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Lecture 1 Introductions of NanoMicro ElectroMechanical System


MEMS/NEMS is a batch-fabricated integrated nano- and microscale system ... low melting point, is easy to fabricate, noncorrosive, may cause spikes in Si ... – PowerPoint PPT presentation

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Title: Lecture 1 Introductions of NanoMicro ElectroMechanical System

Lecture 1Introductions of Nano/Micro
Electro-Mechanical System
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Feynmans Vision
  • There is plenty of room at the bottom (1959)
  • To print Encyclopedia Britannica on a pin head of
    diameter of 1.6 mm? shrink 25,000 times in linear
    scale, i.e., a dot will be 8 nm in size
  • If we can store 24 million books (1015 bits) in a
    1/200 inch crystal, each dot is stored with 5x5x5
  • DNA molecules use approximately 50 atoms to store
    one bit of information
  • Manipulating and controlling things on a small
    (atomic?) scale

(No Transcript)
William McLellans Micro Electric Motor
The motor is 3.81 mm wide. The huge object above
it is the head of a pin.
What are MEMS/NEMS?
  • MEMS/NEMS is a batch-fabricated integrated nano-
    and microscale system performing sensing,
    computing and actuating functions
  • MEMS/NEMS is a way of making things -
    fabrication technology
  • MEMS/NEMS is a methodology operation, design
    and analysis of nano- and microsystems

What are MEMS?
  • MEMS are systems that integrate
  • sensing, actuation, computation, control,
    communication and power subsystems
  • Functional block-diagram of MEMS

Benefits from Micro-systems
  • Miniaturization save materials, save power,
    faster time response, better performance
  • Integration integrated with IC and other
    systems, reduce system size and cost save
    adapters and interconnections.
  • Batch fabrication cheap, disposable (most
    important driving force)

How are NEMS/MEMS made?
  • NEMS/MEMS are not just assembly of very small
    components. System integration is achieved
    through the monolithic process similar to IC
    fabrication (in design and manufacture)
  • NEMS/MEMS fabrication shares a lot of tools and
    process techniques developed for IC industry,
    such as photolithography, etching, etc.
  • There are some novel techniques specifically
    developed for NEMS/MEMS micro-fabrication
    purpose, such as LIGA, Micro-molding, etc.

CMOS based processing techniques
  • Photolithography
  • Oxidation
  • Diffusion
  • Ion Implantation
  • Thin film Deposition
  • Etching
  • Metallization

IC process technology
Novel micromachining techniques
  • Bulk Micro-machining
  • Surface Micro-machining
  • LIGA (Lithographic, Galvanoformung,
    Abformtechnik) process
  • Novel processing techniques
  • Self-assembly techniques

Surface and Bulk Micromachining
LIGA Examples
  • 200mm deep structures
  • Coat with thick resist
  • Pattern with X-rays
  • Electroplate exposed area with Ni
  • Machine to /- 5mm
  • Use titanium and Cu as sacrificial layers

Focused Ion Beam Milling
  • Apply ion beam directly onto substrate through a
  • No resist layer
  • Anisotropic
  • Be able to make thick microstructure (about 100mm)

Laser-assisted Chemical Deposition
  • Chemical deposition from vapor phase by
  • Laser Nd-YAG (neodymium yttrium aluminum garnet)
    or Ar
  • Substrates
  • - silicon
  • - carbon
  • - boron
  • - oxides
  • - nitrides
  • - carbides
  • - borides
  • - metals

SAM (Self-Assembled Monolayers)
The two different thiols are injected into glass
filters. They diffuse slowly and attach to the
gold substrate.
alkanethiolate SAM preparation on gold substrates
in the (111) preferred direction
What are NEMS/MEMS made of?
  • Si, SiO2 and Si3N4 are most popular materials
    used in NEMS/MEMS.
  • - IC process compatible (mature process
  • Si is brittle, strong, good thermal, hydrophilic,
    stable to chemicals, bio-friendly, and can be
    very pure with best known impurity control
  • SiO2 is a good insulator, very stable solid form
    (not easily dissolved or etched), not permeable
    to most molecules except alkali ions (in
    particular sodium and potassium), hydrophobic,
    residual charge have known way to control
  • Si3N4 is also a good insulator, very rigid, very
    stable and not permeable to most molecules,
    serious residual charging

Popular Metals in MEMS
  • Al has low melting point, is easy to fabricate,
    noncorrosive, may cause spikes in Si (but good
    bonding), usually doped with 2 Si for better
  • Au, Ti, W and silicides are also popular
  • For better conductivity Ag, Cu, Au and Al (in
  • For better resistance to electromigration use
    doping or metals with higher atomic weight.
  • Metal bi-layers to solve adhesion (Cr, Ti, Ni,
  • Transparent contact ITO (indium-tin-oxide), but
    notice its high resistivity

Comparison of Si MEMS properties
  • Transducer a device that converts one form of
    energy to another
  • Energy forms as input and output
  • thermal temperature, heat, heat flow,...
  • mechanical position, velocity, acceleration,
  • pressure, ...
  • chemical concentration, composition, reaction
  • optical intensity, wavelength, phase,
  • magnetic field intensity, flux,
    magnetization, etc.
  • electrical voltage, current, charge,

Sensor and Actuator
  • Sensor and actuator are kinds of transducers
  • Sensors
  • magnify/demagnify an environmental perturbation
    (signal/noise) and transform into an observable
    energy form
  • Actuators
  • use small controlled energy to cause an
    observable (or controllable) perturbation
    (movement/energy radiation) to the environment

Transducing Materials Piezoresistivity
  • Piezoresistivity pressure (or stress) to change
    in resistivity
  • Si is the most popular piezoresistive material.
  • Crystalline Si larger sensitivity, poly or
    amorphous less temperature perturbation
  • Piezoresistivity is usually a strong function of
    the carrier type and the crystal orientation

Transducing Materials Piezoelectricity
  • Piezoelectricity pressure (or stress) to charge
    or fields
  • Piezoelectricity only exists in materials with
    ionic bonds and non-cubic lattice structures
    (based on charge polarization asymmetry)
  • Popular piezoelectric materials PZT (lead
    zirconate titanate, a ceramic), ZnO, BaTiO3, PVDF
    (polyvinylidenefluoride), Quartz, GaN and SiC.

Materials with large piezoelctricity usually have
very large permittivity too (the degree of
Perovskite Structure
  • Perovskite is a cubic unit cell with Ti at the
    corners, O at the midpoints of the edges, and Ca
    in the center
  • Stress induces uneven displacement of anions and
    cations (electric dipole)

Transducing Materials Thermoelectricity
  • Thermoelectricity conversion between heat
    (temperature) and electricity
  • Two thermoelectric effect Seebeck effect and
    Peltier effect
  • Applications thermal sensors, refrigerators and
  • Popular thermoelectric materials SiGe, Bi2Te3,
    PbTe, Alumel, Cromel, Nicrosil,

Seebeck effect
Peltier effect
Design of NEMS/MEMS
  • Micro- and Nano-scale operation principles
  • - Microscale Classical Mechanics and
  • - Nanoscale Quantum effects, Nanoelectromechanic
  • Feasible fabrication process flow
  • - Manufacturable
  • - Cost effective
  • Analysis and modeling of devices and systems
  • - Gather learning (many micro- and nanoscale
  • are against intuitions)
  • - Saving development time and cost

Micro- and Nano-scale operation principles
  • Micro- and Nano-scale physics may behave
    differently in macro-scale world, e.g. Sticking
    effect, surface tension, quantum tunneling effect
  • Surface effects are playing more important roles
    in the operational physics of micro- and
    nano-structures and devices
  • - What is the ratio of surface atoms/all atoms
    for a cube of size 1 cm3, 1 mm3 and 1 nm3 ?
  • - Assume atomic size 0.25nm,
  • 1 nm3 (64-8)/640.875
  • 1 mm3 (6x40002)/(4000)30.0015
  • 1 cm3 (6x(4x107)2)/(4x107)31.5x10-7

Scaling analysis
  • Most physical quantities (force, mass, volume,
    etc.) scale differently with dimension L
  • Example weight-lifting of human being. Assume
    the muscle stress is the same for different human
    body size,
  • Body weight L3
  • Weight-lifted
  • (muscle stress) x (area)
  • constant x L2
  • (Body weight)2/3

World weight-lifting record Vs. Body weight
Log weight-lifted
Log body weight
Challenges and Opportunities
  • Proportional scaling only applied to objects in
    limited size range
  • New phenomena and operation principles are
    associated with nano-scale structures and systems
  • More fundamental research activities, engineering
    practices and leading-edge fabrication
    technologies are required for the deployment of

Design strategy
  • System integration systematically analyzes the
    system and its components for every detail to
    make best resource management and scheduling on
    manufacturing, design, functions, cost,
    marketability, and reliability
  • Design integration build model hierarchy through
    reduction and abstraction for reasonable design
    space in each layer and division (divide,
    conquer...., and integrate)

Design process
Standard MEMS design process
Standard IC design process
Examples of MEMS Applications
  • Mechanical transducers
  • Strain gages, Accelerometers, Gyroscopes,
    Pressure sensors, Microphones, Electrostatic
    motor, Shape Memory Alloy, Piezoelectric,
    Mechanical resonators, Mechanical Relays and RF
  • Optical transducers
  • Photo conductive sensors, Junction-based photo
    detectors, Capacitive photo sensors, Thermal
    Optical detector, Light Emitters, Reflective and
    Transmissive Micromechanical light Modulators,
    Fiber optic couplers, Reflective components
    (mirror), Transmissive components (Wave guide,
    lenses), Filters, Integrated Optical systems
  • Magnetic transducers
  • Hall effect sensor, Flux gate, Tunneling,
    Motors, Eddy current detector, Magnetic
    read/write head, Micro-Inductors

Examples of MEMS Applications
  • Thermal transducers
  • Thermal Resistive, Thermal Couple, Junction
    based Thermal sensors, Thermal Gas pressure
    sensor, Flow sensor, Humidity sensor and Peltier
    effect heat pumps
  • Chemical and Biological transducers
  • Passive Chemical Sensors, Electrochemical
    Transducers, Biosensors, Biological Chemical
    Sensors (taste Odor), Thin Film Batteries,
    Penetrating Neural Probes
  • Fluid devices
  • Flow Channel, Mixer, Pumps, Valve, Separator,
    Droplet generators, Filters, Interconnects, Flow
    sensors, Viscosity/Density Sensors, Ink-Jet
    printer heads

Sandias micro mechanical lock
Micro-Motor and Micro-Mirror
Electrostatic Micro Motor fabricated from Si
(Texas Instruments)
Micro Mirror (Lucent Technologies)
Piezoresistive Pressure Sensor
Thickness of diaphragm lt 1 mil. (25 mm)
Die size 105 mil. x 105 mil. (2.67 mm x 2.67 mm)
Magnetic Transducer
Magnetic Read/Write head
Thermoelectric Modules
Laser cooling modules
Fiber optics cooling modules
Telcom cooling module
Infrared sensor
Power generator
Multi-stage module
Bio-chemical transducer
Penetrating Neural Probe
Biological chip (lab-on-a-chip)
Smart Pill (drug delivery system)
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