¿Quien soy y por qué estoy

aquí?Thomas Adams, PhD

En el mundo hispano: Tomás McDaniel Adams McDaniel

Soy profesor de ingeniería mecánica en Rose-Hulman Institute of Technology

Mis estudiantes me llaman “Doctor Tom”.

Más cabello

Más

ca

bello

Terre Haute, Indiana, USA

Private university with ~ 2000 students, mostly undergraduate (pregrado)

Ciencias, ingeniería, y matemáticas

Introduction to MEMS(micro-tecnología)

Movie of a motor

Motor and gear train movies from Sandia National Laboratory

Movie of a motor

Motor and gear train movies from Sandia National Laboratory

Still pictures of motor

A still picture of the motor…

with a spider mite on it!

Another view of the engine

Movie of a motor

Motor and gear train movies from Sandia National Laboratory

Movie of a motor

Motor and gear train movies from Sandia National Laboratory

Movie of a motor

Motor and gear train movies from Sandia National Laboratory

Course overview and objectives

Overview:This course gives an introductory treatment of MEMS, also known as microsystems and micro-technology (MST). Fabrication, device functionality, and modeling strategies are explored.

Objectives (Objetivos):Through the student work in the course program, the student will be able to: Identify the relative importance of different physical phenomena

based on length scale Identify and describe the most commonly used fabrication

processes in making MEMS devices For a simple MEMS device, identify the major required

fabrication steps and put them in the appropriate order (create a process flow)

Use the principles of elastic theory in predicting the stress/strain state of MEMS devices

Course overview and objectives

Objectives (Objetivos) continued:Through the student work in the course program, the student will be able to: List a number of common MEMS transducers and explain

their operating principles Explain in detail the operating principles of a

piezoresistive MEMS pressure sensor, and predict the performance of such a device

Give a well-formed argument considering a microtechnology-based solution for a given problem

Gain experience using English in spoken and written forms as a means of expressing technical ideas

Topics

Specific topics1. Introduction to MEMS: Scaling and basic fabrication2. The Substrate3. Additive Techniques 4. Creating Patterns – Lithography5. Bulk Micromachining 6. Surface Micromachining7. Process flow8. Solid mechanics 9. Overview of MEMS operating principles10. Modeling case study: piezoresistive sensors

References

Required• Introductory MEMS: Fabrication and

Applications by Thomas Adams and Richard Layton, Springer

Disponible (¡gratis! ) en los bases de datos de PUCP: http://biblioteca.pucp.edu.pe/colbasd.html Suggested (sugerencias)• Fundamentals of Microfabrication by Marc J.

Madou, CRC Press.• Microsystem Design by Stephen Senturia,

Springer• Foundations of MEMS by Chang Liu, Prentice

Hall.

¿Cómo va a ser el curso?

Notas:Problems/reading summaries10%Midterm exam 30%Final Exam 35%Report 15%Attendance/participation 10%

100%

En y fuera de

clase Puntos fáciles

Puntos fáciles

No quiero que este curso sea una dictación sino un diálogo. Por eso creo que es importante que nos charlemos en una manera relajada para entender mejor y practicar nuestros idiomas. (Ustedes, inglés y yo, español.)

I will correct your English, but it will not affect your grade. The reading summaries will be based on effort.

¿Cómo va a ser el curso?

Report:Can be about any aspect of MEMS you would like—a new or advanced fabrication technique not covered in the book/lectures, a particular MEMS device, a particular class of MEMS technology, modeling strategies, etc.Some examples:• Focused ion beam instruments• Micro fuel cell technology• Dyanamic systems modeling in MEMS• Advanced photolithography techniques• Digital microfluidics• MEMS gyroscopes• MEMS packaging

Reading summaries:• One each week on assigned

reading• Inlcude a brief summary of

the major points (¡No me den otro libro!)

• Describe the thing you feel you understand the best (Algo que entiendes bien)

• Describe the thing you feel you understand the least (Algo que no entiendes para nada)

What are MEMS?

Acronym (acrónimo) for micro-electro-mechanical systems.

Micro: Small size. The basic unit of measure is the micrometer or micron (μm)

1 μm = 10-6 m

Electro: MEMS have electrical components (quizás)

Mechanical: MEMS have moving parts (quizás)

Systems: Refers to integration of components. (Funcionan juntos.)

Examples of MEMS

You can find MEMS in

• Automobiles (Air bag sensors)

• Computer printers (Ink jet print heads)

• Cell phones (RF devices)• Lab-on-a-chip

(Microfluidics)• Optical devices

(Micromirrors)• Lots of other things

MEMS accelerometer

MEMS accelerometers are used widely to deploy airbags. (Casi todos los coches los tienen.)

MEMS accelerometer

Most accelerometers use electrical capacitance to sense acceleration.Se llama “comb

structure (estructura de

peine)

Adapted from Microsystem Design by Stephen Senturia, Springer

Movie of a motor

Can be used in reverse as an actuator. With alienating current (corriente alterna) it becomes a motor. In MEMS this type of motor is called a comb drive.

Comb

drive

Ink jet print heads

Ink dots are tiny (10-30 per mm) and so are the nozzles that fire them.

Ink jet print heads

• Ink-filled chambers are heated by tiny resistive heating element

• By heating the liquid ink a bubble is generated

Ink jet print heads

• The vaporized part of the ink is propelled towards the paper in a tiny droplet

• Chambers are filled again by the ink through microscopic channels

Micromirrors

Micromirrors are used as optical switches and even computer displays

Micromirrors

An array of micromirrors

Micromirrors

Video of micromirror actuation from Sandia National Labs

More examples

Labs-on-a-chip can replace entire chemical and biological analysis laboratories.

More examples

There are many other MEMS devices in development…

More examples

…some more useful than others.

Why go micro?

• Smaller devices require less material to make. (Earth has limited resources.)

• Smaller devices require less energy to run.

• Redundancy can lead to increased safety. (You can use an array of sensors instead of just one.)

• Micro devices are inexpensive (?) Less material Can be fabricated in

batch processes

What are some reasons that you would want to make micro-sized

devices?

Más cabello

Why go micro?

• Micro devices are minimally invasive and can be treated as disposable. (Especially good for chemical and medical applications.)

• Many physical phenomena are favored at small scales.

What are some reasons that you would want to make micro-sized

devices?

Examples of small scale effects

Hot arm actuator

A poly-silicon hot-arm actuator fabricated using surface micromachining

Examples of small scale effects

Hot arm actuator

A poly-silicon hot-arm actuator fabricated using surface micromachining

I

+V-

Examples of small scale effects

Electro-osmotic flow

Electricity can move fluids!

junction

separation column

entry port

+ V -

Scaling laws

Water spills out of key ring, but it stays in the smaller holes of the key (llave). Why?

Activity – Demo with key and key ring

• Gravity (weight) pulls water down. Surface tension holds water up. Which one wins? (¿Quien gana?)

• Weight depends on volume/area/length

• Surface tension depends on volume/area/length

• Entonces,

~Wweight

tension surface

Scaling laws

Te toca a ti – La musaraña (shrew) es el animal más pequeño que es de sangre caliente. Si no come constantemente, se muere. Usa “scale analysis” para explicar.

Scaling laws

Te toca a ti – Use scale analysis to show that every animal on the planet can jump approximately the same height. Es decir, que la habilidad de saltar no cambia con la dimensión.

Scaling laws

• Heat transfer (tranferencia del calor) is faster

• Frequency response is faster• Electrostatic forces are more

prominent (más fuertes)• Surface tension can move fluids• And more

Favorable scalings at the microscale

How are MEMS made?

• Many techniques borrowed from integrated circuit (IC) fabrication- Silicon wafers are

commonly used- Bulk micromachining

• Surface micromachining• Other techniques

How are MEMS made?

Bulk micromachining example - A diaphragm for a pressure sensor

Adapted from MEMS: A Practical Guide to Design, Analysis, and Applications, Ed. Jan G. Korvink and Oliver Paul, Springer, 2006

Membrane is piezoresistive; i.e., the electrical resistance changes with deformation.

Bulk micromachining

Bulk micromachining example - A diaphragm for a pressure sensor

Silicon wafer

Grow SiO2

Spin on photoresist

Glass plate

Opaque

regionUnexposed photoresist removed by developer

SiO2 chemically etched with

HFl

Unexposed resist

removedSilicon

anisotropically etched with

KOH

Mask

Bulk micromachining

Depending on the chemical/structure combinations, etching can be… isotropic or anisotropic

001 silicon wafer 011 silicon wafer

Anisotropic etches

Surface micromachining

= Surface micromachining

+

The Si wafer functions like the big green flat

plate.

Some Jenga pieces are removed. The ones that remain form the MEMS

structure.

Surface micromachining

Surface micromachining example –

Creating a cantilever

Silicon wafer (Green Lego®

plate)

Deposit aluminum (structural layer—the Jenga pieces that

remain)

Remove sacrificial layer (release)

Deposit polyimide (sacrificial layer—the Jenga pieces that are removed)

Etch part of the layer.

Micromachining

Complicated structures can be made by combining these techniques and repeating

Micromachining

Everything has to be very clean!(¡Ojala estén limpias todas cosas!)

Surface micromachining

Te toca a ti—Come up with the process steps needed to make the cantilever in the last example. (Deposition, photolithography, etc.)

Side view Top view

Hint: You will need two masks and two photolithography steps.