MEMS

NANO51

Foothill College

Overview

• What are MEMS/NEMS?

• History of MEMS

• Applications and examples

• Making MEMS

• Future of MEMS

What are MEMS/NEMS?

Acronym for:

MMicro EElectro MMechanical SSystems

NNano EElectro MMechanical SSystems

But what does this mean????

The Role of MEMS

While the functional elements of MEMS are

miniaturized structures, sensors, actuators,

and microelectronics, the most notable

(and perhaps most interesting) elements

are the microsensors and microactuators.

Microsensors and microactuators are

appropriately categorized as “transducers”,

which are defined as devices that convert

energy from one form to another. In the

case of microsensors, the device typically

converts a measured mechanical signal into

an electrical signal. Micro-Electro-

Mechanical Systems, or MEMS, is a

technology that in its most general form

can be defined as miniaturized mechanical

and electro-mechanical elements (i.e.,

devices and structures) that are made using

the techniques of microfabrication. The

critical physical dimensions of MEMS

devices can vary from well below one

micron on the lower end of the

dimensional spectrum, all the way to

several millimeters.

Michael Huff,Michael Huff is at the MEMS Exchange, Corporation for National Research Initiatives, 1895 Preston White Drive, Suite 100, Reston, Virginia 20191-5434, USA

MEMS – Smart Matter

• MEMS technology combines mechanical devices and electronics on a micro or nano scale

• Examples are sensors, valves, gears, mirrors, and actuators embedded in semiconductor chips.

• MEMS are sometimes referred to as smart matter.

MEMS Ratchet

Imagine a machine so small that it is imperceptible to the human

eye. Imagine working machines no

bigger than a grain of pollen. Imagine

thousands of these machines batch

fabricated on a single piece of silicon, for just a few pennies each. Imagine

a world where gravity and inertia are

no longer important, but atomic forces

and surface science dominate.

Imagine a silicon chip with thousands of microscopic mirrors working in

unison, enabling the all optical

network and removing the bottlenecks

from the global telecommunications

infrastructure. You are now entering the micro-domain, a world occupied

by an explosive technology known as

MEMS. A world of challenge and

opportunity, where traditional

engineering concepts are turned upside down, and the realm of the

"possible" is totally redefined.

http://www.memx.com/

MEMS/NEMS

• Nanosystems and Micro-Electro-

Mechanical Systems (MEMS) are the

integration of mechanical elements,

sensors, actuators, and electronics on a

common silicon substrate through the

utilization of microfabrication

technology.

Foundational Technology

• Paul Saffo of the Institute for the Future

in Palo Alto, California, believes MEMS

or what he calls analog computing will

be "the foundational technology of the

next decade."

Other MEMS Terms

• Microengineering: the technologies and practice of making three dimensional structures and devices with dimensions in the order of micrometers.

• Micromachining: techniques used to produce the structures and moving parts of micro engineered devices

• Microsystems: The integration of microelectronic circuitry into micromachined structures, to produce completely systems

Source: Danny Banks http://www.dbanks.demon.co.uk

Micromachining/MEMS Applications

• Micro-sensors

– Light detectors, pressure sensors, strain gages,

temperature sensors7

• Micro-actuators

– Valves, gears, motors, resonators, cantilevers

• Structures

– Cavities, microneedles, fluidic channels, lenses,

membranes

• Lab-on-a-chip / micro-fluidics / diagnostics in

medicine / BioMEMS

What are Transducers?

A transducer is a medium for transforming

energy between 2 or more domains

A sensor measures something in its surrounding

environment and provides a response related to

the measured parameter

A mechanical actuator converts electrical signals

into a mechanical action

Source: Micromachined Transducers Sourcebook by Gregory Kovacs

MEMS Applications

• Automotive

• Telecommunications

• Sensors

• Actuators

• BioMEMS

http://www.memsnet.org/mems/applications.html

MEMS: Micromachines

As the name implies,

micromachines are very tiny

mechanisms. In fact, they are so

small that the unaided eye cannot

perceive them. Many different

types of professionals, such as

biologists, chemists, physicists,

and engineers, are involved in the

research and development of

these complex devices.

Micromachines can be a wide

variety of different mechanisms,

such as fluid channels, gears,

engines, tweezers, and mirrors -

all smaller than the width of a

human hair. So, what are these

micro-devices used for? Well,

many of them are creeping into

our everyday lives, in places

where you may not expect them.

http://webdocs.cs.ualberta.ca/~database/MEMS/sma_mems/mems.html

MEMS Sensors and Actuators(NTS: get pictures)

• Automotive Force, Pressure, Sound, and

Vibration

• Optical sensors (visible and IR / UV)

• Fluid flow (in micro environments)

• Industrial chemical and gas sensors

• Interfacing MEMS Sensors and Actuators

with Microcontrollers

Accelerometers

• NTS: get pictures and discuss how it

works

• MEMS accelerometers are used for air-

bag deployment in cars

MEMS Accleromters

A device that detects acceleration and tilt. Built using MEMS technology,

accelerometers detect impact and deploy

automobile airbags as well as retract the

hard disk's read/write heads when a laptop

is dropped. Digital cameras employ them in their image stabilization circuits. They

are used in washing machines to detect

excessive vibration and in pedometers for

more accurate distance measurement.

They also enable a handheld display to be switched between portrait and landscape

modes when the unit is turned. MEMS

accelerometers initially used a

microminiaturized cantilever-type spring,

which converts force into a displacement that can be measured. Subsequent

accelerometers use a heated gas bubble

with thermal sensors and function much

like the air bubble in a construction level.

When the accelerometer is tilted or accelerated the sensors pick up the

location of the gas bubble.

http://encyclopedia2.thefreedictionary.com/Accelerometers

Microfabrica Accelerometer

The device at the bottom left with the C-shaped wings is an accelerometer. Built one metal layer at a time, Microfabrica's EFAB system was the first MEMS foundry

process to quickly turn customers' CAD files into micromachines. (Image courtesy

of Microfabrica Inc., www.microfabrica.com)

http://encyclopedia2.thefreedictionary.com/Accelerometers

More MEMS Pictures

• Gears

• Tweezers

• Springs

• Mirrors

• Cavities

• Comb drives

• Microneedles/tips

http://www.bacteria-world.com/mems-hinge.htm

BioMEMS Applications(NTS: get pictures)

• Lab-on-a-chip

• Micro fluidics

– DNA extraction / separation technology

– Protein separation / purification

– Electrophoresis, capillary flow measurements

• Biochips, microarrays, microsensors– In vivo diagnostic sensing

• ‘Smart-sensing’ in implantable devices

Bio-Microelectromechanical Systems

BYU BioMEMS research focuses on using microelectromechanical devices to move DNA and other molecules across biological cell boundaries. The effort uses a revolutionary

method based on nanoelectromechanical principles to place DNA inside of cells without

harming them. The research contributes to our understanding of many diseases, including

cancer, and has promise for future therapies for genetic disorders.

Computational MEMS

• Interfacing microcontrollers and MEMS

• Packaging issues of MEMS and CPU– interconnection reliability similar to standard

plastic IC packaging processes

– based on a standard flow for plastic packages

– applicable for a wide range of plastic packages (e.g. SOIC, QFP, PLCC, SSOP, BGA, CSP)

– can be applied with multi-chip concepts

– (sensors + ASIC)

– package cost for medium to high volumes

System on a Chip

http://www.genome.gov/pressDisplay.cfm?photoID=20017

Making MEMS

When does it make sense to Micromachine?

• Just because something can be built on

a micro or nano scale, doesn’t mean

that it should

• There has to be a significant advantage

over conventional designs

What are the Possible Advantages?

• Low cost from high volume fabrication (example: air bag sensors)

• Mechanical reliability

• Precise sensing techniques

• Access to areas/information where larger components can not reach

• Smaller components may provide convenience

Possible Disadvantages

• Lower tech solutions could be cheaper

• High development costs (motorization of R&D, packaging, and testing costs)

• Mechanical properties are different at the micro and macro scale

• Power supply may dwarf any advantages to smaller size

• Signal quality may be compromised at the microscale

• Thermal instability

• Difficulty in packaging

MEMS Materials / Environments

• Silicon technology

• Carbon based polymers

• Future working environments

– CNT integration

– Colloids / fluids

– Biological systems

– High pressure / reactive gas systems

MEMS Processing

Techniques

• Standard silicon technology (IC fab

techniques)

– Bulk micromachining

– Surface micromachining

• Polymers

• Electro Discharge Machining

• Molding

Micromachining

• Because silicon dominates the IC fabrication industry, it also dominates many of the fabrication techniques for nanotech forerunners such as MEMS and NEMS

• While the electronics are fabricated using IC process sequences, the micromechanical components are usually fabricated using compatible "micromachining" processes that selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices

Bulk versus Surface Micromachining

• Bulk micromachining develops

structures by selectively etching a

silicon wafer

• Surface micromachining develops

structures by selectively adding thin

films and layers on the surface of a

silicon or other appropriate substrate

MEMS Processing

Techniques

• Deposition processes

• Lithography and photolithography

• Etching processes

• Surface treatments and coatings

• Packaging and CPU integration

• Metrology techniques for QA/QC

MEMS Application: Nanoindention for storage

• Discuss process to make,

• show end result, and

• what the advantages are and how it

would work

• Etc.

Current Trends and Future Directions in MEMS

• Downward cost pressure

• Increased / specialized functionality

• Integration in biological systems

• Integrating with CPUs / ASICS / RFID

• Mechanical ‘assembling’ functionality

– Rudimentary mechanical functioning

beyond simple sensors / actuators

MEMS Market Opportunities

• MEMS market size

– 2000 to 2005 (innovation)

– 2005 to 2010 (adoption / growth)

– 2010 to 2015 (maturation / mainstream)

– NTS: Get trend data

Challenges Facing MEMS

• Limits to silicon processing

– Three dimensions of exactness

– Cost and reliability of manufacturing

• Integration in biological systems

• Serviceability, design cycles

• Integration with CPUs / communications

• Needs an industry ‘sponsor’ (like RFID)

• PACKAGING

Micro-sensor

Micro-mirror Micro-gear

Micro-accelerometer

Self Assembly and Micro/Nano

Electronics

What are MEMS/NEMS?Micro-Electro-Mechanical Systems (MEMS) are the integration

of mechanical elements, sensors, actuators, and electronics on a

common silicon substrate through microfabrication technology.

Micro-sensor

Micro-mirror Micro-gear

Micro-accelerometer

MEMS vs. Integrated Circuits (IC’s)

• One way to look at it:

– IC’s move and sense electrons

– MEMS move and sense mass

• MEMS act as transducers (sensors) converting a

physical property into an electrical property (force to

voltage, etc…).

• MEMS can also actuate mechanical devices (switches,

mirrors, etc…)

• In the early 1980s Karlsruhe Nuclear

Research Center in Germany

developed LIGA

• LIGA is a German acronym for X-

ray lithography (X-ray

Lithographie), Electroplating

(Galvanoformung), and Molding

(Abformung)

• It allows for manufacturing of high

aspect ratio microstructures

• High aspect ratio structures are very

skinny and tall

• LIGA structures have precise

dimensions and good surface

roughness

Microfluidic device made using LIGA process

1982 LIGA Process Introduced1982 LIGA Process Introduced

Capacitive Comb drive also made using the LIGA process

• In 1986 IBM developed the atomic force microscope (AFM)

• The AFM maps the surface of an atomic structure

• Measures the force acting on the tip of a microscale cantilever

• It is a very high resolution type of scanning probe microscope with a resolution

of fractions of an Angstrom

1986 Invention of the AFM1986 Invention of the AFM

MEMS Applications

• Pressure Sensors

– Auto and Bio applications

• Ink Jet Print Heads

• Accelerometers

– (Inertial Sensors – “Crash Bags”, Navigation, Safety, iPhones)

• Micromachines

• Micro Fluidic Pumps

– Insulin Pump (drug delivery)

• Spatial Light Modulators (SLM’s)

– MOEM – Micro Optical Electro Mechanical Systems

– DMD – Digital Mirror Device

• Mass Storage Devices

• Chem Lab on a Chip

• Cantilever biosensors

MEMS Pressure Sensors

• Pressure Sensors

– Use piezoresistive silicon

sensors

– The silicon chip flexes as

pressure changes

– The amount the silicon

chip flexes determines the

output voltage signal.

These sensors help improve engine performance including gas mileage.

Pressure Sensors

TRW Commercial Gas Engine Sensor - 1985

Top view of the TRW (1985) pressure sensor, the metal components

are on top of the silicon membrane. The silicon membrane is

stressed when there is a pressure differential.

Intercardial catheter-tip sensors

These MEMS transducers are used in

intercardial catheter-tip sensors for

monitoring blood pressure during cardiac

catheterization.

Photo courtesy of Lucas NovaSensor, Fremont, CA.

0.15 x 0.4 x 0.9 mm

Disposable Blood Pressure SensorsDisposable sensors use MEMS transducers to measure changes in blood pressure.

Photo courtesy of Motorola, Sensor Products Div., Phoenix, AZ.

These $10 devices connect to a patient's

IV line and monitor blood pressure

through the IV solution.

This microphone is made from Silicon and is only

millimeters large. Photo Courtesy of EmKay

EmKay Sisonic Microphone

Ink JetInk jet printers are MEMS based – 1979 IBM and HP

Ink jet printers are MEMS based – 1979 IBM and HP

Ink Jet

1979 HP Micromachined Inkjet Nozzle

Schematic of an array of inkjet

nozzles.

Close-up view of a

commercial inkjet printer

head illustrating the nozzles.This printing technique rapidly heats ink, creating tiny bubbles.

When the bubbles collapse, the ink squirts through an array of

nozzles onto paper and other media. Silicon micromachining

technology is used to manufacture the nozzles. The nozzles

The AccelerometerAnalog Devices – 1993 Saab was the first automobile company to

include MEMS accelerometers to trigger airbags.

These MEMS-based systems sense rapid deceleration and in the event

of a collision send a signal to inflate rapidly an airbag.

The AccelerometerAn accelerometer is a sensor for testing the acceleration along a given axis.

The simplest MEMS accelerometer is an inertial mass suspended by springs.

Deflection of the mass is converted into an electrical signal.

iPhone

Nintendo Wii

IBM Thinkpad

http://www.youtube.com/watch?v=VmDnuqEOLps&feature=related

http://www.youtube.com/watch?v=Z24JP5TBnyE

The square in the middle of the chip is a resistor that heats up a gas

bubble. The next larger squares contain thermal couples that sense the

location of the heated bubble as the device is tilted or accelerated.

(Image courtesy of MEMSIC, Inc.)

MEMSIC's Dual-Axis Thermal Accelerator

MEMS as Machines

MEMS are often referred to as Micro Machines.

Tiny devices that move things.

Gear Train. Each gear tooth is

8 microns wide.

Mirror (popped up)

Micro Machines

• Surface Micromachining takes off in

the 1990’s.

• Sandia National Laboratories

This basically consists of alternating layers of structural materials (polycrystalline silicon) and

sacrificial layers (Silicon Dioxide). The sacrificial layer is a scaffold and acts as a temporary

support and spacing material. The last step of the process is the “release” step, where the

sacrificial layer is removed freeing the structural layers so they can move.

In this image, the square at the top is a microfluidics device with internal passageways

used for a "lab on a chip." The multi-arm device (center) is a fuel injection nozzle. Bottom

left is an accelerometer, and bottom right is an inductor used in RF circuits. (Image

courtesy of Microfabrica Inc., www.microfabrica.com.)

Micromachines

In this image, the square at the top is a microfluidics device with internal passageways

used for a "lab on a chip." The multi-arm device (center) is a fuel injection nozzle. Bottom

left is an accelerometer, and bottom right is an inductor used in RF circuits.

(Image courtesy of Microfabrica Inc., www.microfabrica.com.)

Micromachines

Microfluidics

Device

In this image, the square at the top is a microfluidics device with internal passageways

used for a "lab on a chip." The multi-arm device (center) is a fuel injection nozzle. Bottom

left is an accelerometer, and bottom right is an inductor used in RF circuits.

(Image courtesy of Microfabrica Inc., www.microfabrica.com.)

Micromachines

Fuel Injection

Nozzle

Microfluidics

Device

In this image, the square at the top is a microfluidics device with internal passageways

used for a "lab on a chip." The multi-arm device (center) is a fuel injection nozzle. Bottom

left is an accelerometer, and bottom right is an inductor used in RF circuits.

(Image courtesy of Microfabrica Inc., www.microfabrica.com.)

Micromachines

Accelerometer

Fuel Injection

Nozzle

Microfluidics

Device

In this image, the square at the top is a microfluidics device with internal passageways

used for a "lab on a chip." The multi-arm device (center) is a fuel injection nozzle. Bottom

left is an accelerometer, and bottom right is an inductor used in RF circuits.

(Image courtesy of Microfabrica Inc., www.microfabrica.com.)

Micromachines

Accelerometer

Fuel Injection

Nozzle

Microfluidics

Device

Inducto

r

MEMS-based Optical Switch

These MEMS optical switches utilize micro mirrors to switch or reflect an

optical channel or signal from one location to another.

In 1999 Lucent Technologies developed the

first optical network switch

Micro Optical Electro Mechanical Systems (MOEMS)

Digital Mirror Device (DMD)

A DMD chip has on its surface several hundred thousand microscopic

mirrors which correspond to the pixels in the image to be displayed.

Digital Light Projector (DLP)

Digital Mirror Device (DMD)The mirrors can be individually rotated ±10-12°, to an on

or off state.

How Small are these Mirrors?

Each mirror is about 16µm square!

DMD mirrors – complete DLP units have over 2 million mirrors – all functioning!

Ant LegAnt Leg

Pin PointPin Point

Mass Storage - IBM

IBM’s “Millipede”

100 Tera Bit per square inch!

It works by making small indentations in a polymer

film.

Higher density data capability

Mass Storage - IBM

•A two-dimensional array of V-shaped silicon cantilevers, each 70

µm long.

•Writes divot into polymer by heating tip to 400°C

•Reads by looking at surface with 300°C tip (measures resistance

change with temp drop)

– if the tip is in a divot, the tip cools more than if it is not –

therefore, there is a change in resistivity which is measured by

the electronics.

•Erases by making an offset pit, which causes the nearby pit to

“pop up” and hence erases it.

BioMEMS

The overlap between microbiology and microsystem feature sizes

makes integration between the two possible

Atom

100 µm 10 µm 1 µm 0.1 µm 0.01 µm 0.001 µm

(1 nm)

Eukaryotic cells ProteinsVirusesBacteria

RibosomeNucleus

Gate of Leading

Edge Transistor

Visible Light

Surface Micromachining Features (MEMS)

Molecules

(10 nm)

Biomedical Applications

• Scientists are combining

sensors and actuators with

emerging biotechnology

• Applications include drug

delivery, DNA arrays, and

microfluidics

Biomedical ApplicationsMicromachine needles used to deliver drugs

Procter and

Gamble

Plastic Needle

Array

MEMS

Cantilevers

• Cantilevers are used as

Sensors

• Cantilevers are used as

Switches

• Many MEMS Sensors

use the principles of

Cantilevers as well as

RF Swtiches

What is a Cantilever?

Cantilevers have a resonant frequency that depends on the

length and the mass.

MEMS

Cantilever

sensors

• The ends of the cantilevers are coated with a layer of probe molecules.

• When a target molecule is present, it attaches to the probe molecule, thereby increasing the mass.

• The resonant frequency goes down.

• You just detected the presence of a molecule!

Cantilever Sensors

A gold dot, about 50 nanometers in diameter, fused to the end of a cantilevered

oscillator about 4 micrometers long.

A one-molecule-thick layer of a sulfur-containing chemical deposited on the gold

adds a mass of about 6 attograms (10-18 grams) , which is more than enough to

measure. Craighead Group/Cornell Univeristy

As mass is added to the cantilever shifts the resonance frequency.

Resonance Shift

5 x 15um Cantilever with an

E. Coli cell bound to

antibody layer.

Black is the response before cell attachment,

Red is after cell attachment.

School of Applied and Engineering Physics and the

Nanobiotechnology Center, Cornell University

http://www.news.cornell.edu/releases/April04/attograms.ws.html

Resonance Shift due to Single Cell

Resonance Frequency Shift as a

Function of Mass

Detection of Single DNA

http://www.hgc.cornell.edu/Nems%20Folder/Enumeration%20of%20Sin

gle%20DNA.html

By changing the coating

(Nano) one can functionalize

the cantilever to detect single

strands of DNA.

Mass resolution is on the

order of under 1 ato gram (10-

18grams)

Gold dot = 40nm

SiN thickness = 90nm

Future of MEMS

• Wireless / networked MEMS/BioMEMS

• Advanced biosensors / actuators

• Computational MEMS

• Advanced System on a Chip

• MEMS systems (networks of MEMS)

Summary

• What are MEMs?

• What do MEMs do?

• MEMs applications

• MEMs fabrication

• Future MEMs

– BioMEMS, NMEMS

MEMS References

• MEMS Clearinghouse -

http://www.memsnet.org/news/

• About MEMS – MEMX

http://www.memx.com/

• All about MEMS

http://www.allaboutmems.com/memsappli

cations-optical.html

• Sandia MEMS Homepage -

http://mems.sandia.gov/