化学气相沉积英文相关介绍

AnumberofformsofCVDareinwideuseandarefrequentlyreferencedintheliterature.Theseprocessesdifferinthemeansbywhichchemicalreactionsareinitiated(e.g.,activationprocess)andprocessconditions.Classifiedbyoperatingpressure:oAtmosphericpressureCVD(APCVD)–CVDprocessesatatmosphericpressure.oLow-pressureCVD(LPCVD)–CVDprocessesatsubatmosphericpressures.[1]Reducedpressurestendtoreduceunwantedgas-phasereactionsandimprovefilmuniformityacrossthewafer.MostmodernCVDprocessesareeitherLPCVDorUHVCVD.oUltrahighvacuumCVD(UHVCVD)–CVDprocessesataverylowpressure,typicallybelow10−6Pa(~10−8torr).Notethatinotherfields,alowerdivisionbetweenhighandultra-highvacuumiscommon,often10−7Pa.Classifiedbyphysicalcharacteristicsofvapor:oAerosolassistedCVD(AACVD)–ACVDprocessinwhichtheprecursorsaretransportedtothesubstratebymeansofaliquid/gasaerosol,whichcanbegeneratedultrasonically.Thistechniqueissuitableforusewithnon-volatileprecursors.oDirectliquidinjectionCVD(DLICVD)–ACVDprocessinwhichtheprecursorsareinliquidform(liquidorsoliddissolvedinaconvenientsolvent).Liquidsolutionsareinjectedinavaporizationchambertowardsinjectors(typicallycarinjectors).ThentheprecursorvaporsaretransportedtothesubstrateasinclassicalCVDprocess.Thistechniqueissuitableforuseonliquidorsolidprecursors.Highgrowthratescanbereachedusingthistechnique.Plasmamethods(seealsoPlasmaprocessing):oMicrowaveplasma-assistedCVD(MPCVD)oPlasma-EnhancedCVD(PECVD)–CVDprocessesthatutilizeplasmatoenhancechemicalreactionratesoftheprecursors.[2]PECVDprocessingallowsdepositionatlowertemperatures,whichisoftencriticalinthemanufactureofsemiconductors.oRemoteplasma-enhancedCVD(RPECVD)–SimilartoPECVDexceptthatthewafersubstrateisnotdirectlyintheplasmadischargeregion.Removingthewaferfromtheplasmaregionallowsprocessingtemperaturesdowntoroomtemperature.AtomiclayerCVD(ALCVD)–Depositssuccessivelayersofdifferentsubstancestoproducelayered,crystallinefilms.SeeAtomiclayerepitaxy.CombustionChemicalVaporDeposition(CCVD)–nGimat'sproprietaryCombustionChemicalVaporDepositionprocessisanopen-atmosphere,flame-basedtechniquefordepositinghigh-qualitythinfilmsandnanomaterials.HotwireCVD(HWCVD)–alsoknownascatalyticCVD(Cat-CVD)orhotfilamentCVD(HFCVD).Usesahotfilamenttochemicallydecomposethesourcegases.[3]Metalorganicchemicalvapordeposition(MOCVD)–CVDprocessesbasedonmetalorganicprecursors.HybridPhysical-ChemicalVaporDeposition(HPCVD)–Vapordepositionprocessesthatinvolvebothchemicaldecompositionofprecursorgasandvaporizationofasolidsource.RapidthermalCVD(RTCVD)–CVDprocessesthatuseheatinglampsorothermethodstorapidlyheatthewafersubstrate.Heatingonlythesubstrateratherthanthegasorchamberwallshelpsreduceunwantedgasphasereactionsthatcanleadtoparticleformation.Vaporphaseepitaxy(VPE)UsesIntegratedcircuitsVariousCVDprocessesareusedforintegratedcircuits(ICs).Particularmaterialsaredepositedbestunderparticularconditions.PolysiliconPolycrystallinesiliconisdepositedfromsilane(SiH4),usingthefollowingreaction:SiH4→Si+2H2ThisreactionisusuallyperformedinLPCVDsystems,witheitherpuresilanefeedstock,orasolutionofsilanewith70–80%nitrogen.Temperaturesbetween600and650°Candpressuresbetween25and150Payieldagrowthratebetween10and20nmperminute.Analternativeprocessusesahydrogen-basedsolution.Thehydrogenreducesthegrowthrate,butthetemperatureisraisedto850oreven1050°Ctocompensate.Polysiliconmaybegrowndirectlywithdoping,ifgasessuchasphosphine,arsineordiboraneareaddedtotheCVDchamber.Diboraneincreasesthegrowthrate,butarsineandphosphinedecreaseit.SilicondioxideSilicondioxide(usuallycalledsimplyoxideinthesemiconductorindustry)maybedepositedbyseveraldifferentprocesses.Commonsourcegasesincludesilaneandoxygen,dichlorosilane(SiCl2H2)andnitrousoxide(N2O),ortetraethylorthosilicate(TEOS;Si(OC2H5)4).Thereactionsareasfollows[citationneeded]:SiH4+O2→SiO2+2H2SiCl2H2+2N2O→SiO2+2N2+2HClSi(OC2H5)4→SiO2+byproductsThechoiceofsourcegasdependsonthethermalstabilityofthesubstrate;forinstance,aluminiumissensitivetohightemperature.Silanedepositsbetween300and500°C,dichlorosilaneataround900°C,andTEOSbetween650and750°C,resultinginalayeroflow-temperatureoxide(LTO).However,silaneproducesalower-qualityoxidethantheothermethods(lowerdielectricstrength,forinstance),anditdepositsnonconformally.AnyofthesereactionsmaybeusedinLPCVD,butthesilanereactionisalsodoneinAPCVD.CVDoxideinvariablyhaslowerqualitythanthermaloxide,butthermaloxidationcanonlybeusedintheearlieststagesofICmanufacturing.Oxidemayalsobegrownwithimpurities(alloyingordoping).Thismayhavetwopurposes.Duringfurtherprocessstepsthatoccurathightemperature,theimpuritiesmaydiffusefromtheoxideintoadjacentlayers(mostnotablysilicon)anddopethem.Oxidescontaining5–15%impuritiesbymassareoftenusedforthispurpose.Inaddition,silicondioxidealloyedwithphosphoruspentoxide(P-glass)canbeusedtosmoothoutunevensurfaces.P-glasssoftensandreflowsattemperaturesabove1000°C.Thisprocessrequiresaphosphorusconcentrationofatleast6%,butconcentrationsabove8%cancorrodealuminium.Phosphorusisdepositedfromphosphinegasandoxygen:4PH3+5O2→2P2O5+6H2Glassescontainingbothboronandphosp