making_micro_machines_dvd_lm_pg.pdf

MEMS: Making Micro MEMS: Making Micro

MachinesMachines

Knowledge Probe (PreKnowledge Probe (Pre--test)test)

Activities (3)Activities (3)

Film ScriptFilm Script

Participant GuideParticipant Guide

www.scmewww.scme--nm.orgnm.org

Southwest Center for Microsystems Education (SCME)

University of New Mexico

MEMS: Making Micro Machines

Learning Module

Supports the film by Silicon Run Productions:

This learning module contains the following activities: Knowledge Probe (Pre-quiz)

Activity 1: Microfluidics

Activity 2: Optical MEMS

Activity 3: Sensors

Final Assessment (Post-Quiz)

The MEMS Film Script

Target audiences: High School, Community College, University,

Industry Technologists.

Support for this work was provided by the National Science Foundation's Advanced Technological Education

(ATE) Program through Grants #DUE 0830384.

Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors

and creators, and do not necessarily reflect the views of the National Science Foundation.

Copyright © by the Southwest Center for Microsystems Education

and

The Regents of the University of New Mexico


800 Bradbury Drive SE, Suite 235

Albuquerque, NM 87106-4346

Phone: 505-272-7150

Website: www.scme-nm.org MEMS Film Website: www.siliconrun.com

http://www.scme-nm.org/

http://www.siliconrun.com/

Southwest Center for Microsystems Education (SCME) Page 2 of 6 MEMS_video_KP_PG_082813 Knowledge Probe


Knowledge Probe (Pre-Quiz)

Introduction

This knowledge probe is part of the learning module based on the film MEMS: Making Micro

Machines, an overview of microelectromechanical systems, produced and directed by Ruth

Carranza of Silicon Run Production. The purpose of this knowledge probe is to determine your

knowledge of MEMS, MEMS applications, fabrication, packaging and design prior to viewing the

film and completing the activities. You are not expected to know all of the answers to the questions.

You may be asked to retake this assessment after viewing the film.

There are twenty (20) questions.

1. MEMS is an acronym for

a. Micro Energy Manufacturing Systems

b. Microelectromechanical Systems

c. Microelectronics Memory Systems

d. Micro Electron Machines and Semiconductors

e. Many Engineers Making Stuff

2. MEMS are tiny micromachines that can consist of several types of components. Which of the

following types of components would you find in a MEMS?

a. Mechanical

b. Electrical

c. Optical

d. Fluidic

e. All of the above could be found in MEMS

3. MEMS inertial sensors sense change in which of the following?

a. Acceleration

b. Pressure

c. Rotation

d. Color

e. a and c

4. The MEMS device used to trigger airbag deployment is a(n)

a. Pressure Sensor

b. Actuator

c. Gyroscope

d. Accelerometer

e. Light Meter


5. Which of the following components is used in a MEMS pressure sensor to sense changes in

pressure, for example blood pressure or tire pressure?

a. Proof mass

b. Membrane

c. Gyroscope

d. Moveable mirror

e. a and c

6. Digital Mirror Devices are used in which of the following applications?

a. Digital projectors

b. Medical imaging equipment

c. Computer Monitors

d. Data communication networks

7. MEMS incorporate microfluidic structures in which of the following applications?

a. Inertial Sensors

b. Digital Mirror Devices

c. Inkjet print heads

d. Blood Pressure Monitors

e. b and c

8. In a thermal inkjet print head, which of the following pushes the ink from the micronozzle after

the resistive heater is turned on?

a. Convection Cycle

b. Microdroplet

c. Bubble

d. Powder

e. Pixel

9. What is the optical MEMS device that consists of an array of millions of micromirrors?

a. Digital Mirror Device (DMD)

b. Millions of Mirrors Device (MMD)

c. Digital Pixel Device (DPD)

d. Mirror Array (MA)

e. None of the above

10. What type of MEMS components move other MEMS devices such as micromirrors?

a. Pressure Sensors

b. Actuators

c. Gyroscopes

d. Accelerometers

e. Yokes


11. Which of the following MEMS fabrication process steps transfers a pattern into a light sensitive

film on the wafer’s surface?

a. Etch

b. Photolithography

c. Chemical vapor deposition

d. Sputtering

e. Deep Reactive Ion Etch (DRIE)

12. Which of the following MEMS fabrication process steps is used to remove unwanted material

from a thin film on the surface of the wafer or from within the wafer substrate?

a. Etch

b. Photolithography

c. Chemical vapor deposition

d. Sputtering

13. Much of the technology used to fabricate microelectronics (e.g., CMOS chips) can be applied to

making MEMS devices.

a. True

b. False

14. In MEMS fabrication what is the layer called that provides spacing between two or more

moving components by first being deposited and then later removed?

a. Structural layer

b. Conductive layer

c. Sacrificial layer

d. Masking layer

e. Insulating layer

15. Which of the following fluidic properties allows a liquid to refill a microchannel without the use

of valves or pumps?

a. Stiction

b. Torsion

c. Energy transfer

d. Capillary action

e. Laminar flow

16. Which of the following is an advantage of the micronozzles in an inkjet print head being less

than 100 microns?

a. A higher viscosity of ink

b. Greater print resolution (more pixels)

c. Minimal turbulence in the flow of the ink

d. Self-filling microchannels (no need for a mechanical pump)

e. b and d


17. In the game Guitar Hero, accelerometers measure the movement of the guitar by measuring a

change in which of the following electrical characteristics of the accelerometer?

a. resistance

b. inductance

c. voltage

d. capacitance

e. electromagnetic

18. Which of the following personnel is NOT needed as a member of the design team for a new

MEMS device?

a. Mechanical engineer

b. Electrical engineer

c. Marketing personnel

d. Systems engineer

e. All of the above are needed as members of the design team

19. Before a MEMS device is sent to manufacturing, a model of the design must be constructed and

tested to ensure that the design meets the customer requirements and specifications.

a. True

b. False

c. Most of the time, but not always

20. Which of the following macro-sized devices is LEAST likely to be redesigned to micro size due

to impracticality?

a. A rotary motor

b. Hydraulic pump

c. A gear drive

d. Stadium Lights

e. A syringe

Support for this work was provided by the National Science Foundation's Advanced Technological

Education (ATE) Program.

Southwest Center for Microsystems Education (SCME) Page 1 of 8

MEMS_video_AC1_PG_082813 Activity 1-Microfluidics

Southwest Center for Microsystems

Education (SCME)

University of New Mexico

Optical MEMS Activity

2 Shareable Content Object (SCO)

This SCO supports the film by Silicon Run

Productions:

and is part of the

MEMS: Making Micro Machines Learning

Module

Target audiences: High School, Community College, Industry Technologists.

Support for this work was provided by the National Science

Foundation's Advanced Technological Education (ATE)

Program through Grants #DUE 0830384 and 0902411.

Any opinions, findings and conclusions or recommendations

expressed in this material are those of the authors and creators,

and do not necessarily reflect the views of the National

Science Foundation.

Copyright 2009 - 2011 by the Southwest Center for

Microsystems Education

and

The Regents of the University of New Mexico


800 Bradbury Drive SE, Suite 235

Activity 1 - Microfluidics Participant Guide

Description and Estimated Time to Complete

This is the first of three activities for the film MEMS: Making Micro Machines, an overview of

microelectromechanical systems, produced and directed by Ruth Carranza of Silicon Run Production.

This activity is designed to be completed with the first part of the film: Microfluidics.

This activity consists of two parts:

A crossword puzzle that tests your knowledge of the terminology and acronyms associated with

MEMS applications and microfluidics, and

Post-activity questions that ask you to demonstrate your understanding of microfluidics and

microfluidics fabrication.

Estimated Time to Complete

Allow at least 30 minutes to complete this activity.



Introduction

Microfluidics is a multidisciplinary field that deals with the behavior of fluids in the microliter and

smaller volume range. As volume decreases, the ratio of surface area to volume increases. As a

result, the surface properties of fluids become dominant as one deals with smaller and smaller

volumes. Therefore, the interaction of the fluid with the walls of micro chamber and channel surfaces

dominates fluid behavior. The surface area to volume ratio of a 100μm per side cube is 0.06cm-1

and

that of a 10μm per side cube is 0.6cm-1

, ten times larger! Therefore, a fluid will cool or heat much

faster in a smaller chamber.

This image is of an array of

microfluidic channels and reservoirs

created at the University of California,

Berkeley. The width of the reservoirs

are smaller than the diameter of a strain

of hair (60 to 100 μm). Think about

how small the microchannels are!

[C. Ionescu-Zanetti, R. M. Shaw, J. Seo,

Y. Jan, L. Y. Jan, and L. P. Lee (PNAS,

2005). Printed with permission by Luke

Lee, Dept. of Bioengineering, UC-

Berkeley)



Fluid flow is enhanced as channels decrease in size due to surface tension effects, called capillary

action. The microfluidics field includes the science of these behaviors as well as the technology used

to incorporate and leverage the small-scale behavior of fluids. Microfluidic systems are found in

many application areas such as biomedical, molecular biology, consumer products, filtration and

purification systems, environmental testing and micropumps.

The film MEMS: Making Micro Machines discusses the fabrication of a microfluidic device called a

thermal inkjet printhead, also referred to as a bubblejet printhead. This printhead is a microfluidic

device that uses the capillary effect of a fluid in a microchannel as well as the rapid heating of a fluid

(due to high surface area to volume ratio) to produce a fast, high resolution printhead.

A thermal inkjet printhead is a non-mechanical micropump, meaning it has no moving parts. In this

pump, heat is applied locally to a microchamber filled with ink. Very quickly (0.0001 seconds) the

ink evaporates forming a bubble. The bubble forces a tiny droplet of ink out through the micro nozzle

and onto the paper. When the heat is removed, the bubble collapses bringing more ink into the

chamber through capillary action. Surface tension prevents the ink from flowing out of the nozzle

once the chamber is full.1

Let's take a more detailed look at how this thermal inkjet printhead works. The process of pumping a

droplet of ink from an inkjet printhead (micropump) is a multiple stage process. (Refer to the diagram

and film as you follow this process.)

1. The microchannel fills with ink. Because the microchannel’s dimensions are so small

(approximately a micrometer in diameter) the liquid automatically fills the microchannel due to

capillary action.



2. An electrical voltage is applied to the heater (a resistive element). Current through the heater

creates enough heat energy to evaporate the ink in less than 0.0001 seconds.

3. Evaporation of the ink forms a bubble.

4. As the bubble forms it forces the ink through the nozzle and out of the channel.

5. The ink is sprayed onto the paper below.

6. The voltage is removed, the heater turns off, and the bubble collapses.

7. The microchannel automatically refills due to capillary action.

To make an inkjet printhead, "hundreds of these microscopic MEMS devices are typically fabricated

in pairs of columns that surround an ink supply manifold."2 Some of the newest printers produce

droplets as small as 5 picoliters and can print up to 9 pages per minute in full color (14 pages in black

and white).3 The first part of the film MEMS: Making Micro Machines covers the fabrication of these

inkjet printheads.

Activity Objectives and Outcomes

Activity Objectives

Identify the related terms or acronyms associated with definitions related to MEMS, MEMS

applications, microfluidics and microfluidics fabrication.

Demonstrate your understanding of microfluidics and microfluidics fabrication by correctly

answering the Post-Activity questions.

Resources

MEMS: Making Micro Machines, an overview of microelectromechanical systems, produced and directed

by Ruth Carranza of Silicon Run Production. 2009.

"MEMS Applications". Southwest Center for Microsystems Education (SCME). 2009.

"Photolithograpy". Southwest Center for Microsystems Education (SCME). 2009.

"Deposition". Southwest Center for Microsystems Education (SCME). 2009.

Documentation

1. Completed Crossword Puzzle

2. Questions and Answers to the Post-Activity Questions



Activity 1: Microfluidics Crossword Puzzle

Complete the crossword puzzle using the clues on the following page.

1 2 3

4 5

6

7

8

9 10

11

12

13 14

15 16

17

18

19

20 21

22

23

EclipseCrossword.com



Across

1. MEMS used to stabilize the image of a camcorder or the effect of impact on a football helmet.

4. Acronym for Microelectromechanical Systems.

6. A quartz plate that contains a pattern and is used for the exposed step in photolithography.

8. In CMOS fabrication the metal layer is used as a(n) __________.

9. In a thermal inkjet print head, the heater vaporizes ink to form a _______.

12. Acronym for the optical MEMS that consists of an array of millions of digital micromirrors.

13. The thermo component that is used as a heater in an inkjet printhead.

17. A micro-_________________ is a trench between two rows of nozzles in an inkjet printhead.

18. Acronym for chemical vapor deposition.

21. In a MEMS, the type of components that convert information to and from digital.

22. The fabrication process that removes select material from the surface layer. Process can be wet or dry.

23. In CMOS manufacturing the silicon dioxide layer can be used as a(n) ___________.

Down

2. In an inkjet printhead, ____________ action is the property of microfluids that refills the microchannels.

3. Common term for equipment that moves objects such as wafers from one place to another or one stage of the process to another (pick and place).

4. The study of the behavior of small volume fluids.

5. Acronym for scanning electron microscope.

6. In MEMS, the type of component that “moves” something.

7. A fabrication process that deposits metal layers using a plasma and ion bombardment.

9. A micromachining process that etches into the substrate (bulk, surface or LIGA).

10. A soft ______ evaporates solvents from the photoresist.

11. Micromachining process that etches layers of thin films (bulk, surface or LIGA).

14. The CVD process that deposits a silicon dioxide thin film using a vaporized liquid that contains silicate

is called __________.

15. A MEMS device that moves clinical lab testing out of the laboratory and into the field.

16. A fabrication process that deposits a thin film on the wafer’s surface.

17. Photolithography step that spins resist onto the wafer.

19. Photolithography process that removes the exposed resist.

20. A ____________ of ionized chlorine based gases and inert gases is used to etch metal.



Post-Activity Questions

1. What is microfluidics?

2. Name three applications of microfluidics.

3. Briefly discuss two challenges that engineering might face in the design and fabrication of

microfluidic devices.

4. Create a block diagram of the photolithography process showing the steps as presented in the

MEMS film.

5. Sketch and describe how an inkjet microsystem works.

Summary

Microfluidics is a multidisciplinary field that deals with the behavior of fluids in the micro, nano

and even picoliter scales. The behavior of fluids in these scales can differ from those of larger

volumes. The design and fabrication of microfluidic devices must address these differences and

create effective solutions. The manufacturing of an inkjet print head is an excellent example of how

fluid behavior at these small scales is applied through microsystems fabrication technology in

creating a highly effective consumer product.

References

1. "Micropumps Overview". Southwest Center for Microsystems Education. 2009. 2. MEMS: Making Micro Machines, an overview of microelectromechanical systems, produced and

directed by Ruth Carranza of Silicon Run Production. 3. Canon Bubblejet S520. High speed, high quality printer for the office.



Activity 2 – Optical MEMS

Participant Guide


This is the second of three activities for the film MEMS: Making Micro Machines, an overview

of microelectromechanical systems, produced and directed by Ruth Carranza of Silicon Run

Production. This activity is designed to be completed with the second part of the film: Optical

MEMS.


A crossword puzzle that tests your knowledge of the terminology and acronyms associated

with MEMS applications, optical MEMS, and the packaging and testing of optical MEMS.

Post-activity questions that ask you to demonstrate your understanding of optical MEMS

and optical MEMS fabrication and testing processes.




MEMS_video_AC2_PG_082813 Activity 2 – Optical MEMS



Introduction

The objective for optical MEMS is to integrate optical, mechanical and electronic functions

into one device. Optical MEMS usually consist of moveable micromirrors, lenses, diffraction

elements for modulating light. Actuators for moving these elements, sensors and electronics for

receiving, processing, and transmitting signals as well as providing the inputs for the actuators.

MEMS micromirror arrays are often the key components used in spatial light modulators or

SLM’s. These devices are used in high definition display systems as well as optical switching

networks. Optical micromirror arrays transmit optical information without going through the

timely and costly signal conversion process of optical to electronic and back to optical. The

micromirrors can act as switches that direct light from a fiber optic to another fiber optic or to a

specific output port by moving up and down, left to right or swiveling to a desired position.

This requires the individual mirrors to be actuated, supported on a movable mount or stage, and

integrated into a digital network.

The scanning electron microscope image to the

right shows a popped-up micromirror. Notice

the hinge allowing for the different angles

needed to direct light in different directions.

Also notice the track that assists in positioning

the mirror at the correct angle.

MEMS Pop-up mirror for optical applications [Image Courtesy of Sandia National Laboratories

SUMMITTM

Technologies, www.mems.sandia.gov]



Applications of optical MEMS include the following:

Projection displays (GLV's and DMD’s)

Tunable lasers and filters

Spatial Light Modulators (SLMs)

Variable optical attenuators

Optical Spectrometers

Bar code readers

Maskless lithography

Optical MEMS have already been quite successful in display technologies. This success is

rapidly growing with the innovations of high definition (HD) displays.

Texas Instrument's Digital Mirror Devices (DMD) have been used for several years in a variety

of projection systems including film projection and digital cinema. The technology is called

digital light processing or DLPTM

, a trademark owned by Texas Instruments, Inc. A DMD is an

array of micromirrors (see figure of DMD array below and left). Each micromirror (between

5um and 20um per side) is designed to tilt into (ON) or away from (OFF) a light source. The

mirror tilts when a digital signal energizes an electrode beneath the mirror. The applied actuator

voltage causes the mirror corner to be attracted to the actuator pad resulting in the tilt of the

mirror. When the digital signal is removed, the mirror returns to the "home" position. In the

ON position, the mirror reflects light towards the output lens. In the OFF position, the light is

reflected away from the output optics to a light absorber within the projection system housing.

One mirror can be turned OFF and ON over 30,000 times per second.

There can be over 2 million mirrors in an array with less than 1 μm spacing between each

mirror. The DLP 1080p technology delivers more than 2 million pixels for true 1920x1080p

resolution.(1,2)

The diagram below right illustrates how the DLP projection system works. The

left set of images are scanning electron microscope images of the DMD mirrors and underlying

hinge system.

Levels of a DMD Array (left) and How a DLP system works (right).

[Images Courtesy of Texas Instruments]



The illustration below breaks down a digital mirror of a

DMD into three levels. It shows the mirror, support post,

hinge, yoke and electrodes discussed in the film. The film

MEMS: Making Micro Machines discusses the fabrication,

packaging and testing of this DMD. You should recognize

some of the components mentioned in the film (e.g., mirror,

torsion hinge, yoke). To learn more about the operation of

a digital light projector (DLP), visit Texas Instruments

webpage How DLP Technology Works.

http://www.dlp.com/technology/how-dlp-

works/default.aspx

[Images Courtesy of Texas Instruments]


Activity Objectives

Identify terms or acronyms associated with definitions related to MEMS, optical MEMS, optical

MEMS fabrication, packaging and testing.

Demonstrate your understanding of digital MEMS and DLP fabrication, packaging and testing by

correctly answering the Post-Activity questions.

Resources

MEMS: Making Micro Machines, an overview of microelectromechanical systems, produced and directed by

Ruth Carranza of Silicon Run Production.


"Photolithography". Southwest Center for Microsystems Education (SCME). 2009.

"Deposition". Southwest Center for Microsystems Education (SCME). 2009.

Documentation



http://www.dlp.com/technology/how-dlp-works/default.aspx

http://www.dlp.com/technology/how-dlp-works/default.aspx



Activity 2: Optical MEMS Crossword Puzzle

Complete the crossword puzzles using the clues on the following page.

1

2 3 4

5

6

7 8 9

10 11 12

13

14 15

16 17

18 19 20

21 22

23

24

25




Across

2. MEMS components that move mirrors or other MEMS devices are called _________________.

5. Three or more colored _________ are contained in the color wheel of a DLP system to provide a colored

output from the DMD array.

7. The acronym for digital light processing.

8. After fabrication a DMD goes through a series of tests, most of which are electrical. The final test is a

___________ test.

10. To electrically _____ a DMD array, the mirrors are turned ON and OFF for 2 to 24 hours inside a burn-in

furnace.

13. When a DMD mirror is not reflecting light it is said to be ______.

14. A ____ strip is placed on DMD windows for the purpose of absorbing moisture.

17. To ______ is to join two or more components together.

18. An anti- ________coating that enhances the transmission of light is applied to the protective windows in a DMD

22. The tendency for surface forces to cause small structures to stick.

24. In MEMS fabrication a _____ layer provides spacing between two or more components by first being

deposited then removed.

25. When a micromirror is reflecting light it is said to be ____.

Down

1. The component of a DMD micromirror that supports the mirror's support post.

3. Small spring tips are constructed on the yoke of a DMD mirror to overcome ________, the tendency of a micromirror to stay ON with voltage removed.

4. The fabrication process used to remove the protective resist layer after the develop process step is called a plasma ______________.

6. A microsystems device that integrates optical, mechanical and electrical.

7. The acronym for digital mirror device.

9. The material used to construct the post, hinge and yoke of a DMD micromirror.

11. In a DMD, one micromirror is one _____.

12. A __________ is applied to the electrode of a micromirror to turn the mirror ON.

15. The thin film used as a sacrificial layer that provides spacing and protection for the micromirrors.

16. A(n) ______ is used to harden epoxy.

17. A __________ process uses UV light, heat and pressure to connect the windows of the DMD to the CMOS

wafer.

19. In a DMD the hinge that is fabricated to overcome stiction is called the ____ hinge.

20. The fabrication process that removes unwanted material from a layer.

21. Hundreds and even thousands of micromirrors on a chip is called a(n) _______.

23. The fabricated channels that provide access to the CMOS circuitry.




1. What is the objective of optical MEMS?

2. For the transmission of data optical information, optical mirrors may be faster and cheaper

because they eliminate the conversion process of ______________________________.

3. Micromirrors need to move. What MEMS components are required to move micromirrors?

4. What company developed DMDs?

5. In your own words, briefly explain how a DMD works.

6. How is the resolution of DLP devices increased?

7. Once the DMD array is fabricated, how is it protected during shipping to the packaging

location?

8. In the fabrication of a micromirror, photo resist is used as a sacrificial layer. What is the

purpose of this sacrificial layer?

9. How is mirror movement tested?

10. The output of a DMD is black and white. How is this black and white image converted to

color?

Summary

Optical MEMS integrate optical, mechanical and electronic functions into one device. Micromirror

arrays are used for data transmission and for optical image production in DLP projection systems.

There may be hundreds of thousands and even millions of mirrors in an array, fabricated on a single

chip. Surface micromachining fabrication methods similar to those used in making computer chips are

the primary fabrication technology used to make these devices. In the final tests, all of the mirrors must

work in order for the chip to be used in a DLP device. This creates a special challenge in the

fabrication and packaging of micromirror arrays.

References

1 "How DLP sets work." Tracy V. Wilson and Ryan Johnson. HowStuffWorks.

http://electronics.howstuffworks.com/dlp1.htm 2 "How DLP Technology Works". DLP Texas Instruments. http://www.dlp.com/tech/what.aspx 3 MEMS: Making Micro Machines, an overview of microelectromechanical systems, produced and

directed by Ruth Carranza of Silicon Run Production.



http://electronics.howstuffworks.com/dlp1.htm

http://www.dlp.com/tech/what.aspx

Activity 3 – MEMS Sensors Design

Participant Guide


This is the third of three activities for the film MEMS: Making Micro Machines, an overview

of microelectromechanical systems, produced and directed by Ruth Carranza of Silicon Run

Production. This activity is designed to be completed with the third part of the film: Sensors

(MEMS Design Process and Design Team).


A crossword puzzle that tests your knowledge of the terminology and acronyms associated

with MEMS sensors and the MEMS design process.

Post-activity questions that ask you to demonstrate your understanding of MEMS sensors

and the MEMS design process.



Introduction

Sensor components are critical in microelectromechanical systems (MEMS) and in MEMS

applications. A MEMS sensor receives an input from the environment. It converts its input

signal into a digital or analog electronic representation. For example, a type of MEMS

chemical sensor monitors the change in mechanical stress on a microcantilever as a result of a

chemical reaction occurring on a surface coating. The sensor responds to the change by

producing an electrical output (change in resistance) that represents the amount of chemical

reaction occurring on the microcantilever transducer surface.

Two common types of MEMS sensors are pressure sensors (which sense changes in pressure)

and inertial sensors (which sense movement, acceleration and inclination).

MEMS sensors can be used in combinations with other sensors for multisensing applications.

For example, a MEMS can be designed with sensors to measure the flow rate of a liquid sample

and at the same time identify any contaminates within the sample.

Southwest Center for Microsystems Education (SCME) Page 2 of 8 MEMS_video_AC3_PG_082813 Activity 3 – MEMS Sensors Design


MEMS Pressure Sensors

MEMS pressure sensors are designed to measure absolute or differential pressures. They

typically use a flexible diaphragm as the sensing device as seen in the picture to the right. One

side of the diaphragm is exposed to a sealed,

reference pressure and the other side is open to

an external pressure. The diaphragm moves

with a change in the external pressure. This

movement is measured as a change in

resistance due to additional strain on the

piezoresistive elements fabricated onto the

diaphragm. MEMS pressure sensors are

specified to work over a variety of ranges,

depending on the design and specific

application. There are MEMS pressure

sensors that can measure pressures near 0

ATM or as high as 10 ATM or ~150 psi.

Applications of MEMS pressure sensors include the following areas:

Automotive industry (e.g., measure tire pressure, fuel pressure, intake manifold

pressure)

Biomedical (e.g., measure blood pressure, intracranial pressures, pressure due to

blockage in catheters and infusion pump systems)

Environmental (e.g., measure barometric pressure, ocean pressures sensors, and

pressures found within roads and bridges)

Non-destructive testing (e.g., identify defects and cracks in materials)

MEMS Pressure Sensor

[Courtesy of the MTTC, University

of New Mexico]


MEMS Inertial Sensors

MEMS inertial sensors are designed to sense a change in an object's acceleration, vibration,

orientation and inclination. MEMS inertial sensors include accelerometers and gyroscopes.

Acceleration is defined as a change in velocity (speed and/or direction). In order to accelerate

an object, a force must be applied to that object. If an object changes velocity (accelerates), the

object, including any imbedded MEMS inertial sensor, will experience a force acting on it.

Hence, inertial sensors are used to measure force related variables such as inclination,

orientation, vibration, changes in speed, direction and impact forces.

MEMS inertial sensors can be found in many applications including

navigation devices,

image stabilization systems for high-magnification video cameras,

airbag deployment systems,

the Apple iPhone,

pacemakers, and

stabilization systems found in washing machines.

MEMS inertial sensors are one of the fastest growing segments of the MEMS market. "Driven

by accelerometer applications like the Apple iPhone and the Nintendo Wii, and by the coming

legislation requiring stability-control systems in all vehicles, these devices have moved out of

industrial segments and into consumer ubiquity." ("MEMS-based inertial sensor is not your grandfather's

gyroscope." Randy Torrence, Chipworks. Electronics, Design, Strategy News. December 2008.)

Like pressure sensors, MEMS accelerometers are devices that can be used in a variety of sensing

applications due to their simplicity and versatility.

The simplest MEMS accelerometer sensor consists of an inertial mass suspended by springs (see

SEM image above). Forces affect this mass as a result in an acceleration (change in velocity –

speed and/or direction). The forces cause the mass to be deflected from its nominal position.

As with the movement of the pressure sensor's diaphragm, the deflection of the mass is

converted to an electrical signal as the sensor's output. ("MEMS Targeting Consumer Electronics". EE

Times. Gina Roos. September 2002.)

MEMS Accelerometer [Photo courtesy of

Khalil Najafi, University of Michigan]


MEMS Gyroscopes

Gyroscopes are used to either maintain orientation of a moving object, such as a spacecraft, or to

monitor the orientation changes of an object. The classical gyroscope we are used to seeing consists of

a spinning wheel or disk. The rotating object tends to maintain its axis in a fixed orientation. Think of

a fast spinning top, the top axis tends to point in the same direction. Another example is that of a

bicycle wheel – if you spin a bicycle wheel very quickly, the axis tends to point in the same direction.

Vibrating systems can also act as a gyroscope. An example is a tuning fork device set into motion. The

tines of the fork will vibrate within a plane of motion. This is based on the physical principal that a

vibrating object (proof mass) tends to keep vibrating or oscillating in the same plane. MEMS

gyroscopic based sensors have been made using both methods, spinning and vibrating structures. With

these types of structures, changes in yaw, pitch and roll can be measured.

The third part of the film, MEMS: Making Micro Machines, shows you the process of designing MEMS

sensors. There are many team members who work together and with the customer to achieve success of

the project. Each team member contributes within the area of expertise but must also be

multidisciplined enough to understand and communicate effectively with others in the team. The

design process shown is typical of what is used in most MEMS design and fabrication organizations.

As is obvious in this part of the film, having excellent communication skills is critical, this includes all

aspects, listening, writing, reading and speaking.


Activity Objectives

Identify the terms or acronyms associated with definitions related to MEMS, MEMS sensors, and

MEMS design.

Demonstrate your understanding of MEMS, MEMS sensors, and MEMS design by correctly

answering the Post-Activity questions.

Resources

MEMS: Making Micro Machines, an overview of microelectromechanical systems, produced and

directed by Ruth Carranza of Silicon Run Production. 2009.


"Sensors, Transducers, and Actuators." Southwest Center for Microsystems Education (SCME). 2009.

Documentation




Activity: MEMS Sensors Design Crossword Puzzle

Complete the crossword puzzles using the clues on the following page.

1 2 3 4

5

6

7

8

9 10 11

12

13 14

15

16

17

18



Across

2. A change on the input of a sensor can create a change in capacitance which gets converted to

_______________.

5. The ________ designer creates an architectural design and writes the specifications for the MEMS.

6. The design phase brings together the MEMS and the ASIC blocks to ____________ their performance and

ensure results meet product specifications.

7. The ______ratio is the ratio of etch depth (or height) to its width.

8. The etch process that creates etch profiles with high aspect ratios.

9. A logical sequence of steps for solving a problem is called an ______________.

13. Each block of a MEMS design has a mathematical representation that consists of lines of equations, or ______.

14. A MEMS ______ ______ consists of various engineers, marketing and sales personnel.

15. It is the responsibility of the Microsystems Group to divide or to partition the components of the system into specific ________.

16. In an inertial sensor, the space between the mass and electrode is measured as an electrical _____________.

17. It is the responsibility of the mechanical design engineer to determine transducer _____________

limitations.

18. Deep Reactive _____ ______ or DRIE uses a process known as the Bosch Process to create deep, straight, etched walls.

Down

1. The MEMS inertial sensor that measures rotational movement is called a _________________.

3. A(n) _________ measures linear movement along the x, y, and z axes.

4. MEMS accelerometers use an __________ to sense mass movement and produce an electrical output

representative of the movement.

6. The Application Specific Integrated Circuit designer is also called the _______ designer.

9. ___________ is defined as a change in velocity (speed and/or direction).

10. MEMS ________ sensors are designed to sense a change in an object's acceleration, vibration, orientation

and inclination.

11. A virtual and sometimes physical _______ is constructed to test predictions and different situations.

12. A _______ or diaphragm is the moveable component in a MEMS pressure sensor.

16. Sensors are designed to monitor and detect _______ at the input.

17. In a MEMS accelerometer, a proof _____ moves when affected by an external force.



Based on what is in the film and the Introduction of this activity, answer the following questions:

1. What do MEMS inertial sensors sense?

2. What are two types of MEMS inertial sensors?

3. Name at least three applications of MEMS inertial sensors.

4. Name at least three applications of MEMS pressure sensors.

5. When designing a new MEMS, who determines the requirements (e.g., operating parameters,

specifications)?

6. Why does it take a team of engineers (mechanical, electrical, systems, process and sometimes

chemical, biochemical, etc.), marketing and sales experts to develop MEMS?

7. Virtual models and sometimes, macro-sized models, are constructed before a MEMS device is

fabricated. What is the purpose of these models?

8. If you had to choose one of the roles highlighted in the film, which one would you choose?

Which one is of most interest to you? Why? What sort of education do you think you would

need to fill this role? What subjects should you focus on in school to acquire the necessary

knowledge and skills?

Summary

One of the most common applications of MEMS is as sensors. MEMS pressure sensors and

accelerometers were some of the first MEMS devices to make it to the market. These sensors are

found in cars, planes, medical equipment, and gaming devices.

No matter what the device, all MEMS must go through a rigid design process before being sent to

manufacturing. The design process involves engineers from several areas, all of which play an

important role in the final design. By the time a MEMS device is sent to manufacturing, it has been

tested, tweaked and retested many, many times to ensure that it meets the customer's requirements and

specifications.




Script with Chapters (Scene Selections)

Silicon Run Productions 1 3/10/09

Chapter 1 – Introduction to MEMS

1. Mechanical ingenuity combined with micro or nano manufacturing methods has evolved into

Microelectromechanical Systems known as MEMS, micro machines, or microsystems.

2. These tiny micro machines have both mechanical and electrical components that are either side-by-side

within a single package, or integrated on a single chip. In their mechanical function they move masses,

liquids and light, or sense vibration and pressure. In their electronic function they convert mechanical

information to digital information and digital information to mechanical motion.

3. If microprocessors and microcontrollers are the brains of electronic products, then MEMS are the eyes,

ears, nose, and physical extensions that provide information to that brain.

4. MEMS are all around us in our digitized world. In the thermal inkjet printhead, hundreds of microfluidic

devices direct the flow of ink and eject thousands of tiny drops a second. In medicine, microfluidic

pumps help people monitor insulin levels. Lab-on-a-chip provides tiny channels leading to mini labs used

in chemical and biomedical research.

5. In Digital Light Processing, MEMS devices project the images seen at theaters. Inside this theater

projector are DLP chips that contain millions of microscopic mirrors. Smaller DLP chips are also found

in televisions and business projectors.

6. In cars MEMS pressure sensors monitor things like engine control to improve fuel efficiency. In

camcorders, MEMS accelerometers stabilize the image. In football they monitor the effects of impact on

a player’s head. In gaming accelerometers allow us to be active players. They’re also used in cell phones

and GPS systems. The combination of MEMS gyroscopes and accelerometers are found in the segway

and the space shuttle.

7. MEMS are an international enterprise. In today’s global economy a MEMS device is often researched,

designed, manufactured, and packaged by staff in different countries around the world.

8. While there are many types of MEMS devices three important catagories are microfluidics, optical

MEMS, and sensors.

FABRICATION (Thermal Inkjet Printhead)

Chapter 2 – Inkjet Printheads

9. To see how these devices are fabricated, let's begin at Hewlett Packard’s facility where the inkjet

printhead is manufactured

10. MEMS are fabricated in various ways depending on their application. With silicon based MEMS,

there are two major types of micromachining.

11. Surface Micromachining uses semiconductor processes like deposition, photolithography, etch and

ion implantation to create the MEMS structure. These processes are similar to making computer

chips and use some of the same equipment. In Bulk Micromachining, the silicon wafer itself is bulk

etched to create the MEMS device components within the wafer.




12. The thermal inkjet printhead contains hundreds of microscopic MEMS devices typically fabricated in

pairs of columns that surround an ink supply manifold.

13. Each device has a nozzle, a chamber, a resistor and a slot that connects it to the ink channel.

14. When current is applied, the resistor heats to boiling temperatures. It vaporizes the first layer of ink

into a gas bubble that acts like a piston to eject the ink through the nozzle.

15. With the current off, the collapsing bubble drops back onto the resistor surface. The ink flows in and

refills the chamber. Capillary forces pin the ink back at the nozzle's surface preventing it from

flowing out until the resistor fires again.

16. Inkjet printheads are integrated devices. Both the MEMS devices and the CMOS circuitry, which

provides the electrical current, are fabricated at the same time. Beneath these rows are the transistors,

which have already been built. In this video we'll take a close look at how the MEMS devices are

created from bare crystalline silicon.

17. The materials used in the creation of an inkjet printhead must withstand high heat, high duty cycles,

and liquid environments containing acidic and basic inks. Therefore these materials are selected for

their electrical, mechanical, and chemical properties.

Chapter 3 – Building the Thermal Resistors

18. Before the resistors are built, insulation is needed to protect the wafer. In this chemical vapor

deposition system TEOS, a vaporized liquid that contains silicate, is used to deposit a silicon dioxide

layer at low temperatures. Temperatures higher than 400 degrees Celsius would alter the aluminum

copper used for the integrated circuits on other parts of the wafer.

19. Inside the CVD chamber TEOS reacts with oxygen to form silicon dioxide on the bare silicon surface.

This silicon dioxide layer insulates the silicon wafer from the firing resistor.

20. The wafers move on to a metal deposition system where a conductive layer that will provide leads to

the resistor will be deposited. First the wafers are conditioned by undergoing a physical sputter with

Argon to remove any oxides or trace conductors. Then the wafers move to the metal deposition

chamber. Here sputtering is used to transfer metal from a target to a layer of an aluminum copper

alloy on the wafer.

21. Photolithography is used to pattern the metal layer. As we see here, the exposure system is next to

the coat, develop, and bake track system. As the wafer spins a positive photo resist spreads across the

wafer. The final spin speed of the wafer determines the specific thickness of the resist.

22. A tiny solvent stream removes the resist bead that forms along the edge. This prevents particle

contamination when a wafer touches the cassettes or other tooling.

23. From the back of the track system, we see the wafers move to a hot plate where they are baked to

remove most of the solvent.

24. Wafers then move into the I-line stepper. Here, a light source of a specific wavelength filters through

a mask and a lens to expose the wafer. The resist is positive. The areas exposed to light are changed




chemically. The wafers move back to the track system. Here developer is puddled onto the wafer,

and the exposed areas are rinsed away.

25. To insure quality, measuring feature size is important throughout the process. This SEM, or scanning

electron microscope, is measuring the dimensions produced by the photo resist process.

26. The exposed metal will now be etched using plasma. In this chamber chlorine based and inert gases

etch the aluminum copper alloy. This defines the resistor leads and removes the highly conductive

aluminum copper layer from the area where the resistor material will be. While still under vacuum,

the wafer moves to the ash chamber where the photo resist and etch residues are evaporated and

pumped away.

27. The resistor metal in now deposited. After the wafer's surface is conditioned it goes to the sputter

chamber where a thin layer of resistor metal is deposited.

28. Photolithography once again patterns the resistor metal layer.

29. In the plasma etch system the resistor metal layer is etched from unwanted regions. When current is

eventually forced from two metal layers to one thin metal layer, it will create the heat that fires the

resistors. A thin-film stack of three layers will now be deposited on the resistors to provide electrical,

chemical and mechanical protection.

30. This system deposits the first two dielectric layers over the resistor. The first layer will provide

electrical isolation between the ink and the firing resistor. In the same chamber, new gases deposit

the second layer, which protects against the corrosive chemical attack from the ink.

31. The third protective layer is metallic so it can resist the mechanical forces of the collapsing bubble.

The wafers go into a sputter etch chamber to prepare the surface and then into a sputter deposition

chamber where a thin metal layer is deposited.

Chapter 4 – Building the Chamber Walls

32. Now that the resistors are protected, the chamber walls where the vapor bubble forms are built. The

wafers are washed and prepped. A de-ionized water and ozone treatment removes any residual

33. The deposition of barrier material used for the chamber walls is similar to the photolithography

process. As the wafer spins, a thick negative resist-like material is spiraled onto the wafer. In soft

bake, the solvent is slowly driven out to "set" the barrier material and make it more uniform.

34. In this bake and expose system, the wafers go directly to the stepper where they are exposed. As a

negative resist, the barrier material exposed to light forms a polymer and hardens. Because this resist

is so thick, the exposure times are much longer than for standard photo resist. After exposure, the

wafers move to the bake ovens. The areas exposed to light induce cross-linking and become a

permanent part of the chamber.

35. The non-exposed areas are removed when developed. Instead of the usual puddle develop, spray

develop is used here. Spraying droplets of developer provides a higher surface area that can attack

the thick barrier material more easily.




36. A big open chamber now exists. We can see that small pillars have also been created from the barrier

material. These pillars at the entrance to the chamber serve as a filter to block particles that might be

in the ink from clogging the nozzle.

37. After develop, the wafers are placed in an oven, exposed to higher temperatures and allowed to cure.

Thickness measurements are made after each layer is cured.

38. A thick photo resist resin, called a sacrificial wax, is spiraled onto the wafer and spun. The wax fills

the cavity and covers the entire wafer. A soft bake sets the wax and a portion of it is removed to

bring it flush with the chamber surface. The wax holds up the shape of the chamber as the building

process continues.

Chapter 5 – Creating the Nozzles

39. In a dry process a layer of barrier material is pressed onto the wafers to create the nozzles. The

nozzle material on this roll is sandwiched between two protective sheets of carrier films. The dry

application will minimize the interaction between the nozzle layer and the sacrificial wax. Here, the

bottom carrier film has been peeled away, and we see the nozzle material placed directly on the

wafer.

materials that might remain on the surface from previous steps.

40. After the dry film is applied, a blade cuts around the remaining films and a new layer is prepared for

the next wafer.

41. The robot moves the wafer with the nozzle material and its carrier film to the next stage.

42. In a separate tool, the carrier film is removed. A strip of tape is rolled across the wafer and a pick-up

roll lifts the carrier film off.

43. Photolithography is now used to create the nozzle orifice. The exposed areas become cross-linked

and remain a permanent part of the printhead. When developed, the unexposed nozzle material and

the sacrificial wax are removed.

44. The wafers undergo a final cure.

45. To create the channels the inks will flow through, a laser and etch process forms a trench between two

rows of nozzles. Inside the laser system, the wafers are placed backside up. A pulsating laser scans

the back of the wafer and defines the dimensions of the slot. Without breaking through the silicon, it

then drills a deep narrow trench within the slot.

46. The final slot shape is created in a bulk etch process. In this anisotropic etch, chemicals such as KOH

and TMAH etch the silicon crystal and remove the remaining thin silicon layer left after laser

micromachining.

47. Wafers are automatically mounted onto a ring and tape. This holds the die in place as the wafer is

sawed into individual units.

48. Following singulation, the wafers are rinsed and dried to remove any particulates.




49. In a final visual inspection only the functioning die are examined before they are shipped. The camera

on the microscope is programmed to recognize certain patterns. It highlights defects for the operator

who then confirms or rejects them.

50. The sawed wafers are packed and shipped to various HP sites. There, the good die will be attached to

a pen body like this one, which is becoming a permanent fixture in printers today.

OPTICAL MEMS

Chapter 6 – Digital Mirror Device (DMD)

51. Optical MEMS manipulate light. One of the most common is the Digital Micromirror Device, or

DMD, which is the key component of the DLP technology found in high definition projection

systems.

52. This cinema device contains 2.2 million microscopic mirrors known as pixels. Rows and rows of

these tiny mirrors tilt ON and OFF thousands of times a second in response to digital signals. When a

mirror is ON, it reflects one pixel of source light through a lens, which projects that pixel onto a

screen.

53. A cross section view of the MEMS super structure shows how an individual mirror works. Part of

the mirror is a U-shaped post that is attached to a solid plate known as a yoke. The yoke is attached

to a suspended flexible hinge. When "ON" the hinge allows the yoke and mirror to tilt in response to

electrical signals from the CMOS circuit beneath it.

54. DLP fabrication begins on a standard three metal layer CMOS SRAM wafer that already contains the

circuitry that provides bias voltages to the individual mirrors.

55. Photo resist is deposited as a temporary spacer.

56. Vias provide access to the CMOS circuitry.

57. A layer of aluminum creates the hinge structure and its two posts, which allow the mirrors to move.

58. A silicon dioxide hard mask is patterned.

59. To form the yoke element, a layer of aluminum alloy is deposited.

60. A second silicon dioxide hard mask is created to protect sections of the yoke.

61. The exposed yoke and oxides are etched leaving a hinge that is continuous across the structure from

post to post and which is attached to the yoke.

62. A second sacrificial layer of photo resist is deposited and patterned.

63. A final layer of aluminum alloy creates the support post and the mirrors on top.

64. An oxide layer is deposited and patterned.




65. The aluminum is etched and the oxide layer is removed. This creates the individual pixel mirrors

attached to the yoke.

66. A final layer of resist is spread across the wafer. This protects the mirrors as they travel to different

parts of the world where the DLP chips are packaged and tested.

PACKAGING (DMD Chips)

Chapter 7 – Packaging: DMD Chips

67. To understand how challenging it is to package devices with such tiny moving mechanical

components let's go to Texas Instruments and see how DMD chips are packaged.

68. The packaging process begins with the removal of the spacers and protective photo resist. In a

plasma strip system the photoresist is evaporated from the top, sides, and bottom of the mirrors.

69. This leaves the open spaces that will allow the mirror to tilt. As with all MEMS, these mirrors are

mechanical structures that need to be protected.

70. So first, a protective window is bonded onto the wafer. These windows, with thin rectangular glass

frames, have an anti reflective coat that enhances the transmission of light. They also have getter

strips that absorb moisture. These windows will provide a protective, airtight, environment yet

maintain optical transparency.

71. Meanwhile, the wafers go into an epoxy station. Here, clear epoxy is placed around the edges of each

device.

72. The wafers with epoxy, and the windows with frames, are loaded onto a tool where they will be

bonded together.

73. After the windows are aligned, they are flipped so the windows are up. The wafers, with epoxy

around each die, are also aligned and placed beneath the windows. Light pressure is applied to hold

the two together.

74. The glued wafer and window are then transferred to the bonding chamber where ultra violet light,

heat, and pressure are applied in a vacuum. This bonds the windows to the CMOS wafer and

hermetically seals the MEMS structures.

75. The bonded wafers now go into bake ovens where a thermal cure hardens the epoxy.

76. On a separate floor, to prevent particle contamination, the bonded wafers and windows will be sawed.

A metal frame contains the wafers, which have been placed on sticky dicing tape. The saw cuts or

dices in between and along the edges of the die, and singulates the bonded wafers into individual die.

77. Back in the clean room, epoxy is dispensed inside the package cavities of a header. A computer

selects only the good CMOS die. They are picked off the tape and placed into the cavities.

78. The devices are again baked.




79. At the bonding station, a thin gold wire is used to bond the device pads to the frame's wire leads. The

mirrors can now be electrically and optically tested for the first time.

Chapter 8 – Tests

80. Voltage to the CMOS actuation pads attracts the mirrors and flips them ON and OFF, to ensure that

they are all moving and functioning. The good chips move on to encapsulation.

81. A black epoxy is spread around the mirrors to hide any structures, like the gold wires that might

scatter or reflect light, which would reduce the image contrast.

82. The devices are then baked to harden the epoxy.

83. In these burn-in furnaces the mirrors are electrically tested. For two to twenty four hours the mirrors

flip back and forth continuously. The screen shows the checkered pattern of the pixels as they flip.

84. To overcome stiction, the tendency for surface forces to cause small structures to stick, the mirrors

rely on the restoring force of the torsion hinge to return to a FLAT, ON or OFF state.

85. Looking closely at the yoke we also find small spring tips. These tips deflect slightly as they land on

the lower surface. When released, the stored potential energy provides a slight kick that helps

overcome adhesive forces.

86. After Burn-In, a tester measures whether or not the mirrors tilt.

87. A second tester checks the mirror movement by applying various voltages and measuring the

responses. These movements can vary between devices with different angles and mirror sizes.

88. The final test is a visual test. The image is projected using different colored screens and inspected to

ensure there are no defects. A defect projected on a black screen, for example may not show on a

dark background but will show when projected against a white background.

89. Here we see a test device, which has been programmed with specific images. The mirrors reflect the

image in black and white. These same images, reflected from the DLP device, go through a series of

lenses and color filters to be projected in color.

90. A laser brands the appropriate information on the back of the DLP devices before they are shipped to

the suppliers around the world. They in turn produce the many projectors we use on a daily basis.

DESIGN (Sensors)

Chapter 9 – MEMS Design Process

91. To see how sensors are designed let's go to Freescale Semiconductor. Designing MEMS devices is a

critical part of manufacturing and a team effort. Experts bring together the mechanical and electrical

design and manufacturing aspects to create complete micro systems in different fields.




92. Two of the most common types of sensors monitor pressure and movement.

93. Pressure sensors measure pressure change in gases and liquids. In most cases a thin silicon

membrane responds to a change in pressure and triggers a response. This requires an opening in the

package to keep one side of the membrane exposed to the environment. In cars they monitor things

like combustion pressure to improve fuel efficiency and side crash detection. These sensors monitor

the air pressure of tires. These monitor blood pressure.

94. Inertial Sensors measure a change in movement. They include accelerometers and gyroscopes.

95. Accelerometers measure linear movement along the x, y, and z-axes. They detect acceleration, which

is a change in speed or direction. They are used in cars for safety critical applications to improve

dynamic control. In this electric car they deploy airbags while pressure sensors monitor tire pressure.

96. Accelerometers are found in a variety of motion detection consumer products. In sports like golf they

provide information to help improve one's swing.

97. Gyroscopes measure rotational movement known as yaw, roll, and pitch. These gyros are used in

cars. When they sense a car has lost control and begins to roll they deploy a side airbag.

98. The design of sensors and MEMS in general, is done in an iterative top down workflow that requires

revisions and feedback.

99. This process typically begins when the customer presents requirements to a team of mechanical,

electrical, and systems engineers, as well as marketing and sales experts.

100. The project requirements are then presented to the design team who scope the project and establish a

roadmap.

Chapter 10 – Design Team

101. Let's take a look at the project from the different perspectives of the designers who are working on it.

The mechanical designer determines the limitations of the mechanical transducers. This is the part

that converts motion into a change in electrical signal such as capacitance. This signal is read by the

electrical, or Application Specific Integrated Circuit, known as ASIC. With accelerometers, an abrupt

motion or acceleration moves the proof mass. Each sense electrode, connected to runners, collect the

change in capacitance signal. The runners, connected to electrical leads, carry the signal to the ASIC.

102. The ASIC designer checks that the change in capacitance, which is converted to a voltage, meets the

circuit’s requirements.

103. The systems engineer creates an architectural level design and writes the specifications. These

specifications can include the level of integration or layout of the device.

104. With system-in-package a sensing cell measures the force of acceleration, which results in changing

capacitance. Freescale’s IC design converts capacitance to voltage and allows the sensor to be

calibrated or checked for accuracy. This particular sensor is used in the game Guitar Hero.




105. Some sensors bond the die in a stack formation to reduce the footprint. Here we see the pressure

sensor. On the other side we see three devices: the micro controller, radio frequency transmitter, and

a dual axes accelerometer. These stack devices can track the motion in golf swings. In cars, they

monitor sensors without using wires.

106. After scoping, partitioning and model generation is the next phase. Here, the Microsystems Group

partitions the components of the system into blocks that represent the physics of the mechanical and

electrical chips.

107. Each block has a mathematical representation that consists of lines of equations, or code. The design

often starts with a few lines of code. More lines are added to enhance the model's details and set the

operational parameters.

108. The transducer model allows designers to predict proof mass motion. They do this by applying

different accelerations to the model. The calculations they use address issues like mass and stiffness

of the proof mass and the change in capacitance.

109. Other equations determine electrostatic attraction and internal gas resistance that dampens the motion.

110. The package model determines the effect of the packaging, including stress, on the performance of

the MEMS chip. The result is a transducer systems block that predicts the changes in capacitance.

These changes will be monitored by the ASIC logic chip.

111. The ASIC designer works on the conversion of capacitance to voltage. The voltage is then sampled

and converted to a digital signal. The designer then applies final digital algorithms. Some of these

will be used to set up the conditions for the final testing.

112. Once the System Engineer feels comfortable with the partitioning and modeling of the MEMS and

ASIC designs, the work progresses to the analysis phase.

113. Here, the Systems Designer brings the two together to find out how they work. MEMS and ASIC

blocks simulate performance and ensure the results meet product specifications. While the design

needs to be represented in a mathematical format, it also now needs to include the impact of

fabrication.

114. With surface micromachining, deposition, photolithography and etch produce feature sizes that may

not exactly match the design. The designers need to know how the process works.

115. For example, a deep reactive ion etch, known as the Bosch Process, creates deep straight etched walls

by alternating chemicals used in the etch chamber. These high aspect ratio structures increase the

surface area of the sense elements vertically. As a result, the chips will need fewer elements and can

therefore be made smaller.

116. Designers make adjustments and data moves up and down the process flow two to five times or more.

Models run over and over again as areas are repartitioned or variations tightened. Before the process

finishes, the final data is checked against the design specifications again.




117. In verification, the systems engineer receives and checks analysis data. The mechanical designers

verify their MEMS design with layout 2D CAD tools. And circuit designers execute and verify with

transistor level schematics.

118. Once cleared, the mechanical and electrical designers create their final designs, known as “tape out.”

The project then moves to fabrication.

Chapter 11 – Conclusion & Credits

119. There are many types of MEMS devices. Biochemical microarrays, printed with stacks of specific

peptide sequences and used in DNA studies, can quickly identify the existence of cancer.

Tiny cantilevers, or probes, used in the Atomic Force Microscope map the surface of atomic

structures. MEMS serve as a bridge between the micro world and the even smaller nano world.

120. As technology moves forward the potential of MEMS devices is vast and limited only by our own

mechanical ingenuity.

Revision: 5/20/11 www.scme-nm.org


Learning Modules available for download @ scme-nm.org

MEMS Introductory Topics

MEMS History

MEMS: Making Micro Machines DVD and LM (Kit available)

Units of Weights and Measures

A Comparison of Scale: Macro, Micro, and Nano

Introduction to Transducers, Sensors and Actuators

Wheatstone Bridge (Pressure Sensor Model Kit available)

MEMS Applications

MEMS Applications Overview

Microcantilevers (Dynamic Cantilever Kit available)

Micropumps Overview

BioMEMS

BioMEMS Overview

BioMEMS Applications Overview

DNA Overview

DNA to Protein Overview

Cells – The Building Blocks of Life

Biomolecular Applications for bioMEMS

BioMEMS Therapeutics Overview

BioMEMS Diagnostics Overview

Clinical Laboratory Techniques and MEMS

MEMS for Environmental and Bioterrorism Applications

Regulations of bioMEMS

DNA Microarrays (GeneChip® Model Kit available)

MEMS Fabrication

Crystallography for Microsystems (Breaking Wafers

and Origami Crystal Kits available)

Oxidation Overview for Microsystems (Rainbow Wafer Kit available)

Deposition Overview Microsystems

Photolithography Overview for Microsystems

Etch Overview for Microsystems (Rainbow Wafer and Anisotropic Etch Kits available)

MEMS Micromachining Overview

LIGA Micromachining Simulation Activities (LIGA Simulation Kit available)

Manufacturing Technology Training Center Pressure Sensor Process (Three Activity Kits available)

MEMS Innovators Activity (Activity Kit available)

Safety

Hazardous Materials

Material Safety Data Sheets

Interpreting Chemical Labels / NFPA

Chemical Lab Safety

Personal Protective Equipment (PPE)

Check our website regularly for the most recent

versions of our Learning Modules.

For more information about SCME and its Learning Modules and kits, visit our website

scme-nm.org or contact

Dr. Matthias Pleil at [email protected]

making_micro_machines_dvd_lm_pg.pdf

Documents

knowledge of mems

film mems

micro mems

mems applications

mems device

mems film website

mems pressure sensor

optical mems activity