Point defects in silicon with a titanium disilicide film and vacancy/extrinsic dislocation loop interaction

160 Pages·1996·5.4 MB·English

by  Herner, Scott Brad

POINTDEFECTSINSILICONWITHATITANIUMDISILICIDEFILMAND
VACANCY/EXTRINSICDISLOCATIONLOOPINTERACTION
By
SCOTTBRADHERNER
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOLOFTHE
UNIVERSITYOFFLORIDAINPARTL\LFULFILLMENTOFTHE
REQUIREMENTSFORTHEDEGREEOFDOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
1996
Copyright1996
by
ScottBradHerner
ACKNOWLEDGMENTS
Thisdissertationwouldnothavebeenpossiblewithouthelpfrommany
persons. Theauthoris indebted to his mentor at Bell Labs, Dr. Hans-J.
Gossmann. Dr. Gossmann not only developed and grew the doping
superlatticesamplesusedthroughoutthisstudy,butalsoprovidedmanykey
ideas andmotivationforthis work. Duringtheauthor'stwovisits to Bell
Labs(includingthefullsummerof1995),countlessphonecalls,andelectronic
mail. Dr. Gossmann gave patient mentoring to a young scientist in many
aspects, including lab techniques, the importance of quantifying error,
RutherfordBackscattering,andsoon. Dr.Gossmanneditedalmostallofthe
papersthatresultedfromthiswork,and,indoingso,taughttheauthorhow
towriteascientificpaper. Dr. Gossmann showedremarkable patience and
selflessnessthroughoutthis work. Thanksarealso dueto severalat Bell
Labs, including Dr. John Poate, the chair of the Silicon Processing
Department, Dr. Ray Tung, who performed the co-depositions. Dr. Conor
Rafferty,whoallowedtheuseofhisPROPHETsimulationprogram,andDr.
HenryLuftman,whoperformedtheSIMSanalysis. TheauthorthanksToshi
MogiofCornellUniversity,whoalsoworkedatBellLabsonnitridefilmsand
vacancydiffusivity,fornitridingmanysamplesandmanyhelpfuldiscussions.
At the University of Florida (U.F.), the author is indebted to his
advisor.Prof. KevinJones, forprovidingtheframeworkforthis project and
allowingtheauthormuchlatitudeinthedirectionittook. Prof.Jones'
iii
enthusiasmformaterialsscienceandencouragementhelpedmemaintainmy
motivationforthiswork. TheauthorexpresseshissincereappreciationtoDr.
WishyKrishnamoorthyforhisfriendship andadvice. Wishyinstructedthe
author in the use ofthe TEM and the high resolution X-ray system, and
constantlyofferedmanytechniquesinTEMandphotoprintingfromhismany
yearsexperience. Manyideas and approachesto this workwere generated
withWishy, usuallyoverthe NYTimes crossword and coffee. Wishy also
edited many of the papers that came out of this work, as well as this
dissertation. TheauthorisgratefultothestaffattheMAICfacilityatU.F.,
particularly EricLambers forhishelp withtheAugermeasurements. The
authoralso thankslab mates BrentGila andAnanthNaman forhelp and
instructionontheAFM,andformakinglifeinsideandoutsidethelabmore
enjoyable. The author is grateful to the members of my committee,
particularlyProfs.MarkLawandStephenPearton, fortheirhelpwiththis
dissertation. Theauthorsthankthe SEMATECHconsortium, the National
Science Foundation, and Lucent Technologies, all ofwhich supported this
work financially. Lastly, the author must also thank his parents, who
continuedtosupportthe author'sfurthereducation andfortheirunflagging
faithduringalongcollegecareer.
iv
TABLEOFCONTENTS
ACKNOWLEDGMENTS iii
LISTOFFIGURES vii
LISTOFTABLES xii ..t
ABSTRACT xiii
CHAPTERS
1 INTRODUCTION 1
1.1 PointDefectsandDopantDiffusion 5
1.2 Surfacevs.BulkGenerationofPointDefectsin
Silicon 9
1.3 ThinFilmsandPointDefects 12
1.4 ExtrinsicDislocationLoopsandPointDefects 20
1.5 Approach 23
2 SAMPLEPREPARATIONANDCHARACTERIZATION
TECHNIQUES 25
2.1 DopingSuperlattices 25
2.2 TransmissionElectronMicroscopy 32
2.3 AugerElectronSpectroscopy 34
2.4 AtomicForceMicroscopy 34
2.5 RutherfordBackscatteringSpectroscopy 35
2.4 WaferCurvature 35
3 POINTDEFECTSINSILICONWITH
ATITANIUMDISILICIDEFILM 37
3.1 Introduction 37
V
3.2 AntimonyandBoronDiffusioninSiliconwith 38
TitaniumasaFunctionofTemperature
AnnealedforOneHour
3.3 SIMSArtifactsandChemo-Mechanical
PolishingProcedure 49
3.4 AntimonyandBoronDiffusioninSiliconwitha
30nmTitaniumFilmAnnealedat800°C
asaFunctionofTime 57
3.5 AntimonyandBoronDiffusioninSiliconwith
DifferentThicknessesofTitanium
DepositedandAnnealedforOneHourat
850°C 65
3.6 AntimonyandBoronDiffusioninSiliconAnnealed
at850°CforOneHourwithCo-Deposited
Ti+SiorCo+Si 74
3.7 Morphologyofthefilmsfromco-deposition 79
3.8 Summary 96
4 BEHAVIOROFEXTRINSICDISLOCATIONLOOPS
INSILICONANNEALEDWITHATITANIUM
DISILICIDEORSILICONNITRIDEFILM 97
4.1 Introduction 97
4.2 AntimonyandBoronDiffusionBehaviorin
Ge'''-implantedSiliconAnnealedinNH3 98
4.3 DislocationLoopBehaviorinSiliconwith
aThermallyGrownSiliconNitrideFilm 105
4.4 DislocationLoopBehaviorinSiliconwith
aTitaniumDisilicideFilm 121
4.5 Summary 129
5 CONCLUSIONSANDRECOMMENDATIONS 130
5.1 Conclusions 130
5.2 FutureWork 134
REFERENCES 137
BIOGRAPHICALSKETCH 144
vi
1
LISTOFFIGURES
Figure page
1.1 SchematicofaCMOSFET 2
1.2 Variousdiffusionmodesinsilicon:
(a)interstitial;(b)interstitialcyor"kickout;"
and(c)vacancy 7
1.3 Estimatesof(a)C*;and(b)C*D*values 1
2.1 Diffusivitiesasafunctionoftemperatureanddoping
levelof(a)antimony;and(b)boron. Theextrinsic
diffusivitiesassumeadopinglevelof1xlO^O/cm^ 28
3.1 CrosssectionalTEMmicrographofTiSi2/TiOxNi.x
filmsonsiliconannealed840°C/1hr/forminggas 41
3.2 ElectrondiffractionpatternofTiSi2/TiOxNi.xfilms
onsiliconannealed840°C/1hr/forminggas 41
3.3 Augerspectraofthesampleannealed
800°C/1hr/forminggas 42
3.4 SIMSdepthprofilesofdopingsuperlatticesannealed
840°C/1hr/forminggas.(a)antimony;and(b)boron 44
3.5 Depthprofilesofnormalizedantimonyandboron
diffusivitiesindopingsuperlatticesannealedfor
onehouratvarioustemperatures 45
3.6 Comparisonofintrinsicdiffusivitiesfromthedoping
superlatticesandliteraturevalues 48
vii
111
3.7 AFMmicrographoftheunderlyingsiliconsurfaceafter
30nmTideposition,800°C/1hr/forminggasanneal,and
removalofthefilmbychemicaletching. Therootmean
squareroughnessis22.0nm 5
3.8 SIMSborondepthprofilefi-omtheunpohshedsample
annealed800°C/1hr/forminggas:(a)complete
(SilostisfromTiSi2growthandconsequentetching);
and(b)detailfi-omfigure3.3a 52
3.9 AFMmicrographoftheunderlyingsiliconsurfaceafter
30nmTideposition,800°C/1hr/forminggasanneal,
removalofthefilmbychemicaletching,andCMP. The
rootmeansquareroughnessis0.1nm 53
3.10 CrosssectionalTEMmicrographofdislocationloop
layerpriortoCMP:(a)beforeCMP:and(b)afterCMP 56
3.11 SihconremovalratewithCMP 56
3.12 CrosssectionalTEMmicrographofTiSi2/TiOxNi.xfilms
onsiliconannealed800°C/600min/argon 59
3.13 CrosssectionalTEMmicrographofTiSi2/TiOxNi.xfilms
onsiliconannealed800°C/15min/argon 59
3.14 SIMSdepthprofilesofantimonydopingsuperlattices
annealed800°C/60min/argon 60
3.15 SIMSdepthprofilesofantimonydopingsuperlattices
annealed800°C/600min/argon 60
3.16 Depthprofilesofnormalizedantimonydiffusivities
indopingsuperlatticeswith30nmoftitanium
annealedat800°Cforvarioustimes 6
3.17 Averagenormalizedantimonydiffusivities
indopingsuperlatticeswith30nmoftitanium
annealedat800°Cforvarioustimes 6
3.18 Gaussiandepthprofileofvacanciesassumingafinite
"pulse"ofvacanciesinjectedatt=0 64
viii
3.19 RBSspectra(glancingangle)fortheco-deposited
TiSii.8filmwithnominal312nmTithickness
beforeanneahng 67
3.20 RBSspectra(glancingangle)fortheco-deposited
TiSii.8filmwithnominal4nmTithickness
beforeanneahng 67
3.21 CrosssectionalTEMmicrographoftheannealedTiSii.g
filmwithnominal4nmTithickness
3.22 CrosssectionalTEMmicrographoftheannealedTiSii.s
filmwithnominal312nmTithickness
3.23 SIMSdepthprofilesofdopingsuperlatticesannealed
850°C/1hr/argonwithnominal4nmTi
(a)antimony;and(b)boron
3.24 Depthprofilesofnormalizedantimonydiffusivities
indopingsuperlatticesannealed850°C/1hr/argon
withvariousthicknessesofTi
3.25 Averagenormalizedantimonydiffusivitiesindoping
superlatticesannealed850°C/1hr/argonwith
variousthicknessesofTi
3.26 SIMSdepthprofilesinsilicondopingsuperlattices
annealed850°C/1hr/argonwith22nmTi:
(a)antimony;and(b)boron
3.27 Depthprofilesofnormalizedantimonyandboron
diffusivitiesindopingsuperlatticesannealed
850°C/1hr/argon 77
3.28 CrosssectionalTEMmicrographoftheas-deposited
Ti(only)filmonsilicon ^2
3.29 AugerelectronspectraoftheannealedTiSig.sfilm ®^
3.30 AugerelectronspectraoftheannealedTiSi2.2film
3.31 AugerelectronspectraoftheannealedCoSio.8film ®^
ix
3.32 CrosssectionalTEMmicrographoftheannealedCoSio.8
filmonsiUcon 84
3.33 CrosssectionalTEMmicrographsoftheannealedfilms:
(a)Ti(only)film;(b)TiSio.8film;and(c)TiSi2.2film 86
3.34 AFMmicrographoftheunderlyingsiliconsurface
afterdepositionofTiSio.8(30nmnominalTithickness),
annealedat850°/lhr/argon,andchemicallyetching
offthefilm 88
3.35 PlanviewTEMmicrographsoftheannealedfilms
ontheTi(only)sample:(a)TiOxNi-xfilm;
and(b)TiSi2film 89
3.36 PlanviewTEMmicrographsoftheannealedfilms
ontheannealedTiSi2.2sample:(a)polySifilm;
and(b)TiSi2film 90
3.37 SchematiccrosssectionoftheplanviewTEMsample 92
4.1 SIMSdepthprofilesofdopingsuperlatticesannealed
withoutanimplant,(a)antimony;and(b)boron 100
4.2 SIMSdepthprofilesofdopingsuperlatticesannealed
withanimplant,(a)antimony;and(b)boron 102
4.3 Normalizedantimonydiffusivitiesinloopsamples
withanneal#2inNH3 104
4.4 CrosssectionalTEM(brightfield,g22o)micrograph
ofthelooplayerandsiliconnitridefilm 104
4.5 CrosssectionalhighmagnificationTEM(brightfield,
g22o)micrographofthesiliconnitridefilm. Samplehas
beenannealed910°C/3hrs/NH3 108
4.6 PlanviewTEM(weakbeamdarkfield,g22o)
micrographsofsamplesannealedinvariousconditions,
(a)910°C/0.5hr/Ar;(b)910°C/3hrs/Ar;
(c)910°C/0.5hr/NHa;and(d)910°/3hrs/NHa 109
4.7 Sizedistributionsoftheloopsinsamplesannealedin
argon,(a)810°C;and(b)910°C Ill
X