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ksjp
, 7/0
1
MEMS Design & Fab
Microassembly – deterministic• Sequential: pick and place
• Keller• Yeh
• Wafer scale• On-wafer (Magnetic, triboelectric, motorized,
residual stress, …)• Wafer-to-wafer (Howe, Cohn, Bright)
• Micro-packaging
ksjp
, 7/0
1
MEMS Design & Fab
Micro-Tweezers (memspi.com)
ksjp
, 7/0
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MEMS Design & Fab
Tweezers holding optical fiber
Design: Chris KellerFab: Sandia
Courtesy: MEMS Precision Instruments
ksjp
, 7/0
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MEMS Design & Fab
Tweezer gripping Hexsil gear
Courtesy: MEMS Precision Instruments
ksjp
, 7/0
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MEMS Design & Fab
Comparison with Commercial subretinal tweezer (Storz)
Photos courtesy Chris Keller,MEMS Precision Instrumentswww.memspi.com
ksjp
, 7/0
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MEMS Design & Fab
Synthetic Insects(Smart Dust with Legs)
Goal: Make silicon walk.
•Autonomous•Articulated•Size ~ 1-10 mm•Speed ~ 1mm/s
ksjp
, 7/0
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MEMS Design & Fab
Actuating the Legs
1st LinkMotor
2nd LinkMotor
1mm
ksjp
, 7/0
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MEMS Design & Fab
Magnetic Parallel Assembly
Solid-State Sensor and Actuator WorkshopHilton Head 1998
Figure 1. (a) An SEM micrograph of a Type I structure. The flap is allowed to rotate about the Y- axis. (b) Schematic cross-sectional view of the structure at rest; (c) schematic cross-sectional view of the flap as Hext is increased.
Figure 2. (a) SEM micrograph of a Type II structure. (b) Schematic cross-sectional view of the structure at rest; (c) schematic cross-sectional view of the structure when Hext is increased.
Parallel assembly of Hinged Microstructures Using Magnetic Actuation
Yong Yi and Chang LiuMicroelectronics Laboratory
University of Illinois at Urbana-ChampaignUrbana, IL 61801
ksjp
, 7/0
1
MEMS Design & Fab
Sequential parallel assembly
Solid-State Sensor and Actuator WorkshopHilton Head 1998
Parallel assembly of Hinged Microstructures Using Magnetic Actuation
Yong Yi and Chang LiuMicroelectronics Laboratory
University of Illinois at Urbana-ChampaignUrbana, IL 61801
Figure 8. Schematic of the assembly process for the flap 3-D devices. (a) Both flaps in the resting position; (b) primary flap raised to 90º at Hext = H1; (c) full 3-D assembly is achieved at Hext = H2 (H2 > H1 ).
Figure 9. An SEM micrograph of a 3-D device using three Type I flaps. The sequence of actuation is not critical to the assembly of this device.
ksjp
, 7/0
1
MEMS Design & Fab
Assembly via Residual Stress
Low Insertion Loss Packaged and Fiber-Connectorized SiSurface-Micromachined Reflective Optical Switch
V. Aksyuk, B. Barber, C. R. Giles, R. Ruel, L. Stulz, and D. BishopBell Laboratories, Lucent Technologies, 700 Mountain Ave.
Murray Hill, NJ 07974
Figure 2. Self-Assembling optical shutter. High tensile residual stress metal is deposited on a polysilicon beam anchored at one end. Upon release the metal-poly sandwich structure deforms, moving the free end of the beam upward. The lifting structure engages the cut in the hinged-plate shutter causing it to rotate 90 degrees into tits operating position.
ksjp
, 7/0
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MEMS Design & Fab
Parallel Assembly via Triboelectricity
ksjp
, 7/0
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MEMS Design & Fab
OMM 16x16 switch• From www.omminc.com
• 256 hinged mirrors!
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, 7/0
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MEMS Design & Fab
Parallel Assembly via Surface Tension
• Compact, parallel process assembly
• Accuracy and reliability ?
Silicon substrate Silicon substrate
Reflow
Syms, then Bright
ksjp
, 7/0
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MEMS Design & Fab
Solder-assembly (Rich Syms)
ksjp
, 7/0
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MEMS Design & Fab
Taxonomy of Microassembly
• Parallel microassembly• Multiple parts assembled simultaneously• Deterministic: pre-determined destination for
parts• Stochastic: random process determines
part destinations
• Serial microassembly• “Pick and place” on a microscale
Courtesy: Roger Howe, UCB
ksjp
, 7/0
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MEMS Design & Fab
Parallel Microassembly Processes
K. Böhringer, et al, ICRA, Leuven, Belgium, May 1998
Courtesy: Roger Howe, UCB
ksjp
, 7/0
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MEMS Design & Fab
Stochastic Parallel Microassembly
• Agitated parts find minimum energy state via an annealing process• Gravitational well: J. S. Smith, UC Berkeley and
Alien Technology Corp., Morgan Hill, Calif.• (video)• Patterned chemical “binding sites”
G. M. Whitesides, Harvard: hydrophobic surfaces formed by self-assembled monolayers define the binding site
Courtesy: Roger Howe, UCB
ksjp
, 7/0
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MEMS Design & Fab
Biomimetic Approach
• Pattern part surfaces with hydrophobic and hydrophilic regions using self-assembled monolayers (SAMs).
• free energy cost of SAM-water interface is high
• hydrophobic regions act as binding sites
Terfort, A. et al. Nature, 386, 162-4 (1997).
Courtesy: Roger Howe, UCB
ksjp
, 7/0
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MEMS Design & Fab
Application to Microassembly
• Pattern complementary hydrophobic shapes onto parts and substrates using SAMs.• no shape constraints on parts• no bulk micromachining of
substrate• submicron, orientational alignment
• Uthara Srinivasan, Ph.D. thesis,UC Berkeley Chem.Eng., May 2001
Courtesy: Roger Howe, UCB
ksjp
, 7/0
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MEMS Design & Fab
Mirrors onto Microactuators
• Self-assemble mirrors onto microactuator arrays• Si (100) mirrors• Nickel-polySi bimorph
actuators
U. Srinivasan, M. Helmbrecht, C. Rembe, R. T. Howe, and R. S. Muller, IEEE Opto-MEMS 2000 Workshop, Kawai, Hawaii, Aug. 21-24, 2000
Courtesy: Roger Howe, UCB
ksjp
, 7/0
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MEMS Design & Fab
Unreleased Mirrors
• Si(100) mirror array with binding sites, fabricated from SOI wafer
oxide
Si mirror
binding site
Courtesy: Roger Howe, UCB
ksjp
, 7/0
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MEMS Design & Fab
Mirrors in Solution
Courtesy: Roger Howe, UCB
ksjp
, 7/0
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MEMS Design & Fab
Moore’s Law, take 2
• Nanochips on a dime (Prof. Steve Smith, EECS)
ksjp
, 7/0
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MEMS Design & Fab
Mirror on Released Actuator
assembled mirror
binding site
Courtesy: Roger Howe, UCB
ksjp
, 7/0
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MEMS Design & Fab
Mirrors on Microactuators
assembled mirror
Courtesy: Roger Howe, UCB
ksjp
, 7/0
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MEMS Design & Fab
Mirror Curvature
• Heat-cured acrylate adhesive
• Mirror curvature less than 30 nm
Courtesy: Roger Howe, UCB
ksjp
, 7/0
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MEMS Design & Fab
Research Challenges for Self-Assembly Processes
• Assembly extensions: • multi-pass and multi-part simultaneous assembly• Reduce area consumed by binding site, in order to
achieve:
• “High quality” mechanical interconnects
• “High density” electrical interconnects
Courtesy: Roger Howe, UCB
ksjp
, 7/0
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MEMS Design & Fab
Post-Assembly Processes
• Polymer adhesives are not sufficient for many MEMS applications
• Good interfaces require high temperatures (> 450o C), which can damage micro-components• Potential solutions:
Local heating through laser
Local resistive heating (Prof. Liwei Lin, UC Berkeley)
Courtesy: Roger Howe, UCB
ksjp
, 7/0
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MEMS Design & Fab
Chip-to-chip and wafer-wafer assembly
Flat, thin gold mirror with a thick Copper frame transferred from sourceSubstrate to MUMPS die. Maharbiz, Howe, Pister, Transducers 99MUMPS part by M. Helmbrecht
ksjp
, 7/0
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MEMS Design & Fab
ksjp
, 7/0
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MEMS Design & Fab
ksjp
, 7/0
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MEMS Design & Fab
ksjp
, 7/0
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MEMS Design & Fab
Remove substrate!
ksjp
, 7/0
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MEMS Design & Fab
Could be 2-axis
ksjp
, 7/0
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MEMS Design & Fab
ksjp
, 7/0
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MEMS Design & Fab
Packaging• IC Packaging extremely well developed
• Reliability• Thermal conductivity• Cost• Size
• Not well addressed• Packaging with unfilled volumes• Packaging in non-standard ambients
• Vacuum• Dry N2• Moist N2• 100 mTorr +/- 1%
• Fiber feedthroughs
• Somewhat addressed• Optical I/O• Packaging induced stresses
ksjp
, 7/0
1
MEMS Design & Fab
2x2 MEMS Fiber Optic Switches
2x2 MEMS Fiber Optic Switches with Silicon Sub-Mount for Low-Cost Packaging
Shi-Sheng Lee, Long-Sun Huang, Chang-Jin “CJ” Kim and Ming C. WuElectrical Engineering Department, UCLA
63-128, engineering IV Building, Los Angeles, California 90095-1594Mechanical and Aerospace Engineering Department
Figure 1. SEM of the 2x2 MEMS fiber optic switch.
Figure 3. SEM of the torsion mirror device.
ksjp
, 7/0
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MEMS Design & Fab
2x2 MEMS Fiber Optic SwitchesIntroduction to MEMS
Solid-State Sensor and Actuator WorkshopHilton Head 1998
2x2 MEMS Fiber Optic Switches with Silicon Sub-Mount for Low-Cost Packaging
Shi-Sheng Lee, Long-Sun Huang, Chang-Jin “CJ” Kim and Ming C. WuElectrical Engineering Department, UCLA
63-128, engineering IV Building, Los Angeles, California 90095-1594Mechanical and Aerospace Engineering Department
Figure 4. SEM of the vertical torsion mirror.
Figure 10. SEM of the fiber and ball lens assembly.
ksjp
, 7/0
1
MEMS Design & Fab
ksjp
, 7/0
1
MEMS Design & Fab
ksjp
, 7/0
1
MEMS Design & Fab
Assembly - Summary• Pick-and-place assembly is the standard of
the IC industry!• Chips, passives into lead frames• Bond wires• Cost is ~1 penny/operation
• Parallel assembly is coming• Wafer-wafer transfer (deterministic)• Fluidic self-assembly (stochastic)
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