半导体工艺2：HDP-主要工艺参数详解

HDP主要工艺参数详解WER湿法腐蚀速率湿法腐蚀速率是评价膜质致密性最重要的指标之一。温度对WER的影响很大，见下图：图1-1HDPchamberPressurecontroller随着温度的升高，WER是降低的。2、深宽比与淀积刻蚀比对void的影响图2-1深宽比和淀积刻蚀比对填孔性能的影响深宽比越大，需要的淀积刻蚀比越小，也就是刻蚀速率要提升。3、淀积刻蚀比光片刻蚀速率是在同样的压力下，在氧化膜光片上进行刻蚀，这个条件跟淀积一样，只是没有硅烷。4、温度温度是对应力，WER影响的关键因素，是RI的次要因素；在低压环境中温度是很难从wafer传导到ESC的，因此要引入HE冷却，确保温度在350-400之间。太低的温度会导致oxide中存在过多的H和OH键，这会导致膜质charging。但如果温度超过450度，会导致AL层的合金。5、应力6、均匀性假设He的压力、溅射刻蚀的均匀性都是最优状态；SideSiH4就是粗调，决定淀积速率；TopSiH4就是精调，7、Processwindow工艺窗口8、Waferprocesssteps工艺步骤（1）Processposition2s到工艺位2sWaferonchuck,Gasflowinitiatedwiththrottlevalveclosedtodecreaseoverheadtimefornextstep.Gasflowoptimizedsothatchamberpressurewillnotovershoot.;(2)Pressurize3.5s压力稳定3.5sIntroducestrikechemistry:Argononly.Pressurerisesto50mTorr(controlledstrikepressure).Needminimumpressureforcapacitivelycoupledignition.Ifpressuretoolowortoohigh,thenplasma“flickering”mayoccurasthefrequencytuningspanstofindthematchingregime.Thiscouldleadtodevicedamageonthewafer.Failuretoachieveminimumpressurewithin10sec.willresultinrecipefault(preventhighreflectedpowerduringstrikestep).(3)Stabilize(5.0sec).稳定5s(4).Strike(PlasmaIgnition)1s启辉1sSetTopCoilRFPowerto1000Wforignition.SRFLimits:Toolow–inabilitytostrikeplasma(lowstrikingvoltage).Toohigh–hardwarereliabilityissue(highstrikingvoltageonantenna).(5)、OpenThrottle1s打开蝶阀Opensthrottlevalvetoanintermediatepositiontoreducechamberpressureslowly.ChangingpressuretooabruptlycouldcauselossofchamberRFmatching.SidecoilRFpowerturnedoninthisstep(2000Wsetpoint).(6)、OxygenOn/Chuck_On1sTurnsonoxygenflowtoanintermediatevaluetopreventgasbursting.Throttlevalveopenedtocompensateforincreaseingasflow.ESCChuckingvoltageturnedON(Positivechuckingvoltageiscurrentlypreferredforincreasedreliability).200mm150mm+950VDC+800VDCESCProtectionsetto“ProtectI”tomonitorforexcessleakagecurrent(Delaytimebeforefaultoccursisspecifiedintherecipeheader–shouldbelessthantimebeforebiasRFturnedon).200mm150mmleakagecurrent<200μA<200μATypicalvaluesare125-175μA(7)、Heat-Up(SourceRFonlywaferheating)5s加热SourceRFPowerrampedto:1300WTop,3100WSide(8").Heat~5seconds-toanintermediatetemperature.Insufficienttimeinthisstepcanleadtofilm“hazing”duetopoorinitialdepositionlayer.Argonandoxygenflowsincreasedtofinaldepositionflowrates.8、SilaneOn2s-3s硅烷打开TurnonSilanegasflowusinganintermediatesetpoint.Ittakesabout3secondsforsilanetoflowfromMFCintothechamber.Thistimeisdistributedacrossthisstepandthenextstep(Hecoolon).Whensilaneentersthechamber,theplasmacolorwillchangefromalighterpink-whiteplasmatoadarker,salmon-likecolor.Goal#1:Minimizedepositiononwafer(lowtemp+nobiasRFcanleadtohighhydrogencontent,andhotcarrierissues,and“hazing”).Goal#2:Preventsputteringwithoutdeposition=cornererosionofthegapfillfeatures.Typicalsilaneflowsetpoint~halfflowrateofdep.Process.(典型的流量为工艺流量的一半)9、HeliumCoolingOn1s氦气冷却TurnonHeliumBacksideCoolingtothefinalsetpoint:Typicalvalues:SizeInnerOuter8"3.75Torr7.50Torr6"4.00Torr9.00Torr(outer/innerratio~2:1forbesttemp.unif.)AllowtheIHC(independentheliumcooling)moduletostabilizetransientsinheliumflow.Conductsanitycheckonchuckingbymeasuringheliumleakrate.Minimizetimeofthissteptominimizedecreaseinwafertemp.（用最小的时间弱化对wafer温度的降低）10、Bias_Preset3s偏压预设定Providesfurtherheatingofwaferwhileminimizingdepositionatlowwafertemperature.Builds“coating”layertoreducecornerclippingissues,orsputteringofARClayers(whichcouldleadtoleakagecurrent).Procedure:TurnonBiasRF(BRF)Power~1/2DepositionBRFPower(biaspowerisveryeffectiveatheatingthewaferviaionbombardment).（此时只开一半）Thissteptimeisapplicationdependent.（时间取决于氧化层的厚度）Amountofoxidedeposited~500+200Å.11、Deposition淀积EstablishproperD/Sratioforgapfilling.Increasesilaneflowtoachievedepositionrate,constrainedbymaximumobtainablesputteringrate(biasRFpower).将SiH4和biasRF再开另一半MaintainsufficientO2:SiH4ratiotoensureproperstoichiometry(generallyO2:SiH4>1.7:1).12、Pre-BiasOff5s预偏压关闭Turnoffsilane(stopdepositioncomponent).ReducebiasRFpowerto500W.Keepbiasonwhilethesilaneisbeingpumpedout.13、BiasandHeliumCoolingTurnedOff1s偏压和氦气关掉TurnoffbiasRFpower.Caution:BRFpowermustbeturnedoffpriortoturningoffSRFpower.TurnoffHeliumbacksidecoolingandbegintodumptheHeliumbehindthewaferCaution:Sufficienttimeisrequiredtominimizepotential“skating”or“bumping”ofwaferoncechuckingvoltageisturnedoff-whichcanleadtowafermishandlingorpotentialdevicedamage.Thetimeisincreasednowsincetheheliumdumpisnowconnectedtotheroughingforeline(usedtoberoutedtotheturbo).14、DumpHelium5s氦气降低Sincestep#13istypically1second(mainlytocommandthebiasRFoff),additionaltimeisgiveninthissteptocompletetheheliumdumpstep.15、ChuckOff4s关掉吸力Turnoffchuckingvoltage,whilekeepingtheheliumdumpvalvesstillopen.(SourceRFplasmarequiredtobleedoffresidualelectrostaticchargeonwafer).16\Dechuck2.5s解除吸力Setwaferliftpinpositionto“Release”Position.