Microengineering & Microtechnology
Lecture 2:
The Big Picture – Miniaturised
Prof. Mark Tracey
6ENT1022 [MTECH]
Semester B 2012
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Introduction
• Microtechnology is broad and omnipresent
• You may not realise that you have already studied aspects of it
• It draws upon almost all aspects of technology and science
• This lecture is intentionally broader than the more detailed lectures to follow
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Approach of Lecture
• To introduce Microengineering by referring particularly to the quite recent
history of Microelectronics: the first, and most successful, Microtechnology
• Review the engineering approaches adopted to overcome problems and
hence better understand techniques we know today
• Many of the ‘tricks’ adopted by earlier technologists may still be applicable
or may inspire us to develop further ‘tricks’ derived from them
• The Microelectronics industry has exemplified the effects of scaling as
enshrined in Moore’s Law
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What is Microtechnology ?
• The enhancement of, or unlocking of, physical effects that do not manifest
strongly or cannot be directly exploited, at the macro scale
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What is Microtechnology?
• Facilitation of complexity and the prospect of ‘intelligence’ in compact form
• Integrated Circuits: Intel’s Pentium P6 compared to Tommy Flower’s Colossus
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What is Microtechnology?
•Economy of Manufacture via ‘standard process’
• Standard process is analogous to a high-level programming language
• Moore’s Law
Gordon Moore, co-founder Intel Inc.
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Is it Just Academic Research?
• Global IC industry physical ‘chip’ market is $300 Billion per annum (world
GDP $63,000 Billion) => 0.5% world GDP
• PV panels are ‘large format’ microengineering and have a $50Billion
• Inkjet printer cartridges are microfluidics with a $21 Billion per annum
global market
• Global MEMS market is $9 Billion (2010) with 14% compound projected
growth
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Is it Just Academic Research?
• Flat panel displays are ‘large format’ microengineering
• Consumer electronic orientation and displacement sensors are MEMS:
Nintendo Wii Remote and Apple iPhone (accelerometer) and Playstation 3
Dualshock controller (three axis gyroscope)
• Automotive engine management uses MEMS pressure sensors, Electronic
Stability Systems use MEMS gyros
• Consumer sphygmomanometers (blood pressure monitors) use pressure
sensors
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Production MEMS Chip
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Patterning Planar Surfaces: Structuring
• lithography – printing whole images (text, graphics, microchannels,
microchip metallisation), or steps in a sequence leading to them, in one go
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Resist Layers and Etching
• Daniel Hopfer’s technique, circa 1500, deposited a protective, wax-like layer
(to us ‘resist’) over a metal plate, manually scrapped-away the layer where
metal was to be removed, and immersed the metal in acid
• Hobbyist printed circuit boards can be made in a closely related manner
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Photolithography: Hands off!
• Hopfer’s techniques required manual removal of resist: laborious, error
prone and macro-scale
• Photography provided the next steps: photomasks
• Early photolithography: Nicéphore Niépce, Chalon-sur-Saône, 1826
• Collodion Process (negative glass plates) : Frederick Scott Archer, likely of
Hertford, 1848. These are photomasks!
• Photomasks allow replication: one mask, multiple patterned substrates
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Not all MEMS is small..
Plasma screen photomask
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Tools: Mask Generation
circa 1970: ‘ruby-lith’ mask design
LASI layout editor 2011
Photo-reduction onto mask plate
e-beam mask generator
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Tools: Patterning
Suss MJB4 4 inch diameter wafer photomask exposure and alignment
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Printed Circuits: Structured Layers Commence
• Printed Circuit Board: Paul Eisler: 1943
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Additive, Subtractive and Other Processes
• PCB manufacture is ‘subtractive’: material is removed from a substrate by, in
this case, ‘wet etching’
• In MEMS this is also known as ‘bulk micromachining’
• Microelectronics is generally additive (ignoring doping): for instance
deposition and patterning of metal interconnects (a miniature PCB)
• In MEMS chip and wafer bonding (adhesive free) processes are sometimes
employed to structure vertically
• MEMS also employs replication techniques such as micromolding
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Additive Processes
• ‘screen printing’ is used to apply solder paste in surface mount PCB assembly
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Additive Processes
• A number of techniques allow deposition of thin material layers such as
metals from liquid, or more typically, vapour phase
• Metal deposition used to be normal in filament light bulbs: the darkening of
the bulb-glass is metal deposition
• Layers normally need to be ‘patterned’. This can be by etching as we have
seen, or by other techniques: such as ‘lift off’, as shown here
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Subtractive Processes for Silicon
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How does this relate to Microelectronics?
• Shockley, Bardeen, Brittain produced first transistor at Bell Labs in 1947
• Joint Nobel Prize for Physics in 1956
• Shockley Semiconductor formed , but eight key staff left to form Fairchild
• Fairchild founders included Gordon Moore, Robert Noyce and Andy Grove
• Fairchild produce first silicon IC in 1960 (TI produced a germanium IC in ‘58)
• Noyce, Moore and Grove founded Intel in 1968
• Intel 4004, the first microprocessor in 1970
• Intel now produce 82% of the world’s microprocessors
The first Fairchild silicon
IC: a 4 transistor flip-flop
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Intel 4004 The First Microprocessor: 1970
Grove, Noyce, Moore: Intel
Intel 4004, 4 bit microprocessor
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What has all this got to do with MEMS?
•Two things:
1. Technological infrastructure
• MEMS originated as ‘silicon micromachining’, leveraged by existing silicon
processing techniques, tools and infrastructure
• Much commonality still exists especially for photolithography
• If the microelectronics industry had not existed, MEMS would probably never
have started
2. Innovative Culture
• microelectronics was, and is, the core of ‘Silicon Valley’
• The ‘university spin-out’ venture-capital model of Silicon Valley is the model for
MEMS start-ups
• microelectronics required multidisciplinarity and lateral thinking: so does MEMS
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Isn’t Nanotechnology the New, Cool Thing?
• For politicians and journalists, yes. For engineers, not quite yet.
• Nanotechnology primarily concerns ‘bottom-up’ techniques treating atoms and
molecules as building-blocks, whereas Microtechnology is predominantly top-down
• Behaviour of Nanotechnology is governed by nanoscale effects such as molecular
bonding forces and indeed quantum mechanical behaviour
• Deposition of layers upon, and chemical modification of, component surfaces is
arguably ‘nano’ but widely used in ‘micro’.
• Nanobiology is likely to be ‘the big thing’ of C21
• However, microelectronics breaks several of these assertions: it’s ‘nano-now’ and
top-down: enough money can push technology a long way, fast...
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Scaling: Large Effects of Small Things
(or, conversely, Small Effects of Large Things)
• Example from microfluidics, consider the Hagen-Poiseuille equation governing
laminar liquid flow in pipes:
Where:
Q is volumetric flow rate of liquid;
∆P is pressure drop
L is tube length
r is tube radius
µ is dynamic viscosity
• Small conventional tubing: radius circa 0.5mm
• UH microfabrication of a 5um hydraulic radius channel is relatively easy
• ratio of radii: 102
• ratio of flow rates: 108 !
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Scaling-up Scaled-down: Economy of Scale
• Intel’s 4004 in 1970 employed 10µm ‘design rules’ (all features are multiples of
this dimension) with 2.4x103 transistors on a 144mm2 die;
• Intel’s just released ‘Ivy Bridge’ processor employs 22nm design rules and has
1.4x109 transistors on a 172mm2 die
Interestingly, Colossus had 1500 valves (do you know what a valve is?)
• Minimum definable area has scaled-down by 206x103 times
• Transistor count has scaled-up by a very comparable 583x103 times
• Increase in transistor count is overwhelmingly due to feature size reduction
• This process is the basis of Moore’s Law:
‘transistor count doubles every two years’
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Scaling-up the Scaled-down: Moore’s Law
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Complexity
• Complexity, in terms of transistors per unit area, has scaled similarly
• Calculations per unit area scale by ∆(transistors/unit area) x ∆ clock speed
• Intel 4004 Fck ≈ 0.75MHz
• Current Intel clock speed ≈ 3000MHz
• Fck has scaled by 4x103 during the same period
• Calculations / unit area / unit time has increased by
(583x103) x (4x103) = 2.3x107 times
• However, in reality, calculation capacity scales in a more complex way with
transistor count depending upon processor architecture.
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‘Cheap-fast’ Microengineering
• Whilst silicon provided the initial impetus, it is expensive to access.
• Often silicon’s properties (semiconducting in particular) aren’t required.
• Microcasting of silicone elastomers has become very popular in
microfluidics and is used extensively at UH
• Chrome photomasks cost, at a minimum, £300.
• High resolution, laser-written, plastic film printing can be (and is at UH) used
for features above circa 20µm for a few pounds per mask.
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‘Cheap-fast’ Microengineering
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Structural Photoresist ’SU8’
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PDMS Elastomeric Micropump chips
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PDMS Elastomeric Chips: Micro-pneumatics
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Combining Microstructuring with CNC
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Dean-flow Particle Separator
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Conclusions
• Microtechnology is a very diverse group of applications and techniques
• In fact there are arguably as many as in all of macro technology
• Certain areas have advanced amazingly, in particular Microelectronics
• Despite the apparent gap in sophistication between advanced ICs and
‘cheap-fast’ prototype microfluidics, both are ‘leading edge’
• Universal ‘design rules’ don’t, in general, exist: good engineering principles,
scientific fundamentals and ingenuity are key.
• Multidisciplinary is the norm
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