MEMS Review 2005

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Microsistemas &Nanotecnologias

Microelectromechanical SystemsMEMS: An introduction

Virginia ChuINESC Microsistemas e Nanotecnologias

Lisbon, Portugal

www.inesc-mn.pt ;

Email: vcu!inesc-mn.pt

http://www.inesc-mn.pt/mailto:[email protected]:[email protected]://www.inesc-mn.pt/

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Outline

• Introduction

• Applications

– Passive structures – Sensors

– "ctuators

• Future Applications

• Summary Part I

• MEMS processing technologies – #ul$ micromacining

– Sur%ace micromacining

– LI&"

– 'a%er bon(ing

• Thin film MEMS – Motivation

– Microresonators

• MEMS resources

• Conclusions

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What are MEMS?Micro-electromechanical Systems

Common caracteristics:

• Faricated using micromachining• !sed "or sensing# actuation or are

$assi%e structures

• !sually integrated &ith electronic circuitry"or control and'or in"ormation $rocessing

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(-) Micromachined Structures

Linear Rack ear Reduction !ri"e Triple#Piston Microsteam Engine

Potos %rom San(ia National Lab. 'ebsite: ttp:))mems.san(ia.gov

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(-) Micromachined Structures

Movies %rom San(ia National Lab. 'ebsite: ttp:))mems.san(ia.gov

* dust mites on an o$tical

shutter

)e"lection o" laser light using

a hinged mirror

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A$$lications: +assi%e structuresInk$et Printer %o&&le

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A$$lications: Sensors

+ressure sensor:• +ie,oresisti%e sensing

• Ca$aciti%e sensing

• esonant sensing

A$$lication e.am$les:

• Mani"old asolute $ressure /MA+0 sensor

• )is$osale lood $ressure sensor/1o%asensor0

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+ie,oresisti%e +ressure Sensors

+ressure

+ie,oresisti%e elements

SiO*

$2 Si

34556 Si

sustrate

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+ie,oresisti%e +ressure SensorsWheatstone 7ridge con"iguration

Illustration %rom *"n Intro(uction to MEMS Engineering+, N. Malu%

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A$$lications: Sensors

• Acceleration

– Air ag crash sensing

– Seat elt tension

– Automoile sus$ension control

– 8uman acti%ity "or $acema9er control

• Viration

– Engine management

– Security de%ices

– Monitoring o" seismic acti%ity

• Angle o" inclination

– Vehicle staility and roll

nertial sensors

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Accelerometers

M nertial massF;Ma

S$ring

F;9

)am$ing

F;)v

Static de"ormation:

k

Ma

k

F d static ==

)ynamic eha%ior

Ma F kxdt

dx D

dt

xd M

ext ==++

2

2

M

k r =ω

D

M Q r

ω =

esonance "re

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Accelerometers

Accelerometer $arameters• acceleration range />0 /4>;@4 m's*0• sensiti%ity /V'>0• resolution />0• and&idth /8,0

• cross a.is sensiti%ity

Application Range 'and(idth Comment

Air 7ag )e$loyment B 5 > D 4 98,

Engine %iration B 4 > 6 45 98, resol%e small accelerations /3 4 micro >0

Cardiac +acema9er control B * > 3 5 8, multia.is# ultra-lo& $o&er consum$tion

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Ca$aciti%e Accelerometers

Stationary +olysilicon "ingers

#ase( on "L accelerometers, "nalog evices, Inc.

S$ring nertial Mass

Anchor to

sustrate

)is$lacement

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A$$lications: Actuators

e.as nstruments )igital Micromirror )e%iceEM

• Array o" u$ to 4@( million mirrors

• n%ented y e.as nstruments in 4

/or an animate( (emo o% tis (evice, go to http://www.dlp.com/dlp_technology/

• Each mirror is 4 µm on a side &ith a $itch o" 4G µm

• esolutions: 55.55 $i.els /SV>A0 and 4*5.45*H $i.els /SI>A0

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)igital Micromirror )e%ice

/rom *"n Intro(uction to Microelectromecanical S0stems Engineering+ b0 Na(im Malu%

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)igital Micromirror )e%ice

/rom *"n Intro(uction to Microelectromecanical S0stems Engineering+ b0 Na(im Malu%

12 "ceive gre0 scale b0 a(3usting te (uration o% pulse

• S&itching time: 4 Js /aout 4555 times "aster than the res$onse time o" the eye0

• Mirror is mo%ed y electrostatic actuation /*H V a$$lied to ias electrode0

• +roKection system consists o" the )M)# electronics# light source and $roKection o$tics

• +lacing a "ilter &heel &ith the $rimary colors et&een light source and the micromirrors

12 "cieve %ull color b0 timing te re%lecte( ligt to pass te weel at te rigt color

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Some "uture a$$lications• 7iological a$$lications:

– Micro"luidics

– La-on-a-Chi$

– Micro$um$s

– esonant microalances

–Micro otal Analysis systems

• Moile communications:

– Micromechanical resonator "or resonant circuits and "ilters

• O$tical communications: – O$tical s&itching

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Micro"luidics ' )1A Analysis

n the "uture# a com$lete )1A se

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Summary: A$$lications• ( main classes o" MEMS

– +assi%e structures – Sensors

– Actuators

• +assi%e structures

– Microreser%oirs /inKet $rinter no,,le0 – Micro-channels /micro"luidics0

• Sensors – +ressure sensors

– nertial sensors

• Actuators – )igital micromirrors /$roKection0

– >ears# transmissions# motors# $um$s# %al%es

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Outline• Introduction

• Applications

– Passive structures – Sensors

– "ctuators


• Summary Part I



– LI&"

– 'a%er bon(ing


– Microresonators

• MEMS resources

• Conclusions

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7asic micro"arication technologies• )e$osition

– Chemical %a$or de$osition /CV)'+ECV)'L+CV)0

– E$ita.y – O.idation

– E%a$oration

– S$uttering

– S$in-on methods

• Etching

– Wet chemical etching

• stro$ic• Anisotro$ic

– )ry etching

• +lasma etch

• eacti%e on etch /E# )E0

• +atterning

– O$tical lithogra$hy

– I-ray lithogra$hy

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7ul9 micromachining

Anisotro$ic etching o" silicon

Etchant

111

100

etch

etch

r

r

Selecti"ity top

)# Si

!isad"antages

+otassium 8ydro.ide/NO80

455 es -8ighly corrosi%e-1ot CMOS com$atile

etramethyl ammoniumhydro.ide/MA80

(5-5 yes -"ormation o" $yramidalhilloc9s at ottom o" ca%ity

Ethylenediamine$yrochatechol

/E)+0

( es -carcinogenic %a$ors

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7ul9 micromachining Anisotro$ic etch o" P455Q Si

*+,-+.

{ }111 a

/,-/-a

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7ul9 micromachining: +ressure sensors

+ie,oresisti%e elements

SiO*

$2 Si

34556 Si

sustrate

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Sur"ace Micromachining

sustrate

Important issues0• selecti%ity o" structural# sacri"icial and sustrate materials• stress o" structural material• stiction

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Most commonly used materials "or sur"ace micromachining:• sustrate: silicon

• sacri"icial material: SiO* or $hos$hosilicate glass /+S>0

• structural material: $olysilicon

Su1strates Sacrificial Structural

>lass

+lastic

metals

+olymer

Metals

silicon nitride

hin "ilm silicon /a-Si:8# µc-Si0

silicon nitrides

Silicon caride

Metals

$olymers

ilayer com$osites

Alternati%e materials

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• +olysilicon de$osited y L+CV) /D55 RC0 usually has large stress• 8igh anneal /55-4555 RC0 "or more than * hours rela.es the strain

Poto %rom 4.5. 6owe, 7niv. o% Cali%, #er$ele0, 89

Lo& tem$erature# thin "ilm materials has much less intrinsic stress

Stress

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Sur"ace tension o" li

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L>A – I-ray Lithogra$hy#Electro$lating />al%ano"ormung0# Molding / A"ormung0

)e$osit $lating ase

)e$osit $hotoresistE.$ose and de%elo$ $hotoresist

mmerse in chemical ath and

electro$late the metal

emo%e mold

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L>A

Potos %rom MCNC MEMS group

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Wa"er onding- Anodic

• ring sodium contating glass /+yre.0 and silicon together • heat to high tem$erature /*55-55 RC0 in %acuum# air or inert amient• a$$ly high electric "ield et&een the * materials /VD4555V0 causing moile 2 ions to

migrate to the cathode lea%ing ehind "i.ed negati%e charge at glass'silicon inter"ace• onding is com$lete &hen current %anishes• glass and silicon held together y electrostatic attraction et&een – charge in glass and 2

charges in silicon

SiO*$2 Si

34556 Siglass

Pie&oresisti"e pressure sensor

# # # # # #) ))

) ))

chuc9

silicon

glass

cathode

2

-

2

current

%a)

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Summary: MEMS "arication

• MEMS technology is ased on siliconmicroelectronics technology

• Main MEMS techni

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Outline• Introduction

• Applications – Passive structures

– Sensors

– "ctuators


• Summary Part I



– LI&"

– 'a%er bon(ing


– Microresonators

• MEMS resources

• Conclusions

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hin-"ilm MEMS

Thin films allo(s0• Lo&-tem$erature $rocessing

• Large area# lo& cost# "le.ile or iocom$atile

sustrates

• +ossiility to integrate &ith a CMOS or thin "ilm

electronics ased ac9 $lane

• Control o" structural material "ilm $ro$erties

/mechanical# electronic# o$tical and sur"ace0

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Sacrificial La er !e osition and Patternin

Structural La er !e osition and Patternin

Sacrificial La er Remo"al

d=1 µm; h=500 nm; b=10 µm

Lmax(bridge) ~ 60 µm ; Lmax(cantilever) ~ 30 µm

Sur"ace micromachining on glass

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•

Electrostatic force 1et(een gate and counter#electrode

• Electrostatic force is al(ays attracti"e

Electrostatic Actuation

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• A laser eam is "ocused on the structure and the

re"lected light is collected &ith an intensity /or

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5 45 4 *5 *

5@5

5@

4@5

decreasing lengthHCµm (5µm *Cµm *5µm 4Aµm 4Cµm 4*µm 45µm

(55 nm a-Si:8 ' 455 nm Al 45µm-&ide ridges

) e " l e c t i o

n / n o r m a l i , e

d 0

Fre

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)e$endence o" = on +ressure

5@G 5@A 5@? 4@5 4@4 4@*

5@5

5@C

4@5

n2-a-Si:8 ridge /L ; CA µm# w ; 45 µm# t ; 5@H µm0= -C

; *@*C V# = "C

; 5@H V

>lass sustrate

P 3 -4/ Torr

5@?C M8,#

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esonant detectors o" )1A hyridi,ation

Com$lementary

strandsM M) M

M

k

∆∝∆ω

In order to detect hy1ridi&ation0

Q M

M 1>

∆

y$ically# M1ridge< 5/#= g

!sing strands &ith 4-4G $ and a concentration

o" *55 $mol'cm* ⇒ Moligo< 5/#5; g

3

10−

≈

∆

M

M

7 ≥ 5///

7air

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Microsistemas &

MEMS esources

Reference 'ooks

• 1adim Malu"# An ntroduction to Microelectromechanical Engineering /Artech 8ouse# 7oston#*5550• M@ Ele&ens$oe9 and @ Wiegerin9# Mechanical Microsensors /S$ringer-Verlag# *5540• 8Uctor @ )e Los Santos# ntroduction to Microelectromechanical /MEM0 Micro&a%e Systems /Artech

8ouse# 7oston# 40

>e1sites• Sandia 1ational La: htt$:''mems@sandia@go%

• 7er9eley Sensors and Actuators Center: htt$:''&&&-sac@eecs@er9eley@edu• MEMS Clearinghouse: htt$:''&&&@memsnet@org'

Some companies (ith MEMS products• Accelerometers – Analog )e%ices: htt$:''&&&@analog@com'technology'mems'inde.@html• )igital Light +rocessing +roKector- e.as nstruments: htt$:''&&&@dl$@com• Micro-electro$horesis chi$ – Cali$er echnologies: htt$:''&&&@cali$ertech@com
http://mems.sandia.gov/http://www-bsac.eecs.berkeley.edu/http://www.memsnet.org/http://www.analog.com/technology/mems/index.htmlhttp://www.dlp.com/http://www.calipertech.com/http://www.calipertech.com/http://www.dlp.com/http://www.analog.com/technology/mems/index.htmlhttp://www.memsnet.org/http://www-bsac.eecs.berkeley.edu/http://mems.sandia.gov/

MEMS Review 2005

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