IC工艺技术3-刻蚀.ppt

IC工艺技术系列讲座第三讲 ETCHING刻蚀 讲座提要 1 General1 1Isotropic Anisotropicetch 无定向 定向刻蚀 1 2Facility 动力环境 2 Wetetch2 1Wetetchmechanism 湿化刻蚀机理 2 2BOEetch 氧化硅刻蚀 2 3Aluminumetch 铝刻蚀 2 4Nitrideetch 氮化硅刻蚀 2 5Poly siliconetch 多晶硅 单晶硅刻蚀 2 6DIwaterrinseanddry3 Dryetch3 1PlasmaTheoryandapplication 等离子理论和应用 3 2Typeofplasmaetch 等离子刻蚀种类 3 3Etchinggasesandpressure 刻蚀气体和低压 3 4Etchprocesshighlight 刻蚀工艺简介 3 5Etchprocessparameter 刻蚀工艺参数 3 6Ionmilling 离子铣 3 7BCDplasmaetchingequipmentandapplication5 Nextetchprocess未来的刻蚀工艺 1 1General Isotropicetch 无定向刻蚀 Etchinghasnodirection Wetetchoraplasmaetchwithoutsidewallpassivationprocess Itcausesundercutduringtheetchingandchangecriticaldimension Anisotropicetch 定向刻蚀 EtchwithdirectionorsidewallprotectionIonmilling RIEortheplasmaetchwithenoughsidewallpassivationprocess Afteretch criticaldimensionhasnochangeorveryslightlydifference Isotropicetch 无定向刻蚀 Anisotropicetch 定向刻蚀 Resist 1 2Facility DIwater 去离子水 17mhomDrain 排水 SpecialchemicaldisposesystemExhaust 排风 CompressairandNitrogen 加压空气 氮气 Inhousevacuum 真空管道 Coolingwater 冷却水 Gascabinet Gasline 气柜 气体管道 Gasbottle 气瓶 2 0Wetetch AdvantageanddisadvantageChemicaletch 化学刻蚀 isotropyCDloss 线宽变小 Highparticlecontamination 高颗粒 Unableforsmallgeometry 不能用于小尺寸工艺 Higherprocesscost 工艺费用高 Mostofwetetchprocesshavehighselectivitytotheunderlayer 高选择比 Fastthroughput 产量高 Lowequipment investment cost 投资少 2 1 1Wetetchmechanism 湿化刻蚀机理 WafersurfacewettingandcontactwithetchchemicalChemicalreactiontakesplace solublebyproductformation RemovebyproductfromwafersurfaceTheetchrate anduniformity affectsbyTemperatureThesloweststepofoneofabovestep 2 1 2Wetetchbyproduct 副产物 Partofbyproductwillbeconvertedtowatersolublematerial 水溶性 Partofbyproductwillconvertedtogasform Ifthegascannotberemovedfromthewafersurfacesoonenough theproblemwilloccur Blocketch snow 雪花 Hidingatedgeofresist lifting 浮胶 2 1 3Wetetchimprovement ImprovementmethodPre wet wettingagent 湿润剂 Agitation 搅动 Circulation 循环 Temperaturecontrol 温度控制 Filtration 过滤 Inavacuum 真空 Sprayetch 喷洒 Vaporetch 蒸发 Selectionofhighpurityofchemical 选择高纯度化学药品 2 2 1BOEetch BOE Bufferoxideetch mixedwithHFandNH4FChemicalreactionSiO2 6HFH2SiF6 2H2ONH4FNH3 HFNH4F bufferagent 缓冲剂 keepaconstantHFconcentrationduringreactionNH3 controlPHvalue CDlostinBOEetch 氧化硅刻蚀 BOEetchsink 氧化层刻蚀水槽 2 3Nitrideetch 氮化硅腐蚀 Phosphoricacid 磷酸 H3PO4Heatupto140to200oCConstantwatercontain 稳定水含量 Etchrate 50A minat165oCSelectivitytooxide 10 1Selectivitytoundopedsilicon 30 1SelectivitytoN siliconismuchpoorer higherdopingfasteretchrate 2 4AluminumEtch 铝刻蚀 ChemicalPhosphoricacid77 Aceticacid20 Nitricacid3 EtchTemperature30to70oC keepetchtimefrom3to5min EtchtimeManual autoendpointEtchrateaffectTemperatureAmountofNitricacidByproductAluminumAcid ateHydrogenEquipmentManualetchbathAutomaticetchsinkWaterflowetch Watanabe VacuumetcherSprayetcher Dinippon FewspecialissuesinAluminumEtch Snow TherearealotofH2arereleasedduringetching Inthehighviscosityacid theH2bubbleiseasilytoattachonthewafersurfacebutcannotfloattothesurface Itblockstheetching Agitation mechanical Waterflow mechanical Spray mechanical Vacuum reducesurfacetensionResidue Whenetchaluminumalloyfilm thesiliconisunabletobeetchedintheacid Itwillleaveonwafer Defeckleetch mayattackaluminum Plasmaetch residueisdifficulttobeetchindensearea 2 5Poly siliconetch 硅刻蚀 Chemical1 HNO3 HF 8 1 2 KOHsolution forsignalcrystalsilicon PolyetchPolyneedoxidemaskDilutetheHF HNO3withaceticacidorDIH2OSiliconetchHF HNO3etchwithnodirectionKOHetchwithdirection alongcrystalline Wetetchtable DIwaterrinseequipmentCascade Slow initialbathcontainweakchemicalQDR QuickDumpRinser Fast CreateESD particle Cycletime numberofcycleSprayrinse Runwithdryer HotDIwaterisincreasingtherinseefficiency 2 5DIwaterrinseanddry Waferdry Mechanicaldry particle residue MultiplecassettesspindryFSISinglecassettespindrySemitoolChemicalDryFreonvaporHotwater airdryAlcoholvapordryAlcoholdry 3 0Dryetch 干化刻蚀 AdvantageanddisadvantageAnisotropyetch 定向刻蚀 CDlossundercontrol 线宽可控制 Etchsmallgeometry 小尺寸刻蚀 Simpleprocess dryin dryout 简单程序 Lowprocesscost 低成本工艺 Plasmadamage 刻蚀损害 Lowselectivity 低选择比 Lowerthroughput 产量低 Highequipmentcost 投资高 3 1PlasmaTheoryandapplication 等离子理论和应用 Definitionofaplasmaisapartiallyionizedgasthatiselectricallyconductive Plasmaenergycanbeusedtoactivatechemicalreactionsandtoetchordeposituponsurfacesexposedtotheplasma Often electricalpoweriscoupledintoaplasmabymeansofparallelmetalelectrodesTheaccelerationofelectronsistheprincipalmeansbywhichenergyiscoupledintotheplasma Theamountofenergygainedbyaelectronisequaltotheforceonittimesthedistance PlasmadensityInaplasma wehaveseenthatnewfreeelectronsaregeneratedbyelectron impactionizationgasatomsandmolecules Atthesametime manyofelectronlosttotheelectrodeandothersurroundingsurface Sotheplasmastabilizeatadensityofelectronsforwhichthegenerationrateisbalancedbythelossrate Thisstabilizedelectronleveliscalledtheplasmadensity Foragivenreactor plasmadensityisdeterminedbyfourprincipleinputs 1 ThevoltageappliedtotheelectrodeHigherappliedvoltageleadstomoreelectronenergygainbetweencollisions2 ThegascompositionThemoleculethathasweakermoleculebondiseasierigniteplasma3 ThegaspressureGaspressureaffectsplasmadensitythroughthecollisionrate Inhigherpressure shortermeanfreepath Atlowvoltage toomuchenergylostinnon ionizingcollisionandplasmadiesout Athighvoltage oneelectroninitialssomanyionizingcollisionsthatanexcessivelyconductpathiscreatethroughtheplasma itcausearcing Toolowpressure gascrosstheelectrodegapbeforetheygenerateenoughionizingcollisions 4 TheapplicationofamagneticfieldAmagneticfieldcanbesetupacrossaplasmareactorusingexternalmagnets Electronattemptingtocrossthemagnetizedplasmawillhaveamuchlongerpathlengthinwhichtoencountercollisionwithgasmoleculesbeforetheyarelosttotheelectrode Thismeansthatthepressurecanbemuchlowerbeforethecollisionratebecomesinsufficienttosustaintheplasma Inhighpressureplasma Addedamagneticfield Etchtheory ionbombardmentTheelectronaremuchlessmassivethantheions sotheymovemuchmorerapidly Theresultinadepletionofelectrodeofelectronsfromthespaceabovethecathode Theionslefthereconstituteapositivespacecharge Theregionofpositivespacechargeiscalcathodesheath Constrictingthevoltagedropinthiswayincreasetheforceontheionsinthesheathandcausethemtobeacceleratedintocathodewheretheyarrivewithconsiderableenergy 500electron volts Etchtheory ionbombardmenteffectElectronemission emissionthesecondaryelectronsthathelpsustainthedirect currentplasma Chemicalactivation ChemicalreactiveandphysicalbombardmentMomentumtransfer Nochemicalreaction movesurfaceatomtoremoveofimpurityatomsbyevaporation ACplasma TheaboveDCplasmatheoryistobeusedtoillustrateabasicofplasma TheACplasmaisusedinrealtime ThecathodeandtheanodeisalternatinginaACpowersource ThefrequencyoftheACpowerisselectedtobeusedinthisindustry Thelowestfrequencytomaintainaplasmais100KHz13 56MHzRF radiofrequency ismainlyusedinsemiconductorfieldWaferthatsitsonpowerplatereceivesmorebombardmentWaferthatsitsongroundplatehaslessplasmadamage Plasmaetchmechanism 等离子刻蚀机理 Thepositiveionaredrawntothecathode andthenegativeionstoanode Inamediumpressurediodereactor only1in50 000ofthegasmoleculesareionized Therefore ionsarenotthemaindriversintheetchprocess althoughtheyplayamajorrole Becausefreeradicalsareneutral theybehavemuchlikestandardgasmolecules Whenagasmoleculefragmentsintheplasma eachfreeradicalformedtakesupasmuchspaceastheoriginalmolecule Thisiswhythepressurejumpswhenaplasmaignites Theyaremorereactivethantheywereintheiroriginalform andareimportantetchratedrivers Freeradicalsareverylong livedinavacuumenvironment Plasmaetchmechanism 等离子刻蚀机理 Plasmaetchmechanism CF4etchChemicalreaction CF4刻蚀化学反应 Plasmaetchmechanism 等离子刻蚀机理 Plasmaetchmechanism 等离子刻蚀机理 FewnotesinCF4plasmaetchTheplasmacontainsenergeticionswhichbombardthewafersurface aswellasothersurfaceinthereactorchamber Theyareacceleratedacrossthevoltagedropregionatthesurface andcollidewithitathighspeed Thisionbombardmentisalsocausesanodizationwear Duringthesiliconetch themostprevalentchemicalreactionproceedsasfollows 4F Si SiF4AstheSiF4gasforms itispumpedaway Thebi product CFpolymer depositsonthewaferaswellasinthechamber Onlythepolymeronwafersurfacethatreceivebombardmentwillberemoved Theetchprocesscontinuesaslongasthedepositionrateofthepolymerdosenotexceeditsetchrateduetoionbombardmentandgasreaction Whenetchhitstheunderlayer SiF4formationdecrease ThelightemissionfromtheSiinplasmadecrease Theetchingcanbesignedtoreachendpoint 3 2Typeofplasmaetch 等离子刻蚀种类 OperatingFrequencyPressureEquipmentBarrel13 56MHz500mtIPCDownstream2 45GHz2torrGasonicA1000Parallelplate13 56MHz300mtLamautoetch Rainbow4400 4600 4700Tegal700 800 900Triode13 56MHz T 300mtTegal1500 1600100KHz B Drytek384TSPRP400KHz200mtLamRainbow4500MERIE13 65MHz100mtPrecision5000RIE13 56MH20mtAME8000TCP13 56MHz P 1 5mtLam13 56MHz B DPS13 56MHz P 1 5mtCentrura13 56MHz BMRE13 56MHz T 3mtTegal6000800KHz B ECR2 45GHz T 0 5 5mtHitachi13 56MHz B Helicon0 5 5mt IPCbarreletcher 13 56MHzUseoxygenonlyforresistashingat1torr 500wUseCF4 O2foretchingat0 5torr 250w Tegal900series Parallelplateetcher Lamautoetch490 590 Parallelplateetcher Tegal1500 1600series Triode dualfrequencyetcher AME8300Series AME8100seriesisthemanuallywaferloadingsystemAME8300seriesistheautomaticallywaferloadingsystemAME8310 OxideetcherAME8330 metaletcherAME8340 polyetcher LamRainbowetcher RainbowisthenameofLametchplatform4400isapolyetcherusedRFpower wafersitsonground 4500isanoxideetcherusedSPRPpowersource4600isametaletcher wafersitsonpowerelectrode ECR Gasonic1000 UsemicrowavepowerfordisassociateGas Trendsinplasmaetchchemistry1 3 3Etchinggasesandpressure 腐蚀气体和低压 Trendsinplasmaetchchemistry2 3 3Etchinggasesandpressure 腐蚀气体和低压 3 3Etchinggasesandpressure 腐蚀气体和低压 PumpsusedinsemiconductorprocessAppliedPressureVacuumRangeMechanicpump10 2760 10 3机械泵Mechanicpump blower10 2760 10 3机械泵 罗茨泵Diffusionpump10 510 3 10 7扩散泵Turbomoleculepump10 510 2 10 10分子泵 50000rpm Cryopump10 710 6 10 12冷泵 3 3Etchinggasesandpressure 腐蚀气体和低压 Pumpsusedinetchprocess Drypumpstack Turbopump Oilpump OilpumpStack 3 4Etchprocesshighlight 腐蚀工艺简介 PolysiliconetchNitrideetchOxideetchAluminum aluminumalloyetchPolycidesetchSOGetchW TiW TiNetchResistetch ash Typeofetchprocess Polysilicon salicidesEtch PolysiliconcanbeetchedbyCF4 SF6orCl2chemistryinaparallelplateetcher butonlytheCl2processisananisotropicprocess Herearesomemoreadvancepolysiliconetchrecipesandsaliciderecipes 1 CL2withECRuwaveplasma 875gauss etchrateincreaseswithCL2flow etchingbyneutrals lowerstheflowrate increasesionsandincreasesanisotropicprofile 2 MERIEofsilicideoverpolysilicon salicide ongateoxide CL2at 80Vd c biasforsilicide reduced c biasandpowerdensityforpolyetchtoendpoint switchtoHBrtoclearwindowsofstringers etc Silicondioxideanddopedglasses sidewallspaceretching Useasinglewafersystem thetypicaletchchemistryisCHF3 C2F6 CF4 He Itremovesbulkofoxideintimedcycle reduceC2F6 CF4 flowpower increaseselectivitytopolyto11 1toendpoint Reducetemperatureonwaferelectrodewillincreaseselectivity TCP NF3 He improvedselectivityoxidetopolyof60 1to100 1 600nm minforBPSG Aluminumalloysandsandwichmetalsystems ChlorinebasedcompoundsetchAlandAl Sireadily Theadditionofcopperisaproblem becausethevolatilityofCuClxisverylow Mostmetaletchingisdonebyion enhancedprotectivewithBCL3 CL2 CHF3 followedbypostetchtreatmentinafluorine richplasmatoexchangetheadsorbClwithnon corrosiveF TheadditionofN2andAlincreasestheetchrateofCu Photoresist Oxygenplasmaareastandardmethodforstrippingphotoresistbyashing Damagecanoccurduringthisrelativelyuncontrolledoperation Widelyacceptedarethemetalatomsandioniccontaminationpresentintheresist whicharenotremovedintheplasma Acombinationofdryandwetstrippingispreferred 3 4Etchprocesshighlight 腐蚀工艺简介 BreakthroughRemovena veoxide lowerselectivityBulketch Mainetch Highetchrate maximizedselectivity optimumselectivityOveretchGoodendpointsignal highselectivitytounder layermaterial ResistremovalPartiallyorcompletelyremoveresist Themajoretchsteps 3 5Etchprocessparameter 刻蚀工艺参数 Etchrate everysteps 刻蚀率 etchuniformity everysteps 刻蚀均匀度 Selectivity tobottomlayermaterial resist impurityinfilm 选择比 Endpointdetection 终点检测 Loadingeffect 负载效应 Residue 残余 Damage 损伤 Throughput 产量 Forward reflectivepowerBasepressureLeakratePartialpressure gasflowandpumpspeed MFCcalibrationWafertransferreliabilityWafertransfercycletimePumpmaintenance Theusefulparameterdataistakenfromanequipmentthathasbeenproveditsperformancesareinspecification PreventiveMaintenance EtchRateUniformitySelectivity TypeofEndpointdetection TypeofendpointdetectionEquipmentLaserDryteck AME8110EmissionspectroscopyMostofdryetherInfra redVacuumetcherBrightlightreflectionSprayaluminumwetetch EmissionspectroscopyEndpointdetection Inaplasma excitedatomsandmoleculesemitlightspectrumwhentheirelectronschangeenergystates Thestrengthoftheemittedlightspectrumindicatetheprogressionandcharacterizationofthechemicalandatomicreaction Emissionspectroscopystudythespecificlightspectrumanddetectiontheendofaspecialreaction Lam590Endpointtrace TypicalwavelengthsinEPapplication OxideCO 482 5nmor520nmSiF 440nmPolySiCl2405nmF704nmNitrideSiN405nmAluminumAlCl261 4nm 527nmAl396nmResistCO297 7nm 483 5nm520nmSiliconSiCl2405nm Loadingeffect Theloadingeffectisthephenomenonthatetchingunevenlocally Thisphenomenonisnewandspecialtotheplasmaetchprocesses Theetchratecanbebeststatedbythisequation Plasmaetchrate 1 exposedsurfaceareaLoadingeffectismoreseveretobehappened onthechemicalbehaveetchingplasmaprocess ontheetchprocessthatreliesonsidewallpassivation Waferwithunevenresistpatterndensity Waferwithvarioussizeofopening PolyResidue 1 Causebyunderetch2 Impurityinthefilm POCL3contaminationinpoly3 Contaminationinunderlayerfilm4 Polymerleftover PolyfilmetchedtoendpointinLam490 Damage SomeoftheproblemsassociatedwithanisotropicRIEarelistedasfollow MetallicContamination Deepleveltraps Degradedlifetimes Highcontactresistance LeakagecurrentPolymerFormation HighcontactresistanceUVRadiation TrapgenerationElectroStaticDischarge ESD GateoxidebreakdownPhysicalDamage DuetoenergeticionbombardmentTheetchingprocessisdirectional therefore foreignmaterialonthesurfacecanalsoactasamask changingthedesiredetchedpattern Heavymetals forexample knockedoffchamberwallsortheelectrodebyionbombardment maycontaminatethewafers Radiationdamagecanoccurinthesilicondioxidebythebuildupoftrappedchargeintheoxidelayer 3 6Ionmilling 离子铣 Ionbeammillingusestheenergyimpartedtoabeamofions Theionbeamusuallyconsistsofanionizedinertgassuchasargontoperformetching Theionswithenergiesinthe300 1500eVrangestrikethebondsthatholdthemtoadjacentatoms Thisprocessdependsonimpactandenergytransfer notonthechargeoftheincomingion Thechargeoneachionintheincidentbeammakestheformationofacollimated singleenergybeampossible TheschematicofatypicalionmillingsystemisshowninFigure6 3 7BCDplasmaetchingequipmentandapplication Lam490DiodePoly NitrideLam590DiodeOxideAME8330RIEMetal MetalalloyAME8310RIEOxideTegal1611TriodePoly NitrideTegal1612TriodeMetal MetalalloyTegal903DiodeOxide 4 GasonicA100MicrowaveResist DescumTegal915DiodeResist DescumIPCCapacitiveResist Descum BCDPolyetch Lam490Parallelplateplasmaetcher13 56MHzLoad lockUserecipemoduleDualendpointchannel 405nm BelttransferAnodizedaluminumelectrodeCassettetocassetteChlorinechemistryUpgradeHBr ImproveoxideselectivityEtchrate3700 4100 undopepoly Uniformity 5 Selectivitytooxide40 1SelectivitytoPR2 1 Lam490PolyetchloadingeffectinCl2chemistryprocess improvebyaddingHBr 490Cl2process1 resistpattern 50 resistpattern 1611HBrprocess BCDNitrideetch Lam490Parallelplateplasmaetcher13 56MHzLoad lockUserecipemoduleDualendpointchannel 405 BelttransferAnodizedaluminumelectrodeCassettetocassetteSF6andSF6 O2mixedchemistryUpgradeHBr ImproveoxideselectivityEtchrate1600A LPCVD Uniformity2 1 BCDOxideetch Lam590Parallelplateplasmaetcher13 56MHzLoad lockUserecipemoduleDualendpointchannel 520 BelttransferGraphiteupperelectrodeCassettetocassetteCHF3 CF4mixedchemistryEtchrate3700 4100Uniformity 5 Selectivitytopoly3 1SelectivitytoPR3 1 590oxideetchissues ConsumptionofGraphitecausesloweretchrateandreducingetchuniformityInconsistentcontactresistanceMetalstepcoveragedifficultcausebyhigheraspectratioHighpowerdensityplasmahashigherarcingpotentialPolymerformsinthechamberonthechuckneartheedgeofthewafer endpointviewspot Aluminumalloyetch AME8330RIEetcher13 56MHz1800Wat 50mtorrWallmountingLoad lockCassettetocassetteUnlimitrecipescapacity4endpointchannel AlCl396nm HexagonelectrodeBCl3 Cl2chemistryUpgradeHBr ImprovePRselectivityEtchrate400 undopepoly Uniformity 5 Selectivitytooxide4 1SelectivitytoPR1 1 AME8330etchissue1 1 EtchselectivitytoresistIsverypoorinAME8330duestrongionbombardmentReducepowergascombination AddingHBr Hardmask nitride SOG DeepUVtreatmentbeforeetch2 EtchuniformityProcessadjustment putindummyslot Fusion150 AME8330etchissue2 ResidueReducebulkEtchselectivityReduceBulketchrateIncomealuminumfilmQualityExtentoveretch AME8330etchissue3 Aluminumalloyfilmsurfacehasholesafterresist polymerareremoved thisGalvanicCorrosioncausesinchemicaltreatmentprocess ThischemicalcontainsAminebasechemistryor andHydroylamimeinNMPtoacceleratealuminumetchingaroundthecuppernodule KeepAlgrainsizesmalltominimizeCumigrationbyoptimizingmetaldeposition minimizingthermalcyclesafterdepositionImmediaterinse Alcohol QuickagitateinDIwaterrinse andaddingCO2forneutralizationAddARConmetal AME8330etchissue4 Photosweretakenafterresistremoved Microscope SEM Corrosionremoved AME8330etchissue4 IncreaselastpumpdownFpassivation ionexchange CompletelyresistremovalRinseimmediately Resistash GasonicA1000HighlampturnontimeImplantresistOverashingTemperatureonwafer IPCFinaltemperatureChambertemperaturefordescumQuartzchamberfrostyUniformityfronttoend 5 未来的刻蚀工艺 Polysilicon PolycideThinnerpolysiliconwillbeused 1500 2000A therefore loweretchratecanbetolerated Undopedpolysiliconwillbeused theprofilecontrolwillnotbeaissue afterpolylineformed N dopedforNchannel andP dopedforPchannel Stoponoxintrideorotherexoctichighdielectricconstantmaterialselectivitywillnotbeaissue HBreasilyobtaina100 1selectivity OxideHighdensity lowpressureplasmawillbedormantforthisapplicationEtchstoponSiNwillbeusedforimprovingselectivityC4H8 CO2etchingchemistrywillbeusedextensivelyforSAC selfaligncontact andtrenchstructureNeedlowetchrateandlowdamageplasmaforlowKandporousmaterialetch 5 未来的刻蚀工艺 MetalCupperwillbeusedfornarrowlinetoreplacealuminumalloymaterialUsecupperastheconnectorcannotbeusedtheconventionaletchingprocess thenewprocessscheme etchoxidetrench sputterseedlayer TaN cupperplating CMPstoponTaN etchTaNAluminumalloyfilmforuppermetalonly thickandwidestructureetching 5 未来的刻蚀工艺 ChemicalMechanicalPolish化学机械抛光 The1stCPMequipmentstartedinproductionsince1990 NowmostofsubmicronsemiconductorfabricationsarerunningCMPprocess CMPisaplanarizationprocessthatuseapolishmethod Becausetheprocesscombinesmechanicalforceandchemicalreaction therefore thepolishingcanbestoppedonthebottommaterial Theslurryselectionisparticularimportantforthematerialtobepolishedandtobestoppedon