MEMS 487Session #1Spring 03

INTRODUCTION TO

MICROELECTROMECHANICAL SYSTEMS

(MEMS)

520/530.487

Instructors:Andreou HemkerSharpe

Today:• What are MEMS - TI digital mirror example• The MEMS industry - history and size• The state of MEMS education• The course - schedule, rules, etc.• Accelerometer visual examination• What I do - materials testing

What is (are) MEMS (MEMSs)?

(Microsystems)

MICROELECTROMECHANICAL SYSTEMS

(MEMS)

Small structures, sensors, actuators, machines, and robots

Maximum dimensions on the order of millimeters

Minimum features on the order of micrometers

Issues in Mechanical Testing

• Specimen preparation andhandling

• Friction in mechanism

• Direct strain measurement

Test section is 5 micronswide and 500 microns long.Hair is ~ 80 microns in diameter.

MICROELECTROMECHANICAL SYSTEMS

(MEMS)

• May not be electromechanical; may be electrochemical or purely mechanical

• Originated approximately 16 years ago

• Originally work of electrical engineers

How to make MEMS

Surface micromachining - deposit sacrificial layer, then desiredmaterial, pattern and etch each, dissolve away sacrificial layer

Bulk micromachining - pattern and etch silicon crystal into desired configuration

LIGA related - deposit thicker layers (electroplate) into pre-cut mold

Specimens

Narrow Thin-Film - 14 on 1 cm x 1cm die.Top end fixed; bottom gripped electrostatically. Test section is3.5 µm x 50 µm x 1000 µm.

Wide Thin-Film - One on 1 cm x 1 cm die. Center section released and ends glued into test machine. Test section is 3.5 µm x 600 µm x 4 mm.

Thick-Film - Six on 1 cm X 1 cm die. Each released and placed in test machine.Test section is 200 µm x 200 µm x 2 mm.

AN EXAMPLE

Digital Mirrors

Senturia Ch 20

And

Digital Light Processing: A New MEMS-Based TechnologyBy Larry Hornbeck

See also

Tutorial: Micromachining in OpticsBy Gregory Magel

Both from www.dlp.com (a part of www.ti.com)

The eye is an integrator

NTSC video is 60 Hz

60 Hz is 16 ms period

The amount of time it is exposed to a color mix of RGB determines the color it sees

eye

16 ms

Color mix can be

AnalogReflected as from paintTransmitted as thru transparencyOrDigitalEmitted for different times

3 color -- 5.3 ms for each

256 bits -- 5.3/256 = 0.021 ms for each bit

Switching frequency per bit = 48 kHz

Projection can be

• Different color phosphors as in CRT or TV

• Transmission as in film or in LCD (as in Epson)

• Reflection as in

• DMD – Digital Micromirror Device

• GLV - Grating Light Valve

Hornbeck Fig 2

Hornbeck Fig 15

Hornbeck Fig 5

Hornbeck Fig 4

Hornbeck Fig 6

Hornbeck Fig 7

Hornbeck Fig 20

Hornbeck Fig 19

Each mirror is 16 microns square

Senturia Fig 20.1

Hornbeck Fig 18

Hornbeck Fig 14

Hornbeck Fig 11

Hornbeck Fig 17

Hornbeck Fig 27

Disciplines or topics involved

Electrical engineering – Andreou

Materials science – Hemker

Mechanics – Sharpe

Others such as optics, etc.

Malur Fig 5.2

MEMS is not just planar

The MEMS Industry

History from T. Tsuchiya

0.5

1

1 .5

2

2 .5

3

3 .5

4

1992 1994 1996 1998 2000 2002 2004 2006

Total M EM S M arket

Do

lla

rs -

Bil

lio

ns

From Maluf, Table 1.2

0

40

80

120

160

200

1830 1840 1850 1860 1870 1880 1890 1900

Ra

il M

ile

s -

10

00

Y ear

Telegraph 1844

BessemerSteel1856

Railroad Mileage in U.S.

Historical Statistics of the U.S.

Johns HopkinsUniversity1876

Camden Station - Baltimore

1856 2000

MEMS Industry Group

MEMS Industry Group

MEMS Industry Group

MEMS Industry Group

MEMS Industry Group

The State of MEMS Education

Progression of MEMS

(from Bill Trimmer)

• “Isn’t it neat?”

• Potential uses

• A few applications

• Widespread commercialization

~ 1985

2000

Texts and References

Text - Microsystem Design by Steve Senturia.

or MEMS and Microsystems by Hsu

References

Fundamentals of Microfabrication by Madou

Micromachined Transducers Sourcebook by Kovacs

Micromechanics and MEMS by Trimmer

An Introduction to MEMS by Maluf

The MEMS Handbook by Gad-el-Hak

http://web.mit.edu/microsystem-design/www/

Web site for the text

Major conferences

Each January - IEEE MEMS XX - US, Japan, Europe

June of odd years - Transducers XX - US, Japan, Europe

June of even years - Hilton Head XX - US and limited

Each November - Multiple sessions at ASME meeting

The Course

The prerequisite is Senior or Graduate standing or permission.

Instructors:

Professor Andreas G. Andreou, Stieff Bldg. 120, 410-516-8361, andreou@jhu.eduProfessor Kevin J. Hemker, Latrobe Hall, 410-516-4489, hemker@jhu.eduProfessor William N. Sharpe Jr., Latrobe Hall 126 , 410-516-7101, sharpe@jhu.edu

Website: http://www.ece.jhu.edu/faculty/andreou/487

The class meets ThF 1:30-3:00 in Hodson 210

Lab sequences are three weeks long; students must sign up for one lab session in each three-week period. Lab times and locations to be determined.

The text is Microsystem Design by S. Senturia from Kluwer Academic Publishers.

The tentative grading policy is:

Homework 20%Lab Exercises 20%Midterm Exam 30%Final Exam 30%

Homework is due at the beginning of the class period on the date due. Late homework will notbe accepted without advance arrangements.

Date Topics Instructor Text Homework Lab

30 Jan

31

Introduction

Introduction

BS

AACh 1

6 Feb

7

Materials KHCh 8

Accelero-meters

13

14

ProcessingOxidn, lithog,

KH + AACh 3

By BS

20

21

ProcessingFilm depn, LIGA

KH + AACh 4

By BS

27

28

Mechanics BS Ch 9, 10

6 Mar

7

MIDTERM

Pressure gage

AA

AA

Ch 18

10-14 SPRING BREAK

Some topics will be familiar; Lab exercises are to be arranged

20

21

Fluids BS + colleagues

Ch 13

27

28

Electromagnetics+Electronics

AA Ch 6, 11, 14, 16

By AA

3 Apr

4

Electromagnetics+Electronics

AA By AA

10

11

Modelling and Simulation AA

Ch 5

17

18

DNA case study KH Ch 22

By BS

24

25

Accelerometer case study

BSCh 19

By BS

1 May

2

TBA

8-15 FINAL EXAM

An Accelerometer

Systron Donner Inertial Division

Systron Donner Inertial Division

Analog Devices IncAccelerometer

Commercially available two-axis accelerometer

Mass

Accelerationdirection

AnchorAnchor

Displacement sensor

SupportArms

Microaccelerometers

A Polysilicon Accelerometer(2 Microns Thick)

Mass

SupportArms

SensingElectrodes

Support arms are 2 microns square and ~ 100 microns long

From John Yasaitis, Analog Devices Inc

Overview of ADXL Accelerometer

Closeup of ADI Accelerometer

XL78 Beam DesignInstead of the mass being a central element with Fingers coming out the sides, the mass is a box withFingers coming into the interior of the box

MOVABLEFRAME

AC

CE

LER

AT

ION

UNIT FORCINGCELL

UNIT SENSINGCELL

MOVINGPLATE

FIXEDPLATES

PLATECAPACITORS

ANCHOR

ANCHOR

VIN -

VIN +

VOUT

Amp

VIN -

VIN +

VOUT-

+

+

-

AmpFIXEDPLATES

PLATECAPACITORS

ANCHOR

MOVABLEBEAMEarlier

Designs

XL78

ADXL78 accelerometer

XL78 Beams MagnifiedSpringMass (box shaped)

Finger attached to mass

Second Mass

What I do

Specimens

Narrow Thin-Film - 14 on 1 cm x 1cm die.Top end fixed; bottom gripped electrostatically. Test section is3.5 µm x 50 µm x 1000 µm.

Wide Thin-Film - One on 1 cm x 1 cm die. Center section released and ends glued into test machine. Test section is 3.5 µm x 600 µm x 4 mm.

Thick-Film - Six on 1 cm X 1 cm die. Each released and placed in test machine.Test section is 200 µm x 200 µm x 2 mm.

Preparation and Handling of Wide Polysilicon Specimen

Deposit specimen on die; then etch away part of die

GripEnd

SupportStrip

TensileSpecimen

AS RECEIVED AFTER ETCHING

Wide Specimen

Glued in grips with support strips cut

0.00

0.25

0.50

0.75

1.00

1.25

-0.2 0.0 0.2 0.4 0.6 0.8

Stress vs Biaxial Strain for Polysilicon

AutoCAD Drawing of Microcissors

SEM photos of Microscissors

Microscissors after etching away substrate

Homework

• Look at a journal article

• Look at a website

• Look at an accelerometer

due Thus, Feb 6