MEMS PACKAGING ISSUES and MATERIALS

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MEMS PACKAGING ISSUES and MATERIALS
IMAPS 2000 BOSTON
Intellisense

• Ken Gilleo
• ET-Trends
• gilleo_at_ieee.org

Morphed
Sandia
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OUTLINE

• MEMS Introduction Survey
• Packaging issues
• MOEMS l more challenge
• MEMS materials
• Conclusions

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The New Nano World
Where all technology converges
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MEMS
Micro-Electro-Mechanical System

• Semiconductor processing used
• Merges mechanical motion electronics
• High Versatility
• sensing
• computing
• motion
• control

The convergence point of electronics, mechanics,
physics, chemistry and biology, etc.
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MEMS Processing

• Electronics fab standard methods
• Silicon Machining
• Define mechanical parts by lithography
• Form sacrificial SiO2 in removal areas
• Etch away SiO2 to free mechanical parts
• Many other micro-machining processes are
  available

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MEMS Motion

• Deformable cantilevers, beams, membranes
• Sliding, linear
• Rotating partial, full, multi-plane
• Rotating Inter-contact gears, wheels
• Hinges
• Combinations

Sandia, UW, AD
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MEMS Motors

• Electrostatic very efficient
• Thermal
• Electromagnetic
• Pneumatic
• Hydraulic
• Photoelectric

Surface area is relatively high, mass is very
low surface effects are important
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MEMS Structures
Analog Devices
IBM MEMS DNA Detector
SANDIA
Electrostatic Relay - UW
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More MEMS
Worlds smallest Insertion
UW-Madison
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Packaging
The real problem may be Lack of KNOWLEDGE, not
Lack of TECHNOLOGY
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Packaging Challenges

• MEMS devices can be very fragile
• pre-package handling concerns
• may require etch step by packager
• more protection by package
• Most require hermetic package ()
• MOEMS (later) requires a window controlled
  atmosphere.
• Biggest challenge cost-effective, high volume
  packaging

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MEMS Packaging Types

• Traditional hermetic metal or ceramic
• Cap-on-Chip
• wafer-level
• device-level
• Silicon Sandwich
• Near- and non-hermetic
• Selective/partial packaging

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Packaging
No Standards
DPL Modules, TI (HERMETIC)
(HERMETIC)
Accelerometer (CAP)
Ink Jet MEMS in TAB Package (SELECTIVE)
MicroRelay - Cronos (HERMETIC)
(HERMETIC)
(HERMETIC)
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Selective Encapsulation

MEMS
Ink Jet Gun I-TAB package
This type of machine can be used to selectively
encapsulate MEMS- one like this is used on ink
jet cartridges. Courtesy of Speedline
MEMS bare die
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Cap-on-Carrier
Silicon or Metal Cap
Molded or Liquid Encapsulant
MEMS IC
Solder, weld, or polymer
This packaging method is suitable for
accelerometers, gyroscopes and other motion
detectors that can be sealed.
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Cap-on-Chip(level-0)
CAP
Seal
Vacuum
MEMS Chip
Can now be handled like an ordinary die - almost!
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Cap-on-Chip Variants

• Etched Silicon, ceramic, glass
• Indent Reflow Sealing (IMEC)
• Wafer-Level Protected (AMKOR)
• Silicon Sandwich GIT
• Nitride shell UC-Berkeley, L. Lin
• Metal, low CTE?
• Plastic?

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Cap-on-Chip Overmolding
1. Apply cap to device or wafer solder, weld,
bond.
May require gel coat to protect thin cap
2. Attach bond device
3. Conventional overmolding followed by solder
ball attach.
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MOEMS
Micro-opto-electro-mechanical systems

• Projection Mirrors
• Photonics Switches
• Gratings
• Fiber Aligners
• Modulators, Shutters
• Movable Lenses

A Market powered by the Internet!
A Technology that will power the Internet!
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Optical MEMS or
MOEMS
Fiber Alignor
Lenses Array
Cronos (JDS-Uniphase) Micro-Mirror
Rotating Mirror-UCLA
Pop-Up Lens
Micro-Mirror Array - TI
Cross-switch mirror
Shutter - Sandia
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Micro-Mirror Close-up by TI
Worlds most complex machine?
Boeing 777
Ref. Digital Light Processing TM for
High-Brightness, High-Resolution
Applications Larry J. Hornbeck,
hbek_at_dlep1.itg.ti.com
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MOEMS Micro-Mirror
Getter
Weld or seal
WINDOW
Ceramic
HEAT SINK
HERMETIC
MEMS Digital Mirrors
All from Texas Instruments
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Flip Chip for MOEMS?
Encapsulant
MEMS FLIP CHIP
Underfill
Light Pipe
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MOEMS Flip Chip BGA Package
Seal or dam
MEMS IC
Light Pipe
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MEMS/MOEMS Materials

• Low creep solders e.g., InAg
• Getters
• Controlled atmosphere agents
• Lid seals
• Anti-friction/stiction agents
• Low stress molding compounds

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GETTERS
Agents that counteract harmful contaminants
within a sealed package this includes solids,
liquids, gases and combinations.
Will guard and control package environment over
an extended time.
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Types of Getters

• Particle attracts and holds.
• Moisture desiccant.
• Gas adsorbs/chemically converts to liquid or
  solid.
• Combinations.
• Others are possible.

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Why Use Getters?

• Remove harmful agents from the device
  environment.
• Control atmosphere for many years.
• Provide the maximum security and reliability
  highest life expectance.
• Protect optics from fogging
• Reduce wear

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Available Getters

• Low Temperature Moisture
• High Temperature Moisture
• Micro-Particle
• Hydrogen for GaAs
• H2 H2O

Are Others Needed?
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Friction/Stiction

• MEMS very high area/mass n3/n2
• Atomic attraction forces are high
• Starting forces can be high gt106X
• Stiction stuck surfaces stay stuck

Stiction
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Stiction - Accelerometer Example
For air bags
INOPERABLE
Analog Devices Chip
Sensing Mechanism (AD)
High surface area high attraction STICTION
Result of rough handling dead component
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Stiction Solutions

• Liquid lubricants
• Gases, vapors
• Polymer films Fluorinated Parylene
• Inorganic nitride, metal coating
• Design reduced contact

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Parylene for Antistiction
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Stable to gt 450oC
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What New Getters/Agents?

• Oxygen getter?
• Specific humidity range control?
• Hydrophobic coating on chip?
• Time-release lubricants, etc.?
• Others?

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Conclusions

• MEMS a key 21st century technology
• The packaging is more difficult
• Expect new unusual packages
• Need high-volume packaging
• New guidelines are needed

Lets take the bite out of MEMS