smart Systems, 2004
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Research Projects
CMOS-MEMS Process
Integrated inertial sensors
Interface circuits design
High-Q resonators
Optical MEMSMicromirrors
Microlenses
MEMS-based optical imaging
Electrostatic Micromirror
1mm x 1mm mirrorRadius of curvature: 50 mmCurled combs designed to obtain bi-directional rotationComb pairs placed to achieve differential torque and cancel z displacementZ-actuators included to adjust z-motion
1B
1A’
2B
1B’
1A
2B’
2A’2A
anchor anchor
Z-actuator
+ -V
F+ -V
F
H. Xie, G. Fedder, J. MEMS, 2003
1-D Thermal Micromirror
• 40 µm SCS layer provides very good mirror flatness• Continuous response curve• Measured radius of curvature of the mirror = 50 cm
bimorph actuator
mirrorx
y
Poly-Si heater
Applied current (mA)
Rot
atio
n A
ngle
(deg
ree)
A. Jain, S. Todd, H. Xie, 2003 OSA Annual Meeting
2-D Thermal Micromirror
40 µm SCS layer provides very good mirror flatnessMeasured radius of curvature of the mirror = 0.33m
mirrorbimorph actuators
1mmframe
A’
bimorph frame actuator
A
1mm2
mirror
bimorph mirror actuator
A
A’
Substrate
Second Axis
First Axis
I2I2
frameI1
I1
A. Jain, Y. Pan, G. Fedder, H. Xie, IEEE Journal of Selected Topics in Quantum Electronics, 2004
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• Resonant frequencies:
Mirror Actuator = 445 Hz Frame Actuator = 259 Hz
2-D Mirror for Display
4 x 4 pixel raster scan of a laser beam by the mirror
A. Kopa, A. Jain, H. Xie, OSA Optics in Southeast, 2003
Large-Vertical-Displacement Device
Device size: 0.7mm by 0.4mm
Mirror size: 0.25mm by 0.25mm
Vertical Displacement: 200µm
Drive voltage: 15V
A. Jain, H. Xie, Sensors & Actuators, 2005
mirror
frame
mirror actuatorframe actuator
Substrate
θ
θ
ρ
l
Zmir
frame
Lf
- metal, - oxide- silicon, - polysilicon,
bimorph mirror actuator
frame actuator
mirror
Substrate
θ
θ
ρ
l
Zmir
frame
Lf
- metal,- metal, - oxide- oxide- silicon,- silicon, - polysilicon,- polysilicon,
bimorph mirror actuator
frame actuator
mirror
Tunable Microlens
Device size: 0.7mm by 0.4mm
Lens size: 0.15mm in diameter
Numerical Aperture: 0.35
Focal length: 0.2mm
Vertical Displacement: 200µm
Drive voltage: 15V
A. Jain, H. Xie, IEEE MEMS 2005
PR microlens
reflection of microlens
Research Projects
CMOS-MEMS Process
Integrated inertial sensors
Interface circuits design
High-Q resonators
Optical MEMSMicromirrors
Microlenses
MEMS-based optical imaging
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Optical Bioimaging: Motivation
Heart disease and cancer are the top two killers in US
Lack of in vivo imaging modalities
Lack of high-resolution imaging for early cancer diagnostics
X-ray (safety, dye, resolution, …)
Ultrasound (~100µm)
Higher resolution (1~10µm ) in vivo imaging is needed
Optical Coherence Tomography
x1 x3x2V
x1 x3x2
n×
x
Broadband light source (λ, ∆λ)
BeamsplitterPhoto-
detector
Tissue
Reference mirrorAxial scan
Transverse scanTransverse scanTransverse scanTransverse scanTransverse scan
x
Optical Coherence Tomography first demonstrated by Fujimoto et al in 1991Non-invasive or minimal invasiveBased on low coherence interferometryHigh Resolution (∝ λ2/∆λ, <10µm) cross-sectional images
• Endoscopic imaging requires fiber probes that can transversely scan the tissue
OCT Imaging using Optical MEMS
Our solution: use a small moving mirror inside the probe (MEMS Mirror)Small size for internal organ imagingFast scanning speed for real-time imaging
Sample
Fiber-optic probe
5 mm
BBS
Signal Processing
PD
ReferenceMirror
Beam SplitterMEMS Mirror
GRINLens
Fiber
MichelsonInterferometer
Micromirror
FerruleLaser
Sample
mirror
MEMS-OCT Imaging Experiments
In vivo 2-D Endoscopic OCT of porcine bladder
U
MS
SMU:urothelium, SM:submucosa, MS: muscularis layer. Image size: 500×1000 pixels covering an area of 2.9×2mm2.
3.6×2.8mm2 4.3×2.8mm2
Y. Pan, H. Xie, G. Fedder, Optics Letters, 2001
T. Xie, H. Xie, G. Fedder, Y. Pan, Applied Optics, 2003
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High mortality of cancers is due to lack of early detection modalities. Commonly used biopsy is risky and has low early detection rate. Optical coherence tomography (OCT) is a non-invasive high-resolution imaging technique, but conventional OCT is bulky and not suitable for in vivo internal organ imaging; and OCT has poor lateral resolution.
Motivation Objectives
Design Concept
MEMS-Based Endoscopic Optical Confocal Imaging
Develop miniature optical confocal microscopic (OCM) imaging probes using MEMS technology for noninvasive in vivodiagnosis of early cancers of internal organs.Promote interdisciplinary education, higher engineering and minority enrollment.
The basic idea is to use oppositely tilted bimorph beams to compensate the tilted platform, and thus the mirror or lens will move vertically when a current is applied to both bimorph actuators.
Schematic of the Proposed µ-OCM system: (OCT + MEMS Confocal Microscopy)
µOCM Probe
LVD µlens50:50Broadband
source
Photo detector
Reference µmirror
Fiber
SampleBeamsplitter µOCM
probe
µMirror
Anchor
Bimorph actuator II
Frame
AA’
Bimorph actuator I
FrameSilicon
Al
Oxide
Mirror
Sample
µ-OCM probe includes a MEMS mirror and a z-scan microlens
Bi-directional Micromirror Large Z-scan Microlens
Bimorph actuator IImicrolens
A A’
Bimorph actuator I
Anchor
Frame
Silicon
Frame
Poly-Si
±30°
~2 mm
Summary
Core Research AreasMEMSMicro/nano fabrication technologyIntegrated sensors, gyroscopes, accelerometers, IMUsOptical MEMS, micromirrors, microgratingsFiberoptic sensors
ApplicationsBiomedical imaging, optical coherence tomography (OCT)MEMS-based confocal imagingLaser scanning displaysBeam pointing and beam scanning systems for laser radar systemsNavigation control for space and automobilesInfrastructure vibration monitoringHealth monitoring
AcknowledgementsSponsors
National Science FoundationSemiconductor Research CorporationNASAFlorida Photonics Center of Excellence
Collaborators Dr. Yingtian Pan and Dr. Tuqiang Xie (SUNY-Stony Brook)Dr. Gary Fedder (Carnegie Mellon University)Dr. Jannick Rolland (CREOL, University of Central Florida)
StudentsDeyou Fang Maojiao HeAnkur JainAnthony Kopa Hongwei QuShane ToddBryan Blackburn