Transcript Document

8 MEMS Packaging
•Ken Gilleo PhD
•ET-Trends LLC
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Packaging Classification
1. Package discrete MEMS device (non-WLP)
2. Partial WLP; pre-packaging; e.g. capping
3. Total WLP
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Bond protective wafers with vias
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Bond protective wafers with vias in MEMS
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Integrated package with 2nd-level connectors
Hermetic Packaging
• Metal
• Ceramic
• Combinations
Plastic has not “proven” hermeticity – passing leak test is not enough;
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Result is generally a Near-Hermetic Package (NHP)
Plastic Molded Package
Metal Lead Fame (MLF)
Plastic
OPEN
INSERT
FILL
Conductor Insert
RJR Polymers
Thermoplastic
Quantum Leap Packaging
RJR Polymers
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PCB Fabricated Enclosures
• Fabricated PCB substrate; BGA, QFN
• Add walls; various methods used
• Die attach & wire bond chip (s)
• Seal lid
• Singulate
Knowles Electronics
Used for non-hermetic MEMS
such as microphones
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Ported Flip Chip BGA
Encapsulant
MEMS FLIP CHIP
Underfill
Light pipe or gas access
Dam
Selective; semipermeable
membrane, etc.
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WLP Processes
• Wafer preparation
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MEMS release step
Coat (polymer), treat; anti-stiction, other
• Wafer bonding
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Apply adhesive if required
Bond
• Singulation; cap, MEMS, both
• Secondary packaging if required
• Test
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Partial WLP: Pre-Packaging
• Form package components
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Caps in wafer
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Couplings, fittings, ports, or none
• Assemble
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Place sub-components
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Wafer bonding
• Move to final packaging process
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Capped wafer is transportable
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Packaging foundry may handle
Popular for
inertial sensors;
accelerometers, gyro.
Wafer-Level Capping
(1) Print Adhesive
Printed Adhesive Walls
or use etched features
Cap
(2) Bond
(3) Singulate; may be complex
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MEMS Wafer
WL “Cap & Mold”
Seal
1. Apply cap to device or wafer;
solder, weld, bond.
Cap
Vacuum
MEMS Chip
After singulation steps
2. Attach & bond device
3. Conventional
overmolding or
dispensed
encapsulant
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Cross-section
Lid Sealing/Bonding
• Used for virtually all cavity packages
• WL lid bonding is called “capping”
• Many methods, old and new
• Wafer bonding & lid seal can share methods
Can use many of the same methods as wafer bonding
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Wafer-Level with Polymer Films
1. Form sheet of
polymer film or resin
2. Cut or mold into
matrix; laser or die
3. Bond tack to lens disk
Laser spot or diode bar line
4. Flip lens/LCP array and
align to wafer
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5. Seal/bond to
wafer with laser,
such as near-IR
6. Singulate by sawing
Total WLP
Processes must provide:
• Electrical pass-through; e.g.; TSV
• Enclosure
• Interconnect to PCB (2nd-level)
• Controlled atmosphere as required
• Non-electrical I/Os as required
• General package attributes
TSV = Through Silicon Vias
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Interconnect for WL
1. Through chip (drill & fill; plasma, RIE)
Same methods been
adopted & developed
for 3D stacked chips
2. Route conductors over/under
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Integral Caps
• Form capping structure
• Clean
• Vacuum or gas environment
• Seal port
• Singulate
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Fabricate Caps on Wafer
(Hexal MicroMold Process)
• Etch Recess
• Deep Etch
• Deposit sacrificial & pattern
• Plate Au bumps & seal
• Release
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Micro Cap Assembly
• Transfer caps to MEMS
• Align
• Bond
• Separate
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Integrated Package
Deposited Layer
Sacrificial
MEMS Structure
Base
…or add port or coupling
Evacuate
Seal
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Device-Specific
Packages
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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
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MEMS bare die
Pressure Packages
Cost can be too high
Protective Coating; e.g.; Parylene
Corrosion can occur under the
coating in harsh environments
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Bishnu Gogoi, Motorola
Motorola Unibody Package
Bio-MEMS & Fluidics Packaging
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Bio-MEMS Challenge
• Biocompatibility; inert
• Sample into pressurized system
• Variety of energy transfer modes
• Interfaces in hostile environments
• Protection within life system
• Remakable couplings
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Fluid Coupling Technology
• Fluidic MEMS device (s)
• Inter-chip coupling as required
• Auxiliary unit connections
• Through-package fluidic interface
• Electrical I/Os and 2nd-level
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Fluid Coupling Design
Materials: silicon, polymers
Processes: bulk etching, RIE
Plastic Insertion Using Cryogenics
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Bulk Coupler Assembly
Ellis Meng; California Institute of Technology
BioMEMS
IME Singapore
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Plug-in
MEMS
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Session Summary
• MEMS is a major packaging challenge
• Typically device-specific
• Often application-specific
• Result is non-standard, high customization
• Trend Discrete  pWLP  full-WLP
• More WLP in the future
• Some MEMS packaging suppliers evolving
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