Zheng Cui Nanofabrication_ Principles, Capabilities and Limits 2008

351 Pages·2009·10.9 MB·English

Nanofabrication
Zheng Cui
Nanofabrication
Principles, Capabilities and Limits
1 3
ZhengCui
RutherfordAppletonLaboratory
ScienceandTechnologyFacilityCounsil(STFC)
HarwellScienceandInnovationCampus
Didcot,OX110QX
UnitedKingdom
ISBN:978-0-387-75576-2 e-ISBN:978-0-387-75577-9
DOI:10.1007/978-0-387-75577-9
LibraryofCongressControlNumber:2008924169
#2008SpringerScienceþBusinessMedia,LLC
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Tom yp arents
Preface
The idea of writing a book focusing on nanofabrication came after I gave a
seriesoflecturesin2007.FirstIwasinvitedtogivealectureattheNanoelec-
tronicsResearchCentreinthePekingUniversity,China,inJanuary2007.The
titleofmylecturewas‘‘Nanofabrication:CapabilitiesandLimits’’.ThenIwas
invitedtogiveapresentationwiththesametitleattheUKInstituteofPhysics
Conference on ‘‘Nanoelectronics-Materials and Technologies’’ in February
2007. The audiences, who were mostly working on new nanoelectronic
devices, were keen to know which technology they could use to make the
nanostructures they need. In April 2007, I was on a lecture tour in Taiwan
whereIlecturedatNationalTaiwanUniversity,TaiwanNationalNanodevice
Laboratory and National Cheng-Kung University. Wherever I lectured,
researchers and students were showing great interest in nanofabrication
technologiesandconcernedabouttheircapabilitiesandlimits.Mycollabora-
tion with researchers in China, particularly with the Institute of Physics,
ChineseAcademyofSciences,whereanumberofresearchgroupsaredevoted
tonanomaterialsanddevices,hasalsoexposedmetofrequentquestionssuch
as what are the capabilities and limits of various current nanofabrication
technologies.AlthoughIhavepublishedabook,titled‘‘Micro-Nanofabrica-
tion Technologies and Applications’’ (Springer, 2006), my previous book,
including a number of other books published so far, has not made clear
which technologies can truly claim to be nanofabrication technologies.
The descriptions of nanostructure fabrication are often buried in those of
microstructure fabrication. It is apparent that a book on this subject is
desirable.
It is no surprise that nanofabrication is drawing wide spread interest, as
nanotechnology has been a buzz word in the last few years across the world.
Notonlythetraditionalphysicalsciencecommunityisdrawnintonanotechnol-
ogy, but also researchers in chemistry, medicine, biology, energy and environ-
ment sciences are all becoming interested in nanotechnology. Though
nanoscienceand nanotechnologyare broadly definedasresearchand exploita-
tionofstructuresandsystemsatsub-100nmdimension,thedistinctionbetween
microfabrication and nanofabrication is not too obvious. Many traditional
technologies for fabricating microscale structures are also capable of making
vii
viii Preface
sub-100nmstructures,suchasopticallithography,thoughmanyadvancesinthe
optical lithography taking place over the years have made the sub-100 nm
patterningpossible.Ontheotherhand,someofthetechnologiesareinherently
‘‘nano’’ratherthan‘‘micro’’,suchasfabricationbasedonscanningprobes.Ihave
writtenthebookespeciallywiththesub-100nmdimensionalscaleinmind,and
have selected only those technologies that are capable of making sub-100 nm
structures,oremphasizedon theaspectsofsub-100nmstructuringcapabilities
forthosetechnologieswhichhavebeentraditionallyformicrofabrication.Asthe
book titlesuggested,Ihavedescribednotonlythenanofabrication capabilities
foreachoftheselectedtechnology,butalsotheirlimitswhichareeitheraboutthe
ultimate patterning resolution or about the practicality as a fabrication
technology.
Nanofabricationisamulti-disciplinaryfield.Abookinthisnatureisoften
writtenbymultipleauthors.Iwasabletotakeonthistaskonmyownbecause
ofmymanyyearsworkingwithvariousmicrofabricationandnanofabrication
technologies. The Central Microstructure Facility, Rutherford Appleton
Laboratory, where Ihaveworked for15years,hasbeen aplace withsole job
to provide micro and nanofabrication solutions to researchers of many scien-
tific disciplines. My connection with Laboratory of Microfabrication at the
InstituteofPhysics,ChineseAcademyofScience,inthelast6yearsasavisiting
professor also has given me the opportunity to work with many scientists in
nanoscienceandnanotechnologyareas.ThoughIcannotclaimtobeanexpert
ineverynanofabricationtechnologydescribedinthebook,myexperienceand
insight into how a nanostructure should be made give me the advantage of
knowing which is a viable nanofabrication technology and which is not. This
helpedmetoselectonlythosemostappropriatetechnologiestobeincludedin
the book. I hope the readers of the book should gain useful information and
advice when deciding which technology they should choose for their specific
applications.
Intheera,whenanyinformationcanbe‘‘googled‘‘frominternet,whowould
stillneedabook?Infact,moretitlesofprofessionalbooksarepublishedthan
everbefore.Thoughinternethasprovidedtheconvenienceoffindingrequired
information at a stroke of keyboard, it still needs a trained eye to spot the
correct and best knowledge among the vast amount information presented to
someone. I must admit that internet has helped me a great deal in gathering
informationandpreparingforthebook.IhopethatwithmytrainedeyesIhave
filteredtheusefulinformationthroughtomybook.Inaddition,thebookhas
providedreferences,weblinksandexplanationofterminologies,whichshould
serve as a ‘‘street map’’ for readers to find their way through in the internet
‘‘maze’’.
My gratitude goes to many of my colleagues and friends working at the
CentralMicrostructureFacility,RutherfordAppletonLaboratory,UK,atthe
LaboratoryofMicrofabrication,theInstituteofPhysics,ChineseAcademyof
Sciences,andattheNanoelectronicsCentreofPekingUniversity,China,where
Ialsoserveasavisitingprofessor.Manyoftheirpublishedworkhavebeencited
Preface ix
inthebook,includingworkpublishedbymanyotherexpertsindifferentfields.
My final thanks go to my family, my wife Ling Wang who herself is also an
experienced engineer workingin the micro and nanofabrication field, and my
daughters,HelenandKaty,whohavesupportedmeallalong.
Oxford ZhengCui
Contents
1 Introduction............................................. 1
1.1 Nanotechnology..................................... 1
1.2 Nanofabrication..................................... 2
1.3 PurposeoftheBook.................................. 4
References.............................................. 5
2 NanofabricationbyPhotons................................. 7
2.1 Introduction........................................ 7
2.2 PrincipleofOpticalProjectionLithography ............... 8
2.3 OpticalLithographyatShorterWavelengths .............. 13
2.3.1 DeepUV ..................................... 13
2.3.2 ExtremeUV................................... 16
2.3.3 X-ray ........................................ 20
2.4 OpticalLithographyatHighNA........................ 22
2.5 OpticalLithographyatLowk Factor ................... 30
1
2.5.1 Off-AxisIllumination(OAI)...................... 33
2.5.2 Phase-ShiftingMask(PSM) ...................... 34
2.5.3 OpticalProximityCorrection(OPC)................ 38
2.5.4 Photoresists................................... 44
2.5.5 DesignforManufacturing(DFM) ................. 53
2.5.6 DoubleProcessing.............................. 54
2.6 Near-FieldOpticalLithography ........................ 57
2.7 InterferometricOpticalLithography..................... 63
2.8 MasklessOpticalLithography.......................... 67
References.............................................. 73
3 NanofabricationbyChargedBeams........................... 77
3.1 Introduction........................................ 77
3.2 FocusingChargedParticleBeam........................ 79
3.2.1 ChargedParticleOptics.......................... 79
3.2.2 Sources....................................... 81
3.2.3 Aberrations ................................... 85
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xii Contents
3.3 ScatteringandProximityEffect......................... 89
3.3.1 ElectronScattering ............................. 89
3.3.2 ProximityEffectandCorrection................... 94
3.3.3 EffectofSecondaryElectrons..................... 99
3.3.4 Low-EnergyE-BeamLithography ................. 101
3.3.5 IonScattering ................................. 105
3.4 ResistMaterialsandProcesses.......................... 106
3.4.1 SensitivityofResistMaterials..................... 107
3.4.2 ContrastofResistMaterials...................... 112
3.4.3 ResolutionEnhancementProcesses ................ 114
3.5 IonSputteringandRedeposition........................ 117
3.6 ChargedParticlesProjectionLithography................. 120
References.............................................. 124
4 NanofabricationbyScanningProbes.......................... 129
4.1 Introduction........................................ 129
4.2 PrinciplesofSPMs................................... 130
4.3 ExposureofResists .................................. 133
4.3.1 FieldElectronEmission ......................... 133
4.3.2 ExposureofResistbySTM....................... 135
4.3.3 ExposureofResistbyNSOM..................... 139
4.4 LocalOxidationLithography .......................... 140
4.5 AdditiveNanofabrication ............................. 143
4.5.1 Field-InducedDeposition ........................ 143
4.5.2 Dip-PenNanolithography........................ 145
4.6 SubtractiveNanofabrication ........................... 147
4.6.1 ElectrochemicalEtching ......................... 147
4.6.2 Field-inducedDecomposition..................... 148
4.6.3 ThermomechanicalIndentation ................... 149
4.6.4 MechanicalScratching .......................... 150
4.7 High-ThroughputSPL................................ 153
References.............................................. 156
5 NanofabricationbyReplication .............................. 161
5.1 Introduction........................................ 161
5.2 ThermalPressNanoimprint............................ 162
5.2.1 NanoimprintStamps............................ 164
5.2.2 NanoimprintPolymers .......................... 166
5.2.3 Demolding.................................... 169
5.2.4 Alignment .................................... 172
5.3 RoomTemperatureNanoimprint ....................... 173
5.4 UV-CuredNanoimprint............................... 176
5.4.1 TransparentStamps ............................ 176
5.4.2 UVCurablePolymers........................... 180