lino%eugene%–research%assistant...

Lino Eugene – Research assistant McGill Nanotools Microfab

E-‐mail: [email protected]

Outline �  Introduc@on

-‐  Origins of microfabrica@on -‐  Microtechnology subfields -‐  Towards nanotechnology/nanofabrica@on

�  Fabrica@on basics -‐  Cleanrooms -‐  Wafers -‐  Thin film deposi@on techniques -‐  Lithography -‐  Etching -‐  Example of fabrica@on: SU-‐8 master for PDMS molding

� McGill Nanotools Microfab

Introduc@on to Microfabrica@on 20/02/2012 2

Origins of microfabrica@on �  Key dates

-‐  1947: First point-‐contact transfert resistor (with Germanium crystal), Bell Labs

-‐  1958: First integrated circuit (IC), Texas Instrument

-‐  1961: First silicon IC chip, Fairchild Camera


Origins of microfabrica@on �  Key dates

-‐  1971: First microprocessor, i4004, Intel

-‐  2011: core i7-‐ 3960x, Intel

⇒ Development of microfabrica@on methods Introduc@on to Microfabrica@on

2300 transistors 10 µm node Max CPU frequency: 748 kHz

2.27 billion transistors ! 32 nm node Max CPU frequency: 3.3 GHz

04/03/2012 4

Microtechnology subfields � Microelectronics: transistors, capacitors, inductors, resistors, diodes

�  Optoelectronics: photodiodes, solar cells, CCDs, LEDs, laser diodes, ...

� Microelectromechanical systems (MEMS): ink jet heads, micro-‐accelerometers, gyroscopes, microphones, micromirrors, microbolometers, …

� Microbiotechnology: DNA microarrays, microfluidic systems, BioMEMS, lab-‐on-‐a-‐chip


Towards nanotechnology/nanofabrica@on

� Nanoelectronics: nanowires, nanocrystals, nanotubes for logic and memory ⇒ quantum computer

� Nanoelectromechanical systems (NEMS): @ps for AFM, carbon nanotubes for nanomotors or sensors

� Nanobiotechnology: nanopar@cles as drug delivery systems or as sensors


Cleanrooms � Why? -‐  Reduc@on of par@cle contamina@on from air and people -‐  Control of temperature, humidity, vibra@ons, light

�  How? -‐  Filtered and circula@ng air -‐  Overpressure -‐  Cleanroom suits -‐  Highly pure water, gases and chemicals -‐  Special furniture (notebooks, pencils, fabrics, …) and compa@ble materials


Cleanrooms �  Cleanroom classifica@on

-‐  Intel: class 1 to 100

-‐  Surgery room : class 100 to 10000

-‐  House: ∼300000


Substrates �  Silicon wafer: most widely used in microfabrica@on -‐  Single crystal ingots of various diameters

grown from melted electronic grade silicon (Czochralski method)

-‐  wafers of various sizes and thicknesses sliced from ingots and polished

-‐  Typical wafer diameters: 2, 4, 6, 8 and 12”


Substrates � Quartz (crystalline SiO2), fused silica (amorphous SiO2) and glass (SiO2 and metal oxides) wafers

�  III-‐V wafers: GaAs, AlGaAs, GaP, InAs, InP, etc �  SiC wafer �  Sapphire (crystalline Al2O3) wafer �  Plas@c substrates


Film deposi@on techniques �  Physical Vapor Deposi@on (PVD): elemental metals (Al, Cr, Au, Ni), refractory metals (W, Ta, Ti,...), metal oxides and nitrides, alloys

�  Chemical Vapor Deposi@on (CVD): a-‐Si, poly-‐Si, SiO2, Si3N4, SiOxNy

�  Epitaxy: silicon, germanium, III-‐V materials �  Electrochemical Deposi@on (ECD): Cr, Au, Ni, Ag, Cu

�  Spin and spray coa@ngs: photoresists and polymers




�  Fabrica@on basics -‐  Cleanrooms -‐  Wafers -‐  Thin film deposi@on techniques -‐  Lithography -‐  Etching

�  Example: SU-‐8 master for PDMS molding


Photolithography �  Spin coa@ng:

⇒ Thicknesses from 10 nm to 100 µm

Introduc@on to Microfabrica@on

Main parameters: -‐  viscosity of the resist -‐  spin speed -‐  bake temperature and

dura@on

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Photolithography � UV exposure: Hg lamp, peaks at 365, 405 and 436 nm

⇒ Resolu@on of ∼ 500 nm in the best condi@ons � Development: alkaline developer, typically diluted TMAH


Main parameters: -‐  resist thickness -‐  gap between the substrate

and the photomask -‐  exposure dose or @me

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Photolithography � Nega@ve or posi@ve resist


-‐  For posi@ve resists, dissolu@on of the exposed areas in the developer. -‐  For nega@ve resists, dissolu@on of the unexposed areas

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Electrolithography �  Posi@ve or nega@ve electrosensi@ve resist � Maskless process

⇒Resolu@on dependant on the resist material, the thickness and the electron energy


30 nm spaces/lines in PMMA

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Etching � Wet etching

-‐  solid + liquid etchant ð soluble products -‐  Isotropic, except for crystal silicon or quartz -‐  Mask undercut -‐  Difficult to control precisely with small

geometries, and closely spaced structures -‐  Batch processing


Etching

Paoerned resist

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Etching � Anisotropic wet etching of Si

-‐  Base etchant: KOH or TMAH at T>70 °C -‐  Fast etch in (100) crystal planes, limited in

(111) planes -‐  V-‐groove geometries -‐  Angle between (100) and (111): 54.7°

⇒ Bulk silicon micromachining


Etching �  Reac@ve Ion Etching

-‐  Solid + gaseous etchant ð vola@le products -‐  Chemical and physical (spuoering) etching -‐  Excellent control -‐  High resolu@on -‐  Single wafer processing


Process integra@on Substrate prepara@on

• Chemical wet cleaning • Physical wet cleaning • Dry cleaning

Addi@ve microfabrica@on

• PVD • CVD • Epitaxy • Electropla@ng • Spin and spray coa@ng

Paoerning

• Direct laser wri@ng • Photolithography • EBL • Sos lithography • Nanoimprint

Subtrac@ve microfabrica@on

• Wet etching • Dry etching

Property modifica@on

• Doping • Ion implanta@on • Annealing

Packaging

• Wafer bonding • Dicing • Wire bonding • Characteriza@on • Test


N•  The steps are used and repeated as necessary to build up or take down mul@ple layers (“addi@ve” vs. “subtrac@ve”)

•  Aser microfabrica@on, packaging may be needed for protec@on from and connec@on to the outside world

04/03/2012 24

SU-‐8 master for PDMS molding �  What you should think about prior fabrica@on: -‐  Process flow: tools available, limita@ons, cri@cal steps

-‐  Layout design: linewidths, spacings, wafer size -‐  Feature height ⇒ Dimensions determined by simula@ons some@mes �  What you need: -‐  Materials: Si wafer, SU-‐8 nega@ve epoxy resist, SU-‐8 developer, IPA, diluted HF or BOE, DI water

-‐  Equipment: wet benches, spin coater, hot plate, oven, photomask+UV mask aligner, plasma chamber, op@cal microscope, profiler


SU-‐8 master for PDMS molding �  Process flow

04/03/2012 Introduc@on to Microfabrica@on 27

1) Na@ve oxide etching

2) Dehydra@on

3) SU-‐8 spin coa@ng

4) Resist bake

5) UV exposure

6) Post-‐exposure bake

7) Development

8) Hard bake

9) Plasma treatment

Photolithography Process

Metrology: op@cal microscope and profiler, to verify dimensions

Cri@cal steps -‐ Step 3: air bubbles trapped in the resist -‐ Steps 4 and 6: thermal stress

McGill Nanotools Microfab �  1000 sq. s, class 100 and 1000


Gowning room

Photolithography room, class 100

Deposi@on and etching room, class 1000

20/02/2012 29

McGill Nanotools Microfab �  Process capabili@es

-‐  Thermal oxida@on -‐  Deposi@on: E-‐beam evapora@on of

metals, spuoering of metals and oxides , LPCVD of a-‐Si, poly-‐Si and Si3N4 , PECVD SiO2 and Si3N4

-‐  Lithography: spin coa@ng, spray coa@ng, mask aligner, EBL

-‐  Wet etching: Si, SiO2, metals, resists -‐  Plasma etching: Si, SiO2, Si3N4, III-‐V,

metals, resists -‐  Packaging: wafer bonding, dicing,

wire bonding


McGill Nanotools Microfab �  Characteriza@on

-‐  Visualiza@on/metrology: op@cal microscopes, scanning electron microscope (SEM)

-‐  Metrology: op@cal and mechanical profilers, spectroscopic ellipsometer, reflectometer, atomic force microscope (AFM)

-‐  Electrical measurements: 4-‐point probes, DC probe sta@on


Examples of micro/nanostructures from McGill Nanotools Microfab

� MEMS


Nanopaoerning on micromachined structures

Silicon nitride nanocan@levers

11 nm thick and 260 nm wide Al nanowires

100 µm long, 300 nm high and 400 nm wide can@levers

04/03/2012 32


� Microbiotechnology


Straight SU-‐8 pins Microfluidics

Bond on glass slide to create channels

04/03/2012 33


� Optoelectronics


White LED with InGaN/GaN dot-‐in-‐a-‐wire heterostructures

GaAs/AlGaAs far IR quantum well photodetectors

GaAs/AlGaAs mesa

Schooky gate of 250 nm wide 04/03/2012 34

Have an idea ? Where to start ? �  Gather informa@on in literature and with colleagues �  Dras a process flow �  Schedule an appointment with the fab manager

�  Review process flow and assess feasibility �  Make modifica@ons; revised version of the process flow

�  Get access to the cleanroom and start training process �  WHMIS (hop://www.mcgill.ca/ehs/training/whmis/) �  Safety quiz �  Microfab policies �  Reserva@on sosware and document repository �  Equipment training


McGill Nanotools Microfab �  For more informa@on, please visit us at hop://www.mcgill.ca/microfab/

� Or contact Lino Eugene@ 514-‐398-‐7329 [email protected]


Learn more about microfabrica@on �  hop://mcgill.worldcat.org/oclc/772698654

�  hop://www.amazon.ca/Introduc@on-‐Microfabrica@on-‐Sami-‐Franssila/dp/0470749830



Thank you for your aoen@on !

04/03/2012 38

TSMC fab tour


Physical Vapor Deposi@on �  Electron-‐beam evapora@on


-‐  Elemental metals: Au, Al, Cr, Ti, Ni, Pt,... -‐  HV (10-‐7 Torr) and UHV (10-‐11 Torr) -‐  Line-‐of-‐sight transport -‐  Rates from 1 nm/min to few µm/min -‐  Mul@-‐layers

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Physical Vapor Deposi@on �  Spuoering


-‐  DC field for conduc@ve materials and RF field for insulators -‐  Medium vacuum: 10-‐2-‐10-‐3 Torr -‐  Good step coverage -‐  Rates between 1 and 10 nm/s -‐  Reac@ve spuoering by adding gas -‐  Co-‐spuoering for alloys -‐  Mul@-‐layers

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Chemical Vapor Deposi@on �  Low pressure CVD (LPCVD)


-‐  Reac@on between gases at high temperature, 500-‐900 °C -‐  High purity -‐  Good step coverage and uniformity -‐  Deposi@on of SiO2, Si3N4, poly-‐Si, a-‐Si -‐  Batch processing

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Chemical Vapor Deposi@on �  Plasma-‐enhanced CVD (PECVD)


-‐  Reac@on between gases at ~300 °C, and enhanced by plasma -‐  Less dense and non-‐stoichiometric films -‐  Deposi@on of SiO2, Si3N4, SiOxNy , a-‐Si -‐  Single wafer

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