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Defense Sciences R

esearch Council, L

a Jolla, CA

., July 1995

Micro-O

pto-Mechanical System

sC

ontract No. FQ

8671-9301675

Electronic System

s Technology O

ffice

Advanced R

esearch Projects Agency

Departm

ent of Defense

Program M

anager: Dr. K

aigham J. G

abriel

Principal Investigators:

Prof. Mehran M

ehregany

e-mail: m

ehran@m

ems5.cw

ru.edu Tel: 216-368-6435

Prof. Frank Merat

e-m

ail: merat@

snowhite.eeap.cw

ru.edu Tel: 216-368-4572

Departm

ent of Electrical E

ngineering & A

pplied Physics

Fax: 216-368-2668

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., July 1995

Opto-M

echanical Devices using

ME

MS T

echnology

Prof. Mehran M

ehregany

e-mail: m

ehran@m

ems5.cw

ru.edu Tel: 216-368-6435

Prof. Frank Merat

e-m

ail: merat@

snowhite.eeap.cw

ru.edu Tel: 216-368-4572

Departm

ent of Electrical E

ngineering & A

pplied Physics

Fax: 216-368-2668

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Defense Sciences R

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., July 1995

Outline

m

otivation

devices

system

s

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., July 1995

Motivation

The ultim

ate goal of MO

MS is to integrate

coordinated motions of basic m

icroactuators,passive/active optical com

ponents, microsensors, and

microelectronics in order to realize a com

plete pre-assem

bled optical system that can be m

ass producedw

ith low unit cost.

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Defense Sciences R

esearch Council, L

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., July 1995

MO

MS w

ill allow the developm

ent of new fam

iliesof m

icrofabricated opto-mechanical system

s which:

do not need com

ponent alignment;

can be m

ass produced (i.e., are on the order ofdollars per unit device);

have high packing density;

can be directly integrated w

ith electronics; and

are low

-power, sm

all, and light weight.

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Defense Sciences R

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., July 1995

We are at the device stage

m

icroscanners

tunable laser diodes

optical w

aveguides

m

icrorelays

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., July 1995

Where are are going?

integrated system

s especially for thetelecom

munications industry

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., July 1995

Put individual devices into micro-

optical-mechanical system

s

m

icroscanners → optical sw

itches,

scanners, beam steering

tunable laser diodes →

comm

unications

systems

m

icrorelays → instrum

entation

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Defense Sciences R

esearch Council, L

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., July 1995

Integrate individual devices to createm

icro-optical-mechanical system

s

optical w

aveguides are an enablingtechnology

optical duplexer for subscriber loop services

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Defense Sciences R

esearch Council, L

a Jolla, CA

., July 1995

MO

MS critical to practical im

plementation of large num

bers of fiber opticsubscriber loops

optical m

icrobenches that permit low

-cost manufacture of pre-aligned,

hybrid fiber optic systems (e.g., transm

itters and receivers)

Reliance E

lectric Com

m-T

ech has identified such an optical assembly

microbench as one of the industrys m

ost pressing short-term needs

optical sw

itches which perm

it in-situ testing of optical fibers

low

-cost, mass-produced frequency stabilized laser diode sources for

WD

M and other applications

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., July 1995

Set of basic MO

M com

ponents

LEG

EN

D

SiN

Ox

reflective metal

polysiliconlight

(ii) graded index lenses(i) optical w

aveguides(iii) cantilever scanner

(viii) w

aveguide on a deform

able bridge

(iv) beam splitter

(v) polygon scanner(vi) reflector m

ounted on a linear m

icroactuator

motion

microm

otor

polygon reflector

(vii) graded index lens on alinear m

icroactuator

motion

focusing

(x) m

oveable diffraction grating

(xi) active diffraction grating(ix) stationary diffraction

grating

q=+

1q=

0

q=-1

qλ/Λqλ/Λ

θi Incident B

eam

Z

Incident Beam

Diffracted B

eam

rotation

Scanned arc

(a) beams dow

n

incident/reflected light

(b) beams up

Glass substrate

Anchor

Cantilever beam

Stator electrode S

topper

Mirror surface

Stator electrode

Stopper

(xii) rotary reflector

(xiii) optical etalon

motion

(xix) vee-grooves

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., July 1995

Diffraction grating

incoming light

zero diffraction order

first diffraction order

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Defense Sciences R

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., July 1995

Schematic diagram

of a rotatingdiffraction grating scanner.

Note that the incident beam

reflects from the entire rotor surface.

scanned line

incoming laser beam

rotation

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., July 1995

Schematic illustration of an optical

microbench based on a silicon chip.

microlens

silicon substrate

(a) top view

(b) side view

semiconductor

laser source

optical fiberm

icrolens

silicon substrate

microm

achined v-groove

microm

achined recess

optical axis optical fibersem

iconductor laser source

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esearch Council, L

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., July 1995

Conceptual external cavity frequency

stabilized laser diode using a lateralresonant m

irror translator

output to optical fiber

semiconductor

laser sourceF

abry-perot etalon

photodiode

movable reflector using

laterally resonant m

icroactuator

feedback controller electronics

microlens

* on a silicon substrate

beamsplitter

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Defense Sciences R

esearch Council, L

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., July 1995

A m

icrofabricated 3D scanner for

miniature projection displays

microlens

cantilever beamvertical scanner

microm

otor rotatinghorizontal scanner

semiconductor

laser or LED

Microm

echanical com

ponents which are

part of proposed research

projected scan pattern

V

H

linear translatable lens for dynam

ic focusing and/or 3D

scanning

The m

icromotor scanner w

ill also beused for optical sw

itches.

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Defense Sciences R

esearch Council, L

a Jolla, CA

., July 1995

Our industrial partner, R

eliance Electric

R

eliance Electric is genuinely interested in the technology being

proposed and helped us in defining specific needs and applications. Our

on-site interactions will result in a natural technology transfer path. In

fact, their technical contacts will co-supervise the graduate students

carrying out their research and will be directly involved as the program

proceeds.

T

he results of our basic research on enabling technologies, (generic)device designs, and prototype perform

ance characteristics are notproprietary. H

owever, in the course of the research, devices and

applications with prom

ising markets w

ill be considered proprietary untilappropriate patent protection is obtained by C

WR

U or R

elianceE

lectric. The results of all portions of the program

will be m

adeavailable to A

RPA

for government use.

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Defense Sciences R

esearch Council, L

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., July 1995

Collaboration w

ith Reliance

the fiber optic coupler

a vee-groove multiple optical fiber coupler w

as identifiedas the short term

application of the optical microbench

technology

Specifications for a com

mercial device w

ere provided byR

eliance Electric after several joint m

eetings

a prototype device w

as designed and fabricated at CW

RU

this device w

as sent to Reliance telecom

munications in

Chicago for testing

device passed A

T&

T coupler specifications

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., July 1995

D

r. Jim H

arris, Fred Discenzo, R

elianceR

esearch

D

r. George A

b-Bubu, R

elianceT

elecomm

unications

Prof. Frank M

erat, Prof. Mehran

Mehregany, C

WR

U

Shuvo R

oy, Steve Smith, A

zzamY

aseen, CW

RU

Ph.D. candidates

Co

ntin

uin

g C

ollab

oratio

n w

ith R

eliance

the p

roject team

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., July 1995

Polygon Microscanner

SEM

photo of a rotating polygon optical microscanner m

ade byelectroless-plating of nickel reflecting surfaces on the rotor of a 500m

icron diameter salient-pole m

icromotor. T

he thickness (height) of thenickel is 20 µ

m; the w

idth of the nickel is 10 µm

. The polygon itself is

approximately 175 m

icrons in diameter.

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., July 1995

Scanner optical beam

Digitized video im

age of a 633-nm laser beam

reflecting from the

polygon scanner. The im

age was recorded approxim

ately 10 inchesfrom

the scanner using an ordinary TV

camera.

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., July 1995

Cross-sectional schem

atic of a typicalpolygon m

icroscanner

Typical m

icroscanner after release showing illum

ination of the nickelsurface w

ith a laser beam. N

ote that if the reflector is too far from the

rotor rim the beam

will also reflect from

the rotor surface.

Incident Light

Polysilicon

LT

O

Silicon

Nickel

Substrate

Reflected L

ight

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., July 1995

Reflected signals from

a spinning rotorw

ith a constant rotor speed

The com

plex shape of the reflection is caused by undesired reflections from the rotor.

The low

frequency variation of the reflectivity is hypothesized to be a low frequency

wobble of the rotor about the axis of rotation.

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., July 1995

Electrostatic drive lateraltranslational reflector.

The sidew

all of the surface at the top center of the image is nickel plated

and will be used as an optical reflector.

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., July 1995

Cross-sectional view

of a rib waveguide

in epitaxial silicon

airn=1

p-SI

n=3.5

n-SI substrate

n=3.49-j0.00036

h1h2

w

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., July 1995

Schematic diagram

of opticalduplexer chip

Photodetector to

monitor laser

diode

High-speed

Photodetector for

video information

Laser diode sourceO

ptical fiber to substation

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., July 1995

Single Mode Pigtailed 1.3/1.3 D

uplexerItem

Symbol

Conditions

MIN

MA

XU

nitsO

perating case temp

Tc

-4085

∞ C

Wavelength

lcover T

c1260

1350nm

Output pow

er intoPout

over Tc

6(see Pfth)

µW single m

ode fiberT

hreshold power (L

aser diode)Pfth

over Tc

min Pout/30

µWC

rosstalk (Note 1)

Cr

over Tc

-29dB

Tracking error (N

ote 2)E

rover T

c3, 0.5

dBR

eceiver responsivityR

over Tc

0.3A

/WR

eceiver polarizationR

pover T

c1

dB dependenceR

eceiver capacitanceC

d-5 V

bias1

pFR

eceiver dark currentId

over Tc, -5 V

10nA

SC-PC

connector lossIL

over Tc

0.5dB

Connector reflectance

Rc

over Tc

-33dB

Backw

ard reflectanceR

bover T

c-20

dB

Notes:

1. If total tracking error Er<

0.5 dB, then

crosstalk Cr<

-24 dB2. If total tracking error 0

.5<E

r<3.0 dB

, then crosstalk C

r<-29 dB

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., July 1995

Optical duplexer using planar

microm

echanical light modulator to

replace optical source.

Modulation

monitoring

photodetectoH

igh-speed P

hotodetector for video inform

ation

Fabry-P

erot variable reflector

Optical fiber to

substation

motion

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., July 1995

Optical properties of high-aspect-ratio

(111) silicon plates

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9 1

020

4060

80100

Incident angle [d

egree]

Reflectivity

Rs calculations

(100) surface

(111) surface

Reflectivity as a function of the

light beam incident angle

0.00001

0.0001

0.001

0.01

0.1 10.0010.01

0.11

10100

Thickness [µm

]

Transmissivity

Calculation

Experim

ent

Transm

issivity as a function ofthe thickness of the (111)silicon plate

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., July 1995

Optical applications of high-aspect-ratio

(111) silicon plates

λ1

λ2

g2

g1

Micro E

talonO

n Chip M

ach-Zehnd

er Interferometer

Micro B

eam Splitter

Thin Si Plate

(hundred

s µm tall, few

µm w

ide)

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Defense Sciences R

esearch Council, L

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., July 1995

Schematic diagram

of an integratedlaser diode and m

icromirror

Glass substrate

Anchor

Cantilever beam

Stator electrode

Stopper

Laser beam

Laser d

iode

Mirror surface

Stator electrode

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., July 1995

Fabrication process for theintegrated laser diode/m

icromirror

Si S

hallo

w E

tchin

g b

y RIE

Silico

n-N

itride D

epo

sition

An

isotro

pic D

eep E

tchin

g

by K

OH

Si3N

4

Electro

static Bo

nd

ing

Su

bstrate P

olish

ing

Back

(to release the structure)

Laser D

iod

e chip

Bo

nd

ing

Glass S

ubstrate

Cantilever beam

Anchor

Laser Diode

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., July 1995

An SE

M im

age of the integratedlaser diode and m

icromirror.

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., July 1995

Microm

irror deflection angle as afunction of the applied voltage

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9 1

05

1015

2025

30

Applied

voltage Va [V

]

Deflection angle [degree]

Calculation

Experim

entV

th=23.7 [V

]V

th=25.5 [V

]

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., July 1995

Wavelength variation as a function of the

excitation voltage of the mirror

853

853.5

854

854.5

855

855.5

856

856.5

8570.005.00

10.0015.00

Excitation V

oltage [V]

Center Wavelength [nm]

Vth=

12.6 V

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., July 1995

Cross-sectional view

of a ribw

aveguide in epitaxial silicon

airn=

1

p-SI

n=3.5

n-SI substrate

n=3.49-j0.00036

h1h2

w

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., July 1995

Anisotropically-etched w

aveguideend-face

The dark layer is the region w

here light is guided and the light layeris the heavily doped silicon substrate

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., July 1995

End view

of bulk fabricated U-grooves

Note the rib w

aveguides positioned at the end of the grooves and the cornercom

pensation structures

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., July 1995

Detail of corner com

pensation structure of fiberguiding U

-groove on a (110) silicon substrate

. Note the rib w

aveguide at the right end of the U-groove

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., July 1995

Three dim

ensional intensity profile from a large-

area, all-silicon waveguide w

ith a 10 µm w

ide rib

Horizontal

Vertical

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., July 1995

End view

of bulk fabricated U-grooves using

ultrasonic agitation

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., July 1995

Anistropically etched rib w

aveguide with

ultrasonic agitation

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., July 1995

U-groove surface roughness

Decktak surface roughness of a

typical U-groove bottom

. The value

of Ra is 5606Å

.

Decktak surface roughness of a U

-groove bottom

produced with

ultrasonic etching. The value of R

a is341Å

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., July 1995

•Surface m

icromachining concept

•“T

raditional” high-aspect-ratio microstructures

•N

ew Surface M

icromachining Process

–M

old characteristics

–Structural m

aterial deposition

Microrelays:

Background and M

otivation

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Defense Sciences R

esearch Council, L

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., July 1995

Polysilicon Surface–Microm

achined Relay

(Gretillat et. al at M

EM

S ‘94)

p-type Si substrate

final doped polysilicon

aluminum

silicon nitride

oxide and silicon nitride

initial doped polysilicon

p-type region

n-type region

•L

ow current load ≈ 1 m

A

•H

igh contact resistance ≈ 10 kΩCase W

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., July 1995

Nickel M

icrorelays

*M

etallic contacts•

electrostatic actuation

•rubbing action

•stiff suspension

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., July 1995

•A

ctuation voltages≈ 200 V

olts

•R

esonant frequencies

5–20 kHz

•C

urrent load≈ 250 m

A

•C

ontact resistance

< 20 Ω

Microrelay C

haracterization

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., July 1995

Microrelay Sw

itching Operation

•frequency ≈ 1 kH

z

•sw

itched signal ≈ 5 Volts

•contact travel ≈ 2 µm

•contact force ≈ 20 µN