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

200 Pages·2003·7.5 MB·English
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Preview Characterization of chemical interactions during chemical mechanical polishing (CMP) of copper

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

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