Microassembly – deterministic

1. 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

2. Manual assembly (tweezers)Corner-Cube Retroreflectors Based onStructure-Assisted Assembly for Free-Space Optical Communication, Zhou, Kahn, Pister

4. Micro-Tweezers (memspi.com)

5. Tweezers holding optical fiber Design: Chris Keller Fab: Sandia Courtesy: MEMS Precision Instruments

6. Tweezer gripping Hexsil gear Courtesy: MEMS Precision Instruments

7. Comparison with Commercial subretinal tweezer (Storz) Photos courtesy Chris Keller, MEMS Precision Instruments www.memspi.com

8. Synthetic Insects(Smart Dust with Legs) Goal: Make silicon walk. • Autonomous • Articulated • Size ~ 1-10 mm • Speed ~ 1mm/s

9. 1st Link Motor 2nd Link Motor 1mm Actuating the Legs

10. Magnetic Parallel Assembly Parallel assembly of Hinged Microstructures Using Magnetic Actuation Yong Yi and Chang Liu Microelectronics Laboratory University of Illinois at Urbana-Champaign Urbana, IL 61801 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. Solid-State Sensor and Actuator Workshop Hilton Head 1998

11. Sequential parallel assembly Parallel assembly of Hinged Microstructures Using Magnetic Actuation Yong Yi and Chang Liu Microelectronics Laboratory University of Illinois at Urbana-Champaign Urbana, 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 atHext = 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. Solid-State Sensor and Actuator Workshop Hilton Head 1998

12. Assembly via Residual Stress Low Insertion Loss Packaged and Fiber-Connectorized Si Surface-Micromachined Reflective Optical Switch V. Aksyuk, B. Barber, C. R. Giles, R. Ruel, L. Stulz, and D. Bishop Bell 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.

13. Parallel Assembly via Triboelectricity

14. OMM 16x16 switch • From www.omminc.com • 256 hinged mirrors!

15. Parallel Assembly via Surface Tension • Compact, parallel process assembly • Accuracy and reliability ? Reflow Silicon substrate Silicon substrate Syms, then Bright

16. Solder-assembly (Rich Syms)

17. 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

18. Parallel Microassembly Processes K. Böhringer, et al, ICRA, Leuven, Belgium, May 1998 Courtesy: Roger Howe, UCB

19. 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

20. 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

21. 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

22. 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

23. Si mirror binding site oxide Unreleased Mirrors • Si(100) mirror array with binding sites, fabricated from SOI wafer Courtesy: Roger Howe, UCB

24. Mirrors in Solution Courtesy: Roger Howe, UCB

25. binding site assembled mirror Mirror on Released Actuator Courtesy: Roger Howe, UCB

26. assembled mirror Mirrors on Microactuators Courtesy: Roger Howe, UCB

27. Mirror Curvature • Heat-cured acrylate adhesive • Mirror curvature less than 30 nm Courtesy: Roger Howe, UCB

28. 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

29. 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

30. Chip-to-chip and wafer-wafer assembly Flat, thin gold mirror with a thick Copper frame transferred from source Substrate to MUMPS die. Maharbiz, Howe, Pister, Transducers 99 MUMPS part by M. Helmbrecht

31. Moore’s Law, take 2 Nanochips on a dime (Prof. Steve Smith, EECS)

35. Remove substrate!

36. Could be 2-axis

38. 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

39. 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. Wu Electrical Engineering Department, UCLA 63-128, engineering IV Building, Los Angeles, California 90095-1594 Mechanical and Aerospace Engineering Department Figure 3. SEM of the torsion mirror device. Figure 1. SEM of the 2x2 MEMS fiber optic switch.

40. Introduction to MEMS 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. Wu Electrical Engineering Department, UCLA 63-128, engineering IV Building, Los Angeles, California 90095-1594 Mechanical and Aerospace Engineering Department Figure 4. SEM of the vertical torsion mirror. Figure 10. SEM of the fiber and ball lens assembly. Solid-State Sensor and Actuator Workshop Hilton Head 1998

43. 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)