Lectures onMEMS and MICROSYSTEMS DESIGN

AND MANUFACTURE

Tai-Ran Hsu, ASME Fellow, ProfessorMicrosystems Design and Packaging Laboratory

Department of Mechanical and Aerospace EngineeringSan Jose State UniversitySan Jose, California, USAE-mail: Tai-Ran.Hsu@sjsu.edu

CONTENT

Chapter 1 Overview of MEMS and Microsystems

Chapter 2 Working Principles of Microsystems

Chapter 3 Engineering Science for Microsystems Design and Fabrications

Chapter 4 Engineering Mechanics for Microsystems Design

Chapter 5 Thermofluid Engineering and Microsystems Design

Chapter 6 Scaling Laws in Miniaturization

Chapter 7 Materials for MEMS and Microsystems

Textbook: “MEMS and Microsystems: design , manufacture, and nanoscale engineering,”2nd Edition, by Tai-Ran Hsu, John Wiley & Sons, Inc., Hoboken, New Jersey, 2008(ISBN 978-0-470-08301-7)

Chapter 8 Microsystems Fabrication Processes

Chapter 9 Overview of Micromanufacturing

Chapter 10 Microsystems Design

Chapter 11 Assembly, Packaging, and Testing of Microsystems

Chapter 12 Introduction to Nanoscale Engineering

CONTENT –Cont’d

Chapter 1

Overview of MEMS and Microsystems

Hsu 2008

WHAT IS MEMS?MEMS = MicroElectroMechanical System

Any engineering system that performs electrical and mechanical functions with components in micrometers is a MEMS. (1 µm = 1/10 of human hair)

Available MEMS products include:

● Micro sensors (acoustic wave, biomedical, chemical, inertia, optical, pressure, radiation, thermal, etc.)

● Micro actuators (valves, pumps and microfluidics; electrical and optical relays and switches;grippers, tweezers and tongs; linear and rotary motors, etc.)

● Read/write heads in computer storage systems.● Inkjet printer heads.● Micro device components (e.g., palm-top reconnaissance aircrafts, mini

robots and toys, micro surgical and mobile telecom equipment, etc.)

HOW SMALL ARE MEMS DEVICES?

in plain English please!They can be of the size of a rice grain, or smaller!

Two examples:

- Inertia sensors for air bag deployment systems in automobiles

- Microcars

Inertia Sensor for Automobile “Air Bag” Deployment System

Micro inertia sensor (accelerometer) in place:

(Courtesy of Analog Devices, Inc)

Sensor-on-a-chip:(the size of a

rice grain)

Micro Cars(Courtesy of Denso Research Laboratories, Denso Corporation, Aichi, Japan)

Rice grains

MEMS = a pioneer technology for Miniaturization –

A leading technology for the 21st Century, and

an inevitable trend in industrial products and systems development

Miniaturization of Digital Computers- A remarkable case of miniaturization!

The ENIAC Computer in 1946 A “Lap-top” Computer in 1996

A “Palm-top” Computer in 2001

Size: 106 downPower: 106 up

Size: 108 downPower: 108 up

This spectacular miniaturization took place in 50 years!!

MINIATURIAZATION – The Principal Driving Force for the 21st Century Industrial Technology

There has been increasing strong market demand for:

“Intelligent,”

“Robust,”

“Multi-functional,” and

“Low-cost” industrial products.

Miniaturization is the only viable solution to satisfy such market demand

Market Demand for Intelligent, Robusting, Smaller, Multi-Functional Products - the evolution of cellular phones

Mobil phones 10 Years Ago: Current State-of-the Art:

Transceive voice only

Transceive voice+ multi-media + others (Video-camera, e-mails, calendar, and access to Internet, GPS and a PC with key pad input)

Size reduction

Palm-top Wireless PC

The only solution is to pack many miniature function components into the device

Miniaturization Makes Engineering Sense!!!

• Small systems tend to move or stop more quickly due to low mechanical inertia.It is thus ideal for precision movements and for rapid actuation.

• Miniaturized systems encounter less thermal distortion and mechanical vibration due to low mass.

• Miniaturized devices are particularly suited for biomedical and aerospace applications due to their minute sizes and weight.

• Small systems have higher dimensional stability at high temperature due tolow thermal expansion.

• Smaller size of the systems means less space requirements. This allows the packaging of more functional components in a single device.

• Less material requirements mean low cost of production and transportation.

• Ready mass production in batches.

Enabling Technologies for Miniaturization

Miniature devices(1 nm - 1 mm)

** 1 nm = 10-9 m ≈ span of 10 H2 atoms

Microsystems Technology(MST)

(1 µm - 1 mm)* Initiated in 1947 with the invention of transistors, but the term “Micromachining”was coined in 1982

* 1 µm = 10-6 m ≈ one-tenth of human hair

Nanotechnology (NT)(0.1 nm – 0. 1 µm)**

Inspired by Richard Feynman in 1959, with active R&D began in around 1995There is a long way to building nano devices!

A top-down approach

A bottom-up approach

The Lucrative Revenue Prospects for Miniaturized Industrial Products

Microsystems technology:$43 billion - $132 billion* by Year 2005( *High revenue projection is based on different definitions

used for MST products)

Source: NEXUS http://www.smalltimes.com/document_display.cfm?document_id=3424

Nanotechnology:$50 million in Year 2001$26.5 billion in Year 2003(if include products involving parts produced by nanotechnology)

$1 trillion by Year 2015 (US National Science Foundation)

An enormous opportunity for manufacturing industry!!

● There has been colossal amount of research funding to NT by governments of industrialized countries around the world b/cof this enormous potential.

The Lucrative Revenue Prospects for Miniaturized Industrial Products – Cont’d

MEMS Products

MicroSensingElement

InputSignal

TransductionUnit

OutputSignal

PowerSupply

MEMS as a Microsensor:

Micro pressure sensors

MicroActuatingElement

OutputAction

TransductionUnit

PowerSupply

MEMS as a Microactuator- motor:

Micro motor produced by a LIGA Process

Stators

RotorTorque

TransmissionGear

Components of Microsystems

Sensor

Signal Transduction &

ProcessingUnit

Actuator

PowerSupply

Microsystem

Typical Microsystems Products

Inertia Sensor for “Air Bag” Deployment System(Courtesy of Analog Devices, Inc.)

Inertia Sensor for Automobile “Air Bag” Deployment System

Micro inertia sensor (accelerometer) in place:

(Courtesy of Analog Devices, Inc)

Sensor-on-a-chip:(the size of a

rice grain)

Collision

Unique Features of MEMS and Microsystems - A great challenge to engineers

• Components are in micrometers with complex geometryusing silicon, si-compounds and polymers:

25 µm

25 µm

A micro gear-train bySandia National Laboratories

Capillary Electrophoresis (CE) Network Systems for Biomedic Analysis

A simple capillary tubular network with cross-sectional area of 20x30 µm is illustrated below:

AnalyteReservoir,A

Analyte WasteReservoir,A’

BufferReservoir,B

WasteReservoir,B’

Injection Channel

Sepa

ratio

n C

hann

el

Silicon Substrate

“Plug”

Work on the principle of driving capillary fluid flow by applying electric voltages at the terminals at the reservoirs.

Commercial MEMS and Microsystems Products

Micro Sensors:

Acoustic wave sensorsBiomedical and biosensorsChemical sensorsOptical sensorsPressure sensorsStress sensorsThermal sensors

Micro Actuators:

Grippers, tweezers and tongsMotors - linear and rotaryRelays and switchesValves and pumpsOptical equipment (switches, lenses & mirrors, shutters, phase modulators, filters, waveguide splitters, latching & fiber alignment mechanisms)

Microsystems = sensors + actuators + signal transduction:

• Microfluidics, e.g. Capillary Electrophoresis (CE)• Microaccelerometers (inertia sensors)

INPUT:Desired

Measurements or

functions

Sensing and/oractuatingelement

Transductionunit Signal

Conditioner& Processor

Controller Actuator

SignalProcessor

MeasurementsComparator

OUTPUT:Measurements

or Actions

MEMS

Package on a single “Chip”

Intelligent Microsystems - Micromechatronics systems

Evolution of Microfabrication

● There is no machine tool with today’s technology can produce any device or MEMS component of the size in the micrometer scale (or in mm sizes).

● The complex geometry of these minute MEMS components can only be produced by various physical-chemical processes – the microfabrication techniques originallydeveloped for producing integrated circuit (IC) components.

Significant technological development towards miniaturization was initiated with the invention of transistors by three Nobel Laureates, W.Schockley, J. Bardeen and W.H. Brattain of Bell Laboratories in 1947.

This crucial invention led to the development of the concept of integrated circuits (IC) in 1955, and the production of the first IC three years later by Jack Kilby of Texas Instruments.

ICs have made possible for miniaturization of many devices and engineering systems in the last 50 years.

The invention of transistors is thus regarded as the beginning of the 3rd Industrial Revolution in human civilization.

Comparison of Microelectronics and MicrosystemsMicroelectronics Microsystems (silicon based)

Primarily 2-dimensional structures Complex 3-dimensional structureStationary structures May involve moving componentsTransmit electricity for specific electrical functions Perform a great variety of specific biological, chemical,

electromechanical and optical functionsIC die is protected from contacting media Delicate components are interfaced with working mediaUse single crystal silicon dies, silicon compounds,ceramics and plastic materials

Use single crystal silicon dies and few other materials,e.g. GaAs, quartz, polymers, ceramics and metals

Fewer components to be assembled Many more components to be assembledMature IC design methodologies Lack of engineering design methodology and standardsComplex patterns with high density of electricalcircuitry over substrates

Simpler patterns over substrates with simpler electricalcircuitry

Large number of electrical feed-through and leads Fewer electrical feed-through and leadsIndustrial standards available No industrial standard to follow in design, material

selections, fabrication processes and packagingMass production Batch production, or on customer-need basisFabrication techniques are proven and welldocumented

Many microfabrication techniques are used forproduction, but with no standard procedures

Manufacturing techniques are proven and welldocumented

Distinct manufacturing techniques

Packaging technology is relatively well established Packaging technology is at the infant stagePrimarily involves electrical and chemicalengineering

Involves all disciplines of science and engineering

Natural Science:Physics & Biochemistry

Mechanical Engineering• Machine components design• Precision machine design• Mechanisms & linkages• Thermomechanicas:

(solid & fluid mechanics, heattransfer, fracture mechanics)

• Intelligent control• Micro process equipment

design and manufacturing• Packaging and assembly design

Quantum physicsSolid-state physicsScaling laws

Electrical Engineering• Power supply• Electric systems for

electrohydro-dynamics and signal transduction

• Electric circuit design

•Integration of MEMSand CMOS

Materials Engineering• Materials for substrates

& package• Materials for signal

mapping and transduction• Materials for fabrication

processes

Chemical Engineering• Micro fabrication

processes• Thin film technology

Industrial Engineering• Process design• Production control• Micro assembly

ElectrochemicalProcesses

MaterialScience

The Multi-disciplinary Nature of Microsystems Engineering

Commercialization of MEMS and Microsystems

Major commercial success:

Pressure sensors and inertia sensors (accelerometers) with worldwide market of:

• Airbag inertia sensors at 2 billion units per year.• Manifold absolute pressure sensors at 40 million units per year.• Disposable blood pressure sensors at 20 million units per year.

Recent Market DynamicsOld MEMS New MEMS

Pressure sensorsAccelerometersOther MEMS

BioMEMSIT MEMS for Telecommunication:(OptoMEMS and RF MEMS)

Application of MEMS and Microsystemsin

Automotive Industry

52 million vehicles produced worldwide in 1996There will be 65 million vehicle produced in 2005

Principal areas of application of MEMS and microsystems:

• Safety• Engine and power train

• Comfort and convenience• Vehicle diagnostics and health monitoring

• Telematics, e.g. GPS, etc.

(1)(7)

(10)(2)

(3)(4)

(5)

(6)

(8)(9)

(2) Exhaust gas differential pressure sensor

(1) Manifold or Temperature manifold absolute pressure sensor

(3) Fuel rail pressure sensor(4) Barometric absolute pressure sensor(5) Combustion sensor

(7) Fuel tank evaporative fuel pressure sensor

(6) Gasoline direct injection pressure sensor

(8) Engine oil sensor

(9) Transmission sensor

(10) Tire pressure sensor

Principal Sensors

Silicon Capacitive Manifold Absolute Pressure Sensor

Application of MEMS and Microsystemsin

Aerospace Industry

• Cockpit instrumentation. • Sensors and actuators for safety - e.g. seat ejection• Wind tunnel instrumentation • Sensors for fuel efficiency and safety• Microsattellites• Command and control systems with MEMtronics• Inertial guidance systems with microgyroscopes, accelerometers and fiber optic gyroscope.• Attitude determination and control systems with micro sun and Earth sensors.• Power systems with MEMtronic switches for active solar cell array reconfiguration, and

electric generators• Propulsion systems with micro pressure sensors, chemical sensors for leak detection, arrays

of single-shot thrustors, continuous microthrusters and pulsed microthrousters• Thermal control systems with micro heat pipes, radiators and thermal switches• Communications and radar systems with very high bandwidth, low-resistance radio-frequency

switches, micromirrors and optics for laser communications, and micro variable capacitors, inductors and oscillators.

Application of MEMS and Microsystemsin

Biomedical Industry

Disposable blood pressure transducers:Lifetime 24 to 72 hours; annual production 20 million units/year, unit price $10

Catheter tip pressure sensors

Sphygmomanometers

Respirators

Lung capacity meters

Barometric correction instrumentation

Medical process monitoring

Kidney dialysis equipment

Micro bio-analytic systems: bio-chips, capillary electrophoresis, etc.

Application of MEMS and Microsystemsin

Consumer Products

Scuba diving watches and computers

Bicycle computers

Sensors for fitness gears

Washers with water level controls

Sport shoes with automatic cushioning control

Digital tire pressure gages

Vacuum cleaning with automatic adjustment of brush beaters

Smart toys

Application of MEMS and Microsystemsin the

Telecommunication Industry

• Optical switching and fiber optic couplings

• RF relays and switches

• Tunable resonatorsMicrolenses: Microswitches:

Projected Market for OptoMEMS

Unit: $million

Micro Optical Switches

2-Dimensional

3-Dimensional

Concluding Remarks

1. Miniaturization of machines and devices is an inevitable trend in technological development in the new century.

2. There is a clear trend that microsystems technology will be further scaled down to the nano level. (1 nm = 10-3 µm = 10 shoulder-to-shoulder H2 atoms).

3. Despite the fact that many microelectronics technologies can be used to fabricate silicon-based MEMS components, microsystems engineering requires the application of principles involving multi-disciplines in science and engineering.

4. Team effort involving multi-discipline of science and engineering is the key to success for any MEMS industry.

End of Chapter 1