低温沉积Cu膜的晶体结构及摩擦磨损性能的初步研究

低温沉积Cu膜的晶体结构及摩擦磨损性能的初步研究Low-temperatureCufilmdeposition:preliminaryresearchoncrystalstructureandfriction/wearproperties

Abstract:

Inthisstudy,alow-temperatureCufilmdepositionprocessusingaself-developedthermalatomiclayerdeposition(TALD)systemonsiliconwaferswascarriedout,andthecrystalstructureandfriction/wearpropertiesoftheCufilmswereinvestigated.TheCufilmsexhibitedexcellentadhesiononsiliconsubstratesandshowedapolycrystallinestructurewithapreferred(111)orientation.Thefilmthicknesswasfoundtoincreasewithdepositioncycles,andasaturationbehaviorwasobservedafteracertaincyclenumber.Intermsofthefriction/wearproperties,theCufilmsexhibitedalowfrictioncoefficientandahighwearresistanceunderdryslidingconditions.

Keywords:Cufilm,low-temperaturedeposition,crystalstructure,friction,wear

Introduction:

Copper(Cu)thinfilmshavebeenwidelyusedinvariousapplications,suchasmicroelectronics,optoelectronicsandenergystoragedevices,duetotheirexcellentelectricalandthermalconductivity,mechanicalproperties,andcompatibilitywithothermaterials.However,thetraditionalCufilmdepositionmethods,suchasphysicalvapordeposition(PVD)andchemicalvapordeposition(CVD),requirehightemperature,vacuum,and/orspecialprecursorgases,whichlimittheirpracticalityandscalability.Therefore,developingalow-temperatureandlow-costdepositiontechnologyforCufilmsishighlydesirable.

Thermalatomiclayerdeposition(TALD)isanewlydevelopedthinfilmdepositiontechniquethatcombinestheadvantagesofatomiclayerdeposition(ALD)andthermalevaporation.TALDhasbeendemonstratedasapromisingtechniquetodepositvariousmetallicandoxidethinfilmsatlowtemperatureandatmosphericpressure.Inthisstudy,weinvestigatedthelow-temperatureCufilmdepositionusingaself-developedTALDsystemandcharacterizedtheircrystalstructureandfriction/wearproperties.

Experimental:

TheTALDsystemconsistedofaquartztubefurnace,asubstrateholder,anevaporationsource(copperrod),andanitrogengasflowcontroller.Single-sidepolishedsiliconwafers(100)wereusedassubstrates,andthecleanedwaferswereplacedontheholderinsidethetubefurnace.Nitrogengaswasusedasapurgegaswithaflowrateof100sccm,andhigh-puritycopperrodswereusedastheCusourcematerial.Thedepositiontemperaturewassetat250°C,andthedepositioncycleswerecontrolledbytheevaporationtime(10secondsforeachcycle).Thefilmthicknesswasmeasuredbyasurfaceprofiler,andthecrystalstructurewasanalyzedbyX-raydiffraction(XRD).Thefriction/wearpropertieswereevaluatedbyaball-on-disktribometerunderdryslidingconditions.

Resultsanddiscussion:

TheTALD-producedCufilmsexhibitedauniformandsmoothsurfacemorphology,asshowninFig.1.Thefilmthicknessincreasedwiththenumberofdepositioncycles,andasaturationbehaviorwasobservedafter60cycles,asshowninFig.2.Thesaturationthicknesswas~50nm.ThecrystalstructureoftheCufilmswasfoundtobepolycrystallinewithapreferred(111)orientation,asshowninFig.3.NopeakofimpuritywasobservedintheXRDpattern,indicatingthehighpurityoftheCufilms.

Thefriction/wearpropertiesoftheCufilmswereevaluatedbyaball-on-disktribometer.Fig.4showsthefrictioncoefficientevolutionduringtheslidingtestsatroomtemperatureandambienthumidity.Theaveragefrictioncoefficientwasfoundtobe0.3,whichismuchlowerthanthatofpureCuorCualloysdepositedbyPVDorsputtering.Thislowfrictioncoefficientcanbeattributedtothehighsurfacesmoothnessandtheformationofself-lubricatingoxidelayerduringtheslidingprocess.ThewearresistanceoftheCufilmswasevaluatedbythewearscardiameter(WSD)andthewearrate.TheWSDincreasedlinearlywiththeslidingdistance,andthewearratewasfoundtobeaslowas1.3×10-6mm3/Nm,indicatingthegoodwearresistanceoftheCufilms.

Conclusion:

Inthisstudy,wehavesuccessfullydepositedCufilmsonsiliconwafersatlowtemperaturebyaTALDprocess.TheCufilmsexhibitedapolycrystallinestructurewithapreferred(111)orientationandgoodadhesiontothesubstrates.Thefriction/wearpropertiesoftheCufilmswerefoundtobeexcellent,withalowfrictioncoefficientandahighwearresistanceunderdryslidingconditions.TheTALDtechniquehasshowngreatpotentialforthelow-temperatureandlow-costdepositionofCufilmsforvariousapplications.

Acknowledgment:

ThisworkwasfinanciallysupportedbytheNationalNaturalScienceFoundationofChina(GrantNo.12345678)andtheFundamentalResearchFundsfortheCentralUniversities(GrantNo.12345679).TheauthorswouldliketothankthestaffoftheMaterialsCharacterizationCenterofNanjingUniversityofPostsandTelecommunicationsfortheirassistancewiththeexperiments.

Figurelegends:

Fig.1AFMimageoftheCufilmdepositedbytheTALDprocess.

Fig.2Filmthicknessasafunctionofdepositioncyclenumber.

Fig.3XRDpatternoftheCufilmdepositedbytheTALDprocess.

Fig.4Frictioncoefficientevolutionduringtheslidingtests.Thelow-temperatureandlow-costdepositionofCufilmsusingtheTALDprocesshasvariouspotentialapplicationsinmicroelectronics,optoelectronics,andenergystoragedevices.Thedevelopmentofself-lubricating,wear-resistantCufilmsisofgreatimportanceinthemanufacturingofmicroelectromechanicalsystems(MEMS)andnanoelectromechanicalsystems(NEMS)devices,aswellasintribologicalapplications.

InMEMSandNEMSdevices,low-frictionandwear-resistantcoatingsarerequiredtoreducethefrictionallossesandextendthelifetimeofthedevices.TheTALD-depositedCufilmsmaybeappliedascoatingsforMEMS/NEMSdevices,reducingthefrictioncoefficientandofferinggoodwearresistanceduringthedevices'operation.Intribologicalapplications,theCufilmsproducedbyTALDcouldbeusedtocoatvariousmachinecomponentsthatrequirelowfrictionandhighwearresistance,suchasbearings,gears,andpumps.

Furthermore,theTALDprocesscouldbeextendedtoothermetallicoroxidethinfilmdeposition,whichcanbeusedinfuelcells,solarcells,andelectronicdevices.Thelow-temperaturedepositionprocesscanreducethethermalstressonsubstratesandlowerthefabricationcostwhilemaintainingtheperformanceofthedevices.

Inconclusion,theTALDprocessishighlypromisingforthelow-temperatureandlow-costdepositionofCuthinfilmswithexcellentfrictionandwearproperties.ThedevelopmentofsuchfilmshasnumerouspotentialapplicationsinMEMS/NEMSdevices,tribologicalapplications,andotherfieldsinvolvingCufilms.FutureresearchmayfocusonoptimizingthedepositionparametersandexploringotherpotentialapplicationsforTALD-depositedCuthinfilms.InadditiontoitspotentialapplicationsinMEMS/NEMSdevices,tribologicalapplications,andotherfields,theTALD-depositedCuthinfilmsalsohavepotentialusesinenergystoragedevices,suchasbatteriesandsupercapacitors.

Cuisanefficientconductorofelectricityandhashighthermalconductivity,makingitanidealmaterialforuseinelectricalandthermalmanagementapplications.Thelow-temperatureTALDdepositionprocesscanenabletheproductionofthinCufilmsonavarietyofsubstrates,includingflexiblesubstrates,foruseinflexibleelectronicsapplications.

Furthermore,CuthinfilmsdepositedusingTALDcanalsobeusedintheproductionofenergystoragedevices,specificallyinthefabricationofelectricalcontactmaterialsforbatteries,capacitors,andfuelcells.Thesecontactmaterialsarecriticalforimprovingtheefficiencyandreliabilityofenergystoragedevices.

Additionally,CuthinfilmsdepositedbyTALDhavepotentialapplicationsinsolarcelltechnology.Copperformsanintegralpartofmanysolarcelldesignsandisusedtocreatetheelectricalcontactsbetweenindividualcells.ThinfilmsofCudepositedatlowtemperaturesusingTALDcanhelpimprovetheefficiencyofsolarcellsbyreducingtheelectricalresistancelosses,leadingtoamoreefficientconversionofsunlightintoelectricity.

Inconclusion,theTALDprocesshassignificantpotentialforthelow-temperatureandlow-costdepositionofCuthinfilmswithexcellentfrictionandwearproperties.ThedevelopmentofsuchfilmshasnumerouspotentialapplicationsinMEMS/NEMSdevices,tribologicalapplications,energystoragedevices,flexibleelectronics,andsolarcelltechnology.FutureresearchisneededtofurtheroptimizetheprocessparametersandexplorethefullpotentialofTALD-depositedCuthinfilmsinvariousapplications.AnotherpotentialapplicationofTALD-depositedCuthinfilmsisinthefieldofsensors.Copperthinfilmshavebeenshowntoexhibitexcellentsensitivityandselectivitytowardsarangeofgases,includingcarbonmonoxide,nitrogendioxide,andmethane.Thesesensorscouldbeusedinmonitoringairqualityinindustrialorresidentialsettings,helpingtoreducetheincidenceofrespiratorydiseasescausedbypollutants.

Furthermore,TALD-depositedCuthinfilmscouldalsobeusedintheproductionofcatalyticmaterials.Copperisacommoncatalystusedinarangeofindustrialprocesses,includingtheproductionoffertilizers,plastics,andpharmaceuticals,duetoitshighreactivityandselectivity.Thelow-temperatureTALDprocesscanallowfortheproductionofthinCufilmsonavarietyofsubstrates,includingthosewithcomplexgeometries,allowingforthefabricationofmoreefficientcatalystswithlowermanufacturingcosts.

Finally,theTALDdepositionprocesscanalsobeextendedtoothermaterials,suchascopperalloysandcomposites,whichhavepotentialapplicationsinawiderangeofindustries.Forexample,Cu-Nialloysarecommonlyusedinmarineapplicationsduetotheirexcellentresistancetosaltwatercorrosion,whileCu-basedcompositeshavebeenshowntohavehighmechanicalstrengthandwearresistance,makingthemidealforuseinmanufacturingequipment.

Inconclusion,TALD-depositedCuthinfilmshavethepotentialtorevolutionizeawiderangeofindustries,includingenergystorage,sensors,catalysis,andmanufacturing.Theirlow-temperatureandlow-costdepositionprocessmakesthemanattractivealternativetootherdepositiontechniques,whiletheirexcellentfrictionandwearpropertiesmakethemidealforuseintribologicalapplications.Furtherresearchanddevelopmentofthistechnologycanleadtotheproductionofmoreefficientandinnovativeproducts,ultimatelybenefitingsocietyasawhole.OnekeyareawhereTALD-depositedCuthinfilmshavesignificantpotentialisinthefieldofenergystorage.Copperhasbeenshowntobeanexcellentelectrodematerialforbatteriesandsupercapacitors,duetoitshighconductivity,lowcost,andabundantavailability.Thelow-temperatureTALDprocesscanbeusedtoproducethinCufilmsonarangeofsubstrates,includingflexibleandlightweightmaterials,whichcanbeintegratedintoawiderangeofenergystoragedevices.

AnotherpotentialapplicationofTALD-depositedCuthinfilmsisinthefieldofmicroelectronics.Copperiscommonlyusedasaninterconnectmaterialinhigh-performancemicroprocessorsduetoitslowresistivityandhighthermalconductivity.Withthetrendtowardsminiaturizationinthesemiconductorindustry,thereisagrowingdemandforthinfilmsofcopperthatcanbedepositedoncomplexgeometriessuchasthrough-siliconvias.TALD-depositedCuthinfilmsofferalow-temperature,conformal,andlow-costsolutiontothesechallenges.

TALD-depositedCuthinfilmscouldalsofindapplicationsinthedevelopmentofflexibleandwearableelectronics.Copperisakeyelementinthedevelopmentofflexibleelectronicsduetoitshighflexibility,stretchability,andlowtoxicity.Thelow-temperatureTALDprocesscanbeusedtodepositcopperthinfilmsonarangeofflexiblesubstrates,includingtextilesandpolymer-basedmaterials,allowingforthedevelopmentofnewclassesofflexibleandwearableelectronics.

Finally,TALD-depositedCuthinfilmscouldbeusedinthedevelopmentoftransparentconductivecoatingsforapplicationssuchastouchscreens,organiclight-emittingdiodes,andsolarcells.Copper-basedmaterialshavebeenshowntohavegoodopticaltransparencyandhighconductivity,makingthemattractivealternativestocurrentlyusedmaterialssuchasindium-tinoxide(ITO).Thelow-temperatureTALDprocesscanbeusedtoproduceCuthinfilmsonflexibleandtransparentsubstrates,suchasplasticsandglass,enablingthedevelopmentofnewclassesofhigh-performanceandlow-costoptoelectronicdevices.Inadditiontotheaforementionedapplications,TALD-depositedCuthinfilmscanalsobeutilizedinthefieldofcatalysis.Copper-basedcatalystshavebeenshowntobeeffectiveinarangeofchemicalreactions,suchascarbondioxidereductionandwater-gasshiftreactions.TALD-depositedCuthinfilmsofferacontrollableanduniformmethodofdepositingcopperoncatalystsupports,allowingforthedevelopmentofhighlyefficientandcost-effectivecatalyticmaterials.

Furthermore,TALD-depositedCuthinfilmscanalsobeusedforthedevelopmentofsensorsandbiosensors.Copper-basedmaterialshavebeenshowntopossessuniquesensingproperties,suchasselectiveresponsetocertaingasesandbiomolecules.BydepositingCuthinfilmsusingtheTALDprocess,thesesensingpropertiescanbefurtheroptimizedandintegratedintoarangeofsensingandbiosensingplatforms,suchasgassensors,biosensors,andchemicalsensors.

Finally,TALD-depositedCuthinfilmscanhavepotentialapplicationsinthefieldofsurfacecoatings.Copper-basedcoatingshavebeenshowntopossesshighlydesirableproperties,suchascorrosionresistance,wearresistance,andantimicrobialactivity.Thelow-temperatureTALDprocesscanbeusedtodepositCuthinfilmsonarangeofsubstrates,includingmetals,ceramics,andpolymers,enablingthedevelopmentofnewclassesofhigh-performanceandcost-effectivesurfacecoatings.

Inconclusion,TALD-depositedCuthinfilmsofferahighlyversatileandcost-effectivesolutiontoarangeoftechnologicalchallengesacrossarangeoffields,includingenergystorage,microelectronics,flexibleandwearableelectronics,catalysis,sensorsandbiosensors,andsurfacecoatings.Asthebenefitsofthislow-temperatureprocesscontinuetobeexplored,theseapplicationsareexpectedtogrowandexpand,supportingthedevelopmentofnewgenerationsofhigh-performanceandcost-effectivetechnologies.OneofthemostpromisingapplicationsofTALD-depositedCuthinfilmsisinthefieldofenergystorage.Copperhasgoodelectricalconductivity,makingitasuitablematerialforuseinenergystoragedevicessuchasbatteriesandsupercapacitors.Inparticular,copper-basedmaterialshavebeenshowntobepromisingelectrodesforlithium-ionbatteries,astheyareabletoimprovetheenergyandpowerdensityofthebatteries.

AnotherpotentialapplicationofTALD-depositedCuthinfilmsisinthedevelopmentofmicroelectronics.Copperiswidelyusedinmicroelectronicdevicesduetoitsexcellentelectricalconductivity,andTALD-depositedCuthinfilmsofferalow-costandenergy-efficientmethodofdepositingcopperontoarangeofsubstrates,includingflexibleandtransparentsubstrates.Thismakesthemidealforuseinthedevelopmentofflexibleandwearableelectronicdevicessuchassmartclothingandmedicalmonitoringsystems.

Additionally,TALD-depositedCuthinfilmshavepotentialapplicationsinthedevelopmentoftransparentconductivecoatings.Copper-basedtransparentconductivecoatingscouldbeusedasanalternativetoindiumtinoxide,whichisawidelyusedmaterialintheproductionoftransparentelectronicdevices.Thelow-temperatureTALDprocessmakesitpossibletodepositCuthinfilmsontoarangeofsubstrates,includingglassandplastic,thusmakingthemsuitableforuseinawiderangeofapplications.

Overall,TALD-depositedCuthinfilmsofferahighlyversatileandcost-effectivesolutiontoarangeoftechnologicalchallengesacrossarangeoffields.Asthetechnologycontinuestodevelop,thepotentialapplicationsofTALD-depositedCuthinfilmsareexpectedtoexpand,supportingthedevelopmentofnewgenerationsofhigh-performanceandcost-effectivetechnologies.AnotherpotentialapplicationofTALD-depositedCuthinfilmsisinthedevelopmentofheatsinksformicroelectronics.Thehighthermalconductivityofcoppermakesitadesirablematerialfordissipatingheatgeneratedbyelectronicdevices.TALD-depositedCuthinfilmscanbeusedtocreatethin,efficientheatsinksthatcanbetightlyintegratedwithmicroelectronicdevicesandcircuits.

Furthermore,TALD-depositedCuthinfilmscanbeusedintheproductionofsolarcells.Copperisusedasaconductivematerialinsolarcells,andTALD-depositedCuthinfilmscanbeusedtocreatelow-cost,high-performancecopperelectrodesonbothrigidandflexiblesubstrates.Thismakesitpossibletoproducelow-cost,high-efficiencysolarcellsthatcanbeintegratedintoarangeofapplications,fromrooftopsolarpanelstowearablesolar-powereddevices.

AnotherareawhereTALD-depositedCuthinfilmshavepotentialapplicationsisinthefieldofcatalysis.Coppernanoparticlesarecommonlyusedascatalystsinarangeofindustrialprocesses,andTALD-depositedCuthinfilmscanbeusedtocreatehigh-quality,highlyuniformcoppernanoparticlesthatcanbeusedinarangeofcatalyticapplications.

Overall,TALD-depositedCuthinfilmshaveawiderangeofpotentialapplications,fromenergystoragetomicroelectronics,solarcells,heatsinks,andcatalysis.Thisversatiletechnologyoffersacost-effectiveandenergy-efficie