new trends and technologies for (n)mems michael kraft
Post on 15-Jan-2016
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New Trends and Technologies for (N)MEMS
Michael Kraft
Overview
Innovation sources for MEMS devices requirements for doing MEMSnovel fabrication processes innovative design of micromachined structures
system integration
Key technologies for future MEMS devices Precision wafer bonding Metrology and characterization
Conclusions
Requirements for ‘Doing’ MEMSA reasonable clean cleanroomFlexibility to introduce new materialsNot having to worry about contaminationReasonable good lithography (~1um)Some special tools…Good metrology and measurement equipment
Southampton just opened a £80m facility with state of the art equipment
Southampton Nanofabrication CentreMICRO
Flexible nanotechnology clean roomSilicon, glass, thin film technologies
680m2 clean room (class 100 & 1000)110m2 bioMEMS clean room (class 10000)110m2 thick film clean room (class 1000)
People14 academic staff6 clean room engineers50+ researchers50+ project students
… and many, many collaborators
Carbon Nanotube bundles
Si nanobridge with a single quantum dot cavity
Research ThemesLab-on-a-ChipMicro & Nano Electromechanical SystemsNanoelectronicsNanophotonicsQuantum Information TechnologySilicon Photovoltaics
NEMS bridge as mechanical memory TEM sample preparation in a FIB
Innovation by Process DevelopmentMEMS has revolutionized sensors/actuators by making them small, low power, affordable through batch fabrication.Success stories include: pressure sensors, accelerometers, gyroscopes, flowsensors, etc.Past examples of process innovation: DRIE etching – the Bosch process.
STS Pegasus DRIE etcher
New Process TechnologyExample: Ultra-smooth Optical Cavities
Optical cavities can be used to detect single atomsApplications in quantum information technologyProcess technology challenge: cavities need to be ultra-smooth
Opt
ical
fibr
e
A silicon substrate with 100nm of oxide deposited and patterned100nm of silicon nitride is deposited and patternedThe silicon is etched using a HF based solutionThe silicon nitride is stripped using orthophosphoric acidThe silicon is etched using an ASE isotropic etchA 50nm Chromium and 100nm Gold layer is sputteredPhotoresist is spun and patterned 3µm of Gold is sputteredPhotoresist is spun and patterned and the gold is ion beam milledThe resist is removed creating the finished chip
Silicon
Silicon oxide
Chromium
Gold
Photoresist
Silicon nitride
Fabrication Process
Innovation through novel combination of existing processes
Process Optimization
Various etch rates can be used to make any radius of curvatureLonger etch rates gives smoother mirrorsAchieved around below 1nm rms roughness
Novel Design Approach for MEMSExample: Mechanical amplification
Most MEMS sensors rely on tiny deflections of a proof massThe deflection is detected electronically by measuring a change in capacitanceInnovation: introduce a mechanical amplification stageThis is based on a simple leverage mechanism
Novel Design Approach for MEMSExample: Mechanical amplification
System Integration for MEMSExample: electromechanical control systems
Micromachined sensing element incorporated in an electromechanical sigma-delta modulatorThis forms a force-feedback system with advantages over an open loop systemBetter linearity, dynamic range, bandwidth, direct digital output
Sensing element
xC +
Coriolisforce
CV
Electrostatic feedback
force
Pick-off circuit Phasecompensator
Electronic resonators1 bit A/D
fsOutput bitstream
Elec. 1 bit D/AD
A
+
Elec. 1 bit D/AD
A
Vfb
Reference voltage
+
MEMS gyroscope (collaboration with Peking University)
Spectra of simulated and measured results agree wellReduced sampling frequency compared to low-pass architectureSNR of 92dB with full scale input
‘Butterfly’ sensing element from SensoNor, Norway.
Bandpass SDM Interface for a MEMS Gyro
High c
urrent d
ensi
ty g
old w
ires
Electrostatic xy comb driveElectrostatic z parallel plate
Fibre gold coated at the tip
SiliconBose-Einstein atom cloud
Tuneable optical cavity
Atom Chip: Multi domain integration
Devices for trapping and manipulation of atoms on integrated microchips.
Quantum laboratories on chip.
Fundamental research Quantum behaviourLow dimensional physicsEntanglement and coupling
Atom Chips
New devices – precise sensorsAtom interferometersAtomic clocksAccelerometers/GyroscopesQuantum information processingQuantum computers
Overview
Innovation sources for MEMS devices requirements for doing MEMSnovel fabrication processes innovative design of micromachined structures
system integration
Key technologies for future MEMS devices Precision wafer bonding Metrology and characterization
Conclusions
Aligned Bonding for Multi Wafer MEMS
Conventional approach: Aligner - bonder
For example from EVG
Accuracy ~1um
EVG 620 double sided mask aligner
EVG 520 bonder
(Nano) Alignment Bonding
Demonstrated 200nm alignment bonding at chip level
Only 10% of wafer area required for self-engaging structures
Wafer surface smooth enough for thermo-compression bonding
self-engaging alignment conceptusing cantilevers
SEM image of aligned andbonded chips.
Vernier structures to evaluate bonding alignment
IR image of a bonded sample
2.3mm
‘LEGO on a chip’
‘Repairing’ of N/MEMS: Focussed Ion Beam
Zeiss NVISION40 FIB
Machining of complex 3D structures
Prototype post-processing
‘Repairing’ of N/MEMS: Focussed Ion Beam
Characterization of MEMS
Polytec MSA400 MEMS dynamic tester
In plane and out of plane dynamic measurements
White light interferometer
2D electrostatic actuator
Characterization of MEMS
Characterization of MEMS
Polytec MSA400 MEMS dynamic tester
In plane and out of plane dynamic measurements
White light interferometer Investigation of levitation forces
Characterization of MEMS
High-res imaging: He Ion Microscope
Orion image of CNTs 50nm bar
Description
• Zeiss Orion He ion microscope- Resolution <0.9nm- High depth of focus- High material contrast- Rutherford backscattering analysis: element identification- Nanoengineering
Orion image of CNTs 200nm bar
Orion image of CNTs 100nm bar
Conclusions
Multi-functional MEMS is becoming mainstreamMEMS is in a transition to system-on-chip or system-in-a-package (micro-system-technology)There are few really novel fabrication processes on the horizonRather new combinations of existing processesThere are still plenty of new design concepts to be exploredThere are new characterization tools which are making an impactThe next BIG thing:INTEGRATION INTEGRATION INTEGRATION