Optical MEMS Overview& MARS Modulator Joseph Ford, James Walker, Keith Goossen Lucent Technologies Bell Labs Innovations References: Silicon modulator based on mec hanically-active antire flection layer with 1 Mbit/sec capa bility K Goossen, J. Walker and S. Arney, IEEE Photonics Tech. Lett. 6, p 1119, 1994 Micromechanical fiber-optic attenuator with 3 microsecond response J. Ford, J. Walker, D. Greywall and K Goossen, IEEE J of Lightwave Tech 1609), 1663-1670, September 1998 Dynamic spectral power equalization using micro-opto-mechanics J. Ford and J. Walker, IEEE Photonics Technology Letters 10(10), 1440-1442, October 1998 Micromec hanical gain slope compensator for spectrally linear powerequalization K Goossen,J. Walker, D Neilson, J. Ford, w. Knox, IEEE Photonics Tech. Lett. 12(7), pp 831-833, July 2000 Wavelength add/drop switching using tilting micromirrors J. Ford, V. Aksyuk, D. Bishop and J. Walker, IEEE J of Lightwave Tech. 17(5),904-911, May 1999 A tunable dispersion compensating MEMS all-pass filter Madsen, Walker, Ford Goossen, Nielson, Lenz, IEEE Photonics Tech. Lett. 12(6), pp 651-653, June 2000
Optical MEMS: Overview & MARS Modulator Joseph Ford, James Walker, Keith Goossen References: “Silicon modulator based on mechanically-active antireflection layer with 1 Mbit/sec capability” K. Goossen, J. Walker and S. Arney, IEEE Photonics Tech. Lett. 6, p.1119, 1994 "Micromechanical fiber-optic attenuator with 3 microsecond response" J. Ford, J. Walker, D. Greywall and K. Goossen, IEEE J.of Lightwave Tech. 16(9), 1663-1670, September 1998 "Dynamic spectral power equalization using micro-opto-mechanics" J. Ford and J. Walker, IEEE Photonics Technology Letters 10(10), 1440-1442, October 1998 "Micromechanical gain slope compensator for spectrally linear power equalization" K. Goossen, J. Walker, D. Neilson, J. Ford, W. Knox, IEEE Photonics Tech. Lett.12(7), pp. 831-833, July 2000. "Wavelength add/drop switching using tilting micromirrors" J. Ford, V. Aksyuk, D. Bishop and J. Walker, IEEE J. of Lightwave Tech. 17(5), 904-911, May 1999. "A tunable dispersion compensating MEMS all-pass filter" Madsen, Walker, Ford. Goossen, Nielson, Lenz, IEEE Photonics Tech. Lett. 12(6), pp. 651-653, June 2000
What are MEMS? Micro-Electro-Mechanical Systems manufactured using technology created for VLSI electronics to build micron-scale devices released by selective etching Surface Micromachining ·LGA( electroforming) Deep Reactive lon Etching electrically controlled by Electrostatic attraction Electromagnetic force Photos courtesy Electrostriction Sandia National Labs Resistive heating Note:MEMS”≠ passive silicon v- grooves
What are MEMS? Micro-Electro-Mechanical Systems • Surface Micromachining • LIGA (electroforming) • Deep Reactive Ion Etching • Electrostatic attraction • Electromagnetic force • Electrostriction • Resistive heating Photos courtesy Sandia National Labs … manufactured using technology created for VLSI electronics to build micron-scale devices “released” by selective etching …& electrically controlled by Note: “MEMS” = passive silicon V-grooves
Mass commercial application: Acceleration Sensors Elastic hinge Proof mass Analog Devices' ADXL50 accelerometer Surface micromachining capacitive sensor Spacer 2.5x25 mm die incl. electronic controls Force Silicon substrate Cost: $30 vS -$300 bulk sensor( 93) Cut to $5/axis by 1998 Replaced by 3-axis ADXL 150 Capacitive Accelerometer 4mm CMOS Device area Micromechanical Device Area Mochanical circuit X-Axis Z-AxIs Ref. Circuit n-bpe silicon suberate Every new car sold has micromachined sensors on-board. They Y-Axi ange from MAP( Manifold Absolute Pressure)engine sensor accelerometers for active suspension systems, automatic door locks and antilock braking and airbag systems. The field is also widening considerably in other markets. Micromachined accelerometer sensors are now being used in seismic recording, machine monitoring, and circuitr Master: Clock diagnostic systems-or basically any application where gravity, shock, and vibration are http://w.analog.com/library/techarticles/mems/xlbckgdr4.html
Mass commercial application: Acceleration Sensors http://www.analog.com/library/techArticles/mems/xlbckgdr4.html Analog Devices' ADXL50 accelerometer Surface micromachining capacitive sensor 2.5 x 2.5 mm die incl. electronic controls Cost: $30 vs ~$300 bulk sensor (‘93) Cut to $5/axis by 1998 Replaced by 3-axis ADXL150 “Every new car sold has micromachined sensors on-board. They range from MAP (Manifold Absolute Pressure) engine sensors, accelerometers for active suspension systems, automatic door locks, and antilock braking and airbag systems. The field is also widening considerably in other markets. Micromachined accelerometer sensors are now being used in seismic recording, machine monitoring, and diagnostic systems - or basically any application where gravity, shock, and vibration are factors.” Capacitive Accelerometer Silicon substrate Elastic hinge Proof Mass Spacer Force
Mass commercial application: Pressure Sensors 51258023 s春币Pa13 Membrane RC time P Space Force Silicon substrate Capacitive Pressure Sensor Piezo-resistive pressure sensor High-pressure gas sensor (ceramic surface-mount NovaSensor's piezo-resistive pressure sensors Disposable medical sensor
Mass commercial application: Pressure Sensors Capacitive Pressure Sensor Silicon substrate Pint Pext Spacer Membrane Force Measure RC time NovaSensor’s piezo-resistive pressure sensors Disposable medical sensor High-pressure gas sensor (ceramic surface-mount) Piezo-resistive pressure sensor
Electrical actuation of active MEMS devices Force Apply Apply → EM coil Curren Electrostatic attraction Electromagnetic force Apply Voltage ↑ Force Apply Force Electrostriction Resistive heating
substrate magnetic layer EM coil conductive substrate conductive layer insulator substrate patterned resistive layer substrate electrostrictive layer Force Force Force Force Apply Current Apply Voltage Electrical actuation of active MEMS devices Electrostatic attraction Electrostriction Resistive heating Electromagnetic force Apply Current Apply Voltage
Surface Micromachining: Layer by layer addition Starting from bare silicon wafer, deposit pattern multiple layers to form a(shippable)MEMS wafer 10 mask steps METAL METAL Silicon Substrate Patterned con Substrate Photoresist Completed MEMS wafer Silicon substrat PoLY重 Poly o P。lyo Etch Diced and released mems device Release isotropic chemical etch to remove oxides Special techniques may be used to remove liquid (e.g, critical point drying) Silicon Substrate Assembly= mechanical manipulation of structures (e.g., raising and latching a vertical mirror plate) Various techniques used, some highly proprietary FromCronos/jdsuMumpsuserguideatwww.Memsrus.com
Surface Micromachining: Layer by layer addition Starting from bare silicon wafer, deposit & pattern multiple layers to form a (shippable) MEMS wafer From Cronos/JDSU MUMPS user guide at www.MEMSRUS.com Assembly = mechanical manipulation of structures (e.g., raising and latching a vertical mirror plate) Various techniques used, some highly proprietary Release = isotropic chemical etch to remove oxides Special techniques may be used to remove liquid (e.g., critical point drying) Diced and released MEMS device Completed MEMS wafer ~ 10 mask steps
st TEx Optical mems device PHOTONICS AND MICROMACHINING INSTRUMENTS DIGITAL MICROMIRROR DEVICE DLP PROJECTOR 96365-39 CORPORATE RESEARCH DEVELOPMENT
Texas Instruments Digital Light Projector & DLP PROJECTOR TM 1 st Optical MEMS device
Bulk MEMS Fabrication Pattern selective etch Example:Bulk silicon DRIE: start with unpatterned wafer stack-a wafer-bonded SOl(silicon on insulat (1)Pattern photoresist (2 )DRIE vertical etch photoresist wafer-bonded silicon sacrificial silicon oxide bulk silicon substrate (3)SiO isotropic etch (4)Gold evaporation Narrow features released Wide features just undercut Gold mirrors on top and potentially sides ◎imt rommel
Bulk MEMS Fabrication: Pattern & selective etch (2) DRIE vertical etch samlab bulk silicon substrate Example: Bulk silicon DRIE: start with unpatterned wafer stack – a wafer-bonded SOI (silicon on insulator) wafer-bonded silicon sacrificial silicon oxide (1) Pattern photoresist photoresist (4) Gold evaporation Gold mirrors on top and potentially sides (3) SiO2 isotropic etch Narrow features released, Wide features just undercut
Bulk silicon EMS Devices 100N 726Ku oot Magn WD 070 130 IMT- SAMLAB Single-axis tilt-mirror photo courtesy r Conant, BSAC Comb-drive switch photo courtesy IMT(Neuchatel)
“Bulk Silicon” MEMS Devices Single-axis tilt-mirror photo courtesy R. Conant, BSAC Comb-drive switch photo courtesy IMT (Neuchatel)
MEMS reliability? 171 page report by D M. Tanner et al, SAND2000-0091, January 2000es MEMS Reliability: Infrastructure, Test Structures, Experiments and Failure Mode SN3388- bottom impact Micromotor test device 40,000G impact test Failure by rubbing contact Comb-drive actuator Ceramic package destroyed Wear on silicon surface Flexural contact to gears MEMS Survives() Submicron particles generated Conclusions (1) Properly designed MEMs devices are remarkably shock resistant (2) Flexural failures due to fatigue were not apparent (3)Rubbing wear (& resulting debris)was their primary failure mechanism Sandia national laboratories Intelligent Micromachine Initiative www.sandia.gov
MEMS reliability? Conclusions: (1) Properly designed MEMS devices are remarkably shock resistant (2) Flexural failures due to fatigue were not apparent (3) Rubbing wear (& resulting debris) was their primary failure mechanism 40,000G impact test Ceramic package destroyed MEMS survives (!) Micromotor test device Comb-drive actuator Flexural contact to gears Failure by rubbing contact Wear on silicon surface Submicron particles generated “MEMS Reliability: Infrastructure, Test Structures, Experiments and Failure Modes” 171 page report by D. M. Tanner et al, SAND2000-0091, January 2000. www.sandia.gov
