8 MEMS Packaging

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8 MEMS Packaging

• Ken Gilleo PhD
• ET-Trends LLC

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Packaging Classification

• Package discrete MEMS device (non-WLP)
• Partial WLP pre-packaging e.g. capping
• Total WLP
• Bond protective wafers with vias
• Bond protective wafers with vias in MEMS
• Integrated package with 2nd-level connectors

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Hermetic Packaging

• Metal
• Ceramic
• Combinations

Plastic has not proven hermeticity passing
leak test is not enough Result is generally a
Near-Hermetic Package (NHP)
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Plastic Molded Package
Metal Lead Fame (MLF)
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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

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
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WLP Processes

• Wafer preparation
• MEMS release step
• Coat (polymer), treat anti-stiction, other
• Wafer bonding
• 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
• Caps in wafer
• Couplings, fittings, ports, or none
• Assemble
• Place sub-components
• Wafer bonding
• Move to final packaging process
• Capped wafer is transportable
• Packaging foundry may handle

Popular for inertial sensors accelerometers,
gyro.
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Wafer-Level Capping
(1) Print Adhesive
Printed Adhesive Walls or use etched features
Cap
(2) Bond
MEMS Wafer
(3) Singulate may be complex
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WL Cap Mold
1. Apply cap to device or wafer solder, weld,
bond.
After singulation steps
2. Attach bond device
3. Conventional overmolding or dispensed
encapsulant
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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
5. Seal/bond to wafer with laser, such as near-IR
6. Singulate by sawing
4. Flip lens/LCP array and align to wafer
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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

• Through chip (drill fill plasma, RIE)
• Route conductors over/under

Same methods been adopted developed for 3D
stacked chips
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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
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Device-Specific Packages
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Encapsulation

Selective
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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Pressure Packages
Motorola Unibody Package
Bishnu Gogoi, Motorola
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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
Ellis Meng California Institute of Technology
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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