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MICHAEL B. COHNMEMS DESIGN & FABRICATION
Application Areas
• MEMS & Packaging• Micro Optics• RF• Biomedical• Telerobotics & Tactile Feedback
Skills• Proposal writing, presentation, fundraising• CAD (Ledit, Solidworks)• FEA / Modeling (Ansys, HFSS, Sonnet, ADS,
SPICE)• Vendor Qualification• Prototype • Manufacturing, SPC• Production facility design & build• Embedded controller• Device physics• Circuits: ultra-low noise (MEMS front-end /
interface)
FEA:Thermal Microactuator
• Ratcheting Actuator
• 10,000g tested
Confidential & Proprietary
FEA: Thermal - Mechanical
FEA: Mechanical Transient• Contact / Impact Force
FEA: Mechanical Transient
Thermal actuator
7 mm
• Three-layer stacked Si / ceramic• Room temperature hermetic seal• Thermal inchworm motors• Self-test & shock monitors• Tested to 10,000 g
Optics & 3D Micro-Assembly• 2 DARPA contracts (CCIT)
• MEMS / IC flip-chip integration• Tip-tilt-piston mirror array• Self-assembling electrostatic comb drive
Wafer-to-Wafer Structure Transfer
• Torsional actuator• SOI layer transfer• Au thermocompression bonding
11
Self Assembling Torsional Actuator
• Fabrication
• Self Assembly
• Actuation
Self Assembling Torsional Actuator
Stator
Pull-down electrode
Aircraft Structural Design -- FEA
• Friction & interface slip• Bolt stress
• Cyclic fatigue
Complex structural analysisSteel tube frame (Aircraft)
MEMS Gyroscope• Mechanical – Electrostatic – Electronic – Mechanical• High-Q MEMS coupled resonators• Ultra-low noise analog front end• MCU mode-lock controller• Carousel stage: “3D printed” (CNC)
Dual Mass Gyroscope
• Stability & mode analysis
• Shock• Noise & sensitivity
analysis• Fabrication (SOI / DRIE)• Vacuum Package• Thermal Design
Dual Mass Gyroscope• SPICE simulation of mechanical
structure• Effect of etch CD on mode separation
MEMS Gyroscope(Single Mass)
MEMS Gyroscope: Future?
• High Q / Mode locked• High amplitude• Angle integrating• Thermal anneal trim
MEMS RF Switch• 2 DARPA Contracts (HERMIT)• “5 Chess Games”:
• RF – Mechanical – Electrostatic – Thermal -- Contacts
• Fabrication & Test• Team Leader / CTO• World Record 30W Power Handling
Structural Simulation (Ansys)
• Mechanical – Electrostatic – Contact
RF Design / Simulation• HFSS, ADS, Sonnet
RF Simulation
RF Testing • 0-20 GHz• VNA, Calibration• RF Packaging
RF Switch Reliability
MEMS Switch Resistance Reliability1e9 cycles, 10mW DC, cold-switched
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0.0E+00 2.0E+08 4.0E+08 6.0E+08 8.0E+08 1.0E+09
Cycle #
Res
ista
nce
(o
hm
s)
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
Std
Dev
Resistance Stdev
• 109 cycles / 10 years• HALT / HAST
RF System Level Design
2-bit section(Al2O3 substrate)
ADS Model
• 4-Bit, 35 GHz Phase Shifter
RF Phase Shifter• Alumina ceramic hybrid• MEMS on ceramic• Flip-chip Au stud bump assembly
Wafer 1 Process
Starting wafer
Contactmesa
Passivation
Adhesion
Dopant
Shorting bar
Etch
Etch
Structure
Undercut
Wafer 2 Process
BondVia
RFPassivation
CPW
ThinWafer
Contact
Etch
Spacer
Seal
LayerStack
Fabricated Devices
RF Switch (SOI / DRIE)
Detail: Electroplating
Electroplating Examples
Ceramic Packaging• Al2O3, AlN, glass, sapphire• Thick / thin film• RF, inertial, biomedical• Hermetic vias & cavities• Low-temp / room temp sealing• CTE mismatch locking• Accelerated testing• Integrated Monitoring• Silicon-ceramic wafer-scale packaging• Designed / build process tools• Flip-chip Au stud bump assembly
Ceramic Packaging• 99.6% Al2O3• Via fill with 4-layer metal• Low temperature hermetic seal• Three-layer die stack
Ceramic Packaging• Hermetic cavity• High aspect gold plating• Thermocompression seal
Ceramic PackagingVacuum package with vias and integrated getter1.8x1.8 mm
Ceramic Packaging
Built Q-switched YAG laser for repair of metal traces
Vacuum Packaging
• Silicon resonator design• Glass interposer• Front-end electronics• Design / build packaging tool• Integrated getters
Vacuum Packaging – Polysilicon Shell
• Polysilicon lid with Au seal ring• Eutectic AuSi seal
Vacuum Packaging – Polysilicon Shell
• Polysilicon lid• Au thermocompression seal• Hermetic vias• Wafer scale package
Vacuum Packaging with Leak Rate Monitor
• mpackages achieved 10-17 atm-cc/sec leak rate
• Monitored using resonator ring-down
Designed / Built Vacuum Packaging Tool
• Experience with high vacuum systems
• High bond force capability allows room temp / low temp sealing
Packaging: Wafer Bonding Process Development
• Nonlinear FEA: • Contact• Friction• Mesh morphing
• Use clamping force to counteract CTE mismatch
• Simulation includes friction, mesh morphing
Designed / Built 1,500 sq ft Clean Room
• Floor plan• Facilities• Environmental• Permits• Tool Install
Biomedical / Robotics
• Laparoscopic / Telesurgery System• Mechanical Design • Software (RTOS)• Preliminary Testing (UCSF / UCB)
Biomedical / Robotics• Full two-handed telerobotic
system• 7 DOF each hand• Master controllers with force
feedback
FEA / Simulation Experience• Ansys
• Static, modal, transient• Structural, thermal,
electrical, • Friction, contact, failure,
nonlinear• FEA + lumped element
(RLC)
• SPICE• Ultra-low noise• MEMS front end
• HFSS,ADS, Sonnet