High-density plasma etching of magnetic devices

174 Pages·1999·6.5 MB·English

by  Jung, Kee Bum, 1967-

HIGH-DENSITYPLASMAETCHINGOFMAGNETICDEVICES
By
KEEBUMJUNG
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
1999
TrustintheLordwithallyourheart
andleannotonyourownunderstanding;
inallyourwaysacknowledgehim
andhewillmakeyourpathsstraight.
Proverbs3:5-6
ACKNOWLEDGMENTS
Firstandforemost,Iwouldliketoexpressgreatappreciationwithallmyheartto
ProfessorPeartonforhisexpertadvice,guidance,andinstructionthroughouttheresearch.
Ialsogivespecialthankstomembersofmycommittee-ProfessorAbernathy,Professor
SharifiinDepartmentofPhysics,ProfessorSingh,ProfessorRen,andDr.Childressat
IBMAlmadenResearchCenterinSanJose,CA-fortheirprofessionalinputandsupport.
Additionalspecialthanksarereservedforthepeopleofourresearchgroup-Dr.Hahn,Dr.
Cho, X. Cao, D. C. Hays, P. Leerungnawarat, K. P. Lee, and J. Marburger in the
DepartmentofPhysics-fortheirassistance,care,andfriendship.Iamverygratefulto
pastgroupmembers-Dr.C.B.Vartuli,Dr.J.W.Lee,Dr.J.Hong,andJ.J.Wang.Ialso
givemythankstoP.Mathisforherendlesshelpandkindness.
IamalwaysthankfulforGod'shelpandblessingformetobewhereIamtoday.
In addition, I give my sincere gratitude to my parents and parents-in-law for their
unlimitedloveandencouragement,andespeciallytomylovelywife,HeesunKimJung,
forheremotionalhelp,inspiration,andcontinualprayers.
iii
TABLEOFCONTENTS
page
ACKNOWLEDGMENTS
iii
LISTOFTABLES vi
LISTOFFIGURES vii
ABSTRACT xv
CHAPTERS
INTRODUCTION
1 1
2 MAGNETICDEVICES 5
2.1.TheTheoryofGMR 5
2.2.BasicMechanismofGMR 7
2.3.GMRReadHead 10
2.4.MagneticRandomAccessMemory 12
3 LITERATUREREVIEWOFPLASMAETCHINGPROCESSES 13
3.1.TheTransitionfromWetEtchingtoDryEtching 13
3.2.TheUltimateGoalsofaDryEtchProcess 14
3.3.BasicMechanismoftheEtchProcess 16
3.4.DryEtchingTechniques 21
3.5.High-DensityPlasmaReactor 22
4 HIGH-DENSITYPLASMAETCHINGFORPATTERNINGOFNiFeAND
NiFeCo 27
4.1.Introduction 27
4.2.MaterialsandExperimentalProcedure 28
4.3.ElectronCyclotronResonancePlasmaEtching 29
4.4.InductivelyCoupledPlasmaEtching 44
4.4.1.Cl2-basedPlasmaChemistries 44
IV
4.4.2.Inter-HalogenPlasmaChemistries 55
4.4.3.EffectofInertGasAdditiveonClj-basedPlasmaChemistries 67
4.4.4.Long-TermStabilityafterEtchingandPost-EtchTreatments 75
5 INDUCTIVELYCOUPLEDPLASMAETCHINGOFCoFeB,CoZr,CoSm,
ANDFeMnTHINFILMS 91
5.1.Introduction 91
5.2.MaterialsandExperimentalProcedure 92
5.3.Clj-basedplasmaChemistries 93
5.4.Inter-HalogenPlasmaChemistries 107
6 INDUCTIVELYCOUPLEDPLASMAANDELECTRONCYCLOTRON
RESONANCEPLASMAETCHINGWITHCO/NH3CHEMISTRY 118
6.1.Introduction 118
6.2.MaterialsandExperimentalProcedure 120
6.3.ResultsandDiscussion 121
6.3.1.InductivelyCoupledPlasmaEtching 121
6.3.2.ElectronCyclotronResonancePlasmaEtching 134
7 SUMMARY 146
REFERENCES 151
BIOGRAPHICALSKETCH I55
V
LISTOFTABLES
page
4-1.Boilingpointsofpotentialetchproducts 31
7-1.TypicalresultsfortheetchingofNiFeinHighDensityPlasmaReactor 149
VI
LISTOFFIGURES
2F-igure pgge
3-
2-1 TheGiantMagnetoresistanceeffectisduetothelargedifference
inelectricalresistancebetweentwomagneticstatesofa
3- metallicmultilayerfilm 8
2 StructureandoperationprincipleofGMRhead 11
4-
1 Schematicofplasmaetching:etchingoccursbecauseoftwo
etchmechanisms:chemicalreactionandionbombardment 17
3-2 Thefourbasicmechanismsofplasmaetching 20
3 SchematicsoftypicalReactiveIonEtcher(RIE,top),
ElectronCyclotronResonance(ECR,center)and
InductivelyCoupledPlasma(ICP,bottom) 26
1 NiFeCoetchratesindifferentplasmachemistriesatfixed
rfchuckpower(150W)andpressure(l.SmTorr)asa
functionofmicrowavesourcepower(top)orrfchuck
power(bottom) 32
4-2 NiFeetchratesindifferentplasmachemistriesatfixedrf
chuckpower(150W)andpressure(l.SmTorr)asafunction
ofECRmicrowavesourcepower(top)orrfchuckpower(bottom) 34
4-3 NiFeCoetchratesindifferentplasmachemistriesatfixedrf
chuckpower(150W)andpressure(l.SmTorr)asafunction
ofECRmicrowavesourcepower(top)orrfchuckpower(bottom) 36
4-4 SEMmicrographoffeatureetchedintoNiFelayersusing
anECRlOCySArplasma(800Wmicrowavesourcepower,
ISOWrfpower,l.SmTorr).Theoxidemasksarestillinplace 38
4-S SEMmicrographsoffeaturesetchedintoNiFeusinga10Cl2/SAr,
ISOWrf,2mTorr,lOOOWECRmicrowavesourcepowerdischarge,
withaphotoresistmask(top),whichhasbeensubsequently
vii
removed(bottom) 39
4-6 SEMmicrographsoffeaturesetchedintoNiFeusinglOCySAr,
l.SmTorr,150Wrfchuckpower,lOOOWmicrowavesourcepower
dischargesinaninitially“clean”chamber(nopreviousCljplasma
hadbeenseenforaconsiderableperiod),followedbyalOmin
in-situHjplasmaclean.Thesampleswerethenexposedtoair
ambientfor3weeks.TheSi02maskarestillinplace 41
4-7 SEMmicrographsoffeaturesetchedintoNiFeusingthesame
conditionsasFigure8,butnumerousCI2plasmahadbeen
usedpriortodoingtheetchandsubsequentH2plasmaclean.
Thesampleswerethenexposedtoairambientfor2weeks.
TheSi02masksare stillinplace 42
4-8 EtchselectivityofNiFeandNiFeCooverSi02andSiNxmask
materialsinlOCySAr,l.SmTorr,150Wrfchuckpower
discharges,asafunctionofECRmicrowavesourcepower 43
4-9 EtchratesofNiFe,NiFeCo,TaNandCrSiarefunctionofplasma
compositioninTCPCyArdischarges(75OWsourcepower,
-lOOVdcself-bias,2mTorrpressure) 45
4-10 EtchratesofNiFe,NiFeCo,TaNandCrSiasafunctionofplasma
compositioninICPCI2/N2discharges(750Wsourcepower,
-lOOVdcself-bias,2mTorrpressure) 46
4-11 EtchratesofNiFeCoasafunctionofplasmacompositionin
ICPCyAr,CI2/N2orCXjfHjdischarges(750Wsourcepower,
-lOOVdcself-bias,2mTorrpressure) 48
4-12 EtchratesofNiFe,NiFeCo,TaNandCrSiasafunctionofICP
sourcepowerin10Cy5Ar,2mTorr,-80Vdcself-bias
discharges 49
4-13 EtchratesofNiFe,NiFeCo,TaNandCrSiasafunctionof
rfchuckpowerin10Cy5Ar,2mTorr,750Wsource
powerdischarges 50
4-14 EtchratesofNiFe,NiFeCo,TaNandCrSiasafunction
ofprocesspressurein10Cy5Ar,-lOOVdcself-bias,
75OWsourcepowerdischarges 52
4-15 SEMmicrographsoffeaturesetchedwithNiFeusing10Cl2/5Ar,
2mTorr,-lOOVdcself-bias,750WICPsourcepowerdischarges.
Vlll
usingeitheraSi02mask(top)oraphotoresistmask(bottom),
bothofwhicharestillinplace 53
4-16 AESsurfacescansofNiFeCoafteretchinginlOCySAr,2mTorr,
750Wsourcepowerdischargesateither150W(top)or
400W(bottom)rfchuckpower 54
4-17 AESsurfacescansofTaN(top)orCrSi(bottom)afterICPetching
inlOCySAr,2mTorr,-lOOVdcself-bias,750Wsource
powerdischarges 56
4-18 EtchratesofNi,Fe,NiFeandNiFeCoin750Wsourcepower,
250Wrfchuckpower,SmTorrdischargesofICl/Ar(top)or
IBr/Ar(bottom),asafunctionofplasmacomposition 58
4-19 EtchratesofNi,Fe,NiFeandNiFeCoin250Wrfchuckpower,
5mTorrdischargesof2ICl/13Ar(top)or2IBr/13Ar(bottom),
asafunctionofsourcepower 59
4-20 EtchratesofNi,Fe,NiFeandNiFeCoin750Wsourcepower,
SmTorrdischargesof2ICl/13Ar(top)or2IBr/13Ar(bottom),
asafunctionofrfchuckpower 61
4-21 Etchrates(top)andetchyields(bottom)ofNi,Fe,NiFe
andNiFeCoin2ICl/13Ar,750Wsourcepower,
250Wrfchuckpowerdischarges,asafunctionofprocesspressure 62
4-22 AFMscansofNiFeafteretchingin750Wsourcepower,
250Wrfchuckpower,SmTorrdischarges,asafunctionof
plasmacomposition 64
4-23 AFMscansofNiFeCoafteretchingin7S0Wsourcepower,
2S0Wrfchuckpower,SmTorrdischarges,asafunctionof
plasmacomposition 6S
4-24 AESsurfacescansofNiFeafteretchingineitherICl/Ar(top)or
IBr/Ar(centerandbottom)discharges(7S0Wsourcepower,
2S0Wrfchuckpower,SmTorr),asafunctionofplasmacomposition 66
4-2S EtchratesofNiFeandNiFeCoinICPClj-baseddischarges
atfixedcomposition,pressure(SmTorr)andrfchuckpower(2S0W),
asafunctionofsourcepower 68
4-26 EtchratesofNiFeandNiFeCoinICPClj-baseddischarges
atfixedcomposition,pressure(SmTorr)andsourcepower(7S0W),
IX
asafunctionofrfchuckpower 70
4-27 EtchratesofNiFe,NiFeCo,NiandFeinICP2Cl2/13Xedischarges
(750Wsourcepower,250Wrfchuckpower),asafunctionof
processpressure 72
4-28 AFMscansofNiFesurfacesbeforeandafteretchingin
Clj/He,CyArorCyXeICPdischargesfixedsourcepower(750W),
rfchuckpower(250W)andpressure(SmTorr).
Z-scaleismagnifiedfortheetchedsamples 73
4-29 AFMscansofNiFeCosurfacesbeforeandafteretchingin
Clj/He,CyArorCyXeICPdischargesfixedsourcepower(750W),
rfchuckpower(250W)andpressure(5mTorr).
Z-scaleismagnifiedfortheetchedsamples 74
4-30 AESsurfacescansofNiFesurfacesbefore(first),
orafteretchingin2Cyi3He(second),2Cyi3Ar(third)or
2Cl2/13Xe(fourth)ICPdischargesatfixedsourcepower(750W),
rfchuckpower(250W)andpressure(SmTorr) 76
4-31 AESsurfacescansofNiFeCobefore(first),and
afteretchinginICPdischarges(750Wsourcepower,
250Wrfchuckpower,SmTorr)of2Cl2/I3He(second),
2Cyi3Ar(third)and2Cyi3Xe(fourth) 77
4-32 SESMmTmoircrr,og7rSa0phWssoofurfceeatpuorewsere,tc2hSed0WintrofNchiuFcekupsoinwger2CIIC2P/1d3iAsrc,harges.
TheSi02masksarestillinplace 78
4-33 LayerstructureofMRAlMelement.ThetopSi02layer
isthemaskforICPetchingoftheunderlyinglayers.
Etchingterminatesonthe300AthickSiNxlayer 80
4-34 Saturationmagnetizationversusthicknessremovedby
etchinginSOOAthickfilmsofNi,NiFeandNiFeCo 81
4-3S SEMmicrographsofClj/AretchedMRAMelementstaken
abouttwoweeksafteretching.Forthesesamples,
nopost-etchcleaningofchlorineresidueswasperformed 83
4-36 HysteresisloopsforMRAMstructurebeforeand
afterICPClj/Aretching,andsubsequentcleaningfor
lOminseitherbyH2OrinsingorexposuretoH2orO2plasmas
priortoremovalfromtheetchreactor 84
X