MEMS Review 2005
Transcript of MEMS Review 2005
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INESC MN
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
• 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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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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Sur"ace Micromachining
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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Sur"ace Micromachining
• +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 Micromachining
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*$2 Si
34556 Siglass
Pie&oresisti"e pressure sensor
# # # # # #) ))
) ))
chuc9
silicon
glass
cathode
2
-
2
current
%a)
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Summary: MEMS "arication
• MEMS technology is ased on siliconmicroelectronics technology
• Main MEMS techni
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Outline• Introduction
• Applications – Passive structures
– Sensors
– "ctuators
• Future Applications
• Summary Part I
• MEMS processing technologies – #ul$ micromacining
– Sur%ace micromacining
– LI&"
– 'a%er bon(ing
• Thin film MEMS – Motivation
– Microresonators
• MEMS resources
• Conclusions
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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 $mol'cm* ⇒ Moligo< 5/#5; g
3
10−
≈
∆
M
M
7 ≥ 5///
7air
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MEMS esources
Reference 'ooks
• 1adim Malu"# An ntroduction to Microelectromechanical Engineering /Artech 8ouse# 7oston#*5550• M@ Ele&ens$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/