Transcript No Slide Title

MEMS PACKAGING ISSUES
and MATERIALS
IMAPS 2000
BOSTON
Intellisense
Ken Gilleo
ET-Trends
[email protected]
Morphed
1
Sandia
OUTLINE
• MEMS Introduction & Survey
• Packaging issues
• MOEMS: l = more challenge
• MEMS materials
• Conclusions
2
The New Nano World
MEMS
MOEMS
OE
OM
Optics
Where all technology converges
3
MEMS
Micro-Electro-Mechanical System
• Semiconductor processing used
• Merges mechanical motion & electronics
• High Versatility
– sensing
– computing
The convergence point of
electronics, mechanics,
physics, chemistry and
biology, etc.
– motion
– control
4
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
5
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
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SANDIA
Electrostatic Relay - UW
More MEMS
World’s smallest
“Insertion”
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UW-Madison
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)
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(HERMETIC)
MicroRelay - Cronos (HERMETIC)
(HERMETIC)
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.
MEMS bare die
Courtesy of Speedline
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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.
MEMS IC
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
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Optical MEMS or
Cronos (JDS-Uniphase)
Micro-Mirror
Lenses Array
Fiber Alignor
Rotating Mirror-UCLA
Pop-Up Lens
Micro-Mirror Array - TI
Shutter - Sandia
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Cross-switch mirror
Micro-Mirror Close-up by TI
on
off
Boeing 777
World’s most
complex machine?
Ref. “Digital Light Processing TM for High-Brightness, High-Resolution Applications”
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Larry J. Hornbeck, [email protected]
MOEMS Micro-Mirror
Weld
or
seal
HERMETIC
Getter
WINDOW
Ceramic
HEAT SINK
MEMS Digital Mirrors
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All from Texas Instruments
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
28
Available Getters
• Low Temperature Moisture
• High Temperature Moisture
• Micro-Particle
• Hydrogen; for GaAs
• H2 & H2O
Are Others
Needed?
29
Friction/Stiction
• MEMS; very high area/mass = n3/n2
• Atomic attraction forces are high
• Starting forces can be high; >106X
• Stiction: stuck surfaces stay stuck
Stiction
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Stiction - Accelerometer Example
For air bags
Analog Devices Chip
Sensing Mechanism (AD)
Result of rough
High surface
area = high
attraction =
handling = “dead” component
“STICTION”
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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
Attribute
Stress-free coatings
Thin contiguous film without pinholes
Inert
Even coating of sides and edges
Hydrophobic
Low surface energy, especially fluorinated Nova HT
High temp capability up to 500 degrees C
Low k down to 2.28
Optically clear, UV resistant
MEMS
yes
yes
yes
yes
yes
yes
yes
yes
MOEMS
yes
yes
yes
yes
yes
yes
yes
yes
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Dimer
Monomer
Pyrolyze
Vaporize
100-150C
1.0 Torr
650-750C
0.5 Torr
Polymer
Deposit
20-40C
0.1 Torr
PPX
PX
P arylene N ova H T
DPX
Stable to > 450oC
34
What New Getters/Agents?
• Oxygen getter?
• Specific humidity range control?
• Hydrophobic coating on chip?
• Time-release; lubricants, etc.?
• Others?
35
Conclusions
• MEMS: a key 21st century technology
• The packaging is more difficult
• Expect new & unusual packages
• Need high-volume packaging
• New guidelines are needed
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Let’s take the bite out of MEMS