Microengineering & Microtechnology Lecture 2: The Big Picture – Miniaturised Prof. Mark Tracey

1. Microengineering & MicrotechnologyLecture 2: The Big Picture – MiniaturisedProf. Mark Tracey 6ENT1022 [MTECH] Semester B 2012

2. 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

3. 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

4. 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

5. What is Microtechnology? • Facilitation of complexity and the prospect of ‘intelligence’ in compact form • Integrated Circuits: Intel’s Pentium P6 compared to Tommy Flower’sColossus

6. 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.

7. 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

8. 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 Dualshockcontroller (three axis gyroscope) • Automotive engine management uses MEMS pressure sensors, Electronic Stability Systems use MEMS gyros • Consumer sphygmomanometers (blood pressure monitors) use pressure sensors

9. Production MEMS Chip

10. Patterning Planar Surfaces: Structuring • lithography – printing whole images (text, graphics, microchannels, microchip metallisation), or steps in a sequence leading to them, in one go

11. 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

12. 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

13. Not all MEMS is small.. Plasma screen photomask

14. Tools: Mask Generation circa 1970: ‘ruby-lith’ mask design Photo-reduction onto mask plate LASI layout editor 2011 e-beam mask generator

15. Tools: Patterning Suss MJB4 4 inch diameter wafer photomask exposure and alignment

16. Printed Circuits: Structured Layers Commence • Printed Circuit Board: Paul Eisler: 1943

17. 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

18. Additive Processes • ‘screen printing’ is used to apply solder paste in surface mount PCB assembly

19. 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

20. Subtractive Processes for Silicon

21. How does this relate toMicroelectronics? • 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

22. Intel 4004 The First Microprocessor: 1970 Grove, Noyce, Moore: Intel Intel 4004, 4 bit microprocessor

23. 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

24. 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...

25. 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 • µis 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 !

26. Scaling-up Scaled-down: Economy of Scale • Intel’s 4004 in 1970 employed 10µm ‘design rules’ (all features are multiples of this dimension) with 2.4x103transistors 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’

27. Scaling-up the Scaled-down: Moore’s Law

28. 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 • Fckhas 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.

29. ‘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.

30. ‘Cheap-fast’ Microengineering

31. Structural Photoresist ’SU8’

32. PDMS Elastomeric Micropump chips

33. PDMS Elastomeric Chips: Micro-pneumatics

34. Combining Microstructuring with CNC

35. Dean-flow Particle Separator

36. 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