Books. • Microsystem Design by S. Senturia. • Micromachined Transducers
Sourcebook by. G. Kovacs. • Fundamentals of Microfabrication by M. Madou. 2 ...
Introduction to MEMS E Paul Braineard SRM University
Books • Microsystem Design by S. Senturia • Micromachined Transducers Sourcebook by G. Kovacs • Fundamentals of Microfabrication by M. Madou
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Syllabus 1. Introduction to MEMS 2. Scaling laws 3. Silicon as mechanical material
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MEMS • Microelectromechanical systems – – – –
Micro → Small of the size 10-6 m Electro → Controllable by electrical signals such as computers Mechanical → Moveable for sensing and actuation System → Integration of many devices
• Made using microfabrication technology – Process for production of devices in the submicron to mm range • Hard: for materials like Silicon • Soft: for polymers
• • • • • •
MEMS is a term coined around 1989 by Prof. R. Howe features sizes below 100 µm (size of hair) Interdisciplinary Clean room (Class 10, class 100, class 1000) Not machined by conventional (eg. Lathe etc) MEMS have holes, cavity, channels, cantilevers, membranes, etc,
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Why Silicon? • Not only a semiconductor • Very good structural material comparable with that of steel – Young’s modulus – Poisson’s ratio – Yield strength
• Derives fabrication principles from well established Si based IC technology • Electronic circuits – Solid and compact
• MEMS structures – holes, cavity, channels, cantilevers, membranes, etc,
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MEMS term misleading? • MEMS – Micro system technology (MST) in Europe – Micromachines in Japan • Sensors and actuators
• Bio-MEMS • MOEMS • RF MEMS
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Timeline • MEMS milestones – 1950’s – 1958 Silicon strain gauges commercially available – 1959 “There’s Plenty of Room at the Bottom” – Richard Feynman gives a milestone presentation at California Institute of Technology. He issues a public challenge by offering $1000 to the first person to create an electrical motor smaller than 1/64th of an inch 7
Timeline • MEMS milestones – 1960’s – 1961 First silicon pressure sensor demonstrated – 1967 Invention of surface micromachining. Westinghouse creates the Resonant Gate Field Effect Transistor, (RGT). Description of use of sacrificial material to free micromechanical devices from the silicon substrate.
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Timeline • 1970’s • 1970 First silicon accelerometer demonstrated • 1979 First micromachined inkjet nozzle
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Timeline • 1980’s – Early 1980’s: first experiments in surface micromachined silicon. Late 1980’s: micromachining leverages microelectronics industry and widespread experimentation and documentation increases public interest. – 1982 Disposable blood pressure transducer – 1982 “Silicon as a Mechanical Material” [9]. Instrumental paper to entice the scientific community reference for material properties and etching data for silicon. – 1982 LIGA Process – 1988 First MEMS conference 10
Timeline • 1980’s – Methods of micromachining aimed towards improving sensors. – 1992 MCNC starts the Multi-User MEMS Process (MUMPS) sponsored by Defense Advanced Research Projects Agency (DARPA) – 1992 First micromachined hinge – 1993 First surface micromachined accelerometer sold (Analog Devices, ADXL50) – 1994 Deep Reactive Ion Etching is patented – 1995 BioMEMS rapidly develops – 2000 MEMS optical-networking components become big business 11
MEMS markets
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Advantages of MEMS • Acquired Fab rules from already well established IC industry • Low cost (Batch processing) • High performance • Reduced size and weight • Increased reliability
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Materials for MEMS manufacturing • Choice of materials depends on microfabrication constraints – Silicon • Semiconductor material
– Polymers • class of compounds comprising both natural and synthetic materials
– Metals • Good conductors of electricity and heat
– Ceramics • A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling 14
MEMS products • Cater to – Automotive, optical, wireless etc Product category
Example
Pressure sensor
Manifold pressure, tire pressure, blood pressure..
Inertia sensor
Accelerometer, gyroscope, crash sensor..
Microfluidics/Bio-MEMS
Ink jet printer nozzle, micro total analysis system (µTAS) (Lab-on-a-chip,LOC), DNA
Optical MEMS (MOEMS)
Micromirror array for projection, micrograting array for projection, optical fibre switches..
RF MEMS
High Q inductor, switches, antenna, filter..
Others
Relay, microphone, data storage, toys.. 15
Advantages of MEMS devices • • • •
Small sizes Higher sensitivity Batch processing Cost per device less
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Process flow • Design – Numerical • Coventorware, Intellisuite, COMSOL, ANSYS etc,.
– Analytical
• • • •
Fabrication Assembling Packaging Testing – At die level – At packaging level 17
Thank you
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