ksjp

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1

MEMS Design & Fab

Vertical electrostatic actuation of torsional mirrors

• A typical 1 axis torsional mirror

Torsional spring

Electrostatic actuators

Flat, reflective mirror

ksjp

, 7/0

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MEMS Design & Fab

Vertical electrostatic actuation: problems

• Large angle + stability large gaps

• Large gaps small forces small torque

• Small torque flimsy springs

• Flimsy springs low resonant frequency!

ksjp

, 7/0

1

MEMS Design & Fab

Mirror design• Reflective mirror metallic coating

• Metallic coating thermal bimorph

• Curvature requirement thick silicon

• Thick silicon higher mass slow mirror

ksjp

, 7/0

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MEMS Design & Fab

1DOF 2DOF

ksjp

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MEMS Design & Fab

2DoF Micromirror

anchor

Back-side etched cavity

anchor

ksjp

, 7/0

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MEMS Design & Fab

Challenges with this methodology

Low SCS beam/structure must be compliant in z and stiff in x, yPerformance is aspect-ratio limited => highSCS beam is too stiffLateral actuation displaces the mirror laterally

Lateral pull

x

z

y

ksjp

, 7/0

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MEMS Design & Fab

Challenges – Lateral displacement

Very little rotation due to vertical stiffness of low SCS yank legLateral pull dominates actuation

ksjp

, 7/0

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MEMS Design & Fab

Challenges: 2D mechanisms

ksjp

, 7/0

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MEMS Design & Fab

Bond/transfer results

Long HF Release of TopSCS handle wafer

Target wafer is a regular Si wafer

ksjp

, 7/0

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MEMS Design & Fab

Optical Comm Proof of Concept

Receiver• 1” lens, std. video CCD• PCMCIA Frame grabber• Software decoding

Laser transmitter– 4bps OOK– Laser pointer (Radio

Shack)

ksjp

, 7/0

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MEMS Design & Fab

Laser Comm at 5.2 km

• 14 microW, ~1mrad

• 8 mW, ~1mrad

• 3 mW, ~100mrad

Received by a CCD video camera with 3” aperture. During daylight, through light rain.

ksjp

, 7/0

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MEMS Design & Fab

Video Semaphore Decoding

ksjp

, 7/0

1

MEMS Design & Fab

Smart Dust ’01 Goal

ksjp

, 7/0

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MEMS Design & Fab

CCR Interogator

Top View of the Interrogator

CCD Camera Lens

Frequency-Doubled Beam45o mirror

Polarizing Beamsplitter

Quarter-wavePlateFilter

0.25% reflectance on each surface

YAG Green Laser Expander

ksjp

, 7/0

1

MEMS Design & Fab

Smart Dust Mini Mote

ksjp

, 7/0

1

MEMS Design & Fab

Simulation of CCR reflection

Goal: predict impact of diffraction and non-flat, non-perpendicular mirrorsMethodology: Divide faces into discrete rectangular elements Perform ray-tracing to determine direction and phase of each ray Sum Fraunhofer diffraction integrals from discrete elements.Author: Victor Hsu (with Joe Kahn, K. Pister, UCB; contact jmk@eecs.berkeley.edu)

ksjp

, 7/0

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MEMS Design & Fab

CCR Differential Scattering Cross-section

Angle error, 1 side(Courtesy: Lixia Zhou, UCBlzhou@eecs.berkeley.edu)

0.5m rad

1m rad8m rad

ksjp

, 7/0

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MEMS Design & Fab

2D beam scanning

laser

lens

CMOS ASIC

Steering Mirror

AR coated dome

ksjp

, 7/0

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MEMS Design & Fab

6-bit DAC Driving Scanning Mirror

10 20 30 400

0.2

0.4

0.6

0.8

Time (seconds)

Nor

mal

ized

bea

m p

ositi

on

• Open loop control

• Insensitive to disturbance

• Potentially low power

ksjp

, 7/0

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MEMS Design & Fab

~8mm3 laser scanner

Two 4-bit mechanical DACs control mirror scan angles.

~6 degrees azimuth, 3 elevation

ksjp

, 7/0

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MEMS Design & Fab

Optical Communication

0-25% 25%

Path loss

Loss = Areceiver / (4 d2) / Gant

Antenna Gain = 4 / ½2

ksjp

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MEMS Design & Fab

Theoretical Performance

Ptotal = 100uWPt = 10uW½ = 1mradBR = 5 Mbps

Areceiver = 0.1mm2 Pr = 10nW (-50dBm)Ptotal = 50uWSNR = 15 dB

5m

20pJ/bit!

ksjp

, 7/0

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MEMS Design & Fab

Theoretical Performance

Ptotal = 50mWPt = 5mW½ = 1mradBR = 2 Mbps

Areceiver = 1m2 Pr = 10nW (-50dBm)Ptotal = 50uW /pixelSNR = 17 dB

500km

25nJ/bit!

ksjp

, 7/0

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MEMS Design & Fab

Satellite Imagery

ksjp

, 7/0

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MEMS Design & Fab

Goal:10 Mbps; 10 km; 1 cm3

ksjp

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MEMS Design & Fab

1 Mbps CMOS imaging receiver

1 0 cm

20 0 m

F ield of Viewof S ingle P ixel

5 m m

2 k m

CollectionLens

OpticalF ilter

64x64CMOSImager

10W, 1mrad

Photosensor

Signal ProcessingA/D Conversion

SIPO ShiftRegister

CRC CheckLocal Bus Driver

Off ChipBus Driver

Pixel Array

ksjp

, 7/0

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MEMS Design & Fab

Augmented Reality

100 200 300 400 500 600

50

100

150

200

250

300

350

400

450

100 200 300 400 500 600

50

100

150

200

250

300

350

400

450

Lau, Muller, Solgaard and students

ksjp

, 7/0

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MEMS Design & Fab

Laser pointer projector

R

G

B

EraseClear

3axis gyro

2D RGBprojector

•Stabilized laser pointer•Hand-held projector•Virtual whiteboard

•Track user motions while drawing•Refresh at 30 Hz

ksjp

, 7/0

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MEMS Design & Fab

Displays and screen doors

Display

Array of pixels

RGB(x,y) RGB(x,y,,)

Screen door

ksjp

, 7/0

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MEMS Design & Fab

Virtual window

Pixel arrayEach pixel like a pinhole camera

Max pixel power: 5mW out, 5mm^2 Array power (out): 1kW/m^2

Power in: 50mW/pixel

Power in: 10kW/m^2 !

ksjp

, 7/0

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MEMS Design & Fab

HDTV window

Pixel array •2000x1000 array•1mm^2, 1mW out pixels•Full video on each pixel

•Optical power out: 2kW•Shadows•Heat! (w/o sunburn)•Home defense

•Uncompressed data rate: ~20 Tbps

ksjp

, 7/0

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MEMS Design & Fab

HDTV window – more realistic

Pixel array •Eye tracking (multi-user)~25/cones/pixel/faceData rates ~few video streams

•10W/m^2 (bright indoor)10uW/pixel averageArray power << kW

For each pixelFor each face

draw 5x5 grid ;