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Jv Nap Openday 7 5 08
- 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. History of SmallMechanical 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. Photolithography based machining New-stylemicro-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. Etching Crash testcantilevers, 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. 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. 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. 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