Lecture 1: MEMS Motivation

Prasanna S. GandhiAssistant Professor,Department of Mechanical Engineering,Indian Institute of Technology, Bombay,

Today’s Class

What are MEMS? ImportanceSense of scaleDay-to-day use airbag/dj printersSensors of various kindsIndustrial and research products

Contents of the courseFabrication: VLSI-based, nonconventional laserDesign and analysisCharacterization

What are MEMS?

MEMS refer to miniature mechatronicsystems bulk fabricated using VLSI technologyTechniques and processes to design and create miniature systemsMiniature embedded systems

Motivation

Why study MEMS??MEMS benefits

Micro size sensors and actuators: Integration with electronics on single chip (system or lab on chip)Decreased cost of production: bulk processingMany new features and products previously unthought can be possible.Combination of MEMS with other branches: Example optical MEMS, Bio-MEMS futuristic devices

MEMS in SensorsAccelerometers and Gyroscopes

-In day to day use: Automobile accelerometers (air bag)

ADXL202 dual axis accelerometer

Copyright 1995- 2003 Analog Devices, Inc.

MEMS in SensorsAutonomous airplane

On-boardMicro-controller

GPS

Control surface actuators

Heading sensor

Other sensors

MEMS in AcuatorsDeskjet printer

In day to day use: - Deskjet printer Two possible ways

-Inkjet-Bubble jet

Nozzle on printer cartridge

MEMS in AcuatorsOptical switch

Micro-Optical Components at Bell Labs

MEMS in AcuatorsActuated mirrors

Micro-optical elements: (reflective)

–Micro-mirrors for fiber-to-fiber switching

Bell Lab single-color Mirror Bell Lab cross-color Mirrors

MEMS in AcuatorsActuated mirrors

Fiber, Lenses and Mirrors 4 x 4 Optical Switch

MEMS in AcuatorsActuated mirrorsDLP Technology

Array of micromirrors on chipApplications: projection TV etc.

http://www.dlp.com/dlp_technology/dlp_technology_overview.asp

MEMS in ActuatorMicromotor

Application: cooling of ICsA micro-motor

First one was made by

Mehergany at MIT

MEMS SystemMillibot

Millibots (CMU) Millibot fleet

Gyrover: Single wheeled robot uses gyroscope for stabilization

MEMS SystemCapsule camera

240o viewing angleImages at rate of 2 per secondUnit on belt to receive images2-6 hr journey through intesting0.4 X 1 in sizeFDA approved

MEMS System

Application: cooling of ICs

Micro-actuators

Comb Drive

Micro-actuators

Comb Drive

Micro-actuators

Comb drive operating gears

Bio-MEMS Sensor

Cantilever basedConcept: cantilever structure with antigenEffects:

Change in massDeflection due to repulsive forces

Detection of bacteria by OpticalCapacitiveOther techniques like resonance freq.

Walking Micro-Robots

Silicon microrobotHigh load capacityHeatuatorPrinciple of operationArrayingSteering concept

More MEMS devices

Other micro-sensors:Pressure sensorVibrating gyroscopeBio-MEMS sensors: DNA chips, “lab on chip”

Micro actuatorsComb actuators, micro-motorsThermal actuatorsPiezo-actuators

Micro-gears, micro-enginesMicro-fluidic systems: drug delivery: smart pillGrating light valve (GLV display)Digital optical switches

And many moreYet to come…

Course outline

Course Contents

Introduction to MEMS: Motivation, history and current statusMEMS: Fabrication

Conventional MEMS fabrication using VLSI technologyNonconventional fabrication

Course outline

Materials for MEMS

Other materialsPolycrystalline silicon (polysilicon)Silicon dioxide (SiO2)Silicon nitride (Si3N4)Aluminum (thin film)Gold (thin film)Many more including polymers now a days

Doping of silicon

Course outline

Conventional (VLSI) Fabrication processes

Lithography: patterningChemical etching

IsotropicAnisotropic

Plasma etching: RIEOxidationSputteringChemical vapor deposition (CVD)ElectroplatingSurface micromachiningLIGA

Materialremoval

Materialdeposition

Course outline

NonconventionalMicrofabrication

Laser micromachining and welding, processing of metals and nonmetals with laserElectro Discharge and Electro Chemical micromachining (EDM and ECM)Microstereolithography: scanning process, dynamic mask process Electronic packaging

Course outline

MEMS: Design and Analysis

Basic concepts of design of MEMS devices and processes.Design for fabrication, other design considerations MEM systems theoretic analysisAnalysis of MEMS devices: FEM and Multiphysicsanalysis in continuum domain, Modeling and simulationStatistical methodsMolecular dynamics

Course outline

MEMS: Characterization

Technologies for MEMS characterization: Scanning Probe Microscopy (SPM)

Atomic Force Microscopy (AFM)Scanning Tunneling microscopy (STM) Magnetic Force Microscopy (MFM)

Scanning Electron Microscope (SEM)Laser Doppler VibrometerElectronic Speckle Interference Pattern technology (ESPI)

Course outline

Text & References

Nadim Maluf, “An Introduction to Microelectromechanical Systems Engineering,” Artech House, Boston, 2000.Stephen D. Senturia, “Microsystems Design,” Kluwer Academic Publishers, New York, November 2000S. M. Sze, “VLSI Technology,” McGraw-Hill International Editions, Singapore, 1988.M.Elwenspoek and H. Jansen, “Silicon Micromachining,” Cambridge University Press, Cambridge, UK, 1998.Norio Taniguchi, editor “Nanotechnology,” Oxford University Press, Oxford, UK, 2003. Joseph McGeough, editor “Micromachining of Engineering Materials,” Marcel Dekker, Inc., New York, 2002.Marc Madou, “Fundamentals of Microfabrication: The science of miniaturization,” CRC Press, LLC, 2002.

Demonstration of Practical Samples

Deskjet printer cartridgeAccelerometer chipsMicrocantileversCD ROM technology

Materials for MEMS

SiliconStronger than steelLight as AluminumCan be coated with varieties of materials

Available in form of wafers 2”, 4”, 8”, 12” diaOther materials

<100>

<010>

<001>

<111>

Silicon crystal orientation

MEMS in SensorsEncoders

81,000 grating lines36-mm grating discDiffraction of lightInterference to produce detection signal