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VAPORPHASE TREATMENT OF DELECTRIC MATERALS BACKGROUND OF THE INVENTION 1.FieldoftheInvention TheVoidsinturnmaycauseanincreaseinleakagecurentat elevatedVoltagesandreductioninbreakdownVoltage.The presentinventiondescribesawaytoreducethedamageand resultingisuesbytreatingthewaferswithsilylatingagents byavapordepositionprocesssuchaschemicalvapordepo sition. US 7,678,712B2 1. 2 TheinventionconcernsamethodforapplyingaSurface Onewaytoapproachthischallengeistorepairthedam modificationagentcompositiontoorganosilicateglas dielectricfilms.Moreparticularly,theinventionpertainstoa methodfortreatingasilicateororganosilicatedielectricfilm10 onasubstrate,whichfilmeithercomprisessilanolmoietiesor hashadatleastsomepreviouslypresentcarboncontaining moietiesremovedtherefrom.Thetreatmentaddscarboncon tainingmoietiestothefilmand/orsealssurfaceporesofthe film,whenthefilmisporous.Thesesurfacemodifiedfilms15 areusedasinsulatingmaterialsinthemanufactureofsemi conductordevicessuchasintegratedcircuits(“ICs'),inorder toensurelowdielectricconstantandstabledielectricproper tiesinthesefilms. 2.DescriptionoftheRelatedArt Assemiconductordevicesscaletolowertechnology nodes,therequirementforlowerandlowerdielectricconstant (k)hasbeenidentifiedtomitigateRCdelay.Similarly,as featuresizesinintegratedcircuitsarereduced,problemswith powerconsumptionandsignalcros-talkhavebecome25 increasinglydificulttoresolve.Toachievelowerdielectric constant(2.6-3.0)indenseinorganicmaterials,carbonhas beenaddedtoreducethepolarizabilitythusreducingthe dielectric constant. To achieve ultra low dielectric constant (<2.4)materials,porosityisaddedtothecarbon-richdense30 matrix.Whiletheintroductionofcarbonandporosityhave reducedthedielectricconstant,newchallengesduringback endofthelineprocessinghavealsobeenidentified.Specifi calyduringetchingandashing,reactivegaseshavebeen foundtodamagethecarbonattheSurfaceofdensematerials.35 Porousfilmshavinglowdielectricconstantshaveevenmore deleteriousefectsfromreactiveetchandashgasesdueto difusionthroughthefilm,whichcausesagreaterextentof damageattheinternalporewals.Oncethecarbonhasbeen damaged,thefilmsrehydroxylateandhydrogenbondwith40 water.Becausewaterhasadielectricconstantof70,Small amounts that are absorbed for dense materials and adsorbed forporousmaterialscausethedielectricconstanttogoup significantly.Also,porousmaterialstendtoVoidaftercopper Inaddition,itisalsoknownthatexistenceoftheSiO— annealingduetothehightensilestresfieldswhichwil45 destroydeviceyields.Noneoftheseareacceptableandlead tounviablematerials. SiR OSilinkage(wheretheSiRisoneexampleofasur facemodificationfunctionalitywithinthematrix),thatthe modulusoftheporousmaterialshouldimprove.Modulus retentionandimprovementisrequiredformostporousmate rialstowithstandimposedstreses.TheSurfacemodifying linkage,e.g.,adimethylsilyllinkage,clearlyimprovesthe modulus.Ifappliedtoweakenedareasofthesilicate,an improvementofthematerialtoexternalstresisexpected. Itisbelievedthattheintegrationoflowdielectricconstant materialsforinterleveldielectric(ILD)andintermetaldielec tric(IMD)aplicationswilhelptosolvetheseproblems.50 Whiletherehavebeenpreviousefortstoapplylowdielectric constantmaterialstointegratedcircuits,thereremainsalong standingneedintheartforfurtherimprovementsinprocess Thesurfacemodificationtreatmentperformedafterdielec ingmethodsandintheoptimizationofboththedielectricand mechanicalpropertiesofSuchmaterials.DeviceScalingin55 futureintegratedcircuitsclearlyrequirestheuseoflow dielectricconstantmaterialsasapartoftheinterconnect structure. Most candidates for low dielectric constant mate rialsforuseinsub-100nmgenerationICsarecarboncon TheSurfacemodifyingtreatmentisconductedbyexposing tainingSiOfilmsformedbyeitherCVDorspin-onmethods.60 DuringSubsequentprocessingsteps,suchasplasmaetching andphotoresistremovalusingplasmaorwetstripmethods, significantdamageoccurstotheselow-kmaterials,that causesfluorineaditionandcarbondepletionfromthelow-k materialadjacenttotheetchedsurface.Inaditiontoahigher65 efectivedielectricconstant,theresultantstructuresaresus ceptibletoVoidformation,outgassingandblisterformation. thewaferSurfacetothesilylatingagentinliquidorgasform foraperiodsuficienttocompletethereactionwiththedam agedlowdielectricconstantregion.Optionaly,furthertreat mentscanbedone,e.g.ahightemperaturebaketoremove remainingsolvent,excessSurfacemodificationagent,and by-products.Also,optionaly,awetcleaningoperationcanbe performedimmediatelyaftertheSurfacemodificationagent aplication,orafterthebakingstep,usingacommercially agedareaondenseSurfaces,orinthecaseofporousmaterials ontheinternalporewalswithare-methylatingcompound caledaSurfacemodificationagent.Surfacemodification agentsreactwithre-hydroxylatedSurfacesandre-alkylateor re-arylatethemwhichin-turnrestoresthedielectricconstant. InthecaseofporousinternalporewallSurfaces,there methylationpreventsvoidformation.Manytimes,theuseof aSurfacemodificationagentallowsforconventionaletchand ashprocessestobeutilizedwithlowandultralowdielectric constantmaterials.Thetreatmentcouldresultinreplenish mentofcarbontothelow-kfilm,usualyrestoringhydropho bicityandresistancetofurtherdamageduringawetcleaning operation.Aditionaly,itwouldbedesirableiftherepaired low-kmaterialwasfoundtoberesistanttovoidformation, whichgenerallyoccursinuntreatedporouslowdielectric inter-leveldielectricregionsduringcopperannealingpro ceses.Silylatingagents('surfacemodificationagents')can methylatethesurfaceofSiO,basedmaterials.Contemplated exposureincludesvaporexposurewithorwithoutplasma. Normally,SiCOHbasedporouslow-kmaterialsaresuscep tibletoVoidformationinILDduringCudamasceneprocess ing.AfteraSurfacemodificationagenttreatment,theresult ingstructureissignificantlymoreresistanttoVoidformation. Withoutbeingboundtoanyspecifictheoryormechanism,it isbelievedthatplasmadamagecausescarbondepletioninthe dielectric,byreplacingSi-CHbondswithSiOHbonds. Indamagedporousdielectrics,theporesurfaceisnowcov eredwithSi OHbonds.Inthepresenceoftensilestres (suchasafterCuanealing),adjacentSi-OHgroupscan condense,thuscausinglocaldensification.Theevolving reactionproductsandthestretchingofthemoleculesdueto thenewlinksformed,causesVoidstooccurnearthecenterof theILDspace.Surfacemodificationagentspreventvoidfor mationbyreplacingmostSiOHbondsbySi-OSiRX bonds,whichavoidcondensationreactions.Thereforevoid formationdoesnotoccur. trictrenchandviaformationandetchingandashingsteps repairscarbondepletionanddamagetothelow-kmaterials. Bythismeans,voidsaredeterredandthelatercanwithstand internalstresescausedbyannealingtreatmentstothemetal filingthetrenchesandvias.PDF Image | VAPOR PHASE TREATMENT OF DELECTRIC MATERALS
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