Nanofabrication: Principles and Applications

84 Pages·2016·3.558 MB·English

by  Christo Papadopoulos (auth.)

SPRINGER BRIEFS IN MATERIALS
Christo Papadopoulos
Nanofabrication
Principles and
Applications
123
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Christo Papadopoulos
Nanofabrication
Principles and Applications
123
Christo Papadopoulos
Electrical andComputer Engineering
University of Victoria
Victoria
Canada
ISSN 2192-1091 ISSN 2192-1105 (electronic)
SpringerBriefs inMaterials
ISBN978-3-319-31740-3 ISBN978-3-319-31742-7 (eBook)
DOI 10.1007/978-3-319-31742-7
LibraryofCongressControlNumber:2016943135
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Contents
1 Introduction.... .... .... ..... .... .... .... .... .... ..... .... 1
1.1 Nanostructure Fabrication... .... .... .... .... .... ..... .... 3
1.2 Overview of Brief.... ..... .... .... .... .... .... ..... .... 4
Reference .. .... .... .... ..... .... .... .... .... .... ..... .... 5
2 Silicon Planar Processing and Photolithography.... .... ..... .... 7
2.1 Photolithographic Patterning. .... .... .... .... .... ..... .... 8
2.2 Thin Film Deposition. ..... .... .... .... .... .... ..... .... 12
2.3 Summary .. .... .... ..... .... .... .... .... .... ..... .... 13
References.. .... .... .... ..... .... .... .... .... .... ..... .... 14
3 Direct-Write Lithography Approaches ... .... .... .... ..... .... 15
3.1 Electron-Beam Lithography . .... .... .... .... .... ..... .... 15
3.2 Focused Ion-Beam Lithography .. .... .... .... .... ..... .... 19
3.2.1 Resist Patterning.... .... .... .... .... .... ..... .... 19
3.2.2 Milling .. .... ..... .... .... .... .... .... ..... .... 19
3.3 Summary .. .... .... ..... .... .... .... .... .... ..... .... 21
References.. .... .... .... ..... .... .... .... .... .... ..... .... 21
4 Stamping Methods... .... ..... .... .... .... .... .... ..... .... 23
4.1 Nanoimprint Lithography... .... .... .... .... .... ..... .... 23
4.2 Microcontact Printing. ..... .... .... .... .... .... ..... .... 26
4.3 Summary .. .... .... ..... .... .... .... .... .... ..... .... 28
Reference .. .... .... .... ..... .... .... .... .... .... ..... .... 28
5 Scanning-Probe Methods . ..... .... .... .... .... .... ..... .... 29
5.1 Single Atom/Molecule Manipulation .. .... .... .... ..... .... 30
5.2 Nanolithography. .... ..... .... .... .... .... .... ..... .... 31
5.2.1 Subtractive Patterning.... .... .... .... .... ..... .... 32
5.2.2 Additive Patterning.. .... .... .... .... .... ..... .... 32
5.3 Summary .. .... .... ..... .... .... .... .... .... ..... .... 34
References.. .... .... .... ..... .... .... .... .... .... ..... .... 35
v
vi Contents
6 Natural Lithography. .... ..... .... .... .... .... .... ..... .... 37
6.1 Self-assembled Masks. ..... .... .... .... .... .... ..... .... 37
6.1.1 Colloidal Lithography.... .... .... .... .... ..... .... 37
6.1.2 Anodic Aluminum Oxide . .... .... .... .... ..... .... 39
6.1.3 Block Copolymers... .... .... .... .... .... ..... .... 41
6.2 Templated Growth ... ..... .... .... .... .... .... ..... .... 42
6.3 Summary .. .... .... ..... .... .... .... .... .... ..... .... 44
References.. .... .... .... ..... .... .... .... .... .... ..... .... 44
7 Direct-Growth and Self-assembly.... .... .... .... .... ..... .... 45
7.1 Vapor-Based Growth . ..... .... .... .... .... .... ..... .... 45
7.1.1 Metallic Clusters and Quantum Wells/Dots.... ..... .... 45
7.1.2 Carbon Nanotubes and Semiconductor Nanowires ... .... 49
7.2 Liquid-Based Growth. ..... .... .... .... .... .... ..... .... 52
7.2.1 Colloids.. .... ..... .... .... .... .... .... ..... .... 52
7.2.2 Composites... ..... .... .... .... .... .... ..... .... 53
7.2.3 Molecular Structures. .... .... .... .... .... ..... .... 55
7.3 Hybrid Methods. .... ..... .... .... .... .... .... ..... .... 59
7.4 Summary .. .... .... ..... .... .... .... .... .... ..... .... 60
References.. .... .... .... ..... .... .... .... .... .... ..... .... 61
8 Practical Examples and Case Studies of Nanofabrication ..... .... 63
8.1 Tri-Gate Field-Effect Transistors (3D FETs). .... .... ..... .... 63
8.2 Patterned Two-Dimensional Electron Gas (2DEG) Structures. .... 65
8.3 Nanoscale Biosensors. ..... .... .... .... .... .... ..... .... 67
8.4 Photonic Crystals and Nanophotonics.. .... .... .... ..... .... 68
8.5 Nanomechanical Structures.. .... .... .... .... .... ..... .... 71
8.6 Polymer-CNT Composites .. .... .... .... .... .... ..... .... 73
8.7 CNT Arrays and Junctions.. .... .... .... .... .... ..... .... 77
Reference .. .... .... .... ..... .... .... .... .... .... ..... .... 81
Chapter 1
Introduction
Alltechnologyisultimatelybasedonthepropertiesofthematerial(s)fromwhichit
ismade.Thetraditionaldivisionofhistoryintoe.g.,stoneorironages,pointstothe
importantrolematerialsandtechnologyhaveplayedinhumancivilization.Wenow
know that the different interactions among atoms and their arrangement in space
leads to the wide diversity of materials found in nature; from individual molecules
to complex organisms. The periodic table describes elements at the scale of indi-
vidual atoms.1 Just beyond the atomic level, the properties we normally associate
withmosttypesofmatter(solids,liquids,etc.)begintoappear(e.g.,color,density,
viscosity,conductivity).Nanotechnologyisessentiallyaboutengineeringmaterials
andtheirpropertiesattheseverysmalllengthscales(approximatelyintherangeof
1–100 nm) to create new types of structures and devices.
Astheextentofamaterialisreducedinoneormorespatialdimensionsmanyof
its properties can be dramatically altered. This makes nanotechnology a subject of
both fundamental and practical interest. By controlling the size and shape of a
structureatthenanometerscale(ornanoscale),themechanical,chemical,electrical,
optical, etc., properties of materials can be tailored for specific applications.
Nanofabrication seeks to make or construct such structures using a variety of
approaches,whichisthetopicofthisBrief.Weshallseethatnanoscalefabrication
oftenrequiresuniquetechniquesandtoolsthatmakeitdistinctfromthecreationof
larger scale man-made structures such as bridges, towers and even miniature parts
or machines.
1Roughly1Åor10−10m.
©TheAuthor(s)2016 1
C.Papadopoulos,Nanofabrication,SpringerBriefsinMaterials,
DOI10.1007/978-3-319-31742-7_1
2 1 Introduction
Fig.1.1 Numberof
nanoscalescienceand
technologyrelatedpatents
(whitecircles,USPTO)and
publications(blackdots,Web
ofScience)peryearbetween
1991and2012[adaptedfrom
H.Chenetal.,
J.Nanopart.Res.15,
1951(2013)]
A now famous lecture given by Richard Feynman in December 1959,2 is often
credited with first discussing nanofabrication approaches and nanotechnology in
general. While this may not have been the earliest exposition or account3 of
nanofabricationitwascertainlyapioneeringvisionofthegreatpotentialthatexists
withinnanoscalescienceandtechnology.TheinitialideasmentionedinFeynman’s
talk and many others would continue to be developed in the following decades,
which has led to the practical implementation of structures and applications based
on nanoscale materials.
Figure 1.1 displays the number of patents (USPTO) and scientific publications
(worldwide) related to nanoscale science and technology from 1991 to 2012. The
tremendous recent growth in the area has been fueled by a comprehensive global
effort involving governments, academia and industry. Large corporations such
as IBM, Samsung, Xerox, Intel, GE, 3M, etc. are all involved in nanomaterials
research and development and it is now commonplace to see nanotechnology
occupyingacentralrolebothinscientificresearchandaspartofmanycommercial
products from electronics to textiles, medicine, automobiles/aircraft and beyond,
whilethefieldcontinuestogrowatarapidpace.4This“nano”ubiquity(stilljustin
its nascent stages)haslargelybeenenabled byadvancesinnanofabrication, which
underpins the application of nanoscale materials.
2R.P. Feynman, “There’s Plenty of Room at the Bottom”, Annual Meeting of the American
PhysicalSociety,1959.TranscriptreprintedinJ.Microelectromech.Syst.1,60(1992).
3See,e.g.,M.Faraday,Philos.Trans.R.Soc.London147,145(1857).
4The market for products incorporating nanomaterials is expected to be several trillion USD by
2020.
1.1 NanostructureFabrication 3
Fig.1.2 Nanostructure examples, from left to right—high-resolution transmission electron
microscope(HRTEM)cross-sectionimageofaCdSe-CdScore-shellquantumdotshowingatomic
latticeplanes,scalebar=2nm[sourceO.Chenetal.,Nat.Mater.12,445(2013)];Single-walled
carbon nanotube schematic model; HRTEM cross-section image of GaN/AlN quantum wells
consistingof2–3atomicmonolayersofgalliumnitridesandwichedbetweenlayersofaluminum
nitride[sourceJ.Sellésetal.,Sci.Rep.6,21650(2016)]
1.1 Nanostructure Fabrication
Inthistextwedefineananostructuretobeanymaterialwhichhasnanometerscale
(*1–100 nm)extentinatleastonespatialdimension.Oneoftenspeaksof2D,1D
or0Dstructures,5whichreferstomaterialsconfined,i.e.,withnanoscaleextent,in
one, two or all three dimensions, respectively. Examples of 0D structures include
semiconductor quantum dots, C buckyballs and metal nanoparticles. 1D objects
60
include carbon nanotubes, semiconductor nanowires and long molecules such as
DNA, polymers, etc. 2D materials have been studied for many years with the
semiconductor quantumwell beingthemostwell-knownexample.Applicationsof
nanostructures include: 0D materials ascatalysts, inbiosensors and advanced laser
structures; 1D structures in various composite materials, electronics and energy
generation/storage; Quantum wells in laser diodes (e.g., in optical telecommunica-
tionsandopticaldiscstorage)andalsoforhigh-speedtransistors(e.g.,inmicrowave/
RF applications). Figure 1.2 contains examples of some of the nanostructures that
willappearinsubsequentchapters.
Thenanofabricationmethodsusedtocreatenanostructuresareusuallyclassified
as either top-down or bottom-up (Fig. 1.3). Top-down methods are usually sub-
tractive,i.e.,materialisremovedtoformthedesiredstructure(e.g.,bychemicalor
physical etching), and in particular always involve the reduction of a pre-existing
material or structure. On the other hand, bottom-up approaches are additive, i.e.,
material is grown or assembled to form nanostructures (e.g., from vapor or liquid
phases). The two standard examples used to represent top-down and bottom-up
approaches are lithography and self-assembly (or growth), respectively. It is
5Generally,2D,1Dand0Dstructuresarealsooftenreferredtoasquantumwells,wiresanddots,
respectively.However,thesetermsmayalsobeusedtodescribespecificnanostructuresdepending
onthecontext(e.g.,“quantumdots”typicallyimpliesa0Dstructuremadefromasemiconducting
material,unlessotherwisenoted).