Jv Nap Openday 7 5 08


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This is a presentation I gave about MEMS processing at Tyndall in 2008. It goes over the various fabrication possibilities at Tyndall.
I personally like slide 3 and 4 trying to hook the history of watch making in with MEMS fabrication. This drive to go smaller and smaller with watch making can also be seen in electronics. Coincidentally, the first MEMS device was a time-keeping pendulum.

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Jv Nap Openday 7 5 08

  1. 1. Tyndall National Institute MEMS Fabrication at Tyndall NAP Open Day Presentations Wednesday 7th May 2008 – Jaap Verheggen www.tyndall.ie Introduction Contents • Introduction – A history of small mechanical things – How MEMS came about • MEMS fabrication • MEMS is a big word – Micro ‘Electro’ Mechanical systems – Photolithography • Or Microsystems Technology or – Etching Micromechatronics or – Deposition Micromachines – Growing – Small Movable Parts – Embossing, Bonding – Applications in: bio, opto, RF, thermal, radio, electro, etc… – Either Sensor, process or actuator MEMS fabrication: the process of making small movable MEMS fabrication: the process of making small movable things by transferring a mask to the surface of the device things by transferring a mask to the surface of the device www.tyndall.ie 1
  2. 2. History of Small Mechanical Things The watch 1480 - P.Henlein creates a springloaded pocketwatch 1659 - C.Huygens invents the Remontoire, more accurate 1709 - Jewel bearings are used 1844 - A.LeCoultre invents the millionometre, Micrometer. 1957 - Battery driven watch 1960 – First electronic watch (transistor pulser) Quartz resonator 1962 - First quarz-based watch Transistor pulser 1972 - First LCD watch Ruby Watchmakers lathe, Old-style ‘micro’fabrication equipment achieves accuracy of Drill, lathe, milling, cutting ‘10 μm’ by sharp edge, laser, plasma, discharge, water, sand, etc. Limited to ~25 μm accuracy Not a parallel method, takes a long time to make (this is not MEMS) www.tyndall.ie History of MEMS devices 1987 – The term MEMS ‘invented’ at a transducers conference • 1991 – AD commercialize MEMS accelerometer • 1993 – Raytheon Commercialize RF MEMS Switch • 1993 – TI commercialize DMD (research started in 1977) Today, application of MEMS are in automotive, gyroscopes, mobile com, microphones, displays, bio medical, etc. Back in history • 1977 – First inkjet nozzle • 1972 – First Pressure sensor • 1967 – Resonant gate transistor – Transistor with a micro-pendulum for oscillation www.tyndall.ie 2
  3. 3. Photolithography based machining New-style micro-fabrication, MEMS fab • To make small movable things by transferring a mask to the surface of the device • Photolithography – Photoresist is light sensitive, when exposed it will either harden or break down – The design on the mask is transferred to the photoresist – For positive resist, exposed parts become soluble and are washed away – Leaves a soft mask on the wafer 30 µm EV420 Photolithography for further processing www.tyndall.ie Etching MEMS fabrication Etching • Photolithography • (Deep) Reactive ion etching, a • Etching chemically reactive plasma • Deposition etches the surface • Growing • Chemical vapor etching, a • Embossing chemical gas that reacts on the surface is pumped in the chamber • Chemical wet etching, The wafer is placed in a chemical 30 µm bath • Examples: – NAP 87, Stokes Inst, crash test cantilevers – NAP 124, Waterford IT, Preparation of molecular imprinted polymer beads – DRIE etch, high aspect ratio etch, geometry dependent www.tyndall.ie 3
  4. 4. Etching Crash test cantilevers, NAP 87, Stokes Inst. – KOH wet etch from the back – Deposit etch, Aluminum, polyimide – Deep reactive Ion Etch from the top – Wet etch of polyimide and aluminum to release the device – Shock test, acceleration as function of time to obtain material properties of silicon Si Wafer, 525 µm 100 µm = Silicon Oxide, 50nm = Polyimide, Sacrificial 10µm = Alumium, Sacrificial, 6µm www.tyndall.ie Deposition Deposition MEMS fabrication • Sputtering, argon atoms in a • Photolithography plasma are accelerated towards a • Etching solid target, this bombardment • Deposition ejects target atoms that deposit • Growing on the wafer • Embossing • Spin casting, an uncured resin is poured on a spinning wafer to form a thin layer, solidified afterwards • Evaporation, deposition by condensation • Chemical vapour deposition, volatile gasses pumped in the chamber react on the surface • Examples: – NAP 35, CIT Ultrasonic membranes – Humidity sensors, CTVR – Wafer level Packaging of MEMS www.tyndall.ie 4
  5. 5. Deposition Multi-MEMS process • Multi-Project Wafer (MPW) – 3 by 3 mm dies • MEMS and Zero-Level packaging • Use of 17 mask layers, +120 fabrication steps – Sputtered Aluminium as structural material – CVD Silicon oxide as passivation – Spin on and cured polyimide as sacrificial layer • 8 projects involved Capacitor plates Moisture-sensitive polyimide www.tyndall.ie Growing MEMS fabrication Growing • Photolithography • Electroplating, a metal is plated onto the surface in a photoresist mould to • Etching form a structure • Deposition • Oxidizing, in a oxide rich environment, • Growing a layer of silicon oxide is created on • Embossing the surface, this also consumes some silicon Examples: • For Nap 103, TCD, 25 µm copper pillars were electroplated. – The pillars are connected to 30 µm electrodes – A channel is created over the pillars for electrohydrodynamic flow • For Nap 112, CIT, 2 µm thick, 100 µm diameter discs were grown on Si. – Optical signal could be coupled in the disc by use of an elongated glass fiber, the light would resonate in the disc. www.tyndall.ie 5
  6. 6. Bonding, Embossing MEMS fabrication Embossing • Photolithography • Hot-emboss, a thermoplastic • Etching polymer is heated above its glass • Deposition transition temperature and forced • Growing against a mould • Embossing • PDMS can be poured on a mould, it hardens when baked Bonding • Si to glass bonding, field assisted • Fusion bonding of Si to Si, high temperature • Adhesive bonding: adhesive is spun on and activated, other wafer is placed on top Si channel wafer Glass wafer with electrodes, drilled through holes NAP 103, TCD www.tyndall.ie Summary • Fabrication at Tyndall • Silicon Fabrication • Compound semiconductor fabrication • MEMS fabrication • All there to make small things Irish (ROI + NI) Researcher • Many variations Fabrication Design, Modeling Theory, Idea Device Integration Measurement www.tyndall.ie 6
  7. 7. know more & more & more… – Thanks for your attention For more information, visit www.Tyndall.ie, www.Tyndall.ie/research/MEMS and www.Tyndall.ie/NAP www.tyndall.ie 7