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9/13/2002 Liwei Lin, University of California at Berkeley 1

Packaging Issues of MEMS DevicesPackaging Issues of MEMS Devices

Liwei Lin

Associate Professor, Department of Mechanical EngineeringCo-Director, Berkeley Sensor and ActuatorCenter

University of California at Berkeley

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Presentation OutlinePresentation Outline

zMEMS Products & Packaging Issues

zMicroelectronics Packaging

zMEMS Packaging Approaches

Integrated microfabrication processes

Water bonding processes

z Summary

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Existing MEMS ProductsExisting MEMS Products

Device Year Units Sale Comment

(M) (M)Blood Pressure 1998 20 22 price drop, sale flat

Auto MAP 2000 52 400 price dropping

Auto Accelerom. 2002 100 ~400 price dropping

Auto Gyro 2002 20 ~200 newer market

Ink-Jet Head 2002 470 8,400 huge market

Disk-Drive Head 2002 1,500 12,000 huge market

Head Positioner 2002 400 ~800 new marketDisplays 2000 1 300 High chip cost

Valves 2005 1~2 100 small market

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MEMS Packaging IssuesMEMS Packaging Issuesz MEMS Accelerometer

Example: Surface-Micromachined

Accelerometers by

Analog Devices, Inc.

ADXL50 by Analog Devices, Inc.

z Key Issues

Free standing

microstructures Hermetic sealing, Vacuum

Temperature sensitive

microelectronics

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ExampleExample

Optical MEMSOptical MEMS

z Optical MEMS

Example: surface-micromachined DMDby Texas Instrument

z Key Issues Free standing

microstructures

Hermetic sealing Temperature sensitive

microelectronics

DMD

Projected

ImageLamp

Color

Wheel

Projection

Optics

TIs DMDTM Chip for Projection Display

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ExampleExampleBioMEMS &BioMEMS & MicrofluidicsMicrofluidicsz Microfluidics

Example: diffusion-based sensor byMicronics Inc.

z Key Issues Micro-to-Macro

interconnector

Good sealing Temperature sensitive

materials

Micronics Inc.s T sensor

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ExampleExampleRF MEMSRF MEMS

z MEMS Relay Example:

micromachined RFrelay by Omron with a

needle (1 billionoperation, 0.5 msec)

z Key Issues

Free standingmicrostructures

Hermetic sealing

Vacuumencapsulation ? Omrons MEMS RF relay

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IC and MEMS PackagingIC and MEMS Packaging

z IC Packaging well-developed (dicing, wire bonding ...)

30% to 95% of the whole manufacturing cost

z MEMS Packaging specially designed packaging processes

difficult due to moving structures, chemicals ...

the most expensive process inmicromachining

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Microelectronics PackagingMicroelectronics Packaging

z Electronic Package Hierarchy

Chip Module (1st level)

Card (2nd level)

Board (3rd level)

Gate (4th level)

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ApproachApproach

z To adopt IC packaging

processes as much aspossible

z To protect MEMS

devices and follow ICpackaging processes

z Encapsulations (caps)

are required

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MEMS PostMEMS Post

--PackagingPackaging

z MEMS Packaging Processes

Integrated Processes Highly process dependent, not versatile

Not suitable forpost-processing

Wafer Bonding Processes Need high temperature which may damage

microelectronics or temperature sensitive MEMS materials

Require very smooth and flat surfaces

z Localized Heating & Bonding Processes

Localized Eutectic, Fusion bonding and others

NSF CAREER Award, Division of Electrical & Communication Systems, 5/98-4/2002

Rated No. 1 in the panel

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Massively Parallel PostMassively Parallel Post--PackagingPackaging

DARPA BAA98-43, MTO/MEMS Program, 5/98 - 4/2001

Innovative Approach Industrial Participants

- Analog Devices Inc.

- Motorola Inc.

- Delco Electronics Corp.- Honeywell Inc.

- Ford Motor Company

- SiTek Inc....

US patent, No. 6,232,150, May 15, 2001

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Rationale: Localized HeatingRationale: Localized Heating High temperature is confined Temperature is controllable

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Localized Eutectic BondingLocalized Eutectic Bonding

Conventional oven, Si-Au

eutectic bonding - uniformity??

Localized eutectic bonding

excellent bonding strength

Lin, Cheng and Najafi, Japanese Journal of Applied Physics, Vol. 11B, pp. 1412-1414, 1998

Surface +

Ch Li d N j fi IEEE/ASME J f MEMS V l 9 3 8 2000

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Localized Fusion BondingLocalized Fusion Bonding

Silicon-to-glass fusion

bonding - heater disappeared

After HF dipping

excellent bonding result

Cheng, Lin and Najafi, IEEE/ASME J. of MEMS, Vol. 9, pp. 3-8, 2000

Surface +

Ch Li d N j fi IEEE/ASME J f MEMS V l 10 392 399 2001

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Localized Solder BondingLocalized Solder Bonding

Surface +

Indium solder as intermediate

layer - Al Dew Point Sensor

Before Bonding

After Bonding

Cheng, Lin and Najafi, IEEE/ASME J. of MEMS, Vol. 10, pp. 392-399, 2001

S d Li MEMS01

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Localized Plastics BondingLocalized Plastics Bonding

z Plastics to Silicon, to Glassand to Plastics bonding

Su and Lin, MEMS01

Surface +

z Direct encapsulation

of liquid

L d Li T d 01

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Nanosecond Laser WeldingNanosecond Laser Welding

Luo and Lin, Transducers01

Bonding

results

Mask

Mask

Patterns

which

pre-define

Bonding

areas

Ultrafast bonding, Restricted heating zone,

Parallel packaging

Surface +

Kim and Lin MEMS02 pp 415 418 2002

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Ultrasonic Bonding and SealingUltrasonic Bonding and Sealing

Kim and Lin, MEMS02, pp. 415-418, 2002

Lateral vibration setup for ultrasonic bonding

Horn

PiezoelectricActuator

Guide-Slider

Die

Holder

Load

Fixture

Control Unit

Native Al

Oxide

Al

Al

Al

Al

Before

Bonding AfterBonding

Si Chip

Glass Cover

Au/Al (0.6, 1 m)

In/Al (5 m)

Cao and Lin HH02 2002

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Selective Induction BondingSelective Induction Bonding

z This method has great potential for wafer-levelselective packaging processes

z The bonding time can be very fast and the heatingzone can be well confined by remote heating source

Cao and Lin, HH02, 2002

Sample

CoilSubstrate

Platform

Substrate

SolderRing

Glass to

metal

bonding

Glass to glass

bondng

10m

50m

Chiao and Lin Sensors and Actuators Vol 91A pp 404 408 2001

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RTP Bonding (Al to Glass or Nitride)RTP Bonding (Al to Glass or Nitride)

Chiao and Lin, Sensors and Actuators, Vol. 91A, pp. 404-408, 2001

RTP (Rapid Thermal Processing) for device

encapsulations (750o

C for 10 seconds)

Surface +

Lin et al Microelectromechanical Filters for Signal Processing

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LPCVD Selective EncapsulationLPCVD Selective Encapsulation

SEM Microphoto Measured Spectrum, Q = 2200

Lin et. al., Microelectromechanical Filters for Signal Processing,

IEEE/ASME J. of Microelectromechanical Systems, Vol. 7, pp.286-294, 1998

Cheng Hsu Lin Najafi and Nguyen MEMS01 pp 18 21 2001

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Localized Vacuum EncapsulationLocalized Vacuum Encapsulation

Cheng, Hsu, Lin, Najafi and Nguyen, MEMS 01, pp. 18-21, 2001

Surface +

Vacuum encapsulated comb

resonator under a glass cap

0

3000

6000

9000

12000

0 4 8 12 16 20 24

Weeks

Qf

actor

Long-term testing under the

vacuum packaged cavity

Chiao and Lin Hilton Head02

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RTP Vacuum Packaging ResultsRTP Vacuum Packaging Results

z Quality Factor~ 1800?200z

Pressure inside the package ~200mTorr

0

500

1000

1500

2000

0 4 12

200

400

1800

Time of Pre-Baking in Vacuum ( hours)

Quality

Factor

z Quality factor increases with

the pre-baking time

Chiao and Lin, Hilton Head 02

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MEMS Packaging SummaryMEMS Packaging Summary

z Localized thermal bonding processes

Eutectic, fusion, solder, laser welding,ultrasonic, plastic bonding processes

z RTP bonding

Aluminum-to-glass, aluminum-to-nitridez Vacuum packaging processes

Integrated LPCVD nitride sealing

Localized aluminum-glass bonding RTP aluminum-nitride bonding

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AcknowledgementsAcknowledgements

z Researchers

Dr. Y.T. Cheng Localized resistive heating & bonding

Dr. M. Chiao RTP bonding

Dr. C. Luo Nanosecond laser welding

Mr. Y.C. Su Plastic bonding

Mr. J.B. Kim Ultrasonic bonding Mr. A. Cao Inductive heating and bonding

z Funding sources

NSF CAREER AWARD, DMII grant DARPA/MTO/MEMS Program, DARPA/DSO/BioFlips program