process technology to fabricate high …process technology to fabricate high performance mems on top...
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Process Technology to Fabricate High Performance MEMS on Top of Advanced LSI
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Shuji TanakaTohoku University, Sendai, Japan
2
Mor
e M
oore
: Min
iatu
rizat
ion
Integrated inertia
sensors Integrated health care
devices
3 µm
0.8 µm DMD
~202
0
~202
5
One-chip multiband/ tunable
wireless chips
Implantable devices
~201
5 Self-controlled one-chip sensors
Pre
sent
High performance integrated sensors
SmallerMore inteillentMore distributed
JSAP Integrated MEMS Technology Roadmap
Nanoelectronics
More than Moore: Diversification
W-LANW-LAN
Digital TVDigital TVW-CDMAW-CDMA
PHSPHS WiMAXWiMAX
GSM/PDCGSM/PDC5.16~5.35 GHz2.4~2.48 GHz
470~770 MHz
2.5~2.7 GHz
1.92~1.98 GHz UL2.11~2.17 GHZ DL
800 MHz 900 MHz1.9 GHz
4th Gen.4th Gen.
1.88~1.92 GHz
Multiband Wireless Communication
3
Tx
RxMulti-band wireless communication chip for W-CDMA + GSM/GPRS/EDGE(Qualcomm, QSC6240)
Integration of Wireless Communication System
LNA 0/90 ºA/D
A/D
Digital signalprocessor
FilterMixer
Discrete devicesIntegrated devices based on RF CMOS technology
Frequency tuning circuit
Unimplemented system
Real one-chip solution enables not only advanced mobile communication systems but also ubiquitous network sensors, wireless healthcare chips etc.
Integration of advanced LSI and “mechanical” devices (SAW/BAW filters, clock oscillators, RF MEMS switches, variable capacitors) is a key.
Rx
4
ADXRS150 2-axis gyro
Inertia Sensors (Analog Devices)
Detection circuit
G sensor
Safety steel ball sensor
125 μm
1.3 μm
2 μm
5
A tiny capacitance change (12 zF) corresponding to 1.6×10-4 Å displacement is detectable by the embedded integrated circuit in the gyro.
Integrated Accelerometer (Analog Devices)
Poly-Si sensor structure on 3 µm-ruled, W-metalized BiCMOSPoly-Si annealing at 1100 °C for 30 min, Impossible to fabricate in LSI foundry
Circuit(NPN, NMOS)
Poly Si sensor structure
On-CMOS structure
SOI MEMS structureSensor structure release from this trench Sensor structure Circuit
Single crystal Si sensor structure beside 0.6 μm-ruled, Al-metalized CMOSCompatible with advanced LSI from LSI foundry, Low space efficiency
Judy et al., Hilton Head Island WS 2004, 27
SOI
Trench isolation
6
Digital Micromirror Device (TI)
• 10~16 μm square micromirrors• ~2 μs response time• 8.5 V driving voltage• ±12 ° tilt angle• 848×600 = 508800 pixels for SVGA
~ 1280×1024 = 1310720 pixels for SXGA
Hornbeck, IEDM 2007, 17-24
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Applications of DMD
Rear-projection television
Panasonic
Projector for cinema complex
NEC
Mobile projector
NEC Weight: 1 kg
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Metal Surface Micromachining for DMD (TI)
0.8 µm CMOS
address circuit
(SRAM) Al SiO2
SiO2 Al
AlResist
Kessel et al., Proc. IEEE, 86 (1998) 1687
1. Sacrificial resist layer
2. Al and SiO2 mask for hinges
3. Al and SiO2 mask for beams
4. Al etching for beams and hinges
5. Sacrificial resist layer and Al mirror
6. Sacrificial resist etching
Resist
Hornbeck, IEDM 2007, 17-249
MEMS-LSI Integration using Ge Sacrificial Layer
Ge
Al
Au/Cr
AlN
1. Ge patterning and SiO2 deposition
2. Metal patterning and AlN deposition
3. AlN and Au/Cr patterning
4. Ge sacrificial etching
SiO2
Mo
LSI
Collaboration with NDK• Multi-freq. AlN Lamb wave resonator monolithically integrated with LSI
• Application to one-chip high-speed communication devices
100 μm
310 MHz
LSI
10
Electrostatic-Actuated Capacitive Shunt Switch
Ni bridgeDielectric layer(SiO2)
-30
-25-20
-15-10
-5
0
510
1520
1 3 5 7Freqency(GHz)
-0.5
-0.45-0.4
-0.35-0.3
-0.25
-0.2
-0.15-0.1
-0.050
Insert loss
Isolation
Frequency (GHz)
Isol
atio
n (d
B)
Inse
rtion
loss
(dB
)
Off state
On state
Signal
Ground
Actuation pad Ground
200 µm
Notches for close contact
GND GNDSignal
Sacrificial PR (3.5 µm)
Sacrificial PR (1.5 µm)
Driving voltage: 38 V
Yuki et al., Sensor Symposium 2007
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Wafer-Level Packaging of RF MEMS Switch
DC in (Au/Cr)
CPWCPW
Dry film resistCavity
RF MEMS switch packaged by dry film resist
Exposed part
Polyolefin moldDry film resist
1. Molding dry film resist
3. Laminating molded dry film resist and exposing
4. Developing and over-coating
Device wafer
2. Exposing dry film resist
Exposed part
Yuki et al., Sensor Symposium 2007
12
Phase Shifter Using RF MEMS Switches
Z0
Z 1
Z0
Z 2
Capacitive shunt SW
Reflection typeSwitching line type
SW downReflect here
SW upReflect here
Capacitive shunt SW
0°
90°
22.5°
180°
45°
Reflection-type phase shifter using RF MEMS switch
(Taiko Denki & Tohoku Univ.)13
Memory Effect of Metal Hinges in DMDA. B. Southeimer, IEEE 40th Annual International Reliability Physics Symposium, Dallas, TX, 2002
50 % / 50% 5 % / 95%
Shi
ft (%
) of
bia
s vo
ltage
at
whi
ch a
hal
f of m
irror
s la
nd o
n th
e le
ft si
de
Duty cycle in accelerating test
Simulating random image Simulating static image
Test duration Mirrors exhibiting hinge memory
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Wafer Bonding-based MEMS-LSI Integration
1. Preparation of a device layer on a support wafer Adhesion layer
Device layere.g.) Single crystal Si, Piezoelectric materials, Diamond, Compound semiconductors
Support wafer
Interlayer
2. Fabrication of a LSI wafer
3. Low temperature bonding of the device layer and the LSI wafer
LSI wafer
e.g.) SiO2, Polymer
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4. Removal of the support wafer/Thinning of the device wafer
5. Fabrication of MEMS (e.g. RF MEMS switch, variable capacitor) or SAW/BAW devices
6. Release of the device by sacrificial etching
LSI wafer
Electrical connection
Polymer
Single Crystal RF MEMS Switch on Top of LSI
Actuation electrode
Metal anchor
Single crystal Si cantilever
Signal line
RF MEMS switches on a dummy LSI wafer
Metal anchor
200 μm Single crystal Si cantilever
200 μm
Metal anchor
Single crystal Si bridge0
5
10
15
20
25
0 200 400 600 800 1000
Hig
ht (μ
m)
Lateral length (μm)
OFF (Vdrive = 0 V)
ON (Vdrive = 8 V)
OFF ON
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Single-Crystal-Si-on-LSI (SOL) Technology
1. Fabrication of metal padson a (dummy) LSI wafer
2. Bonding a SOI wafer onthe LSI wafer usingpolymer interlayer
3. Etching of the handle andBOX layers
4. Patterning of metalelectrodes
5. Shape formation of thedevice by reactive ionetching
6. Cu electroplating usingphotoresist molds for electrical connection
7. Removal of thephotoresist molds
8. Sacrificial polymer etchingby O2 ashing to releasethe device
LSI wafer
SOI wafer
Polymer
Cu
Photoresist mold17
200 μm
AlN/Si Composite Resonators on Top of LSI
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1. Electrically-coupled AlN/Si composite thickness-mode filter
2. Mechanical-coupled AlN/Si composite disk array filter
Si
In Out
GND
Coupling Beam4λ
Si
In Out
GND
SiO2
Out-of-phase mode In-phase mode
Collaboration withMr. Matsumura (NiCT)
AlNSi
AlNSi
Single-Crystal-Si-on-LSI (SOL) Technology
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1. Wafer bonding using polymer
PolymerLSI
SOI wafer
3. Metal patterning
5. Metal patterning
6. Si etching
7. Sacrificial polymer etchingRu Au/Cr
Al Au/Cr
Au/Ti
2. Handle layer and BOX layer etching
4. AlN deposition and patterningAlN
Resist
SiO2
AlN/Si Composite Resonators on Top of LSI
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Unpublished data
Share Wafer System in Tohoku University
Given process→ Call for devicesGiven process→ Call for devices
Registration from A corp., B univ. …Registration from A corp., B univ. …
A B CD E FG H I
A
B
Group ASensor circuitGroup ASensor circuit
Group BDriver circuitGroup BDriver circuit
Group COscillator circuitGroup COscillator circuit
Coordination with LSI foundry
Coordination with LSI foundry
A B
CD
A B
CD
A B
CD
Is there a common process?
Is there a common process?
Multiple devices in each shot
Group DActuator circuitGroup DActuator circuit
Delivery after chip separation
Delivery after chip separation
Full wafers to each groupFull wafers to each groupProject members (NDA is concluded.)
Shuttle service
Share wafer system
MEMS fabrication by each groupMEMS fabrication by each group21
Summary
• There is strong demands for monolithic integration of advanced LSI and “mechanical” devices such as clock oscillators, mechanical filters, switches and sensors. “More than Moore” with “Moore Moore” and “Biyond CMOS”
• There are varieties of existing MEMS-LSI integration technology, but they are not suitable for the above applications.
• We have developed new versatile microprocess technology for the monolithic integration of high-performance MEMS on top of advanced LSI.
• Using the developed technology, we fabricated RF MEMS switches/variable capacitors, RF mechanical resonators and filters etc.Acknowledgement: This study was partly supported by Special Coordination Funds for Promoting Science and Technology.22