1 8 MEMS Packaging Ken Gilleo PhD ET-Trends LLC

2 Packaging Classification 1.Package discrete MEMS device (non-WLP) 2.Partial WLP; pre-packaging; e.g. capping 3.Total WLP  Bond protective wafers with vias  Bond protective wafers with vias in MEMS  Integrated package with 2 nd -level connectors

3 Hermetic Packaging Metal Ceramic Combinations Plastic has not “proven” hermeticity – passing leak test is not enough; Result is generally a Near-Hermetic Package (NHP)

4 OPENINSERTFILL Plastic Conductor Insert Plastic Molded Package Metal Lead Fame (MLF) Thermoplastic Quantum Leap Packaging RJR Polymers

5 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 Knowles Electronics

6 Ported Flip Chip BGA Encapsulant MEMS FLIP CHIP Light pipe or gas access Underfill Dam Selective; semipermeable membrane, etc.

7 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

8 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.

9 MEMS Wafer Cap Printed Adhesive Walls or use etched features Wafer-Level Capping (1) Print Adhesive (2) Bond (3) Singulate ; may be complex

10 WL “Cap & Mold” 2. Attach & bond device 1. Apply cap to device or wafer; solder, weld, bond. 3. Conventional overmolding or dispensed encapsulant MEMS Chip Cap Vacuum Seal After singulation steps Cross-section

11 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

12 1. Form sheet of polymer film or resin 2. Cut or mold into matrix; laser or die 3. Bond tack to lens disk 4. Flip lens/LCP array and align to wafer 5. Seal/bond to wafer with laser, such as near-IR 6. Singulate by sawing Wafer-Level with Polymer Films Laser spot or diode bar line

13 Total WLP Electrical pass-through; e.g.; TSV Enclosure Interconnect to PCB (2 nd -level) Controlled atmosphere as required Non-electrical I/Os as required General package attributes Processes must provide: TSV = Through Silicon Vias

14 Interconnect for WL 1.Through chip (drill & fill; plasma, RIE) 2.Route conductors over/under Same methods been adopted & developed for 3D stacked chips

15 Integral Caps Form capping structure Clean Vacuum or gas environment Seal port Singulate

16 Fabricate Caps on Wafer (Hexal MicroMold Process) Etch Recess Deep Etch Deposit sacrificial & pattern Plate Au bumps & seal Release

17 Micro Cap Assembly Transfer caps to MEMS Align Bond Separate

18 Sacrificial Integrated Package Base MEMS Structure Deposited Layer Evacuate Seal …or add port or coupling

19 Device-Specific Packages

20 This type of machine can be used to selectively encapsulate MEMS- one like this is used on ink jet cartridges. Courtesy of Speedline Ink Jet “Gun” I-TAB package Ink Jet “Gun” I-TAB package MEMS bare die MEMS Encapsulation Selective

21 Pressure Packages Bishnu Gogoi, Motorola Motorola Unibody Package Cost can be too high Protective Coating; e.g.; Parylene Corrosion can occur under the coating in harsh environments

22 Bio-MEMS & Fluidics Packaging

23 Bio-MEMS Challenge Biocompatibility; inert Sample into pressurized system Variety of energy transfer modes Interfaces in hostile environments Protection within life system Remakable couplings

24 Fluid Coupling Technology Fluidic MEMS device (s) Inter-chip coupling as required Auxiliary unit connections Through-package fluidic interface Electrical I/Os and 2 nd -level

25 Fluid Coupling Design Ellis Meng; California Institute of Technology Materials: silicon, polymers Processes: bulk etching, RIE Bulk Coupler Assembly Plastic Insertion Using Cryogenics

26 BioMEMS IME Singapore

27 Plug-in MEMS Plug-in MEMS

28 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