Tutorial on Micro Electro Mechanical

8/8/2019 Tutorial on Micro Electro Mechanical

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Power Engineering concepts for Industrial Engineers


Arizona State University

Arizona State University1

Tutorial on Micro Electro MechanicalSystems (MEMS)

Bruce Kim

Department of Electrical Engineering,








MEMS! What is MEMS

! Why MEMS

! Applications

! MEMS Fabrication

!MEMS Packaging

! Conclusion







WHAT IS MEMS! MEMS CONTAINS COMPONENTS OF 1

MICROMETER TO 1 MILLIMETER

! CONSTRUCTED TO ACHIEVE A CERTAINENGINEERING OR FUNCTIONS BYELECTROMECHANICAL OR ELECTROCHEMICAL

MEANS.



Power Engineering concepts for Industrial EngineersPower Engineering concepts for Industrial Engineers

Arizona State University Arizona State University4

A MEMS structure





A gear chain with a mite





ELEMENTS OF MEMS! TWO PRINCIPLE COMPONENTS

! SENSING OR ACTUATING ELEMENT

! SIGNAL TRANSDUCTION UNIT





MEMS AS MICROSENSOR

Micro sensing

element

Trans duction

unit

Output

signal

Input

signal

Power

supply





Background of MEMS

! The first monolithic integrated piezo resistive pressure sensor wasin 1971 at CWRU

! High volume commercial by National semiconductors in 1974! First capacitive pressure sensor was built in 1980





Why MEMS! Small Size

! Light Weight

! Enhanced performance and reliability! Array Of Devices

! Low Cost

! High Integration

! Added functionality





SILICON BASED MICRO SENSOR MARKET

17.966.862593.8387921999

18.472.472199.8303551998

18.7791857.6235141997

18.986.31564.4181271996

17.994.161316.3139801995

14.21031116.2108361994

5.6110.83977.188161993

8.6119.25925.477601992

14.4124.4851.768441991

30.5129.7744.657411990

Revenue growth

Rate,%

Avg unitprice,$

REVENUE,million $

UNITS,

1000

YEAR





APPLICATIONS! In automotive Industries

! Health care Industry

! Aerospace Industry

! Telecommunications





MEMS IN AUTOMOTIVE INDUSTRY

! Air Bag deployment

! Antilock Braking Systems! Fuel Pump Pressure and Fuel Injection Control

! Suspension Systems

! Tire Pressure

! Engine coolant Temperature and quality





Accelerometers





MEMS IN HEALTH CARE! Disposable Blood Pressure

! Infusion pump pressure sensors --- to control the flow of

intravenous fluids.! Respirators

! Kidney dialysis equipment

! Lung capacity meters





A pressure sensor

P E i i t f I d t i l E i





MEMS IN AEROSPACE! COCKPIT INSTRUMENTATION – PRESSURE SENSORS FOR OIL, FUEL,

TRANSMISSION AND HYDRAULIC SYSTEM.

! SAFETY DEVICES – EJECTION SEAT CONTROLS

! MICROGYROSCOPES FOR NAVIGATION AND STABILITY CONTROL

! ALTIMETERS

! AIRSPEED MEASUREMENT

! WIND TUNNEL INSTRUMENTATION

! MICROSATELLITES






•Biocompatibility

•Harsh environment

•Used Today: Space Missions

•used on shuttle flights

•RF interrogation

•JPL looking to add functionality

Micro needles






MEMS IN COMMUNICATION






OPTICAL MEMS

P E i i f I d i l E i






MEMS







FABRICATION

! SURFACE MICROMACHINING

! The structural layer has the desired thermal and mechanicalproperties.

! The sacrificial layer supports the structural layer until it is etched

Si substrate







Surface micromachining







Surface micromachining





Power Engineering concepts for Industrial Engineersg g p g


Si substrate Si substrate

Si substrate

Poly siliconanchor

cantilever

oxideDeposit and pattern

oxide

Deposit andpattern poly

Sacrificial etch

1.

2.3.







Fabrication

! LIGA – LIthography Galvanoformung [Electroplating]Abformung[Injection moulding]! Used to make very high aspect ratio micro moulds that can

be used for high for high volume manufacture

Plasticstructures







Actuation of MEMS

! Thermal Forces

! Shape-memory alloys

! Piezoelectric crystals

! Electrostatic forces

! Electromagnetic forces







Actuation- Thermal Forces

! Bimetallic strips are actuators

! Bonding two materials with distinct thermal expansions

! The strip bends when heated or cooled due todifference in thermal expansion.

a1

a2

a1>a2





g g p g


Shape memory alloys

! The alloy tend to turn to their original shape at a presettemperature.

Resistanceheating strip

Silicon cantilever beam

SMA(TiNi,Nitinolor)

Constraint base






Piezoelectric crystals

! Certain crystals (like quartz) deform with application of electricvoltage and vice versa.

!

Displacement X = dVL/Hd=piezo coefficient V= applied voltage L = length

H= height of dielectric in between the electrodes

Constraint base

cantilever

crystalelectrodes V






Electrostatic forces

! Electrostatic forces are more widely used as thedrivers for actuators

! Coulomb's law – force between two particles F =q1q2/(4Πεr

2)

Distance r

q1 q2

F






Electrostatic forces in parallel plate

V d

L

W

F = εo εεεεr w LV/(2d)

F

electrodes

A micro gripper






MEMS FOR HIGH POWER

! A HIGH RATING IS OBTAINED BY USING MANY COMPONENTS OF LOW

RATINGS.! USING ELECTROMAGNETIC ACTUATION METHOD

LOAD

S E

R I

E S

PARALLEL

v






MEMS PACKAGING

! MEMS cannot be packaged using conventional ICtechniques

! Fragile MEMS structure and delicate membranes!Must be packaged immediately to prevent stiction, etc.

!A hermetically sealed environment should be present.






MEMS packaging

! At wafer level Release and packaging is done for

low cost

! At Die level they are packaged in ceramic cavitypackages. But they are expensive.

Singulate andrelease






MEMS packaging

! Efficient way is to do the release at Wafer LevelPackaging(WLP)

! Much smaller packages are possible






packaging

! Wafer level MEMS packages used in industries

BULK WAFER CAPS






BULK wafer cap

! Advantages! Robust

!Hermetic

! Wafer Level

Used in accelerometers,gyroscopes,image sensors






Micro assembled caps

ALIGN BOND SEPERATE






PACKAGING OF EXISTING MEMS








CONCLUSION

! MEMS is a fast growing technology

! Success of MEMS is in Design,Process and packaging

! Low integration devices

! Various packaging techniques present

! Wafer level packaging in necessary for low cost MEMS

Tutorial on Micro Electro Mechanical

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