Tutorial on Micro Electro Mechanical Systems …...SILICON BASED MICRO SENSOR MARKET 1999 38792 2593.8 66.86 17.9 1998 30355 2199.8 72.47 18.4 1997 23514 1857.6 79 18.7 1996 18127

Power Engineering concepts for Industrial EngineersPower Engineering concepts for Industrial Engineers

Arizona State UniversityArizona State University1

Tutorial on Micro Electro Mechanical Systems (MEMS)

Bruce KimDepartment of Electrical Engineering,

Arizona State University



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 CERTAIN

ENGINEERING OR FUNCTIONS BY ELECTROMECHANICAL OR ELECTROCHEMICAL MEANS.



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 sensingelement

Trans ductionunit

Outputsignal

Inputsignal

Powersupply



Background of MEMS

! The first monolithic integrated piezo resistive pressure sensor was in 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 growthRate,%

Avg unit price,$

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



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



MEMS



FABRICATION

! SURFACE MICROMACHINING! The structural layer has the desired thermal and mechanical

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

Si substrate



Surface micromachining



Surface micromachining



Si substrate Si substrate

Si substrate

Poly siliconanchor cantilever

oxideDeposit and pattern

oxide

Deposit and pattern 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

Plastic structures



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 to

difference in thermal expansion.a1

a2

a1>a2



Shape memory alloys! The alloy tend to turn to their original shape at a preset

temperature.

Resistance heating strip

Silicon cantilever beam

SMA (TiNi,Nitinolor)

Constraint base



Piezoelectric crystals! Certain crystals (like quartz) deform with application of electric

voltage and vice versa. ! Displacement X = dVL/H

d=piezo coefficient V= applied voltage L = length H= height of dielectric in between the electrodes

Constraint base

cantilevercrystalelectrodes V



Electrostatic forces! Electrostatic forces are more widely used as the

drivers for actuators! Coulomb's law � force between two particles F =

q1q2/(4Πεr2)

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 ER

I ES

PARALLEL

v



MEMS PACKAGING! MEMS cannot be packaged using conventional IC

techniques! 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 cavity packages. But they are expensive.

Singulate and release



MEMS packaging! Efficient way is to do the release at Wafer Level

Packaging(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



MEMS market Breakdown



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

Documents

Tutorial on Micro Electro Mechanical Systems …...SILICON BASED MICRO SENSOR MARKET 1999 38792 2593.8 66.86 17.9 1998 30355 2199.8 72.47 18.4 1997 23514 1857.6 79 18.7 1996 18127