Lecture 7: Silicon Micromachininggandhi/me645/05L7... · LIGA Fabrication of pressure sensor. 14...
Transcript of Lecture 7: Silicon Micromachininggandhi/me645/05L7... · LIGA Fabrication of pressure sensor. 14...
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Prof P.S. Gandhi, ME, IIT Bombay
Lecture 7: Silicon Micromachining
Prasanna S. GandhiAssistant Professor,Department of Mechanical Engineering,Indian Institute of Technology, Bombay,
MEMS: Fabrication
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Prof P.S. Gandhi, ME, IIT Bombay
Recap: Last Class
Plasma fundamentals Processes
Material removalEtchingReactive Ion Etching
Material additionSputtering
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Prof P.S. Gandhi, ME, IIT Bombay
Today’s Class
SFB + DRIE Surface micromachiningLift-off processLIGAFabrication examples:
Pressure sensor
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Prof P.S. Gandhi, ME, IIT Bombay
DRIE
Etch-deposition alternate cycles: patent by Robert Bosch GmbH in inductively coupled plasma (ICP)-RIELimitation: etch rates dependent on aspect ratioComparison of dry vs wet etching for Si and other materials
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Prof P.S. Gandhi, ME, IIT Bombay
Silicon Fusion Bonding (SFB)
Silicon on Insulator (SOI) technologyProcess
CleaningNaOH solution at 100o (hydration step OH groups on bond surface hydrophilic)Hold together at 800-1100o
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Prof P.S. Gandhi, ME, IIT Bombay
Silicon Fusion Bonding + DRIE
Combination of CMOS electronics with MEMS structure
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Prof P.S. Gandhi, ME, IIT Bombay
Surface Micromachining
Combination of lithography and etchingDefined with respect to deposited films instead of Si substrate
List process detailsAny problems??
Wafer
U-V RAYS
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Prof P.S. Gandhi, ME, IIT Bombay
Surface Micromachining
At DARPA, USA
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Prof P.S. Gandhi, ME, IIT Bombay
Electroplating
SUBSTRATE
ADHESION LAYERCOPPER LAYER
U V LIGHT
OPTICAL MASK
CHROMIUM LAYER
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Prof P.S. Gandhi, ME, IIT Bombay
LIGA
Combined Lithography, electroplating and molding process for high aspect ratio (depth/width) structures
SUBSTRATE
PMMA RESIST
MASK
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Prof P.S. Gandhi, ME, IIT Bombay
LIGA
Micromotor fabricated using LIGA
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Prof P.S. Gandhi, ME, IIT Bombay
Pressure Sensor
Process??
Applications
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Prof P.S. Gandhi, ME, IIT Bombay
Conclusions
Surface micromachiningDeep RIE + Silicon fusion bondingLIGAFabrication of pressure sensor
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Prof P.S. Gandhi, ME, IIT Bombay
Next class
Extra class: Electronic Packaging
Non-conventional machining processes at micro-scale
Electro discharge machining