多片垂直HWLPCVD系统生长的3C-SiC异质外延膜的研究

1、Multi-wafer3C-SiCthinfilmsgrownonSi(100)inaverticalHWLPCVDreactor󰀃YanGuoguo(闫果果)1;󰂎,SunGuosheng(孙国胜)1,WuHailei(吴海雷)1,WangLei(王雷)1,ZhaoWanshun(赵万顺)1,LiuXingfang(刘兴昉)1,ZengYiping(曾一平)1,andWenJialiang(温家良)21Institute2ChinaofSemiconductors,ChineseAcademyofSciences,Beijing100083,ChinaElec

2、tricPowerResearchInstitute,Beijing100192,ChinaAbstract:Wereportthelatestresultsofthe3C-SiClayergrowthonSi(100)substratesbyemployinganovelhome-madehorizontalhotwalllowpressurechemicalvapourdeposition(HWLPCVD)systemwitharotatingsusceptorthatwasdesignedtosupportuptothree50mm-diameterwafers.3C-SiCfilmpr

3、opertiesoftheintra-waferandthewafer-to-wafer,includingcrystallinemorphologiesandelectronics,arecharacterizedsystematically.Intra-waferlayerthicknessandsheetresistanceuniformity(󰀆/mean)of󰀅3.40%and󰀅5.37%havebeenachievedinthe3󰀂50mmconfiguration.Withinarun,thedeviationsof

4、wafer-to-waferthicknessandsheetresistancearelessthan4%and4.24%,respectively.Keywords:3C-SiC;verticalmulti-waferHWLPCVD;heteroepitaxialgrowth;uniformityDOI:10.1088/1674-4926/32/6/063001PACC:6855;8110B;8115H1.IntroductionSiliconCarbide(SiC)isanimportantelectronicandstruc-turalmaterialsuitableforhigh-p

5、ower,hightemperatureelec-tronicdevicesandmicro-electromechanicalsystem(MEMS)devicesinharshenvironmentsduetoitsexcellentstability1;2󰂍.Inaddition,amongSiCpolytypes,cubicsiliconcarbide(3C-SiC)istheonlytypethatcanbegrownontheSisubstrate,givingitaremarkableadvantageinthelow-costfabricationoflarge

6、diameterwafers3󰂍.However,deviceapplicationsusing3C-SiCgrownonSisubstratehavelagged,owingtothedif-ficultyinrealizingahighthroughputofhighqualitymaterialwithhighintra-waferandwafer-to-waferuniformity.3C-SiCgrowthwithgooduniformityandexcellentcrys-tallinityisakeytechnologyforSiCelectronicandMEM

7、Sdevices4󰂍.Heteroepitaxialgrowthofmulti-waferswithgoodcharacteristicshasbeenreportedindifferentreactorsusingdifferentgassystem5󰂍.Chemicalvapordeposition(CVD)isalwaysconsideredasthemosteffectivemethodofgrowinghigh-qualitySiCfilms,whichhasbeenperformedusingava-rietyofprecursorsandvario

8、usdepositionconditions.OneofthedesirablequalitiesofCVDfilmgrowthisuniformity.Foramulti-waferCVDsystem,highintra-waferuniformityandhighwafer-to-waferuniformityarebothimportanttoensurethepropertiesofallfinaldevicesmadefromthesefilms.AsforSiCfilmgrowth,thetraditionalgrowthmethodwasper-formedwiththestan

9、dardreactantsofSiH4andeitherC3H8orC2H4inH2asthecarriergasbyusingahot-walllowpressurechemicalvapordeposition(HWLPCVD),whichisoftense-lectedoveratmosphericpressureCVD(APCVD)becausethelargediffusioncoefficientsatlowerpressurestendtoobtainmoreuniformfilms6;7󰂍.Inourexperiments,3C-SiCfilmshavebeen

10、depositedinanovelhome-mademulti-waferhot-wallLPCVDreactor(Fig.1)witharotatingsusceptor,whichcanholduptothree50-mm-diameterwafers.SpecificsregardingtheLPCVDre-actorsetuparealsodetailedinanearlierpaper8󰂍.Gasflowdistributionismorecontrollableanduniforminsuchaconfig-uration;also,temperaturecanbe

11、higher,therebyyieldingSiCepilayerswithhighuniformity.2.ExperimentalprocedureN-dopedpolycrystalline3C-SiCfilmsweregrownonSi(100)substratesinourhome-madeverticalhot-wallLPCVDreactor,aschematicillustrationofwhichisshowninFig.1.Thereactorchamberconsistsofwatercooledcylindricalquartztube,positionedvertic

12、allywiththegasflowscomingfromthetop,perpendiculartothesusceptor9󰂍.ThechamberhasaSiC-coatedgraphitesusceptor,wrappedwithgraphitefoamforthermalinsulation.Substratesareplacedinthegas-flowchan-nelofthesusceptoranduniformlyheatedbyaradio-frequency(RF)-induction.Siwafers1,2and3wereplacedinsidearot

13、atingsuscep-tor,asshowninFig.1.Beforebeingloadedintothereactiontube,SiwafersweresoakedinHFdilutedsolutionfor5mintoremovethenativeoxidationfromthesurface.Thegrowingpro-cessconsistedoftwostages.Inthefirststage,4.5sccmC2H4dilutedin10slmH2wasusedforcarbonizationandintroducedintothegrowthchamberat1000C.T

14、henthechambertemper-atureincreasedslowlyto1250Cin10min.Asforthesecondstep,trichlorosilane(SiHCl3/andthylene(C2H4/wereusedassiliconandcarbonsources,andammonia(NH3/astheNdopantgas,respectively.Thesourcesweredilutedandcarried*ProjectsupportedbytheNationalNaturalScienceFoundationofChina(No.60876003),the

15、ChineseAcademyofSciences(No.Y072011000),theBeijingMunicipalScience&TechnologyCommission(No.D09080300500903),andtheKnowledgeInnovationPro-gramoftheChineseAcademyofSciences(No.ISCAS2008T04).󰂎Correspondingauthor.Email:ggyanc2011ChineseInstituteofElectronicsReceived15November2010󰀄063

16、001-1J.Semicond.2011,32(6)YanGuoguoetal.Fig.1.Schematicpictureofthehome-madeverticalmulti-waferhot-wallCVDreactor.bypureH2gas,andthenfedintothegrowthchamber.Het-eroepitaxialgrowthwasperformedat1250CwithfluxesofH2,NH3,SiHCl3andC2H4being10slm,0.18sccm,4.5sccmand4.5sccm,respectively.Thedepositionpressu

17、rewasheldat40Torrandthegrowthprocesslasted120minforthesefilms.Afterthegrowthstage,thesampleswerecooleddowninH2ambient.Aftergrowth,thegrownfilmswerecharacterizedandana-lyzedbyX-raydiffraction(XRD),Ramanscattering,scanningelectronmicroscopy(SEM),andsheetresistancemeasurement(SRM),separately.XRDwasperf

18、ormedtoanalyzethefilmstructuresbyusingaPhilipsdiffractometerwithCuKradia-tionandÂ2Âgeometry.Cross-sectionalSEMwasusedtoesti-matethefilmthicknessbyobservingthecross-sectionalshape.SRMwasobtainedbyNapsonNC-40non-contactsheetresis-tancemeasurementinstrument.XRDandSEMmeasurementsweretakenatfiv

19、epoints:onewaslocatedinthewafercen-terandtheothersattheperiphery(12.5mmfromcenter).Thevalueoftheuniformitywascalculatedbyuniformity=󰀆/mean,where󰀆andmeanrefertothestandarddeviationandthemeanvalue9󰂍.3.ResultsanddiscussionThesurfacesofSiCfilmsweremirror-likeandXRDwasusedtoinvest

20、igatethecrystallinityofthe3C-SiCfilms.Fig-ure2showstheX-raydiffractionpatternsofthe3C-SiCfilmswithinarun.Foronewafer,thefivepointsshowninthepic-turesweremeasured.Thedatawerefromthefiveareasacrossthewafer(shownintheinset).The200peakof3C-SiCwasclearlyvisibleineachscan.Thesubstrateswerehighlyori-ented(

21、100)siliconfilms.Figures2(a)2(c)showthatthede-positedSiCfilmsarealsohighlyorientedalongthe(200)di-rection.Thespectrawerehighlyuniform,peakpositionswerealmostthesame,andtheFWHMwerenarrow,lessthan0.4.ThespectraexhibitedastrongSiC(200)texture,thereforeSiCfilmsshowedanorientationmuchthesameasthatoftheSi

22、(100)substrate,whichindicatedthatthefilmswereofhomocrystallinecubic3C-SiC.Theseindicatedthatthefilmswerehighly-orientedandhadalmostthesamecrystallinity,whichalsoprovedthatthethreewaferswerehighlyuniform.Thegrowthrateisabout56󰀄m/h,anditshouldbenotedthatifthegrowthratewashigherthanacertainvalu

23、e,theFig.2.(a,b,c)XRDspectraof3C-SiCfilmsgrownonSi(100)sub-strate.Thepeakpositionsofwafers(a,b,c)were41.4,41.5and41.5,respectively.SiC(111)texturewouldappeartogetherwiththeSiC(100)textureintheheteroepitaxial3C-SiCfilms.Therefore,anex-tremelyweakpeakofSiC(222)textureat75.5appears,anditmaybecausedbyth

24、etiltSiCplaneswhenislandscoalesce,wheretheAPDisformed,asreportedbefore8󰂍.Apeakat61.8arisesduetothediffractionfromtheSi(400)plane.ThequalityofthefilmswassupportedbyRamanmeasure-ments.Figure3showsthetypicalRamanspectraobtainedforthe3C-SiCfilmsonSi(100).Predominantlyonesharplineof796cm󰀁

25、1correspondingtothetransversal(TO)modeof3C-SiCcanbeobservedclearlyinthethreewafers.Thepeakof970.3cm󰀁1correspondingtothelongitudinal(LO)modeof3C-SiCalsoprovedthatthefilmswerecubic3C-SiC.Thisre-sultwasconsistentwiththeX-rayresultsandalsoshowedagoodSiCcrystallinestructure10󰂍.063001-2J.S

26、emicond.2011,32(6)YanGuoguoetal.Fig.4.Thicknessuniformitiesandsheetresistanceuniformitiesof3C-SiCfilmsgrownonSi(100)substrates.(a)Thicknessanduniformities(󰀆/M)of3C-SiCsamples1,2and3,respectively,withinarun.(b)Sheetresistancesanduniformitiesofthethree3C-SiCsamples.thewafer-to-waferuniformityw

27、ereabout3.40%and4.00%,respectively,whichindicatedthatgoodthicknessuniformitywasobtainedinthemulti-wafer3C-SiCheteroepitaxialthinfilms.Meanwhile,comparedtotheresultsreportedbefore(theintra-waferthicknessuniformitywas6%7%),thepropertiesofoursystemhavebeengreatlyoptimized.Fig.3.Ramanspectraofthewafers1

28、,2and3withinarun,respec-tively.Thicknessuniformitywasanalyzedbyinvestigatingthethreewaferswithinarun.SEMmeasurementofeachwaferwastakenatfivepositionsmentionedinthesecondpart.ThedetailedpositionsandtheresultscanbeseeninFig.4(a).Thethicknessuniformityofeachwaferwascalculatedbythefol-lowingmethod,vuPun.x󰀁m/2uNtiD1iPxiNiD1󰀂100%;mD;uniformityDmNwherexiisthethicknessofthei-thpositionandNisthetotalsamplecounts.Forthesethreewafers,ND5.Forthefilmswithathicknessofabout11󰀄m,theintra-waferuniformityandSheetresistancemeasurementofeachwaferwa