IC-process---etch

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1.1GeneralIsotropicetch(无定向刻蚀)Etchinghasnodirection.•Wetetchoraplasmaetchwithoutsidewallpassivationprocess.•Itcausesundercutduringtheetchingandchangecriticaldimension.Anisotropicetch(定向刻蚀)Etchwithdirectionorsidewallprotection•Ionmilling,RIEortheplasmaetchwithenoughsidewallpassivationprocess.•Afteretch,criticaldimensionhasnochangeorveryslightlydifference.Isotropicetch(无定向刻蚀)Anisotropicetch(定向刻蚀)Resist1.2Facility•DIwater(去离子水)17mhom•Drain(排水)•Specialchemicaldisposesystem•Exhaust(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)2.0WetetchAdvantageanddisadvantage•Chemicaletch(化学刻蚀）---isotropy•CDloss（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）•Wafersurfacewettingandcontactwithetchchemical•Chemicalreactiontakesplace,solublebyproductformation.•RemovebyproductfromwafersurfaceTheetchrate(anduniformity)affectsby•Temperature•Thesloweststepofoneofabovestep2.1.2Wetetchbyproduct(副产物)•Partofbyproductwillbeconvertedtowatersolublematerial.(水溶性)•Partofbyproductwillconvertedtogasform.Ifthegascannotberemovedfromthewafersurfacesoonenough,theproblemwilloccur*Blocketch---snow(雪花)*Hidingatedgeofresist---lifting(浮胶)2.1.3WetetchimprovementImprovementmethod•Pre-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）2.2.1BOEetchBOE(Bufferoxideetch)mixedwithHFandNH4FChemicalreactionSiO2+6HFH2SiF6+2H2ONH4FNH3+HFNH4F(bufferagent–缓冲剂)keepaconstantHFconcentrationduringreactionNH3---controlPHvalueCDlostinBOEetch（氧化硅刻蚀)BOEetchsink（氧化层刻蚀水槽)2.3Nitrideetch（氮化硅腐蚀）•Phosphoricacid(磷酸）---H3PO4•Heatupto140to200oC•Constantwatercontain（稳定水含量）•Etchrate~50A/minat165oC•Selectivitytooxide~10:1•Selectivitytoundopedsilicon30:1•SelectivitytoN-siliconismuchpoorer(higherdopingfasteretchrate)2.4AluminumEtch(铝刻蚀)ChemicalPhosphoricacid77%Aceticacid20%Nitricacid3%EtchTemperature30to70oC(keepetchtimefrom3to5min)EtchtimeManual/autoendpointEtchrateaffectTemperatureAmountofNitricacidByproductAluminumAcid-ateHydrogenEquipmentManualetchbathAutomaticetchsinkWaterflowetch(Watanabe)VacuumetcherSprayetcher(Dinippon)FewspecialissuesinAluminumEtchSnow---TherearealotofH2arereleasedduringetching.Inthehighviscosityacid,theH2bubbleiseasilytoattachonthewafersurfacebutcannotfloattothesurface.Itblockstheetching.*Agitation---mechanical*Waterflow---mechanical*Spray---mechanical*Vacuum---reducesurfacetensionResidue---Whenetchaluminumalloyfilm,thesiliconisunabletobeetchedintheacid.Itwillleaveonwafer.*Defeckleetch---mayattackaluminum*Plasmaetch---residueisdifficulttobeetchindensearea2.5Poly/siliconetch(硅刻蚀）Chemical1.HNO3+HF(8:1)2.KOHsolution(forsignalcrystalsilicon)PolyetchPolyneedoxidemaskDilutetheHF/HNO3withaceticacidorDIH2OSiliconetchHF/HNO3etchwithnodirectionKOHetchwithdirection---alongcrystallineWetetchtableDIwaterrinseequipment•Cascade---Slow,initialbathcontainweakchemical•QDR(QuickDumpRinser)Fast,CreateESD(particle),Cycletime,numberofcycle•Sprayrinse---Runwithdryer*HotDIwaterisincreasingtherinseefficiency2.5DIwaterrinseanddryWaferdryMechanicaldry---(particle,residue)•MultiplecassettesspindryFSI•SinglecassettespindrySemitoolChemicalDry•Freonvapor•Hotwater/airdry•Alcoholvapordry•Alcoholdry3.0Dryetch（干化刻蚀）Advantageanddisadvantage•Anisotropyetch(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,electricalpoweriscoupledintoaplasmabymeansofparallelmetalelectrodes•Theaccelerationofelectronsistheprincipalmeansbywhichenergyiscoupledintotheplasma.TheamountofenergygainedbyaelectronisequaltotheforceonittimesthedistancePlasmadensityInaplasma,wehaveseenthatnewfreeelectronsaregeneratedbyelectron-impactionizationgasatomsandmolecules.Atthesametime,manyofelectronlosttotheelectrodeandothersurroundingsurface.Sotheplasmastabilizeatadensityofelectronsforwhichthegenerationrateisbalancedbythelossrate.Thisstabilizedelectronleveliscalledtheplasmadensity.Foragivenreactor,plasmadensityisdetermi