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InSituEllipsometryofSurfacesinanUltrahighVacuumThinFilmDepositionChamberJosephChoiDepartmentofPhysicsandAstronomy,BrighamYoungUniversityJune19,200111/26/20231DefinitionofTermsUHV(ultrahighvacuum)-Basepressure<10-9torr. (Atmosphericpressureis7.6x102torr)Ellipsometry-Opticalmeasurementtechniqueofreflection,transmission,opticalconstants,andthicknessusingpolarizationoflight.Insitu-Measurementinsidethechamberwithoutopeningtotheatmosphere.Evaporation-Depositionofmaterialbythermallyheatingitusingmetallicboatswithhighresistance.Sputtering-Depositionbybombardingpositiveionsontothematerial,andphysicallyvaporizingit.11/26/20232ResearchGoalsBuilding: BuildaUHV(ultrahighvacuum)chamberwithinsituellipsometry,sputtering,andevaporationcapabilities.Measurement/Modeling: Measureanddevelopmodelforthinfilmoxidation.11/26/20233Motivation–StudyofOxidationReflectanceofasiliconfilmcanvaryfrom70%tobelow5%dependentonoxidation.Immediateoxidizationwhenexposedtoatmosphere.(ModelofasiliconfilmproducedusingIMD©)11/26/20234ThesisDescriptionDesignandbuildingofvacuumchamberfromstainlesssteelbodymadebyVarian,Inc.–SinceApril2000.UHV,ellipsometry,deposition,procedures.Rutheniumthinfilm(

290Å)sputteredinHV(highvacuum;10-8-10-6torr).Real-timeinsituellipsometricmeasurementstoanalyzeRuthinfilmanditsoxidation.11/26/20235UHVVacuum(

10-9torr)Benefit-Purityoffilm:

-ComparisonwithHV(10-6torr):Gasflux

1cm2/sec.AchievingUHV:

-Cleanliness:Nooil;cleaningagents(hexane,methanol). -Bakeout:>250ºCtoeliminatewater,hydrogen,speeddegassing. -Parts:Minimizeo-rings,usemetal-to-metalseals. -Material:Lowoutgasrates(Aluminum,stainlesssteel). -Machining:Inertgasweldingorvacuumbrazing.11/26/20236Conflatflange-CoppersealThermocoupleHeatingtape-BakeoutCleaningagent-MethanolBakeoutpowercontrol-Variac+Transformer11/26/20237VacuumPumpsPrinciple

-Coldtrap. -Largesurfacearea.Sorptionpumps

-Atmospheretoroughingpressure(10-3torr).Cryopump

-ToUHVpressure.11/26/20238OverviewofComponentsTheEllipsometer[1]Usageofp-ands-polarizationoftheE(Electric)-field.MeasurementofΨandΔ:

Ψ:Magnitudeofp-tos-reflectanceratio.

Δ:Differenceinphaseofp-ands-reflection.ΨandΔrelatedbyreflectance:Opticalconstants,thicknessobtainablewithcomputerusingΨ,Δ.[1]J.A.WoollamCo.,Inc.,GuidetoUsingWVASE32TM.Geometryofanellipsometricexperiment,showingthep-ands-directions11/26/20239

11/26/202310OverviewofComponents(cont.)SputterGunWeuseMightyMAK4〞fromUSInc.PrincipleofOperation:[2] 1.Undervacuum,fillchamberwithnoblegas.OurchamberusesAr. 2.Byapplyingamostlynegativepotential(0.5-5kV)tothetargetmaterial,whilegroundingtheouterparts,Arispositivelyionizedandbombardsthetargetmaterial,physicallyknockingtheatomsoffontothefilm.[2]11/26/202311SputterGunMechanisminVacuumChamber11/26/202312OverviewofComponents(cont.)EvaporatorA3boatevaporatorusing4mediumcurrentfeedthroughsfromMDC.Aluminaceramicshieldstoprotectcross-contamination.PrincipleofOperation: Heatingofmetallicboatsusingcurrent;thermallyevaporatematerial.11/26/202313OverviewofComponents(cont.)SampleStage -Holdfilm.Shutter -Controlleddeposition.CrystalMonitor

(MaxTek,Inc.) -Measuredepositionrateandamount.11/26/202314OverviewofComponents(cont.)Oxygenline

-UHVleakvalve. -Controlledoxidationofsample.Argonline

-Gasmediumforplasma. -Toventchamber.O2Ar11/26/202315RutheniumThinFilmMay3,2001:Rusputteredin1x10-6torr.Real-timeinsituanalysis:inHV,Arventing,atmosphere.ImprovedRuopticalconstants.RuO2thicknessfit.Littleapparentoxidation.11/26/202316CurrentStatusBasevacuumpressure-1.5x10-7torr.Training:Evaporatorinstalledwithchromiumboat.Bakeoutandpumpdownchamber.Insituanalysisofchromium.11/26/202317CommentsonLengthofThesisMajorityofresearchwasinbuildingtheUHVsystem-overayear.Trainingpurpose:Recordingofeffortthatgoesintobuildingavacuumdepositionsystem.Understandingofproceduresandcomponents.Detailstoclarifypos