eecs179fall2015_lecture01

Mark Bachman, EECS179 Fall Quarter, UCI

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Engineering the Microworld

UCI EECS179: Lecture 01 Professor Mark Bachman


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Small Dreams: Visions of miniaturization


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Small Dreams: Visions of miniaturization


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How small is small? From macro to nano

Macro (meters)

Bridges Airplanes Cars Human beings Birds

Snails Rice Ants Watch gears Sand

Meso (millimeters)

Micro (micrometers)

Nano (nanometers)

Hair Dust Pollen Cells Bacteria

Viruses Nuclei Transistors Cell apparatus Proteins


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Scaling laws of small

Laws of physics make the small world look different.

Volume V ~ L3

Mass M ~ L3

Surface SA ~ L2

Strength S ~ L2

Force F ~ L2

Acceleration A ~ 1/L

Frequency f ~ 1/L

Power P ~ L2

Power density P ~ 1/L

Voltage V ~ constant

E Field E ~ 1/L

Resistance R ~ 1/L

Capacitance C ~ L

Current I ~ L

Magnetic wire B ~ constant

Heat capacity Cv ~ L3

Heat flow dT/dt ~ 1/L2

Turbulence Re ~ L

* Assumes constant mass density * Assumes constant voltage


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Typical small values

How the world looks to a micro sized device

Quantity Size = 100 m Size = 10 m

Typical volume 1 nanoliter 1 picoliter

Typical mass 1 microgram 1 nanogram

Typical force 10-100 nN (1-10 ug) 0.1-1 nN (10-100 ng)

Typical E field (at 1 V) 10,000 V/m 100,000 V/m

Typical frequency 10-100 kHz 0.1-1 MHz

Typical time constant 10-100 sec 1-10 sec


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Some small scale phenomena: Surface tension

Surface tension force for 100 m opening = 5.7 N Typical force for 100 m device is 10 nN

Surface tension over 500x greater!

Surface tension P = /d

Practical significance: Surface tension rules at the microscale. Deal with it!


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Some small scale phenomena: Laminar flow

Reynolds Number (Re)scales as length. Typical Reynolds Number for 100 m device is Re ~ 0.1

Onset of turbulence is at Re ~ 2000

Characteristic flows in micro channels are smooth and viscous with no mixing.

Blood flow Three channel flow

Three channel flow

Multi-stream channel flow


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Some small scale phenomena: Rapid heat transfer

Surface area to volume is large at small scales. Heat capacity depends on mass.

Heat transfer is very fast at small scales.

Temperature of small filament in 75 W light bulb is ~2500 C. Ramp up time is ~20 ms. Ramp down time is ~60 ms.

Heat flows through small devices quickly. Hard to maintain temperature gradient.


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Some small scale phenomena: Surface area/volume

Surface area to volume is large at small scales. Mass flow saturates quickly in small volumes.

Equilibrium can be reached very quickly.

Mass flows through small devices quickly. Hard to maintain concentration gradient.

Micro-scale systems must utilize physical barriers (cell walls) to maintain concentration gradients. Surface contamination is a serious issue at small scales.


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Some small scale phenomena: Loss of continuity

At sizes below ~50 m, granularity of nature becomes relevant. Many bulk-scale physical laws no longer accurate.

Typical grain size is ~10 m. Affects physical, thermal and electrical properties.

Mean free path of N2 at atmosphere is 60 nm. Affects dynamics in air. Example: Paschen effect.

Metals and materials are not continuous materials. They have microscopic grain structure.

Stainless steel NF709


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Some small scale phenomena: Atomic granularity

At sizes below ~100 nm, bulk properties are meaningless. Atomic level understanding required.

Hypothetical molecular motors (science fiction) From: Institute for Molecular Manufacturing

Real molecular motors inside living cells


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Some small scale phenomena: Noise

At sizes below ~50 m, thermal induced fluctuations are noticeable. Heat is not a continuous fluid.

Heat is not fluid. Vibrations and Brownian motion add statistical fluctuation and noise.

Thermal fluctuations depend on size and temperature.

Microscopic flow of milk particles showing Brownian motion (random vibrations).

2% Milk under magnification


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Some small scale phenomena: Residual forces

Residual forces, such as local electrostatic charging, hydrogen bonding, dipole interactions, and Van der waals forces play an

important role.

Micro-machined gecko hairs (0.2 m x 2 m) made of plastic make dry tape and sticky fabric.

Small scales allow very close interaction (e.g., Van der waals) and large surface interface.

Dry state is favorable for electrostatic charging

Wet/humid state mediates hydrogen bonding

Hydrogen bonding


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Some small scale phenomena: Fast time scales

Typical time constant is 10-100 sec (10 sec = 10 mm of bullet fired from high speed gun)

Shotgun blast using 1 sec strobes

Hummingbird heart beat: 50 msec Honeybee wing beat: 4 msec Vibrating drop of water (100m): 120 sec


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Small is fast: Visions of life in the fast lane


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How small is small enough?

Miniature guitar micromachined in silicon at Cornell University, 1997. Fun demo.

From engineering perspective, need to solve a real problem.

After a point, integration more important than miniaturization.

Academic research: Hubris and professional standing push for smaller.

Technology for technology sake?

Engineering small: How small is small enough?


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Engineering small: How small is small enough?

Different perspectives, different communities

Sub-miniature (~ 1 mm) Conventional precision engineering, primarily metals, glass

Micro-electrical mechanical systems (MEMS) (~10-100 m) Sensors and useful devices, primarily in silicon

Nano-electrical mechanical systems (NEMS) (~100 nm -1 m) Electronic devices, concept devices, primarily in silicon

Nanotechnology (


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Engineered systems

How is a system engineered today?

Materials Basic building stuff, often with special properties. Processed in batch.

Components

Simple parts designed to be put together

Devices Assembly of components that can perform a simple function

Sub-systems (modules) Assembly of devices designed to perform a complex function

Systems Assembly of sub-systems designed to perform desired application


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Engineered systems

Example system: automobile

Final system: automobile

Sub-systems

Device (brake)

Component

Material


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Engineered systems

Example system: human body

System: Human body

Device (Ribosomes) Material

(amino acids)

Sub-systems (organs, cells)

Component (proteins)


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Engineered systems with nanotech

Engineered systems can take us wonderful places

Enabled by very small technology

Nanotechnology

Application


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The promise of nanotechnology: integration

Macro world

Nano world Microsystems

Nano is an enabling technology; integration is the key!

Integrated Nanosystems


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Micro-manufacturing: Shrinking visions


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Micro-manufacturing: Shrinking machines?


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How to manufacture in the microworld?

No such thing as a shrinking machine Must learn how to Build Em Small

Micromachining the hard way


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Conventional manufacturing

Assembly 1. Materials are processed, formed into components 2. Components are assembled together to build more complex modules 3. Materials are standardized 4. Interfaces are standardized 5. Manufacturing methods are standardized 6. Design method is mature 7. Test methods are mature

Primary method of manufacturing for engineered systems.


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Conventional manufacturing

Batch fabrication 1. Materials are processed in batch 2. New materials are layered and patterned over other materials 3. Final devices are packaged and assembled on host system

Primary method of manufacturing for semiconductor systems.


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How to manufacture microsystems?

Assembly (top down) 1. High precision actuators move atoms from place to place 2. Micro tips emboss or imprint materials 3. Electron (or ion) beams are directly moved over a surface

Nano-scale assembly has been demonstrated using atomic force microscopes. Slow and not suitable for large scale production.


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Growth (bottom up) 1. Chemical reactors create conditions for special growth 2. Biological agents sometimes used to help process 3. Materials are harvested for integration

Nano-scale structures are readily formed using bottom up approaches. Mostly materials. Hard to directly integrate or build devices.



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Growth and patterning (top down and bottom up) 1. Chemical reactors used to grow nanomaterials 2. Lithographic techniques used to selectively remove some materials 3. Process is repeated multiple times

Nano-scale structures and micro-scale structures are readily formed using top down and bottom up approaches. Best chance for integration.



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Biological manufacturing of microsystems

Batch growth Small creatures often farm their materials. Many biostructures are made by successively layering of materials and letting them harden.


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Mechanical assembly Insects and other small creatures regularly assemble microsystems


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Molecular assembly Complex molecules (natures engines) are manufactured using molecular assembly. RNA acts as coding template to attach specific amino acids to form a peptide chain.


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Conventional micro-manufacturing today

Semiconductor processing


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Originally developed by NASA and the aerospace industry for satellite manufacturing. Clean rooms now in use for all MEMS and semiconductor manufacturing.

Clean rooms for micro and nano fabrication

Clean room for mercury program, 1960s Semiconductor clean room facility, today

Semiconductor clean room processing facilities

noneSticky NoteNASA Clean room


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Particle free walls, furniture, and accessories must be used. Airflow through 0.3 microns (or better) filters. Positive pressure inside clean room ensures removal of particles.

Clean environments available in full room, modular room, local units, and benches.


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Class 10,000

Printed circuit boards, Electronic packaging,

Medical devices


Clean room classifications and applications

Class 1,000

MEMS, Electronic packaging,

Hard disk drives

Class 100

MEMS, RF/Photonic ICs

Class 10

Integrated Circuits

Main function of clean rooms is control of particle contamination. Requires control of air flow, water and chemical filtrations, human protocol, and operational procedures.

noneSticky Note0.3 micrones is the smalles particle we calculate for finding class number


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Clean room classifications

Class 1000: fewer than 1,000 particles (>0.5 m) in 1 cubic foot of air

Class 100: Fewer than 100 particles (>0.5 m) in 1 cubic foot of air

noneSticky NoteFor information


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A world class facility devoted to interdisciplinary research in micro and nano-engineering. 8600 sq. ft. clean room space (class 10000, 1000, 100) with all major fabrication tools.

www.inrf.uci.edu

UCIINRF


Semiconductor clean room processing facilities


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Basic idea behind lithographic processing

Coat, protect, expose, etch, repeat

noneSticky NoteSilicon diacside =glass

noneSticky NoteColor =polymer =for protecting


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Basic idea behind lithographic processing

Result: Multiple patterned layers of different materials.


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Lithographic processing: Wafers

Start with wafer (a clean, flat surface)

Single crystal silicon boule Single crystal silicon wafers


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Grow a thin film of desired material

Wafers coated in furnace (artificially colored)

Lithographic processing: Film growth/deposition


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Spin coat a protective polymer resist layer

Polymer goes on wet, then is dried after spinning

Lithographic processing: Photoresist spinning


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Expose resist to UV light through a mask

Mask is aligned to wafer before exposure.

Lithographic processing: Masking and exposure


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Resist is removed from exposed areas

Remaining resist faithfully reproduces mask pattern.

Lithographic processing: Developing the pattern


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Resist protects selected regions during etch.

Pattern is transferred to substrate material.

Lithographic processing: Etch the material


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Strip resist and do process again and again.

Eventually, a 3-D structure is built up

Lithographic processing: Repeat process


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Etch away one of the sacrificial materials to release the part.

Voila! Thousands of micromachined devices.

Lithographic processing: Final release


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For the microdevice to be useful, it must be packaged

Packaged device can be inserted into system

Micro device integration: Packaging

80% of cost of MEMS is in the packaging!


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Pressure sensors, ink jet nozzles and accelerometers are biggest markets.

Commercial micro devices: sensors and actuators

Pressure sensors Gas sensors Accelerometers Gyros

Specialty structures Mirror arrays Micro array plates Microfluidics


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Future directions (industry)

From industrial perspective

Develop robust, standardized manufacturing Every MEMS device is a one-of-a-kind manufacturing operation.

Solve the packaging/interface problem 80% of the cost is in packaging. MEMS are so delicate!

Understand reliability, QC Need to understand reliability of MEMS better.

Evolve robust design tools Need comprehensive software, design libraries.

Killer applications! Need economic incentive to justify investment in MEMS development.


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Future directions (research)

From research perspective

Novel, integrated manufacturing Creative new ways to build things, more materials, more 3D.

Push smaller, discover new materials Exciting opportunities to develop new materials with unique properties.

High performance masterpieces Demonstrate the potential of miniaturization and nanotechnology.

Bio/Nano Bring biological sciences and engineering together. Molecular engineering?

Killer applications! Need public benefit to justify investment in research.


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Engineering the Microworld: 1959

1959 Jack Kilby (TI) invented the monolithic integrated circuit.

Design was improved by Robert Noyce (Fairchild Semiconductor) to produce planar technology.

First micro-engineered device: Integrated Circuit


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Engineering the Microworld: 1959

Theres plenty of room at the bottom Lecture given by Dr. Richard Feynman in 1959

What I want to talk about is the problem of manipulating and controlling things on a small scale.

It is a staggeringly small world that is below. In the year 2000, when they look back at this age, they will wonder why it was not until the year 1960 that anybody began seriously to move in this direction.

Why cannot we write the entire 24 volumes of the Encyclopedia Brittanica on the head of a pin?


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Engineering the Microworld: Today

Theres still plenty of room at the bottom!


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