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1、Inthecurrentetchingtechnology,plasmatechnologyhasbeenwidelyusedinsemiconductorindustry.Etchingprocessrequiresgoodrepeatabilityandstability,sotheplasmadischargestabilityandreliabilityrequirementsarerelativelyhigh.Inthispaper,wereportaplasmainstabilityintheetchingofsiliconnitride(Si3N4)films.HeretheSi
2、3N4isahardmaskforshallowtrenchisolation(STI)processasshowninFig.1.TheSi3N4layeris1625inthickness,amixtureofCF4,HBr,He,O2areusedastheetchinggas.Theplasmaintensitydecreasesveryasshownbyopticalemissionspectroscopy(OES)inFig.2.Fig.1TheetchinglayersinSTIprocessFig.2OESintensitydecreasesfastinHMOSiNetchin
3、g2.Experiments 4.ConclusionsPlasmaInstabilityinHMOSi3N4Xing-cunLI1,2,Shi-jieJIAN2,Xiao-dongZHU1(1.ModernPhysicsDepartment,UniversityofScienceandTechnologyofChina,Hefei,Anhui,2300262.BeijingNAURAMicroelectronicsEquipmentCo.,Ltd,Beijing,Anhui,100176Email:)TheplasmainstabilityofSi3N4etchingwasstudiedin
4、thispaper.Theuseofdiagnosticequipment such as OES spectroscopy,Langmuir probes and SEERS to characterize theinstabilityfromplasmacompositionandplasmaparameters.ThediagnosticresultsshowthattheCNrelatedspeciesarethemainchemicalcomponentsthatcausetheinstabilityoftheplasma.Theelectroncollisionrateisinan
5、unsaturatedstatebeforetheplasmaisstabilized.ThisshowsthatCNby-productshaveparticipatedintheplasmadischarge.Byshorteningtheresidencetimeofthegas,itispossibletosuppresstheoccurrenceofsuchaninstabilityphenomenon.1.IntroductionFig.3Briefstructureofthe13.56MHzICPetchingtool3.Results and DiscussionnTest r
6、ecipes and wafersFig.3showsthestructureofthe13.56MHzICPetchingtoolusedinthisexperiment,herethefrequencyforICPsourceandbiasareboth13.56MHz,andthebiasgeneratoristhemasterphaseoutputtopreventthecrosstalkwithICPgenerator.Fig.4showstheplasmadiagnosticsplatforminthiswork.TheplasmaetchingmechanismforSi3N4s
7、howsthattheCF4gasisthemainreactivegas,theFradicalsfromCF4willreactedwithSiinSi3N4,andthemainbyproductsareSiF4,N2,CN.Basedontheetchingmechanism,theetchingmaterialsandfloweffectsareconsideredtostudytheunstablerootcause.Fig.5ElectrondensitymeasuredbySEERSFig.6FullspectrumofSiNandSietchingwiththesamerec
8、ipeFig.5andFig.6showtheelectrondensity(collectedbySEERS)andspecies(collectedbyOES)forSi3N4andSiwiththeHMOrecipe.CN*isthemainbyproductinHMOSi3N4etchingshownasinFig.6.WhenetchingtheSi3N4,theplasmadensityishigherthanSietching.Fig.7andFig.8showtheelectrondensityandelectrontemperaturecollectedbyLangmuirp
9、robewhenetchingSi3N4.Theplasmadensityislowerfortheunstableetching.Meanwhile,theelectrontemperatureishigherintheinitialperiodfortheunstableetching.Fig.7ElectrondensitymeasuredbyLangmuirprobeFig.8ElectrontemperaturemeasuredbyLangmuirprobeFig.9ElectrondensitymeasuredbyLangmuirprobeFig.10Electrontempera
10、turemeasuredbyLangmuirprobeFig.9andFig.10showtheresiduetimeeffectontheHMOSi3N4etching.Whenincreasingthetotalflowofthegases,theinstabletimebecomesshorter,andfinallyitisstablewhenthetotalflowis157sccm.TheelectroncollisionratesmeasuredbySEERSareshowninFig.10,thedatahasthesimilartrendasOES.Issues Actions Variations Etching materialsSi20mT/600W SRF/70CF4/30HBr/10HeO2/80W BiasSiN20mT/600W SRF/70CF4/30HBr/10HeO2/80W BiasProcess windowFlow HMO gas total flow from 110sccm to 157sccmnHMO Si3N4 etching mechanismFig.5Theplasmadiagnosticsplatform