Transcript Overview of manufacturing methods for small devices

Fundamentals of Microfabrication
Fall 2013
Prof. Marc Madou
MSTB 120
http://www.almaden.ibm.com:
80/vis/stm/gallery.html
NovaSensor (Now GE Sensing)
Accelerometer
Fundamentals of Microfabrication
Content
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Definitions of ICs
MEMS
Why miniaturization ?
Taxonomy of Microfabrication Processes
Accuracy/precision
Accuracy/precision and standard deviation
Relative vs. absolute tolerance in manufacturing
Merging of two approaches: Top-down and bottom-up machining
methodologies
Biomimetics
A few concluding words about manufacturing methods
From ICs to MEMS and NEMS
http://www.almaden.ibm.com:
80/vis/stm/gallery.html
NovaSensor (Now GE Sensing)
Accelerometer
From ICs to MEMS and NEMS
Today’s car differs from those of the immediate post-war years on
a number of counts. But suppose for a moment that the automobile
industry had developed at the same rate as computers and over the
same period: how much cheaper and more efficient would current
models be? Today you would be able to buy a Rolce-Royce for $
2.15, it would do three million miles to the gallon, and it would
deliver enough power to drive the Queen Elizabeth II. And if you
were interested in miniaturization, you could place half a dozen of
them on a pinhead.
Christopher Evans, 1979
Definitions of ICs
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The transistor was invented 1948
by three Bell Laboratory engineers
and physicists. John Bardeen was
the physicist, Walter Brattain the
experimentalist, and William
Shockley, who became involved
later in the development, was the
instigator and idea man. The team
won the 1956 Nobel Prize in
physics for their efforts. The
transistor demonstrated for the
first time that amplification in
solids was possible.
Definitions of ICs
Diodes
Definitions of ICs
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There are many different types
of transistors, but the basic
theory of their operation is all
the same. The three elements of
the two-junction transistor are
(1) the EMITTER, which gives
off, or emits," current carriers
(electrons or holes); (2) the
BASE, which controls the flow
of current carriers; and (3) the
COLLECTOR, which collects
the current carriers.
Definitions of ICs
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The arrow always points in the
direction of hole flow, or from
the P to N sections, no matter
whether the P section is the
emitter or base. On the other
hand, electron flow is always
toward or against the arrow,
just like in the junction diode.
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Definitions of ICs
A forward biased PN junction is comparable to a low-resistance
circuit element because it passes a high current for a given voltage.
In turn, a reverse-biased PN junction is comparable to a highresistance circuit element. By using the Ohm's law formula for
power (P = I2R) and assuming current is held constant, you can
conclude that the power developed across a high resistance is greater
than that developed across a low resistance. Thus, if a crystal were to
contain two PN junctions (one forward-biased and the other reversebiased), a low-power signal could be injected into the forward-biased
junction and produce a high-power signal at the reverse-biased
junction. In this manner, a power gain would be obtained across the
crystal. This concept is the basic theory behind how the transistor
amplifies.
Definitions of ICs
Definitions of ICs
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The term transistor is derived from the words TRANSfer and
resISTOR. This term was adopted because it best describes the
operation of the transistor - the transfer of an input signal current
from a low-resistance circuit to a high-resistance circuit.
Basically, the transistor is a solid-state device that amplifies by
controlling the flow of current carriers through its semiconductor
materials.
Definitions of ICs
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Types of transistors:
– Bipolar
Junction
Transistor (BJT)
– MOS transistor [see
Metal
Oxide
Semiconductor (MOS)
Capacitor]
Definitions of ICs
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A chip or an integrated circuit (IC) is a small electronic device
made out of a semiconductor material. The integrated circuit
consists of elements inseparably associated and formed on or
within a single SUBSTRATE (mounting surface). In other words,
the circuit components and all interconnections are formed as a
unit. The first integrated circuit was developed in the 1950s by
Jack Kilby of Texas Instruments and Robert Noyce of Fairchild
Semiconductor.
Definitions of ICs
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Integrated circuits used to be classified by the number of transistors
and other electronic components they contain:
–
–
–
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SSI (small-scale integration): Up to 100 electronic components per chip
MSI (medium-scale integration): From 100 to 3,000 electronic components per chip
LSI (large-scale integration): From 3,000 to 100,000 electronic components per chip
VLSI (very large-scale integration): From 100,000 to 1,000,000 electronic
components per chip
– ULSI (ultra large-scale integration): More than 1 million electronic components per
chip
-----------------------------------------------------------------------------------------------------------– WSI (Wafer-scale integration): Is a system of building very-large integrated circuits
that uses an entire silicon wafer to produce a single "super-chip".
– SoC or SOC( A system-on-a-chip): This is an integrated circuit in which all the
components needed for a computer or other system are included on a single chip.
– 3D-IC (A three-dimensional integrated circuit): this has two or more layers of
active electronic components that are integrated both vertically and horizontally into a
single circuit.
Definition of MEMS
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Micro electromechanical systems (MEMS), or micromachining (also micromanufacturing and microfabrication), in the narrow sense, comprises the use of
a set of manufacturing tools based on batch thin and thick film fabrication
techniques commonly used in the integrated circuit industry or IC industry. This
involved originally mainly Si based mechanical devices.
DARPA: Hybrid Insect Micro
Electromechanical Systems (HI-MEMS)
Definition of MEMS
MEMS: Micro electro mechanical systems. In recent years, it has become obvious that Si
is not always the right substrate, that batch is often not good enough and that a
modular approach is sometimes better than an integrated one. This has especially
become clear in the case of biomedical applications (see BIOMEMS course). The
‘science of miniaturization’ has become a much more appropriate name than MEMS
and it involves a good understanding of the intended application, scaling laws,
different manufacturing methods and materials .
Why miniaturization?
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Minimizing energy and materials use in manufacturing
Redundancy and arrays
Integration with electronics, simplifying systems (e.g., single point vs. multipoint
measurement)
Reduction of power budget
Faster devices
Increased selectivity and sensitivity
Wider dynamic range
Exploitation of new effects through the breakdown of continuum theory in the
microdomain
Why miniaturization?
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Cost/performance advantages
Improved reproducibility (batch
concept)
Improved
accuracy
and
reliability
Minimal invasive ( e.g.
mosquito project)
Do we have a choice? (see next
viewgraph- - the Law of
Accelerating Returns)
probiscus is about 75 µm 
Why miniaturization?
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Evolution (sophistication) of life-forms or technology speeds up because
they are build on their own recorded degree of order. Ray Kurzweil calls
this The Law of Accelerating Returns*
This Law of Accelerating Returns gave us ever greater order in technology
which led to computation -- the essence of order.
For life-forms DNA provides the record. In the case of technology it is the
ever improving methods to record information.
*Ray Kurzweil in The Age of Spiritual
Machines
Why miniaturization?
Why miniaturization?

Moore’s law (based on a temporary methodology i.e.,
lithography) is only an example of the Law of Accelerating
Returns. Beyond lithography we may expect further
progress in miniaturization based on DNA, quantum
devices, AFM lithography, nanotubes, etc.
Why miniaturization?

Moore’s ‘Law’: The amounts of information storable on a given amount of
silicon roughly doubled every year since the technology was invented. This
relation, first mentioned in 1964 by semiconductor engineer Gordon Moore
(who co-founded Intel four years later) held until the late 1970s, at which
point the doubling period slowed to 18 months. The doubling period remained
at that value up to late 1999. Moore's Law is apparently self-fulfilling.
Taxonomy of Microfabrication Processes
Accuracy /precision
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Accuracy is the degree of
correctness with which a
measuring system yields the
“true value” of a measured
quantity (e.g. bull’s eye).
Accuracy is typically described
in terms of a maximum
percentage of deviation expected
based on a full-scale reading.
Qui ckTi me™ and a
Gr aphi cs decompr essor
ar e needed t o see t hi s pi ct ur e.
http://ull.chemistry.uakron.
edu/analytical/animations/
Accuracy/precision
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Precision is the difference
between the instrument’s
reported values during
repeated measurements of
the same quantity
Precision is typically
determined by statistical
analysis
of
repeated
measurements
http://ull.chemistry.uakron.
edu/analytical/animations/
Accuracy/precision
Accuracy, precision and standard deviation
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A measurement can be precise, but
Qui ckTi me™ and a
Gr aphi cs decompr essor
may not not be accurate.
ar e needed t o see t hi s pi ct ur e.
The standard deviation (s) is a
statistical measure of the precision
in
a
series
of
repetitive
measurements (also often given as
 with N the number of data, xi is
each individual measurement, and x
the mean of all measurements.
The value xi - X is called the residual
for each measurement.
Relative vs. absolute tolerance in manufacturing
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Lithography is excellent for achieving small absolute tolerances - we can make much smaller devices with lithography than with
mechanical machining. The relative tolerance on those dimensions
though is not so good; on a 100 µm line we might perhaps achieve 1
%. In mechanical machining terms this does not even qualify as
precision machining !
For a small relative tolerance, ultra-fine diamond milling is better. Can
be better than 0.01 %. Of course we cannot make things as small as
we can with lithography.
The above argument might decide your choice of machining
approach or decide the size of the device you want to make.
Relative vs. absolute tolerance in
manufacturing
Precision Machining Application Domain
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Lithography (e.g. Simicromachining)
is
excellent
for
small
absolute tolerances
For relative tolerances,
ultra-fine diamond milling
is better
In some cases we might
want
to
keep
our
micromachine somewhat
larger to optimize relative
tolerances
(see
Mass
Spectrometer example)
City
10 km
Re lat ive Tole r ance
1 km
100 % 10 % 1% 0.1 % 0.01 % 0.01 % 0.0001 %
100 m
100 m
House
10 m
Pr e cis ion M achining
1m
Arm
1m
A bs olute s iz e
10 c m
1 cm
Optic
al
f iber
1 mm
100 µm
10 µm
Bac teria
1 cm
1 µm
100 µm
A bs olute toler ance
1 µm
0.1 µm
V ir us
0.01 µm
0.01 µm
Re lat ive t ole r ance s f or building
a hous e and a lit hography bas e d
m icrom achine
1 nm
A tom
1Å
Line ar dim e ns ion
Line ar dim e ns ion
Relative vs. absolute tolerance in manufacturing
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Lawrence
Livermore
National
Laboratories
(LLNL), at one point used
LIGA to make the next
generation
mass
spectrometer
The picture below shows an
array of holes in PMMA to
electroplate Ni posts (poles)
The diameter of each hole is
40 µm !!
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A larger mass spectrometer
is
machined
with
‘traditional’
ultra
fine
diamond milling at JPL
Relative tolerance is better
than with the LIGA
machined one, so its
performance is better
Relative vs. absolute tolerance in
manufacturing
Merging of two approaches: Top-down and bottomup machining methodologies
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Most human manufacturing methods of small
devices involve top-down approaches. Starting
from larger blocks of material we make smaller
and smaller things. Nature works the other way,
i.e., from the bottom-up. All living things are
made atom by atom , molecule by molecule;
from the small to the large. As manufacturing of
very small things with top-down techniques
(NEMS or nano mechanical devices) become too
expensive or hit other barriers we are looking at
nature for guidance (biomimetics).
Nature and mankind have developed competitive
manufacturing methods on the macro level (e.g.,
steel versus bone). Biomimetics mostly failed in
the larger world (see Icarus). Background
reading: Cats’ Paws and Catapults by Steven
Vogel (Efficiency of mechanical systems in
biology and human engineering in the macroworld).
Merging of two approaches: Top-down and
bottom-up machining methodologies
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On the nanoscale nature is
outperforming us by far (perhaps
because nature has had more time
working
towards
biological
molecules/ cells than towards
making larger organisms such as
trees and us).
Further miniaturization might be
inspired by biology but will most
likely be different again from
nature -- the drivers for human
and
natural
manufacturing
techniques are very different.
Merging of two approaches: Top-down and
bottom-up machining methodologies
Merging of two approaches: Top-down and
bottom-up machining methodologies --NEMS
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MEMS’ little brother is NEMS, the topdown approach to nano devices. This
biomimetic approach to nano devices I
like to call nanochemistry. To succeed in
the latter we will need :
– self-assembly and directed assembly
(e.,g, using electrical fields -see next
viewgraph)
– massive parallelism
– understanding of molecular
mechanisms -- chemomechanics
– engineers/scientists who understand
‘wet’ and ‘dry’ disciplines
Seeman
Eigler
Montemagno
Merging of two approaches: Top-down and
bottom-up machining methodologies --NEMS
 Example
nano chemistry approaches:
– Natural polymers: e.g., NAs and proteins not
only as sensors but also as actuators and
building blocks (Genetic engineer NA’s and
proteins-rely on extremophiles for guidance)
– Mechanosynthesis
– NEMS/biology hybrids --to learn only
Biomimetics
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Bimimetics:
Many examples in nature provide hints
for future manufacturing methods but as
stated earlier the purpose for their
development is different from the
reasons for human manufacturing
methods (e.g., teeth and sea shells might
be excellent strong building materials but
their growth is typically way too slow to
be attractive for human manufacturing)
A few concluding words about manufacturing
methods
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Serial versus batch versus
continuous manufacturing
methods
Projected versus truly 3D
Additive process versus
subtractive process
Top-down versus bottomup
Something to think about
Looking back at the worst times, it always seems that they were times in
which there were people who believed with absolute faith and absolute
dogmatism in something. And they were so serious in this matter that
they insisted that the rest of the world agree with them. And then they
would do things that were directly inconsistent with their own beliefs
in order to maintain that what they said was true.
From Richard P. Feynman in The Meaning of it All.
If in the course of these lectures I can make you doubt most of the things
you have come to believe then I probably put you on the path of
becoming a true scientist/engineer.
Something to think about
Homework
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Describe to a 12 year old, in the shortest and clearest
fashion how a transistor works and why it is so
important in applications all around us (figure is ok
but words are required).
Characterize using the following criteria:
– projected versus 3D,
– serial, batch or continuous
– top-down versus bottom-up
Laser machining
Mechanical machining
E-beam machining and plastic molding.
Calculate the number atoms in a 100 µm long Ag
line (1 µm wide and 1 µm heigh). If we put one
atom down per second (e.g., using an STM) how
long will it take to finish this Ag line ?