Lectures on
MEMS and MICROSYSTEMS DESIGN AND MANUFACTURE Tai-Ran Hsu, ASME Fellow, Professor Microsystems Design and Packaging Laboratory Department of Mechanical and Aerospace Engineering San Jose State University San Jose, California, USA E-mail:
[email protected]
Textbook: “MEMS and Microsys Microsystems tems:: design design , manufa manufacture cture,, and and nanoscale nanoscale engineerin engineering,” g,” 2nd Edition, by Tai-Ran Hsu, John Wiley & Sons, Inc., Hoboken, New Jersey, 2008 (ISBN 978-0-470-08301-7)
CONTENT Ch ap t er 1
Ov er v i ew o f MEMS an d Mi c r o s y s t em s
Ch ap t er 2
Wo r k i n g Pr i n c i p l es o f Mi c r o s y s t em s
Ch ap t er 3
En g i n eer i n g Sc Sc i en c e f o r Mi Mi c r o s y s t em s De Des i g n an an d Fa Fab r i c at i o n s
Ch ap t er 4
En g i n eer i n g Mec h an i c s f o r Mi c r o s y s t em s Des i g n
Ch ap t er 5
Th er m o f l u i d En g i n eer i n g an d Mi c r o s y s t em s Des i g n
Ch ap t er 6
Sc al i n g L aw s i n Mi n i at u r i zat i o n
Ch ap t er 7
Mat er i al s f o r MEMS an d Mi c r o s y s t em s
CONTENT –Cont’d Chapter 8
Microsystems Fabrication Processes
Chapter 9
Overview of Micromanufacturing
Chapter 10
Microsystems Design
Chapter 11 11
Assembly, Pa Packaging, an and Te Testing of of Mi Microsystems
Chapter 12
Introduction to Nanoscale Engineering
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:
Sensor-on-a-chip: (the size of a rice grain)
(Courtesy of Analog Devices, Inc)
Micro Cars (Courtesy of Denso Research Laboratories, Denso Corporation, Aichi, Japan)
Rice grains
MEMS = a pioneer technology for Miniaturization – A leading technology for the 21 st Century, and an inevitable trend in industrial products and systems development
Miniaturization of Digital Computers - A remarkable case of miniaturization!
Size: 106 down Power: 106 up
The ENIAC Computer in 1946
A “Lap-top” Computer in 1996
Size: 108 down Power: 108 up
A “Palm-top” Computer in 2001
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,”
“Low-cost”
and
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:
Size reduction
Palm-top Wireless PC
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)
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 to low 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 Microsystems Technology
A top-down approach
(MST) (1 m - 1 mm)*
Initiated in 1947 with the invention of transistors, but the term “ Micromachining” was coined in 1982
Miniature devices (1 nm - 1 mm) A bottom-up approach
Nanotechnology (NT) (0.1 nm – 0. 1 m)**
* 1 m = 10-6 m ** 1 nm = 10-9 m
one-tenth of human hair span of 10 H 2 atoms
Inspired by Richard Feynman in 1959, with active R&D began in around 1995 There is a long way to building nano devices!
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
The Lucrative Revenue Prospects for Miniaturized Industrial Products – Cont’d 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/c of this enormous potential.
MEMS Products
MEMS as a Microsensor: Power Supply
Input Signal
Micro Sensing Element
Transduction Unit
Micro pressure sensors
Output Signal
MEMS as a Microactuator- motor:
Output Action
Micro Actuating Element
Rotor Stators
Torque Transmission Gear
Power Supply
Transduction Unit
Micro motor produced by a LIGA Process
Components of Microsystems Power Supply
Signal Transduction & Processing Unit Sensor
Actuator
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:
Sensor-on-a-chip: (the size of a rice grain) Collision
(Courtesy of Analog Devices, Inc)
Unique Features of MEMS and Microsystems - A great challenge to engineers
•
Components are in micrometers with complex geometry using silicon, si-compounds and polymers:
25 µm
A micro gear-train by Sandia National Laboratories 25 m
Capillary Electrophoresis (CE) Network Systems for Biomedic Analysis A simple capillary tubular network with cross-sectional area of 20x30 µm is illustrated below: Buffer Reservoir,B Analyte Reservoir,A Injection Channel l e n n a h C n o i t a r a p e S
Analyte Waste Reservoir,A’
“Plug”
Waste Reservoir,B’
Silicon Substrate
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 sensors Biomedical and biosensors Chemical sensors Optical sensors Pressure sensors Stress sensors Thermal sensors
Micro Actuators: Grippers, tweezers and tongs Motors - linear and rotary Relays and switches Valves and pumps Optical 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)
Intelligent Microsystems - Micromechatronics systems Package on a single “ Chip”
INPUT: Desired Measurements or functions
Sensing and/or actuating element
Transduction unit
MEMS
Signal Conditioner & Processor
OUTPUT:
Controller
Actuator
Signal Processor Comparator
Measurements
Measurements or Actions
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 originally developed 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 Microsystems Microelectronics Primarily 2-dimensional structures Stationary structures Transmit electricity for specific electrical functions IC die is protected from contacting media Use single crystal silicon dies, silicon compounds, ceramics and plastic materials Fewer components to be assembled Mature IC design methodologies Complex patterns with high density of electrical circuitry over substrates Large number of electrical feed-through and leads Industrial standards available Mass production Fabrication techniques are proven and well documented Manufacturing techniques are proven and well documented Packaging technology is relatively well established Primarily involves electrical and chemical engineering
Microsystems (silicon based) Complex 3-dimensional structure May involve moving components Perform a great variety of specific biological, chemical, electromechanical and optical functions Delicate components are interfaced with working media Use single crystal silicon dies and few other materials, e.g. GaAs, quartz, polymers, ceramics and metals Many more components to be assembled Lack of engineering design methodology and standards Simpler patterns over substrates with simpler electrical circuitry Fewer electrical feed-through and leads No industrial standard to follow in design, material selections, fabrication processes and packaging Batch production, or on customer-need basis Many microfabrication techniques are used for production, but with no standard procedures Distinct manufacturing techniques Packaging technology is at the infant stage Involves all disciplines of science and engineering
The Multi-disciplinary Nature of Microsystems Engineering Natural Science: Physics & Biochemistry Quantum physics Solid-state physics Scaling laws
Electrochemical Processes
Electrical Engineering • Power supply Electric systems for electrohydrodynamics and signal transduction Electric circuit design •Integration of MEMS and CMOS
Material Science
Mechanical Engineering • Machine components design Precision machine design Mechanisms & linkages Thermomechanicas: (solid & fluid mechanics, heat transfer, fracture mechanics) Intelligent control Micro process equipment design and manufacturing • Packaging and assembly design
Chemical Engineering • Micro fabrication processes Thin film technology
Materials Engineering • Materials for substrates & package Materials for signal mapping and transduction Materials for fabrication processes
Industrial Engineering • Process design Production control Micro assembly
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 Dynamics Old MEMS Pressure sensors Accelerometers Other MEMS
New MEMS BioMEMS IT MEMS for Telecommunication: (OptoMEMS and RF MEMS)
Application of MEMS and Microsystems in Automotive Industry 52 million vehicles produced worldwide in 1996 There 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. •
•
•
•
•
Principal Sensors (7) (1) (6)
(4) (3)
(2) (10) (9)
(5)
(8)
(1) Manifold or Temperature manifold absolute pressure sensor (2) Exhaust gas differential pressure sensor (3) Fuel rail pressure sensor (4) Barometric absolute pressure sensor (5) Combustion sensor
(6) Gasoline direct injection pressure sensor (7) Fuel tank evaporative fuel pressure sensor (8) Engine oil sensor (9) Transmission sensor (10) Tire pressure sensor
Silicon Capacitive Manifold Absolute Pressure Sensor
Application of MEMS and Microsystems in 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 mic ro 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 Microsystems in Biomedical Industry Disposable blood pressure transducers:
Lifetime 24 to 72 hours; annual production 20 million units/year, unit price $10 Catheter tip pr essure 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 Microsystems in 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 Microsystems in the Telecommunication Industry Optical switching and fiber optic couplings RF relays and switches Tunable resonators Microlenses:
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 multidisciplines in science and engineering. 4. Team effort involving multi-discipline of science and engineering is the key to success for any MEMS industry.
