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 A brief introduction to MEMS

Dr. M.S.SureshHOD, Electronics and Communication Department

BNMIT, Bangalore

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What are MEMS?

Micro Electro Mechanical Systems

(MEMS)

System size 1-100µm Merges with NEMS 10- 1000nm

Need not involve any mechanical motion

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Examples

Sensors

RF switches

Scan mirrors Print heads

TV displays

Already in commercial use

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Materials used

Silicon

Polymers

MetalsBasic processes

DepositionPatterning Etching

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Silicon

Hookean material

 ± Perfect elasticity

 ± No loss of energy when flexed ± Low fatigue; stands billons of cycles

Material properties well understood

Easily available Amenable to well known VLSI processes

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Polymers

Silicon is costly; polymers are cheap

Bulk production possible

Used in micro fluidics Injection moulding possible

Ease of fabrication

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Metals

Are not Hookean at small dimensions

Still used as reflectors, conductors

Gold, nickel, aluminium, silver, platinum ,vanadium are used

Simpler to deposit

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Deposition

Physical vapour deposition (PVD)

 ± Sputtering

 ± Evaporation ± Ion implantation

Chemical vapour deposition (CVD)

 ± Reacting chemicals

 ± Thermal oxidation

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Patterning

Optical lithography

Electron beam lithography

Ion beam lithography Xray lithography

Method depends on feature size

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Etching

Wet etching

Isotrphic

Anisotropic

Electrochemical

Dry etching

 ± Xenondifluride

 ± Hydrogen fluride

Plasma etching

 ± Sputtering

 ± Reactive ion etching

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Design process

Concept

Paper design

Concept simulation Prototyping

FEM analysis (modelling)

Simulated testing Hardware to foundry

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Software used

ANSYS

COMSOL

Covntorware Intellisuite

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Design process

Masks

Etch process

Deposition Modelling

Testing

Foundry/ real device

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MEMES devices

Adaptive optics for ophthalmicapplications

Air bag accelerometer 

Pressure sensor 

Mirror arrays for TV display

RF switches

Biomedical sensors

Disposable devices

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Challenges

Limited Options Most companies who wish to explore the potential of MEMS and

Nanotechnology have very limited options for prototyping or manufacturing

devices, and have no capability or expertise in microfabrication technology.

Few companies will build their own fabrication facilities because of the highcost. A mechanism giving smaller organizations responsive and affordable

access to MEMS and Nano fabrication is essential.

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Challenges

Packaging

The packaging of MEMS devices and systems needs to improveconsiderably from its current primitive state. MEMS packaging ismore challenging than IC packaging due to the diversity of MEMSdevices and the requirement that many of these devices be in

contact with their environment. Currently almost all MEMS and Nanodevelopment efforts must develop a new and specialized packagefor each new device. Most companies find that packaging is thesingle most expensive and time consuming task in their overallproduct development program. As for the components themselves,numerical modeling and simulation tools for MEMS packaging arevirtually non-existent. Approaches which allow designers to select

from a catalog of existing standardized packages for a new MEMSdevice without compromising performance would be beneficial.

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Challenges

Fabr ication Knowledge Requir ed

Currently the designer of a MEMS device

requires a high level of fabrication knowledge in

order to create a successful design. Often thedevelopment of even the most mundane MEMS

device requires a dedicated research effort to

find a suitable process sequence for fabricating

it. MEMS device design needs to be separated

from the complexities of the process sequence.

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What are you going to do?

Select a MEMS device from existing

literature

Learn comsol and coventorware/ intllisuite Design a device by choosing proper 

proces

Model Test

No fabrication

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Scan mirror  Actuator 

Hinge structure MEMS mirror 

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 An early optical switch. An electrostatic actuator is used to

drive a geared transmission connected to a rack and pinion

system. Running the actuator will raise and lower the mirror 

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Thank you for not sleeping