Characterization of chemical interactions during chemical mechanical polishing (CMP) of copper

200 Pages·2003·7.5 MB·English

by  Lee, Seung-Mahn

CHARACTERIZATIONOFCHEMICALINTERACTIONSDURINGCHEMICAL
MECHANICALPOLISHING(CMP)OFCOPPER
By
SEUNG-MAHNLEE
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
2003
Tomyparents,mywife,andmydaughters,fortheirloveandsupport.
ACKNOWLEDGMENTS
IwouldliketoexpressmydeepestappreciationtoDr.RajivK.Singh,myadvisor,
forhisprofessionalguidance,support,andencouragement.Theopenenvironmentthathe
hasprovidedovertheyearsthatIhaveworkedwithhimhasmadeforaverydynamic
andrewardinggraduateschoolexperience.IwouldalsoliketothankDr.BrijM.
Moudgil,Dr.StephenJ.Pearton,Dr.CammyR.Abernethy,andDr.DineshO.Shahfor
kindlyparticipatingonmydissertationcommittee.
Iwouldliketothankallthefriendsandcoworkerswhomadegraduateschoolsuch
amemorabletime.Dong-Gu,Kyu-Gong,Uday,Zhan,Mike,Wonseop,Sang-Yup,
Jaeyoung,Joodong,Won-Seok,Hano,Sang-Hyun,Hyuk-Soo,Jeremiah,Karthik,Vishal,
Nabil,Josh,Srini,Chad,Joo-Han,Jin-Ki,Chad,Kyo-Se,Seemant,andothersprovided
socialperspectivethatisalwaysnecessaryinlife.
Inaddition,Itrulythankmyfriends,whoareinKorea,Kun-Chang,Hoo-Sung,and
Nam-Junfortheirencouragementandfriendshipthrutheyears.
IwouldliketoacknowledgethefinancialsupportoftheParticleEngineering
ResearchCenter(PERC)attheUniversityofFlorida,theNationalScienceFoundation
(NSFgrant#EEC-94-02989),andtheIndustrialPartnersofthePERCforsupportofthis
research.
IwouldliketothankMargaretandGregfortheirkindsupport.Ireallyappreciate
theirhelpforeverythingtheydidforme.Iwouldalsoliketothanksupportstaffs,Gary,
111
Gill,John,andSophieinPERCfortheirdedicationandtechnicalsupport.Iwouldliketo
thankLanceKhunforhistremendoushelpinthenanoindentation.
Iwouldliketoexpressmygratitudetomyparents,Suk-JooLeeandSo-YaKim,
mybrother,Yoon-Ho,sister,Hee-Jung,parents-in-law,Sang-HakNamandJung-Soon
Lee,brothers-in-law,andtherestofmyfamilyfortheloveandsupporttheyhave
providedoverthemanyyearsofmyeducation.
Finally,withoutmywife,Jung-LyunNam,Iwouldnothavebeenabletopersevere
andsustainthelongandhardyearsofstudyawayfromfamilyandfriends.Mytwo
daughters.BoraandGah-Eun,andmywifehavebeenandremainaconstantsourceof
strength,joy,andsupportformethroughalltheseyears.Iwouldliketoexpressmy
deepestgratitudetothem.
IV
7
TABLEOFCONTENTS
Page
ACKNOWLEDGMENTS
iii
LISTOFTABLES viii
LISTOFFIGURES ix
ABSTRACT xv
CHAPTER
1. INTRODUCTION 1
Objectives 4
DissertationOutline 5
2. LITERATURESURVEY 6
InterconnectsonCircuitPerformance 6
RCTimeDelay 8
PowerConsumption 14
CircuitReliability 14
MultilevelInterconnection 15
CopperMetallization 17
AdvantagesofCopperMetallization 1
Lowerresistivity 19
Electromigrationresistance 19
Lowermanufacturingcost 22
ChallengeinIntegratingCopper 26
Lackofvolatilecoppercompound 26
Copperdiffusionintodielectriclayer 28
Low-kMaterials 29
CMP 31
Planarity 33
PlanarizationMechanisminMetalCMPProcess 37
CMPRemovalModels 43
v
3. POTENTIODYNAMICANDXPSSTUDYOFTHECHEMICALLYMODIFIED
SURFACELAYER 48
Introduction 48
Experimental 50
SamplePreparation 50
SolutionsofVariousChemicalAdditiveMixtures 52
Electrochemistry 54
X-rayphotoelectronSpectroscopy 54
ResultandDiscussion 55
ElectrochemicalBehaviorofCopper 55
ChemicalCompositionoftheChemicallyModifiedSurfaceLayer 66
Summary 73
4. THEKINETICSOFTHEFORMATIONOFTHECHEMICALLYMODIFIED
SURFACELAYERDURINGCOPPERCMPWITHINSITU
ELECTROCHEMISTRY 75
Introduction 75
Experimental 80
Chronoamperometry 80
SolutionChemistry 82
CharacterizationoftheLayer 85
ResultsandDiscussion 86
Summary 113
5. MECHANICALPROPERTIESOFTHECHEMICALLYMODIFIEDSURFACE
LAYERONTHECOPPERSURFACE 115
Introduction 115
Experimental 116
Nanoindentation 116
Result 122
pHEffect 124
TheEffectoftheConcentrationofanOxidizer 131
TheEffectoftheConcentrationofBTA 136
TheEffectoftheConcentrationofCitricAcid 139
Summary 142
6. INTERPRETATIONOFCOPPERCMPPERFORMANCEBASEDONNANO
ANDMICROSCALEINTERACTIONS 146
Introduction 146
Experimental 147
ResultsandDiscussion 147
CMPRemovalModelbasedontheNano-andMicro-ScaleInteractions....147
Thecontactareabetweenpadandwafer(Ac) 148
vi
Thenumberofparticlesparticipatinginthematerialremoval(Na) -153
Indentationdepthofsingleparticleintothewafersurface(c),,,) 154
Determinationofcopperremovalrate 161
EvaluationoftheModel 164
EffectofChemicalInteractiononCopperCMPPerformance 167
Summary 170
7. CONCLUSION 172
LISTOFREFERENCES 175
BIOGRAPHICALSKETCH 182
vii
1-
LISTOFTABLES
2-
Table page
2-1. CtohreroeultaptuitonpaorfasmyestteermslienvCelMvPari[aSbilne0s2,]withmicroandnanoscaleinteractionsand 3
3-
3-1. TargetvaluesforMicroprocessor(MPU)interconnecttechnologyaccordingto
ITRS2002update[ITR02] 7
4-
2-2. Lowresistivitymaterialsforinterconnectconductormaterials [Mur93,Ste97]....20
3. Themostpromisingcandidatesforlow-kILDmaterialsininterconnect[Chi99],
30
1. Comparisonofthepotentiodynamicparameters 62
2. ReferenceXPSparametersforcopperandcoppercompounds[Der92,Mou95]....67
1. Comparisonofcorrosionrate. 89
1
1-
LISTOFFIGURES
2-
Figure page
1. CScMhPema[tLeiec0d2,iaSgirna0m2]todepictmicroandnanoscalephenomenaoccurringduring 2
1. Timedelaycausedbyinterconnectionandgateatdifferentdevicesizes
[Mur96],Interconnectdelayisbeingdominantintotaltimedelayasthedevice
isshrinking 9
2-2. Schematicoftheclosed-packedICinterconnect 1
2-3. Capacitancesassociatedwithmetallines.Line-to-linecapacitancebecomes
dominantduetothescalingofthedevicesize[Den74] 12
2-4. Therelativesizechangeincentralprocessingunit(CPU)from
http://www.intel.com 16
2-5. Theexampleofthemultilevelinterconnect(MLI)bydualdamasceneprocess 18
2-6. Manifestationofelectromigrationdamageinaluminumfilms:(a)Hillock
formation,(b)whiskerbridgingbetweentwoconductorlines,and(c)mass
accumulationanddepletion[Vai80] 21
2-7. Copperandaluminumfailureratesduetotheelectromigration[CunOO] 23
2-8. ExpectedinterconnectRCtimedelaywithcopperandlow-k(k=2.0)deviceas
wellasaluminumandsilicadevice[Pet98] 24
2-9. Thereductionofthenumberofmetallevelswithcopperandlow-kmaterialto
achievethesameperformance[Sin98] 25
2-10.SchematicdiagramofthedualdamasceneprocessandtwostepcopperCMP
process 27
2-11.SchematicillustrationofatypicalCMPtool 32
2-12.DegreesofPlanarity;(a)Unplanarized,(b)SurfaceSmoothing,(c)Local
Planarizationand(d)GlobalPlanarization[01s93] 34
2-13.Acumulativeincreaseintopographybymulti-levelinterconnectionwithout
usingaplanarizationmethod[VieOl] 36
IX
2-14.Anexampleofthepotentiodynamicscansfortungstenwith0.5MH2SO4
[Bie98] 38
2-15.Currentrecordedforonestrokeduringthetribologicalexperimentsforanodic
appliedpotential(+2V)in0.5MH2SO4foraspheremotioncycleof0.2second
2- [BieOO] 40
32--16.aWneaalrutmriancakbvaollluamte5vHsz.awpiptlhie5dNpoltoeandtiaaglaifnosrteaxpfeirxiemdefnltatstcuonngdsutcetnesdabmpylreubbing
immersedin0.5MH2SO4for25minutes[BieOO] 41
17.Anodiccurrentvs.timetransientsfortungstenmeasuredin0.5MH2SO4at
severalpotentials[BieOO] 42
1. Across-sectionalSEMpictureofas-receivedwafer(a);pre-existedoxidelayer
ontheas-receivedcopperwaferobservedbyTEM(b);andsurfacelayer
thicknessbydippingcoppersamplesinthreeetchingsolutions,measuredby
ellipsometry(c) 51
3-2. Potential-pHdiagramofcopper-nitricacid/hydrogenperoxide-watersystem 53
3-3. Thetypicalpotentiodynamiccurvewithpassivatedlayeronthemetal surface 56
3-4. Thepotentiodynamiccurvesofcopperin5%hydrogenperoxideatdifferentpH...58
3-5. Thepotentiodynamiccurvesofcopperinvariousconcentrationofhydrogen
3- peroxideatpH7 59
43--6. BTAconcentrationeffectontheanodicelectrochemicalbehaviorofcopperin
5%hydrogenperoxideatpH7 60
3-7. Thepotentiodynamiccurvesmeasuredincitricacidbasedsolutions(a)and
pcietrroicxiedfefeactndon10thmeManoBdTicAealtecptHro7chemicalbehaviorofcopperin5%hydrogen 61
3-8. TheXPSspectraoftheas-receivedandpre-treatedcoppersurface:(a)surface
analysis,(b)CuAugerLMMline,and(c)Olslineonthecoppersamples 68
3-9. XPSanalysesoncoppersamplesdippedin3differentsolutionsatpH7:(a)5%
h5y%drhoygdernogpeenropxeirdoexiondley;an(db)1500%mhyMdrcoitgreincapceirdoxideandlOmMBTA;and(c) 69
10.mThMeXciPtrSicaancaildysaitspoHn7afcoorpp1emrinsuatmep,lew,itdhipdpiefdferinen5t%sphutytderroigngentipmeeroxideand100 72
1. SchematicofmetalCMPremovalmechanism 77
x